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Rushda Hussein:

<StructureSection load='7pui' size='350' side='right' caption='SHOC2-PP1C-MRAS (PDB entry [[7upi]])' scene='95/952718/Mras/2'>

=SHOC2-PP1C-MRAS=

=Introduction=
<scene name='95/952717/Zoom_out/1'>SHOC2-PP1C-MRAS</scene> (SMP) is a ternary holophosphotase complex formed by the individual proteins: SHOC2, PP1C, and MRAS. The SMP complex is involved in signaling the initiation of [https://www.nature.com/articles/7290105. MAPK pathways], which is responsible for cellular growth and development, cell proliferation, and apoptosis <ref name="Hauseman">PMID:35830882</ref>. Formation of this complex begins with an extracellular signal binding to a membrane embedded receptor [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2536775/. tyrosine kinase receptor(RTK)] <ref name="Hauseman"/>. This causes membrane-bound MRAS to exchange GDP for GTP. Initiating the SMP complex formation at the plasma membrane consists of the SHOC2 and PP1C binding first. When the MRAS exchanges GDP to GTP, it then assembles with the combined SHOC2 and PP1C. Based on MRAS targeting, PP1C catalyzes the [https://www.cell.com/fulltext/S0092-8674(00)81356-2. dephosphorylation] of the N-terminal phosphoserine (NTpS) on the [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3128629/. RAF complex] leading to the amplification of MAPK signaling <ref name="Hauseman"/>. In a normal cell, this would regulate cell proliferation but dysfunction in the ternary complex has shown signs to lead to tumor formation due to unregulated cell growth <ref name="Hauseman"/>.

=Overall Structure=

==SHOC2==
<scene name='95/952717/Shoc2/1'>SHOC2</scene> is a scaffold protein composed of 20 [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3901792/. leucine-rich repeat (LRR)] domains that form a solenoid structure <ref name="Hauseman"/>. The leucine rich region forms a concave hydrophobic core which is necessary for binding with PP1C and MRAS. SHOC2 is the crucial mediator for SHOC2-PP1C-MRAS complex formation <ref name="Hauseman"/>. The leucine rich domain is very important in creating selectivity for the PP1C protein, as that protein is used for so many other complex pathways <ref name="Hauseman"/>. The LRR domains are stabilized by an N-terminal flanking 𝝰-helix and a C-terminal helix-turn-helix <ref name="Kwon">PMID:35831509</ref>. Alongside the conserved leucine residues in the LRR domain, there is a group of conserved asparagine residues that creates a stabilizing [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7184636/. “asparagine ladder”] that is necessary for the LRR fold, giving the SHOC2 its concave structure <ref name="Kwon" />.

SHOC2 is also capable of causing various forms of cancers and [https://dceg.cancer.gov/research/what-we-study/rasopathies. rasopathies]. A common one is caused by a mutation known as p.S2G <ref name="Rauen">Rauen KA. The RASopathies. Annu Rev Genomics Hum Genet. 2013;14:355-69. [http://dx.doi.org/10.1146/annurev-genom-091212-153523 doi: 10.1146/annurev-genom-091212-153523.]</ref>. This mutation causes the formation of an additional 14-carbon saturated fatty acid chain on the N-terminal glycine of SHOC2 <ref name="Rauen" />. This causes SHOC2 to become attached to the cell membrane, resulting in a prolonged dephosphorylation of RAF by PP1C <ref name="Rauen" />. With this abnormality, there is overexpression of the MAPK pathway and increased cell proliferation genes <ref name="Rauen" />. This can cause the formation of various tumors in the body. Other mutations of the SMP ternary structure as a whole can also lead to the development of Noonan syndrome <ref name="Hauseman"/>.
==PP1C==
<scene name='95/952717/Pp1c/2'>PP1C</scene> is a phosphatase. After forming a ternary complex, the hydrophobic active site on PP1C interacts with Raf and dephosphorylate Ser 259. PP1C's active site is adjacent to a hydrophobic binding pocket that binds to the C-terminal phosphoserine, located on the N-terminus of RAF, the target for dephosphorylation. PP1C can act as a phosphatase in the absence of SHOC2 but PP1C lacks intrinsic substrate selectively. The SMP complex formation endows PP1C with specificity for RAF <ref name="Hauseman" />.

The mechanism that PP1C uses to catalyze the dephosphorylation is mainly through donating a hydrogen atom to a phosphate group on the C-terminal of a phosphoserine on Raf <ref name="Kubicek"/>. This makes the phosphate group a good leaving group and it breaks off <ref name="Kubicek"/>. This catalysis is done by the serine-threonine alpha catalytic site on PP1C <ref name="Kubicek"/>. In this catalytic site, there are two Manganese ions and one calcium ion <ref name="Kubicek"/>. These metal ions are necessary in stablizing this catalytic site and there are a lot of polar negative residues in this region <ref name="Kubicek"/>.

The catalytic site is also capable of causing various rasopathies if there is a mutation present <ref name="Rauen" />. Typically the mutation is centered around the catalytic site not being able to attach to the dephosphorylation site on Ras <ref name="Rauen" />. This causes an underproduction of cell proliferation pathways and leads to Rasopathies. RASopathy is a broad term used to describe developmental syndromes that stem from germline mutations of proteins along the RAS/MAPK pathway. These mutations can be either gain or loss of function. Rasopathies can also lead to cancer <ref name="Rauen" />. The mutation in PP1C can result in damages in growth and development in multiple areas of the body .<ref name="Rauen" />

===SHOC2 and PP1C interactions===

<scene name='95/952717/Shoc2_and_pp1c/1'>PP1C binds to SHOC2</scene> on its leucine rich region(LRR). Between LRR2 and LRR5 and between LRR7 and LRR11. Mutations between SHOC2 and PP1C to the LRR were shown to completely inhibit the binding of PP1C. Five main <scene name='95/952716/Shoc2_and_pp1c/3'>hydrogen and ionic bonds</scene> are made between PP1C and SHOC2 respectively: E56-R182, E167-R203, E54-K180, R187-H178, R188-E155 <ref name="Kwon">PMID:35831509</ref>. Reflecting this ionic character, the binding regions are contained within extensive acidic and basic patches on <scene name='95/952718/Acid_base_pp1c/1'>PP1C</scene> and <scene name='95/952718/Acid_base_shoc2/2'>SHOC2</scene>. The negative acidic patches of PP1C interact with the positive basic patches of SHOC2 and vice versa to form a <scene name='95/952718/Acid_base_shoc2pp1c/1'>binary complex</scene>. These interactions do not result in significant conformational changes to PP1C in comparison to other protein interactions that can be made with PP1C <ref name="Kwon">PMID:35831509</ref>.

==MRAS==
<scene name='95/952818/Membrane/2'>MRAS</scene> is a monomeric GTPase. MRAS is membrane-bound due to post-translational lipidation, which results in lipidated residues located near the C-terminus. This lipidation allows the protein to interact with the inner membrane leaflet <ref name="Seabra">PMID:9607139</ref><ref name=”Simanshu”>PMID:28666118</ref>. MRAS localizes the SMP complex near RAF and other components of downstream signaling. The region of MRAS not directly bound to the membrane binds SHOC2 and PP1C to orient the complex such that PP1C’s active site faces the serine that will get dephosphorylated on RAF. MRAS also controls SMP complex formation in connection with extracellular signaling based on its dualistic switching between its inactive and active state. In its inactive state, MRAS is bound to GDP. When signaled by growth factors, the GDP is exchanged for GTP when a ligand binds to the RTK <ref name="Hauseman" />. The now <scene name='95/952718/Zoom_in_gtp/2'>GTP bound MRAS</scene> undergoes a conformational change of the <scene name='95/952716/Newras-sw1-2/2'>switch I and II regions</scene>. These regions are the major binding sites with SHOC2. This conformational change activates MRAS allowing it to bind with the SHOC2-PP1C complex. In its inactive GDP-bound state, MRAS is sterically occluded from binding SHOC2. For example, R83 of GDP-bound MRAS directly clashes with SHOC2 as shown in figure 2. In comparison to other RAS proteins such as H/K/NRAS, MRAS has a greater affinity for the SHOC2-PP1C complex<ref name="Kubicek">Kubicek M, Pacher M, Abraham D, Podar K, Eulitz M, Baccarini M. Dephosphorylation of Ser-259 regulates Raf-1 membrane association. J Biol Chem. 2002 Mar 8;277(10):7913-9. [http://10.1074/jbc.M108733200 doi: 10.1074/jbc.M108733200.]</ref>. This indicates that the specific structure of MRAS is necessary for SMP function. While MRAS engages the SHOC2-PP1C complex to bring the complex to the membrane, an additional membrane-bound RAS binds RAF nearby. This binding is also stimulated by ligand binding to the RTK. This indicates that for full RAF activation and continuous signaling of Raf, two separate active RAS proteins are needed. Having two MRASs also help with the co-localization of PP1C to the NTpS region on RAF. To inactivate Raf signaling, MRAS uses its intrinsic GTPase to remove the activating gamma-phosphate on GTP. In the GDP-bound state, switch I and II move to the position shown in green in Figure 2. This inactivates SHOC2 binding due to steric clashing which causes the SMP structure to dissociate.

===SHOC2 and MRAS interactions===
[[Image:Freak2.png|500 px|thumb|'''Figure 2:'''Steric clashing of Switch I and II of GDP bound MRAS, in green, with the surface of SHOC2, in magenta. GTP-bound MRAS, in white, shows no steric clashing with SHOC2s surface.</div>]]

MRAS is initially bound to GDP causing it to be in its inactive state. Inactive GDP-MRAS cannot bind to the SHOC2-PP1C complex due to steric clashing of the switch I and II regions of MRAS and its binding zone on SHOC2. Once GDP is exchanged for GTP when signaled by growth factors, MRAS is activated and conformational changes occur within the switch I and switch II regions to allow <scene name='95/952716/Newmras-shco2/10'>MRAS to interact with SHOC2</scene>. These <scene name='95/952716/Scho2-mras-interactions/1'>interactions</scene> between SHOC2 and the switch I and II regions of MRAS include hydrogen bonds, ionic interactions, and π stacking. There is a hydrogen bond at R288-Q71 and ionic interaction at R177-E47. π staking occurs at R104-R83. These interactions occur between SHOC2 and MRAS respectively <ref name="Lavoie">Lavoie H, Therrien M. Structural keys unlock RAS-MAPK cellular signaling pathway. Nature. 2022 Sep;609(7926):248-249. [http://dx.doi.org/10.1038/d41586-022-02189-7 doi: 10.1038/d41586-022-02189-7. PMID: 35970881.]</ref>.

===PP1C and MRAS===

[[Image:Hydro.jpg|500 px|thumb|'''Figure 1:'''Active site of PP1C on SMP.</div>]]

The interactions between <scene name='95/952718/Mras_and_pp1c/1'>PP1C and MRAS</scene> are respectively mediated by four main <scene name='95/952716/Mras_and_pp1c/3'>polar interactions</scene>: ionic interactions are between D48-R188 and H53-D197, hydrogen bonds are between K36-Q198 and Q35-M190. As the complex forms, the active site for the dephosphorylation of RAF's S259 is oriented such that it remains accessible for RAF <ref name="Hauseman" />. The relative order of complex ordering is still an area of debate. Some experiments indicate that PP1C must bind to SHOC2 before MRAS binds<ref name="Lavoie" /> but others indicated that PP1C and MRAS can bind to SHOC2 at the same time <ref name="Hauseman" />.

=Signaling Pathway=
The SMP signaling pathway begins with the formation of the SMP complex. Initially, a ligand must bind to a receptor tyrosine kinase. This signals SHOC2 to bind to PP1C forming a binary complex that then binds to the membrane bound MRAS. There is some discrepancy about when the different proteins of the SMP complex come together <ref name="Liau">PMID:35768504</ref>, however we chose to depict the order ass shown in Figure 3 for a more clear visualization. Some experiments indicate that the three proteins bind at the same time but the order is largely unknown. Once the SMP complex forms, its intracellular target is a key inactivation phosphorylation (Ser259) on MAPK Raf1. The serine is directly dephosphorylated by PP1C, while SHOC2 and MRAS increase PP1C’s specificity for S259 on Raf <ref name="Liau" />. When analyzing the surface structure of SHOC1-PP1C-MRAS, there was a hydrophobic groove on the SHOC2 terminus and another hydrophobic groove near the active site on PP1C <ref name="Liau" />. This region is crucial in making PP1C specific to Raf, because the NTpS region that is right next to the phosphoserine on Raf is able to bind to the hydrophobic patch on both SHOC2 and PP1C <ref name="Liau" />.
Mutations affecting SMP complex formation and stability can increase or decrease MAPK signaling, where increased stability of the complex increases MAPK signaling while decreased stability decreases signaling <ref name="Liau" />. There are a set of mutations that can happen on the SMP complex as a whole that can cause [https://www.mayoclinic.org/diseases-conditions/noonan-syndrome/symptoms-causes/syc-20354422. Noonan syndrome], a rasopathy disorder <ref name="Liau" />. On SHOC2, if the following mutations S2G, C260Y, and P510L caused differences in the complex formation with PP1C <ref name="Liau" />. On PP1C, the mutation P50R resulted in stronger ionic interactions with residues on SHOC2, resulting in a more stabilized complex <ref name="Liau" />. On MRAS, mutations such as G23V and T681I, can increase the proportion of MRAS that is GTP bound, which results in increased affinity in the SMP complex overall <ref name="Liau" />. If these mutations happen all at once, or just one or two at a time, it can still significantly alter the functionality of the SMP complex <ref name="Liau" />. This can lead to diseases like Noonan syndrome, which is where there are developmental and growth issues, and can even lead to cancers <ref name="Liau" />.

===Future Studies===
With this understood knowledge about how the SMP is able to contribute to an increase or decrease of MAPK pathways, there can be further research done to develop treatments for various cancers and rasopathies <ref name="Liau" />. Research can be done to develop inhibitors that can alter the affinity of the SMP complex in order to regulate MAPK signaling pathways <ref name="Liau" />. This can help treat diseases that are caused by unregulated cell proliferation <ref name="Liau" />. Another possible point of inhibition is the growth factor that signals SHOC2-PP1C and Raf to the cell membrane. <ref name="Liau" /> .

[[Image:Complex.png|800 px|thumb|center|'''Figure 3:'''Signaling cascade is shown with SHOC2 (magenta), PP1C (blue), and MRAS (white). SHOC2 binds to PP1C then to MRAS at the cell membrane. The SMP complex is now oriented near the membrane bound RAF complex (green). ]]

[[Image:Dephosphorylate.png|900 px|thumb|center|'''Figure 4:'''PP1C dephosphorylates RAF protein at serine 259 ]]

=References=

<references/>

==Student Contributors==
Madeline Gilbert
Inaya Patel
Rushda Hussein

[[Category:Featured in BAMBED]]
[[Category:Topic Page]]

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Rushda Hussein:

<StructureSection load='7pui' size='350' side='right' caption='SHOC2-PP1C-MRAS (PDB entry [[7upi]])' scene='95/952718/Mras/2'>

=SHOC2-PP1C-MRAS=

=Introduction=
<scene name='95/952717/Zoom_out/1'>SHOC2-PP1C-MRAS</scene> (SMP) is a ternary holophosphotase complex formed by the individual proteins: SHOC2, PP1C, and MRAS. The SMP complex is involved in signaling the initiation of [https://www.nature.com/articles/7290105. MAPK pathways], which is responsible for cellular growth and development, cell proliferation, and apoptosis <ref name="Hauseman">PMID:35830882</ref>. Formation of this complex begins with an extracellular signal binding to a membrane embedded receptor [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2536775/. tyrosine kinase receptor(RTK)] <ref name="Hauseman"/>. This causes membrane-bound MRAS to exchange GDP for GTP. Initiating the SMP complex formation at the plasma membrane consists of the SHOC2 and PP1C binding first. When the MRAS exchanges GDP to GTP, it then assembles with the combined SHOC2 and PP1C. Based on MRAS targeting, PP1C catalyzes the [https://www.cell.com/fulltext/S0092-8674(00)81356-2. dephosphorylation] of the N-terminal phosphoserine (NTpS) on the [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3128629/. RAF complex] leading to the amplification of MAPK signaling <ref name="Hauseman"/>. In a normal cell, this would regulate cell proliferation but dysfunction in the ternary complex has shown signs to lead to tumor formation due to unregulated cell growth <ref name="Hauseman"/>.

=Overall Structure=

==SHOC2==
<scene name='95/952717/Shoc2/1'>SHOC2</scene> is a scaffold protein composed of 20 [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3901792/. leucine-rich repeat (LRR)] domains that form a solenoid structure <ref name="Hauseman"/>. The leucine rich region forms a concave hydrophobic core which is necessary for binding with PP1C and MRAS. SHOC2 is the crucial mediator for SHOC2-PP1C-MRAS complex formation <ref name="Hauseman"/>. The leucine rich domain is very important in creating selectivity for the PP1C protein, as that protein is used for so many other complex pathways <ref name="Hauseman"/>. The LRR domains are stabilized by an N-terminal flanking 𝝰-helix and a C-terminal helix-turn-helix <ref name="Kwon">PMID:35831509</ref>. Alongside the conserved leucine residues in the LRR domain, there is a group of conserved asparagine residues that creates a stabilizing [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7184636/. “asparagine ladder”] that is necessary for the LRR fold, giving the SHOC2 its concave structure <ref name="Kwon" />.

SHOC2 is also capable of causing various forms of cancers and rasopathies. A common one is caused by a mutation known as p.S2G <ref name="Rauen">Rauen KA. The RASopathies. Annu Rev Genomics Hum Genet. 2013;14:355-69. [http://dx.doi.org/10.1146/annurev-genom-091212-153523 doi: 10.1146/annurev-genom-091212-153523.]</ref>. This mutation causes the formation of an additional 14-carbon saturated fatty acid chain on the N-terminal glycine of SHOC2 <ref name="Rauen" />. This causes SHOC2 to become attached to the cell membrane, resulting in a prolonged dephosphorylation of RAF by PP1C <ref name="Rauen" />. With this abnormality, there is overexpression of the MAPK pathway and increased cell proliferation genes <ref name="Rauen" />. This can cause the formation of various tumors in the body. Other mutations of the SMP ternary structure as a whole can also lead to the development of Noonan syndrome <ref name="Hauseman"/>.
==PP1C==
<scene name='95/952717/Pp1c/2'>PP1C</scene> is a phosphatase. After forming a ternary complex, the hydrophobic active site on PP1C interacts with Raf and dephosphorylate Ser 259. PP1C's active site is adjacent to a hydrophobic binding pocket that binds to the C-terminal phosphoserine, located on the N-terminus of RAF, the target for dephosphorylation. PP1C can act as a phosphatase in the absence of SHOC2 but PP1C lacks intrinsic substrate selectively. The SMP complex formation endows PP1C with specificity for RAF <ref name="Hauseman" />.

The mechanism that PP1C uses to catalyze the dephosphorylation is mainly through donating a hydrogen atom to a phosphate group on the C-terminal of a phosphoserine on Raf <ref name="Kubicek"/>. This makes the phosphate group a good leaving group and it breaks off <ref name="Kubicek"/>. This catalysis is done by the serine-threonine alpha catalytic site on PP1C <ref name="Kubicek"/>. In this catalytic site, there are two Manganese ions and one calcium ion <ref name="Kubicek"/>. These metal ions are necessary in stablizing this catalytic site and there are a lot of polar negative residues in this region <ref name="Kubicek"/>.

The catalytic site is also capable of causing various rasopathies if there is a mutation present <ref name="Rauen" />. Typically the mutation is centered around the catalytic site not being able to attach to the dephosphorylation site on Ras <ref name="Rauen" />. This causes an underproduction of cell proliferation pathways and leads to Rasopathies. RASopathy is a broad term used to describe developmental syndromes that stem from germline mutations of proteins along the RAS/MAPK pathway. These mutations can be either gain or loss of function. Rasopathies can also lead to cancer <ref name="Rauen" />. The mutation in PP1C can result in damages in growth and development in multiple areas of the body .<ref name="Rauen" />

===SHOC2 and PP1C interactions===

<scene name='95/952717/Shoc2_and_pp1c/1'>PP1C binds to SHOC2</scene> on its leucine rich region(LRR). Between LRR2 and LRR5 and between LRR7 and LRR11. Mutations between SHOC2 and PP1C to the LRR were shown to completely inhibit the binding of PP1C. Five main <scene name='95/952716/Shoc2_and_pp1c/3'>hydrogen and ionic bonds</scene> are made between PP1C and SHOC2 respectively: E56-R182, E167-R203, E54-K180, R187-H178, R188-E155 <ref name="Kwon">PMID:35831509</ref>. Reflecting this ionic character, the binding regions are contained within extensive acidic and basic patches on <scene name='95/952718/Acid_base_pp1c/1'>PP1C</scene> and <scene name='95/952718/Acid_base_shoc2/2'>SHOC2</scene>. The negative acidic patches of PP1C interact with the positive basic patches of SHOC2 and vice versa to form a <scene name='95/952718/Acid_base_shoc2pp1c/1'>binary complex</scene>. These interactions do not result in significant conformational changes to PP1C in comparison to other protein interactions that can be made with PP1C <ref name="Kwon">PMID:35831509</ref>.

==MRAS==
<scene name='95/952717/Mras/2'>MRAS</scene> is a monomeric GTPase. MRAS is membrane-bound due to post-translational lipidation which allows the protein to interact with the inner membrane leaflet. <ref name="Seabra">PMID:9607139</ref> MRAS localizes the SMP complex near RAF and other components of downstream signaling. The region of MRAS not directly bound to the membrane binds SHOC2 and PP1C to orient the complex such that PP1C’s active site faces the serine that will get dephosphorylated on RAF. MRAS also controls SMP complex formation in connection with extracellular signaling based on its dualistic switching between its inactive and active state. In its inactive state, MRAS is bound to GDP. When signaled by growth factors, the GDP is exchanged for GTP when a ligand binds to the RTK <ref name="Hauseman" />. The now <scene name='95/952718/Zoom_in_gtp/2'>GTP bound MRAS</scene> undergoes a conformational change of the <scene name='95/952716/Newras-sw1-2/2'>switch I and II regions</scene>. These regions are the major binding sites with SHOC2. This conformational change activates MRAS allowing it to bind with the SHOC2-PP1C complex. In its inactive GDP-bound state, MRAS is sterically occluded from binding SHOC2. For example, R83 of GDP-bound MRAS directly clashes with SHOC2 as shown in figure 2. In comparison to other RAS proteins such as H/K/NRAS, MRAS has a greater affinity for the SHOC2-PP1C complex<ref name="Kubicek">Kubicek M, Pacher M, Abraham D, Podar K, Eulitz M, Baccarini M. Dephosphorylation of Ser-259 regulates Raf-1 membrane association. J Biol Chem. 2002 Mar 8;277(10):7913-9. [http://10.1074/jbc.M108733200 doi: 10.1074/jbc.M108733200.]</ref>. This indicates that the specific structure of MRAS is necessary for SMP function. While MRAS engages the SHOC2-PP1C complex to bring the complex to the membrane, an additional membrane-bound RAS binds RAF nearby. This binding is also stimulated by ligand binding to the RTK. This indicates that for full RAF activation and continuous signaling of Raf, two separate active RAS proteins are needed. Having two MRASs also help with the co-localization of PP1C to the NTpS region on RAF. To inactivate Raf signaling, MRAS uses its intrinsic GTPase to remove the activating gamma-phosphate on GTP. In the GDP-bound state, switch I and II move to the position shown in green in Figure 2. This inactivates SHOC2 binding due to steric clashing which causes the SMP structure to dissociate.

===SHOC2 and MRAS interactions===
[[Image:Freak2.png|500 px|thumb|'''Figure 2:'''Steric clashing of Switch I and II of GDP bound MRAS, in green, with the surface of SHOC2, in magenta. GTP-bound MRAS, in white, shows no steric clashing with SHOC2s surface.</div>]]

MRAS is initially bound to GDP causing it to be in its inactive state. Inactive GDP-MRAS cannot bind to the SHOC2-PP1C complex due to steric clashing of the switch I and II regions of MRAS and its binding zone on SHOC2. Once GDP is exchanged for GTP when signaled by growth factors, MRAS is activated and conformational changes occur within the switch I and switch II regions to allow <scene name='95/952716/Newmras-shco2/10'>MRAS to interact with SHOC2</scene>. These <scene name='95/952716/Scho2-mras-interactions/1'>interactions</scene> between SHOC2 and the switch I and II regions of MRAS include hydrogen bonds, ionic interactions, and π stacking. There is a hydrogen bond at R288-Q71 and ionic interaction at R177-E47. π staking occurs at R104-R83. These interactions occur between SHOC2 and MRAS respectively <ref name="Lavoie">Lavoie H, Therrien M. Structural keys unlock RAS-MAPK cellular signaling pathway. Nature. 2022 Sep;609(7926):248-249. [http://dx.doi.org/10.1038/d41586-022-02189-7 doi: 10.1038/d41586-022-02189-7. PMID: 35970881.]</ref>.

===PP1C and MRAS===

[[Image:ActiveSiteProto.png|500 px|thumb|'''Figure 1:'''Active site of PP1C on SMP.</div>]]

The interactions between <scene name='95/952718/Mras_and_pp1c/1'>PP1C and MRAS</scene> are respectively mediated by four main <scene name='95/952716/Mras_and_pp1c/3'>polar interactions</scene>: ionic interactions are between D48-R188 and H53-D197, hydrogen bonds are between K36-Q198 and Q35-M190. As the complex forms, the active site for the dephosphorylation of RAF's S259 is oriented such that it remains accessible for RAF <ref name="Hauseman" />. The relative order of complex ordering is still an area of debate. Some experiments indicate that PP1C must bind to SHOC2 before MRAS binds<ref name="Lavoie" /> but others indicated that PP1C and MRAS can bind to SHOC2 at the same time <ref name="Hauseman" />.

=Signaling Pathway=
The SMP signaling pathway begins with the formation of the SMP complex. Initially, a ligand must bind to a receptor tyrosine kinase. This signals SHOC2 to bind to PP1C forming a binary complex that then binds to the membrane bound MRAS. There is some discrepancy about when the different proteins of the SMP complex come together <ref name="Liau">PMID:35768504</ref>, however we chose to depict the order ass shown in Figure 3 for a more clear visualization. Some experiments indicate that the three proteins bind at the same time but the order is largely unknown. Once the SMP complex forms, its intracellular target is a key inactivation phosphorylation (Ser259) on MAPK Raf1. The serine is directly dephosphorylated by PP1C, while SHOC2 and MRAS increase PP1C’s specificity for S259 on Raf <ref name="Liau" />. When analyzing the surface structure of SHOC1-PP1C-MRAS, there was a hydrophobic groove on the SHOC2 terminus and another hydrophobic groove near the active site on PP1C <ref name="Liau" />. This region is crucial in making PP1C specific to Raf, because the NTpS region that is right next to the phosphoserine on Raf is able to bind to the hydrophobic patch on both SHOC2 and PP1C <ref name="Liau" />.
Mutations affecting SMP complex formation and stability can increase or decrease MAPK signaling, where increased stability of the complex increases MAPK signaling while decreased stability decreases signaling <ref name="Liau" />. There are a set of mutations that can happen on the SMP complex as a whole that can cause [https://www.mayoclinic.org/diseases-conditions/noonan-syndrome/symptoms-causes/syc-20354422. Noonan syndrome], a rasopathy disorder <ref name="Liau" />. On SHOC2, if the following mutations S2G, C260Y, and P510L caused differences in the complex formation with PP1C <ref name="Liau" />. On PP1C, the mutation P50R resulted in stronger ionic interactions with residues on SHOC2, resulting in a more stabilized complex <ref name="Liau" />. On MRAS, mutations such as G23V and T681I, can increase the proportion of MRAS that is GTP bound, which results in increased affinity in the SMP complex overall <ref name="Liau" />. If these mutations happen all at once, or just one or two at a time, it can still significantly alter the functionality of the SMP complex <ref name="Liau" />. This can lead to diseases like Noonan syndrome, which is where there are developmental and growth issues, and can even lead to cancers <ref name="Liau" />.

===Future Studies===
With this understood knowledge about how the SMP is able to contribute to an increase or decrease of MAPK pathways, there can be further research done to develop treatments for various cancers and rasopathies <ref name="Liau" />. Research can be done to develop inhibitors that can alter the affinity of the SMP complex in order to regulate MAPK signaling pathways <ref name="Liau" />. This can help treat diseases that are caused by unregulated cell proliferation <ref name="Liau" />. Another possible point of inhibition is the growth factor that signals SHOC2-PP1C and Raf to the cell membrane. <ref name="Liau" /> .

[[Image:Complex.png|800 px|thumb|center|'''Figure 3:'''Signaling cascade is shown with SHOC2 (magenta), PP1C (blue), and MRAS (white). SHOC2 binds to PP1C then to MRAS at the cell membrane. The SMP complex is now oriented near the membrane bound RAF complex (green). ]]

[[Image:Dephosphorylation.jpg|600 px|thumb|center|'''Figure 4:'''PP1C dephosphorylates RAF protein at serine 259 ]]

=References=

<references/>

==Student Contributors==
Madeline Gilbert
Inaya Patel
Rushda Hussein

[[Category:Featured in BAMBED]]
[[Category:Topic Page]]

Sandbox Reserved 1790

2023-04-20T22:36:00Z

Rushda Hussein:

<StructureSection load='7pui' size='350' side='right' caption='SHOC2-PP1C-MRAS (PDB entry [[7upi]])' scene='95/952718/Mras/2'>

=SHOC2-PP1C-MRAS=

=Introduction=
<scene name='95/952717/Zoom_out/1'>SHOC2-PP1C-MRAS</scene> (SMP) is a ternary holophosphotase complex formed by the individual proteins: SHOC2, PP1C, and MRAS. The SMP complex is involved in signaling the initiation of [https://www.nature.com/articles/7290105. MAPK pathways], which is responsible for cellular growth and development, cell proliferation, and apoptosis <ref name="Hauseman">PMID:35830882</ref>. Formation of this complex begins with an extracellular signal binding to a membrane embedded receptor [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2536775/. tyrosine kinase receptor(RTK)] <ref name="Hauseman"/>. This causes membrane-bound MRAS to exchange GDP for GTP. Initiating the SMP complex formation at the plasma membrane consists of the SHOC2 and PP1C binding first. When the MRAS exchanges GDP to GTP, it then assembles with the combined SHOC2 and PP1C. Based on MRAS targeting, PP1C catalyzes the [https://www.cell.com/fulltext/S0092-8674(00)81356-2. dephosphorylation] of the N-terminal phosphoserine (NTpS) on the [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3128629/. RAF complex] leading to the amplification of MAPK signaling <ref name="Hauseman"/>. In a normal cell, this would regulate cell proliferation but dysfunction in the ternary complex has shown signs to lead to tumor formation due to unregulated cell growth <ref name="Hauseman"/>.

=Overall Structure=

==SHOC2==
<scene name='95/952717/Shoc2/1'>SHOC2</scene> is a scaffold protein composed of 20 [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3901792/. leucine-rich repeat (LRR)] domains that form a solenoid structure <ref name="Hauseman"/>. The leucine rich region forms a concave hydrophobic core which is necessary for binding with PP1C and MRAS. SHOC2 is the crucial mediator for SHOC2-PP1C-MRAS complex formation <ref name="Hauseman"/>. The leucine rich domain is very important in creating selectivity for the PP1C protein, as that protein is used for so many other complex pathways <ref name="Hauseman"/>. The LRR domains are stabilized by an N-terminal flanking 𝝰-helix and a C-terminal helix-turn-helix <ref name="Kwon">PMID:35831509</ref>. Alongside the conserved leucine residues in the LRR domain, there is a group of conserved asparagine residues that creates a stabilizing [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7184636/. “asparagine ladder”] that is necessary for the LRR fold, giving the SHOC2 its concave structure <ref name="Kwon" />.

SHOC2 is also capable of causing various forms of cancers and rasopathies. A common one is caused by a mutation known as p.S2G <ref name="Rauen">Rauen KA. The RASopathies. Annu Rev Genomics Hum Genet. 2013;14:355-69. [http://dx.doi.org/10.1146/annurev-genom-091212-153523 doi: 10.1146/annurev-genom-091212-153523.]</ref>. This mutation causes the formation of an additional 14-carbon saturated fatty acid chain on the N-terminal glycine of SHOC2 <ref name="Rauen" />. This causes SHOC2 to become attached to the cell membrane, resulting in a prolonged dephosphorylation of RAF by PP1C <ref name="Rauen" />. With this abnormality, there is overexpression of the MAPK pathway and increased cell proliferation genes <ref name="Rauen" />. This can cause the formation of various tumors in the body. Other mutations of the SMP ternary structure as a whole can also lead to the development of Noonan syndrome <ref name="Hauseman"/>.
==PP1C==
<scene name='95/952717/Pp1c/2'>PP1C</scene> is a phosphatase. After forming a ternary complex, the hydrophobic active site on PP1C interacts with Raf and dephosphorylate Ser 259. PP1C's active site is adjacent to a hydrophobic binding pocket that binds to the C-terminal phosphoserine, located on the N-terminus of RAF, the target for dephosphorylation. PP1C can act as a phosphatase in the absence of SHOC2 but PP1C lacks intrinsic substrate selectively. The SMP complex formation endows PP1C with specificity for RAF <ref name="Hauseman" />.

The mechanism that PP1C uses to catalyze the dephosphorylation is mainly through donating a hydrogen atom to a phosphate group on the C-terminal of a phosphoserine on Raf <ref name="Kubicek"/>. This makes the phosphate group a good leaving group and it breaks off <ref name="Kubicek"/>. This catalysis is done by the serine-threonine alpha catalytic site on PP1C <ref name="Kubicek"/>. In this catalytic site, there are two Manganese ions and one calcium ion <ref name="Kubicek"/>. These metal ions are necessary in stablizing this catalytic site and there are a lot of polar negative residues in this region <ref name="Kubicek"/>.

The catalytic site is also capable of causing various rasopathies if there is a mutation present <ref name="Rauen" />. Typically the mutation is centered around the catalytic site not being able to attach to the dephosphorylation site on Ras <ref name="Rauen" />. This causes an underproduction of cell proliferation pathways and leads to Rasopathies. RASopathy is a broad term used to describe developmental syndromes that stem from germline mutations of proteins along the RAS/MAPK pathway. These mutations can be either gain or loss of function. Rasopathies can also lead to cancer <ref name="Rauen" />. The mutation in PP1C can result in damages in growth and development in multiple areas of the body .<ref name="Rauen" />

===SHOC2 and PP1C interactions===

<scene name='95/952717/Shoc2_and_pp1c/1'>PP1C binds to SHOC2</scene> on its leucine rich region(LRR). Between LRR2 and LRR5 and between LRR7 and LRR11. Mutations between SHOC2 and PP1C to the LRR were shown to completely inhibit the binding of PP1C. Five main <scene name='95/952716/Shoc2_and_pp1c/3'>hydrogen and ionic bonds</scene> are made between PP1C and SHOC2 respectively: E56-R182, E167-R203, E54-K180, R187-H178, R188-E155 <ref name="Kwon">PMID:35831509</ref>. Reflecting this ionic character, the binding regions are contained within extensive acidic and basic patches on <scene name='95/952718/Acid_base_pp1c/1'>PP1C</scene> and <scene name='95/952718/Acid_base_shoc2/2'>SHOC2</scene>. The negative acidic patches of PP1C interact with the positive basic patches of SHOC2 and vice versa to form a <scene name='95/952718/Acid_base_shoc2pp1c/1'>binary complex</scene>. These interactions do not result in significant conformational changes to PP1C in comparison to other protein interactions that can be made with PP1C <ref name="Kwon">PMID:35831509</ref>.

==MRAS==
<scene name='95/952717/Mras/2'>MRAS</scene> is a monomeric GTPase. MRAS is membrane-bound due to post-translational lipidation which allows the protein to interact with the inner membrane leaflet. <ref name="Seabra">PMID:9607139</ref> MRAS localizes the SMP complex near RAF and other components of downstream signaling. The region of MRAS not directly bound to the membrane binds SHOC2 and PP1C to orient the complex such that PP1C’s active site faces the serine that will get dephosphorylated on RAF. MRAS also controls SMP complex formation in connection with extracellular signaling based on its dualistic switching between its inactive and active state. In its inactive state, MRAS is bound to GDP. When signaled by growth factors, the GDP is exchanged for GTP when a ligand binds to the RTK <ref name="Hauseman" />. The now <scene name='95/952718/Zoom_in_gtp/2'>GTP bound MRAS</scene> undergoes a conformational change of the <scene name='95/952716/Newras-sw1-2/2'>switch I and II regions</scene>. These regions are the major binding sites with SHOC2. This conformational change activates MRAS allowing it to bind with the SHOC2-PP1C complex. In its inactive GDP-bound state, MRAS is sterically occluded from binding SHOC2. For example, R83 of GDP-bound MRAS directly clashes with SHOC2 as shown in figure 2. In comparison to other RAS proteins such as H/K/NRAS, MRAS has a greater affinity for the SHOC2-PP1C complex<ref name="Kubicek">Kubicek M, Pacher M, Abraham D, Podar K, Eulitz M, Baccarini M. Dephosphorylation of Ser-259 regulates Raf-1 membrane association. J Biol Chem. 2002 Mar 8;277(10):7913-9. [http://10.1074/jbc.M108733200 doi: 10.1074/jbc.M108733200.]</ref>. This indicates that the specific structure of MRAS is necessary for SMP function. While MRAS engages the SHOC2-PP1C complex to bring the complex to the membrane, an additional membrane-bound RAS binds RAF nearby. This binding is also stimulated by ligand binding to the RTK. This indicates that for full RAF activation and continuous signaling of Raf, two separate active RAS proteins are needed. Having two MRASs also help with the co-localization of PP1C to the NTpS region on RAF. To inactivate Raf signaling, MRAS uses its intrinsic GTPase to remove the activating gamma-phosphate on GTP. In the GDP-bound state, switch I and II move to the position shown in green in Figure 2. This inactivates SHOC2 binding due to steric clashing which causes the SMP structure to dissociate.

===SHOC2 and MRAS interactions===
[[Image:Freak2.png|500 px|thumb|'''Figure 2:'''Steric clashing of Switch I and II of GDP bound MRAS, in green, with the surface of SHOC2, in magenta. GTP-bound MRAS, in white, shows no steric clashing with SHOC2s surface.</div>]]

MRAS is initially bound to GDP causing it to be in its inactive state. Inactive GDP-MRAS cannot bind to the SHOC2-PP1C complex due to steric clashing of the switch I and II regions of MRAS and its binding zone on SHOC2. Once GDP is exchanged for GTP when signaled by growth factors, MRAS is activated and conformational changes occur within the switch I and switch II regions to allow <scene name='95/952716/Newmras-shco2/10'>MRAS to interact with SHOC2</scene>. These <scene name='95/952716/Scho2-mras-interactions/1'>interactions</scene> between SHOC2 and the switch I and II regions of MRAS include hydrogen bonds, ionic interactions, and π stacking. There is a hydrogen bond at R288-Q71 and ionic interaction at R177-E47. π staking occurs at R104-R83. These interactions occur between SHOC2 and MRAS respectively <ref name="Lavoie">Lavoie H, Therrien M. Structural keys unlock RAS-MAPK cellular signaling pathway. Nature. 2022 Sep;609(7926):248-249. [http://dx.doi.org/10.1038/d41586-022-02189-7 doi: 10.1038/d41586-022-02189-7. PMID: 35970881.]</ref>.

===PP1C and MRAS===

[[Image:ActiveSiteProto.png|500 px|thumb|'''Figure 1:'''Active site of PP1C on SMP.</div>]]

The interactions between <scene name='95/952718/Mras_and_pp1c/1'>PP1C and MRAS</scene> are respectively mediated by four main <scene name='95/952716/Mras_and_pp1c/3'>polar interactions</scene>: ionic interactions are between D48-R188 and H53-D197, hydrogen bonds are between K36-Q198 and Q35-M190. As the complex forms, the active site for the dephosphorylation of RAF's S259 is oriented such that it remains accessible for RAF <ref name="Hauseman" />. The relative order of complex ordering is still an area of debate. Some experiments indicate that PP1C must bind to SHOC2 before MRAS binds<ref name="Lavoie" /> but others indicated that PP1C and MRAS can bind to SHOC2 at the same time <ref name="Hauseman" />.

=Signaling Pathway=
The SMP signaling pathway begins with the formation of the SMP complex. Initially, a ligand must bind to a receptor tyrosine kinase. This signals SHOC2 to bind to PP1C forming a binary complex that then binds to the membrane bound MRAS. There is some discrepancy about when the different proteins of the SMP complex come together <ref name="Liau">PMID:35768504</ref>. Some experiments indicate that the three proteins bind at the same time but the order is largely unknown. Once the SMP complex forms, its intracellular target is a key inactivation phosphorylation (Ser259) on MAPK Raf1. The serine is directly dephosphorylated by PP1C, while SHOC2 and MRAS increase PP1C’s specificity for S259 on Raf <ref name="Liau" />. When analyzing the surface structure of SHOC1-PP1C-MRAS, there was a hydrophobic groove on the SHOC2 terminus and another hydrophobic groove near the active site on PP1C <ref name="Liau" />. This region is crucial in making PP1C specific to Raf, because the NTpS region that is right next to the phosphoserine on Raf is able to bind to the hydrophobic patch on both SHOC2 and PP1C <ref name="Liau" />.
Mutations affecting SMP complex formation and stability can increase or decrease MAPK signaling, where increased stability of the complex increases MAPK signaling while decreased stability decreases signaling <ref name="Liau" />. There are a set of mutations that can happen on the SMP complex as a whole that can cause [https://www.mayoclinic.org/diseases-conditions/noonan-syndrome/symptoms-causes/syc-20354422. Noonan syndrome], a rasopathy disorder <ref name="Liau" />. On SHOC2, if the following mutations S2G, C260Y, and P510L caused differences in the complex formation with PP1C <ref name="Liau" />. On PP1C, the mutation P50R resulted in stronger ionic interactions with residues on SHOC2, resulting in a more stabilized complex <ref name="Liau" />. On MRAS, mutations such as G23V and T681I, can increase the proportion of MRAS that is GTP bound, which results in increased affinity in the SMP complex overall <ref name="Liau" />. If these mutations happen all at once, or just one or two at a time, it can still significantly alter the functionality of the SMP complex <ref name="Liau" />. This can lead to diseases like Noonan syndrome, which is where there are developmental and growth issues, and can even lead to cancers <ref name="Liau" />.

===Future Studies===
With this understood knowledge about how the SMP is able to contribute to an increase or decrease of MAPK pathways, there can be further research done to develop treatments for various cancers and rasopathies <ref name="Liau" />. Research can be done to develop inhibitors that can alter the affinity of the SMP complex in order to regulate MAPK signaling pathways <ref name="Liau" />. This can help treat diseases that are caused by unregulated cell proliferation <ref name="Liau" />.

[[Image:Complex.png|800 px|thumb|center|'''Figure 3:'''Signaling cascade is shown with SHOC2 (magenta), PP1C (blue), and MRAS (white). SHOC2 binds to PP1C then to MRAS at the cell membrane. The SMP complex is now oriented near the membrane bound RAF complex (green). ]]

[[Image:Dephosphorylation.jpg|600 px|thumb|center|'''Figure 4:'''PP1C dephosphorylates RAF protein at serine 259 ]]
=Disease Relevance=

==RASopathies==

RASopathy is a broad term used to describe developmental syndromes that stem from [https://www.sciencedirect.com/topics/medicine-and-dentistry/germline-mutation. germline mutations] of proteins along the RAS/MAPK pathway such as SHOC2, PP1C, and MRAS. These mutations can be either gain or loss of function. Rasopathies can also lead to cancer <ref name=”Rauen”>Rauen KA. The RASopathies. Annu Rev Genomics Hum Genet. 2013;14:355-69. [http://dx.doi.org/10.1146/annurev-genom-091212-153523 doi: 10.1146/annurev-genom-091212-153523.]</ref>.

==Cancer==

Because the RAS/MAPK pathway activated by SMP regulates cell proliferation and survival, overactivity can cause tumor formation and cancer. For example, the complex has been found to play a role in the perpetuation of melanoma, leukemia, and lung cancer <ref name="Kwon" />.

=Future Studies=

Further study of the SMP complex includes clarification of the steps of the pathway. Firstly, the order of binding to form the SMP complex is unclear. Furthermore, the interaction between SMP and the Raf complex is largely unknown. Study into this step is especially important to understand how SMP activates downstream signaling.
The current knowledge of SMP can be used to study possible treatments for rasopathies and cancer. For example, the development of inhibitors that target SMP binding could prevent the effects caused by mutations that overactivate SMP. Another possible point of inhibition is the growth factor that signals SHOC2-PP1C and Raf to the cell membrane. <ref name="Liau" /> .

=References=

<references/>

==Student Contributors==
Madeline Gilbert
Inaya Patel
Rushda Hussein

[[Category:Featured in BAMBED]]
[[Category:Topic Page]]

Sandbox Reserved 1790

2023-04-20T22:33:42Z

Rushda Hussein:

<StructureSection load='7pui' size='350' side='right' caption='SHOC2-PP1C-MRAS (PDB entry [[7upi]])' scene='95/952718/Mras/2'>

=SHOC2-PP1C-MRAS=

=Introduction=
<scene name='95/952717/Zoom_out/1'>SHOC2-PP1C-MRAS</scene> (SMP) is a ternary holophosphotase complex formed by the individual proteins: SHOC2, PP1C, and MRAS. The SMP complex is involved in signaling the initiation of [https://www.nature.com/articles/7290105. MAPK pathways], which is responsible for cellular growth and development, cell proliferation, and apoptosis <ref name="Hauseman">PMID:35830882</ref>. Formation of this complex begins with an extracellular signal binding to a membrane embedded receptor [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2536775/. tyrosine kinase receptor(RTK)] <ref name="Hauseman"/>. This causes membrane-bound MRAS to exchange GDP for GTP. Initiating the SMP complex formation at the plasma membrane consists of the SHOC2 and PP1C binding first. When the MRAS exchanges GDP to GTP, it then assembles with the combined SHOC2 and PP1C. Based on MRAS targeting, PP1C catalyzes the [https://www.cell.com/fulltext/S0092-8674(00)81356-2. dephosphorylation] of the N-terminal phosphoserine (NTpS) on the [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3128629/. RAF complex] leading to the amplification of MAPK signaling <ref name="Hauseman"/>. In a normal cell, this would regulate cell proliferation but dysfunction in the ternary complex has shown signs to lead to tumor formation due to unregulated cell growth <ref name="Hauseman"/>.

=Overall Structure=

==SHOC2==
<scene name='95/952717/Shoc2/1'>SHOC2</scene> is a scaffold protein composed of 20 [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3901792/. leucine-rich repeat (LRR)] domains that form a solenoid structure <ref name="Hauseman"/>. The leucine rich region forms a concave hydrophobic core which is necessary for binding with PP1C and MRAS. SHOC2 is the crucial mediator for SHOC2-PP1C-MRAS complex formation <ref name="Hauseman"/>. The leucine rich domain is very important in creating selectivity for the PP1C protein, as that protein is used for so many other complex pathways <ref name="Hauseman"/>. The LRR domains are stabilized by an N-terminal flanking 𝝰-helix and a C-terminal helix-turn-helix <ref name="Kwon">PMID:35831509</ref>. Alongside the conserved leucine residues in the LRR domain, there is a group of conserved asparagine residues that creates a stabilizing [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7184636/. “asparagine ladder”] that is necessary for the LRR fold, giving the SHOC2 its concave structure <ref name="Kwon" />.

SHOC2 is also capable of causing various forms of cancers and rasopathies. A common one is caused by a mutation known as p.S2G <ref name="Rauen">Rauen KA. The RASopathies. Annu Rev Genomics Hum Genet. 2013;14:355-69. [http://dx.doi.org/10.1146/annurev-genom-091212-153523 doi: 10.1146/annurev-genom-091212-153523.]</ref>. This mutation causes the formation of an additional 14-carbon saturated fatty acid chain on the N-terminal glycine of SHOC2 <ref name="Rauen" />. This causes SHOC2 to become attached to the cell membrane, resulting in a prolonged dephosphorylation of RAF by PP1C <ref name="Rauen" />. With this abnormality, there is overexpression of the MAPK pathway and increased cell proliferation genes <ref name="Rauen" />. This can cause the formation of various tumors in the body. Other mutations of the SMP ternary structure as a whole can also lead to the development of Noonan syndrome <ref name="Hauseman"/>.
==PP1C==
<scene name='95/952717/Pp1c/2'>PP1C</scene> is a phosphatase. After forming a ternary complex, the hydrophobic active site on PP1C interacts with Raf and dephosphorylate Ser 259. PP1C's active site is adjacent to a hydrophobic binding pocket that binds to the C-terminal phosphoserine, located on the N-terminus of RAF, the target for dephosphorylation. PP1C can act as a phosphatase in the absence of SHOC2 but PP1C lacks intrinsic substrate selectively. The SMP complex formation endows PP1C with specificity for RAF <ref name="Hauseman" />.

The mechanism that PP1C uses to catalyze the dephosphorylation is mainly through donating a hydrogen atom to a phosphate group on the C-terminal of a phosphoserine on Raf <ref name="Kubicek"/>. This makes the phosphate group a good leaving group and it breaks off <ref name="Kubicek"/>. This catalysis is done by the serine-threonine alpha catalytic site on PP1C <ref name="Kubicek"/>. In this catalytic site, there are two Manganese ions and one calcium ion <ref name="Kubicek"/>. These metal ions are necessary in stablizing this catalytic site and there are a lot of polar negative residues in this region <ref name="Kubicek"/>.

The catalytic site is also capable of causing various rasopathies if there is a mutation present <ref name="Rauen" />. Typically the mutation is centered around the catalytic site not being able to attach to the dephosphorylation site on Ras <ref name="Rauen" />. This causes an underproduction of cell proliferation pathways and leads to Rasopathies. RASopathy is a broad term used to describe developmental syndromes that stem from germline mutations of proteins along the RAS/MAPK pathway. These mutations can be either gain or loss of function. Rasopathies can also lead to cancer <ref name="Rauen" />. The mutation in PP1C can result in damages in growth and development in multiple areas of the body .<ref name="Rauen" />

===SHOC2 and PP1C interactions===

<scene name='95/952717/Shoc2_and_pp1c/1'>PP1C binds to SHOC2</scene> on its leucine rich region(LRR). Between LRR2 and LRR5 and between LRR7 and LRR11. Mutations between SHOC2 and PP1C to the LRR were shown to completely inhibit the binding of PP1C. Five main <scene name='95/952716/Shoc2_and_pp1c/3'>hydrogen and ionic bonds</scene> are made between PP1C and SHOC2 respectively: E56-R182, E167-R203, E54-K180, R187-H178, R188-E155 <ref name="Kwon">PMID:35831509</ref>. Reflecting this ionic character, the binding regions are contained within extensive acidic and basic patches on <scene name='95/952718/Acid_base_pp1c/1'>PP1C</scene> and <scene name='95/952718/Acid_base_shoc2/2'>SHOC2</scene>. The negative acidic patches of PP1C interact with the positive basic patches of SHOC2 and vice versa to form a <scene name='95/952718/Acid_base_shoc2pp1c/1'>binary complex</scene>. These interactions do not result in significant conformational changes to PP1C in comparison to other protein interactions that can be made with PP1C <ref name="Kwon">PMID:35831509</ref>.

==MRAS==
<scene name='95/952717/Mras/2'>MRAS</scene> is a monomeric GTPase. MRAS is membrane-bound due to post-translational lipidation which allows the protein to interact with the inner membrane leaflet. <ref name="Seabra">PMID:9607139</ref> MRAS localizes the SMP complex near RAF and other components of downstream signaling. The region of MRAS not directly bound to the membrane binds SHOC2 and PP1C to orient the complex such that PP1C’s active site faces the serine that will get dephosphorylated on RAF. MRAS also controls SMP complex formation in connection with extracellular signaling based on its dualistic switching between its inactive and active state. In its inactive state, MRAS is bound to GDP. When signaled by growth factors, the GDP is exchanged for GTP when a ligand binds to the RTK <ref name="Hauseman" />. The now <scene name='95/952718/Zoom_in_gtp/2'>GTP bound MRAS</scene> undergoes a conformational change of the <scene name='95/952716/Newras-sw1-2/2'>switch I and II regions</scene>. These regions are the major binding sites with SHOC2. This conformational change activates MRAS allowing it to bind with the SHOC2-PP1C complex. In its inactive GDP-bound state, MRAS is sterically occluded from binding SHOC2. For example, R83 of GDP-bound MRAS directly clashes with SHOC2 as shown in figure 2. In comparison to other RAS proteins such as H/K/NRAS, MRAS has a greater affinity for the SHOC2-PP1C complex<ref name="Kubicek">Kubicek M, Pacher M, Abraham D, Podar K, Eulitz M, Baccarini M. Dephosphorylation of Ser-259 regulates Raf-1 membrane association. J Biol Chem. 2002 Mar 8;277(10):7913-9. [http://10.1074/jbc.M108733200 doi: 10.1074/jbc.M108733200.]</ref>. This indicates that the specific structure of MRAS is necessary for SMP function. While MRAS engages the SHOC2-PP1C complex to bring the complex to the membrane, an additional membrane-bound RAS binds RAF nearby. This binding is also stimulated by ligand binding to the RTK. This indicates that for full RAF activation and continuous signaling of Raf, two separate active RAS proteins are needed. Having two MRASs also help with the co-localization of PP1C to the NTpS region on RAF. To inactivate Raf signaling, MRAS uses its intrinsic GTPase to remove the activating gamma-phosphate on GTP. In the GDP-bound state, switch I and II move to the position shown in green in Figure 2. This inactivates SHOC2 binding due to steric clashing which causes the SMP structure to dissociate.

===SHOC2 and MRAS interactions===
[[Image:Freak2.png|500 px|thumb|'''Figure 2:'''Steric clashing of Switch I and II of GDP bound MRAS, in green, with the surface of SHOC2, in magenta. GTP-bound MRAS, in white, shows no steric clashing with SHOC2s surface.</div>]]

MRAS is initially bound to GDP causing it to be in its inactive state. Inactive GDP-MRAS cannot bind to the SHOC2-PP1C complex due to steric clashing of the switch I and II regions of MRAS and its binding zone on SHOC2. Once GDP is exchanged for GTP when signaled by growth factors, MRAS is activated and conformational changes occur within the switch I and switch II regions to allow <scene name='95/952716/Newmras-shco2/10'>MRAS to interact with SHOC2</scene>. These <scene name='95/952716/Scho2-mras-interactions/1'>interactions</scene> between SHOC2 and the switch I and II regions of MRAS include hydrogen bonds, ionic interactions, and π stacking. There is a hydrogen bond at R288-Q71 and ionic interaction at R177-E47. π staking occurs at R104-R83. These interactions occur between SHOC2 and MRAS respectively <ref name="Lavoie">Lavoie H, Therrien M. Structural keys unlock RAS-MAPK cellular signaling pathway. Nature. 2022 Sep;609(7926):248-249. [http://dx.doi.org/10.1038/d41586-022-02189-7 doi: 10.1038/d41586-022-02189-7. PMID: 35970881.]</ref>.

===PP1C and MRAS===

[[Image:ActiveSiteProto.png|500 px|thumb|'''Figure 1:'''Active site of PP1C on SMP.</div>]]

The interactions between <scene name='95/952718/Mras_and_pp1c/1'>PP1C and MRAS</scene> are respectively mediated by four main <scene name='95/952716/Mras_and_pp1c/3'>polar interactions</scene>: ionic interactions are between D48-R188 and H53-D197, hydrogen bonds are between K36-Q198 and Q35-M190. As the complex forms, the active site for the dephosphorylation of RAF's S259 is oriented such that it remains accessible for RAF <ref name="Hauseman" />. The relative order of complex ordering is still an area of debate. Some experiments indicate that PP1C must bind to SHOC2 before MRAS binds<ref name="Lavoie" /> but others indicated that PP1C and MRAS can bind to SHOC2 at the same time <ref name="Hauseman" />.

=Signaling Pathway=
The SMP signaling pathway begins with the formation of the SMP complex. Initially, a ligand must bind to a receptor tyrosine kinase. This signals SHOC2 to bind to PP1C forming a binary complex that then binds to the membrane bound MRAS. There is some discrepancy about when the different proteins of the SMP complex come together <ref name="Liau">PMID:35768504</ref>. Some experiments indicate that the three proteins bind at the same time but the order is largely unknown. Once the SMP complex forms, its intracellular target is a key inactivation phosphorylation (Ser259) on MAPK Raf1. The serine is directly dephosphorylated by PP1C, while SHOC2 and MRAS increase PP1C’s specificity for S259 on Raf <ref name="Liau" />. When analyzing the surface structure of SHOC1-PP1C-MRAS, there was a hydrophobic groove on the SHOC2 terminus and another hydrophobic groove near the active site on PP1C <ref name="Liau" />. This region is crucial in making PP1C specific to Raf, because the NTpS region that is right next to the phosphoserine on Raf is able to bind to the hydrophobic patch on both SHOC2 and PP1C <ref name="Liau" />.
Mutations affecting SMP complex formation and stability can increase or decrease MAPK signaling, where increased stability of the complex increases MAPK signaling while decreased stability decreases signaling <ref name="Liau" />. There are a set of mutations that can happen on the SMP complex as a whole that can cause [https://www.mayoclinic.org/diseases-conditions/noonan-syndrome/symptoms-causes/syc-20354422. Noonan syndrome], a rasopathy disorder <ref name="Liau" />. On SHOC2, if the following mutations S2G, C260Y, and P510L caused differences in the complex formation with PP1C <ref name="Liau" />. On PP1C, the mutation P50R resulted in stronger ionic interactions with residues on SHOC2, resulting in a more stabilized complex <ref name="Liau" />. On MRAS, mutations such as G23V and T681I, can increase the proportion of MRAS that is GTP bound, which results in increased affinity in the SMP complex overall <ref name="Liau" />. If these mutations happen all at once, or just one or two at a time, it can still significantly alter the functionality of the SMP complex <ref name="Liau" />. This can lead to diseases like Noonan syndrome, which is where there are developmental and growth issues, and can even lead to cancers <ref name="Liau" />.
With this understood knowledge about how the SMP is able to contribute to an increase or decrease of MAPK pathways, there can be further research done to develop treatments for various cancers and rasopathies <ref name="Liau" />. Research can be done to develop inhibitors that can alter the affinity of the SMP complex in order to regulate MAPK signaling pathways <ref name="Liau" />. This can help treat diseases that are caused by unregulated cell proliferation <ref name="Liau" />.

[[Image:Complex.png|800 px|thumb|center|'''Figure 3:'''Signaling cascade is shown with SHOC2 (magenta), PP1C (blue), and MRAS (white). SHOC2 binds to PP1C then to MRAS at the cell membrane. The SMP complex is now oriented near the membrane bound RAF complex (green). ]]

[[Image:Dephosphorylation.jpg|600 px|thumb|center|'''Figure 4:'''PP1C dephosphorylates RAF protein at serine 259 ]]
=Disease Relevance=

==RASopathies==

RASopathy is a broad term used to describe developmental syndromes that stem from [https://www.sciencedirect.com/topics/medicine-and-dentistry/germline-mutation. germline mutations] of proteins along the RAS/MAPK pathway such as SHOC2, PP1C, and MRAS. These mutations can be either gain or loss of function. Rasopathies can also lead to cancer <ref name=”Rauen”>Rauen KA. The RASopathies. Annu Rev Genomics Hum Genet. 2013;14:355-69. [http://dx.doi.org/10.1146/annurev-genom-091212-153523 doi: 10.1146/annurev-genom-091212-153523.]</ref>.

==Cancer==

Because the RAS/MAPK pathway activated by SMP regulates cell proliferation and survival, overactivity can cause tumor formation and cancer. For example, the complex has been found to play a role in the perpetuation of melanoma, leukemia, and lung cancer <ref name="Kwon" />.

=Future Studies=

Further study of the SMP complex includes clarification of the steps of the pathway. Firstly, the order of binding to form the SMP complex is unclear. Furthermore, the interaction between SMP and the Raf complex is largely unknown. Study into this step is especially important to understand how SMP activates downstream signaling.
The current knowledge of SMP can be used to study possible treatments for rasopathies and cancer. For example, the development of inhibitors that target SMP binding could prevent the effects caused by mutations that overactivate SMP. Another possible point of inhibition is the growth factor that signals SHOC2-PP1C and Raf to the cell membrane. <ref name="Liau" /> .

=References=

<references/>

==Student Contributors==
Madeline Gilbert
Inaya Patel
Rushda Hussein

[[Category:Featured in BAMBED]]
[[Category:Topic Page]]

Sandbox Reserved 1790

2023-04-20T22:14:25Z

Rushda Hussein:

<StructureSection load='7pui' size='350' side='right' caption='SHOC2-PP1C-MRAS (PDB entry [[7upi]])' scene='95/952718/Mras/2'>

=SHOC2-PP1C-MRAS=

=Introduction=
<scene name='95/952717/Zoom_out/1'>SHOC2-PP1C-MRAS</scene> (SMP) is a ternary holophosphotase complex formed by the individual proteins: SHOC2, PP1C, and MRAS. The SMP complex is involved in signaling the initiation of [https://www.nature.com/articles/7290105. MAPK pathways], which is responsible for cellular growth and development, cell proliferation, and apoptosis <ref name="Hauseman">PMID:35830882</ref>. Formation of this complex begins with an extracellular signal binding to a membrane embedded receptor [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2536775/. tyrosine kinase receptor(RTK)] <ref name="Hauseman"/>. This causes membrane-bound MRAS to exchange GDP for GTP. Initiating the SMP complex formation at the plasma membrane consists of the SHOC2 and PP1C binding first. When the MRAS exchanges GDP to GTP, it then assembles with the combined SHOC2 and PP1C. Based on MRAS targeting, PP1C catalyzes the [https://www.cell.com/fulltext/S0092-8674(00)81356-2. dephosphorylation] of the N-terminal phosphoserine (NTpS) on the [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3128629/. RAF complex] leading to the amplification of MAPK signaling <ref name="Hauseman"/>. In a normal cell, this would regulate cell proliferation but dysfunction in the ternary complex has shown signs to lead to tumor formation due to unregulated cell growth <ref name="Hauseman"/>.

=Overall Structure=

==SHOC2==
<scene name='95/952717/Shoc2/1'>SHOC2</scene> is a scaffold protein composed of 20 [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3901792/. leucine-rich repeat (LRR)] domains that form a solenoid structure <ref name="Hauseman"/>. The leucine rich region forms a concave hydrophobic core which is necessary for binding with PP1C and MRAS. SHOC2 is the crucial mediator for SHOC2-PP1C-MRAS complex formation <ref name="Hauseman"/>. The leucine rich domain is very important in creating selectivity for the PP1C protein, as that protein is used for so many other complex pathways <ref name="Hauseman"/>. The LRR domains are stabilized by an N-terminal flanking 𝝰-helix and a C-terminal helix-turn-helix <ref name="Kwon">PMID:35831509</ref>. Alongside the conserved leucine residues in the LRR domain, there is a group of conserved asparagine residues that creates a stabilizing [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7184636/. “asparagine ladder”] that is necessary for the LRR fold, giving the SHOC2 its concave structure <ref name="Kwon" />.

SHOC2 is also capable of causing various forms of cancers and rasopathies. A common one is caused by a mutation known as p.S2G <ref name="Rauen">Rauen KA. The RASopathies. Annu Rev Genomics Hum Genet. 2013;14:355-69. [http://dx.doi.org/10.1146/annurev-genom-091212-153523 doi: 10.1146/annurev-genom-091212-153523.]</ref>. This mutation causes the formation of an additional 14-carbon saturated fatty acid chain on the N-terminal glycine of SHOC2 <ref name="Rauen" />. This causes SHOC2 to become attached to the cell membrane, resulting in a prolonged dephosphorylation of RAF by PP1C <ref name="Rauen" />. With this abnormality, there is overexpression of the MAPK pathway and increased cell proliferation genes <ref name="Rauen" />. This can cause the formation of various tumors in the body. Other mutations of the SMP ternary structure as a whole can also lead to the development of Noonan syndrome <ref name="Hauseman"/>.
==PP1C==
<scene name='95/952717/Pp1c/2'>PP1C</scene> is a phosphatase. After forming a ternary complex, the hydrophobic active site on PP1C interacts with Raf and dephosphorylate Ser 259. PP1C's active site is adjacent to a hydrophobic binding pocket that binds to the C-terminal phosphoserine, located on the N-terminus of RAF, the target for dephosphorylation. PP1C can act as a phosphatase in the absence of SHOC2 but PP1C lacks intrinsic substrate selectively. The SMP complex formation endows PP1C with specificity for RAF <ref name="Hauseman" />.

The mechanism that PP1C uses to catalyze the dephosphorylation is mainly through donating a hydrogen atom to a phosphate group on the C-terminal of a phosphoserine on Raf <ref name="Kubicek"/>. This makes the phosphate group a good leaving group and it breaks off <ref name="Kubicek"/>. This catalysis is done by the serine-threonine alpha catalytic site on PP1C <ref name="Kubicek"/>. In this catalytic site, there are two Manganese ions and one calcium ion <ref name="Kubicek"/>. These metal ions are necessary in stablizing this catalytic site and there are a lot of polar negative residues in this region <ref name="Kubicek"/>.

The catalytic site is also capable of causing various rasopathies if there is a mutation present <ref name="Rauen" />. Typically the mutation is centered around the catalytic site not being able to attach to the dephosphorylation site on Ras <ref name="Rauen" />. This causes an underproduction of cell proliferation pathways and leads to Rasopathies. RASopathy is a broad term used to describe developmental syndromes that stem from germline mutations of proteins along the RAS/MAPK pathway. These mutations can be either gain or loss of function. Rasopathies can also lead to cancer <ref name="Rauen" />. The mutation in PP1C can result in damages in growth and development in multiple areas of the body .<ref name="Rauen" />

===SHOC2 and PP1C interactions===

<scene name='95/952717/Shoc2_and_pp1c/1'>PP1C binds to SHOC2</scene> on its leucine rich region(LRR). Between LRR2 and LRR5 and between LRR7 and LRR11. Mutations between SHOC2 and PP1C to the LRR were shown to completely inhibit the binding of PP1C. Five main <scene name='95/952716/Shoc2_and_pp1c/3'>hydrogen and ionic bonds</scene> are made between PP1C and SHOC2 respectively: E56-R182, E167-R203, E54-K180, R187-H178, R188-E155 <ref name="Kwon">PMID:35831509</ref>. Reflecting this ionic character, the binding regions are contained within extensive acidic and basic patches on <scene name='95/952718/Acid_base_pp1c/1'>PP1C</scene> and <scene name='95/952718/Acid_base_shoc2/2'>SHOC2</scene>. The negative acidic patches of PP1C interact with the positive basic patches of SHOC2 and vice versa to form a <scene name='95/952718/Acid_base_shoc2pp1c/1'>binary complex</scene>. These interactions do not result in significant conformational changes to PP1C in comparison to other protein interactions that can be made with PP1C <ref name="Kwon">PMID:35831509</ref>.

==MRAS==
<scene name='95/952717/Mras/2'>MRAS</scene> is a monomeric GTPase. MRAS is membrane-bound due to post-translational lipidation which allows the protein to interact with the inner membrane leaflet. <ref name="Seabra">PMID:9607139</ref> MRAS localizes the SMP complex near RAF and other components of downstream signaling. The region of MRAS not directly bound to the membrane binds SHOC2 and PP1C to orient the complex such that PP1C’s active site faces the serine that will get dephosphorylated on RAF. MRAS also controls SMP complex formation in connection with extracellular signaling based on its dualistic switching between its inactive and active state. In its inactive state, MRAS is bound to GDP. When signaled by growth factors, the GDP is exchanged for GTP when a ligand binds to the RTK <ref name="Hauseman" />. The now <scene name='95/952718/Zoom_in_gtp/2'>GTP bound MRAS</scene> undergoes a conformational change of the <scene name='95/952716/Newras-sw1-2/2'>switch I and II regions</scene>. These regions are the major binding sites with SHOC2. This conformational change activates MRAS allowing it to bind with the SHOC2-PP1C complex. In its inactive GDP-bound state, MRAS is sterically occluded from binding SHOC2. For example, R83 of GDP-bound MRAS directly clashes with SHOC2 as shown in figure 2. In comparison to other RAS proteins such as H/K/NRAS, MRAS has a greater affinity for the SHOC2-PP1C complex<ref name="Kubicek">Kubicek M, Pacher M, Abraham D, Podar K, Eulitz M, Baccarini M. Dephosphorylation of Ser-259 regulates Raf-1 membrane association. J Biol Chem. 2002 Mar 8;277(10):7913-9. [http://10.1074/jbc.M108733200 doi: 10.1074/jbc.M108733200.]</ref>. This indicates that the specific structure of MRAS is necessary for SMP function. While MRAS engages the SHOC2-PP1C complex to bring the complex to the membrane, an additional membrane-bound RAS binds RAF nearby. This binding is also stimulated by ligand binding to the RTK. This indicates that for full RAF activation and continuous signaling of Raf, two separate active RAS proteins are needed. Having two MRASs also help with the co-localization of PP1C to the NTpS region on RAF. To inactivate Raf signaling, MRAS uses its intrinsic GTPase to remove the activating gamma-phosphate on GTP. In the GDP-bound state, switch I and II move to the position shown in green in Figure 2. This inactivates SHOC2 binding due to steric clashing which causes the SMP structure to dissociate.

===SHOC2 and MRAS interactions===
[[Image:Switches.png|500 px|thumb|'''Figure 2:'''Steric clashing of Switch I and II of GDP bound MRAS, in green, with the surface of SHOC2, in magenta. GTP-bound MRAS, in white, shows no steric clashing with SHOC2s surface.</div>]]

MRAS is initially bound to GDP causing it to be in its inactive state. Inactive GDP-MRAS cannot bind to the SHOC2-PP1C complex due to steric clashing of the switch I and II regions of MRAS and its binding zone on SHOC2. Once GDP is exchanged for GTP when signaled by growth factors, MRAS is activated and conformational changes occur within the switch I and switch II regions to allow <scene name='95/952716/Newmras-shco2/10'>MRAS to interact with SHOC2</scene>. These <scene name='95/952716/Scho2-mras-interactions/1'>interactions</scene> between SHOC2 and the switch I and II regions of MRAS include hydrogen bonds, ionic interactions, and π stacking. There is a hydrogen bond at R288-Q71 and ionic interaction at R177-E47. π staking occurs at R104-R83. These interactions occur between SHOC2 and MRAS respectively <ref name="Lavoie">Lavoie H, Therrien M. Structural keys unlock RAS-MAPK cellular signaling pathway. Nature. 2022 Sep;609(7926):248-249. [http://dx.doi.org/10.1038/d41586-022-02189-7 doi: 10.1038/d41586-022-02189-7. PMID: 35970881.]</ref>.

===PP1C and MRAS===

[[Image:ActiveSiteProto.png|500 px|thumb|'''Figure 1:'''Active site of PP1C on SMP.</div>]]

The interactions between <scene name='95/952718/Mras_and_pp1c/1'>PP1C and MRAS</scene> are respectively mediated by four main <scene name='95/952716/Mras_and_pp1c/3'>polar interactions</scene>: ionic interactions are between D48-R188 and H53-D197, hydrogen bonds are between K36-Q198 and Q35-M190. As the complex forms, the active site for the dephosphorylation of RAF's S259 is oriented such that it remains accessible for RAF <ref name="Hauseman" />. The relative order of complex ordering is still an area of debate. Some experiments indicate that PP1C must bind to SHOC2 before MRAS binds<ref name="Lavoie" /> but others indicated that PP1C and MRAS can bind to SHOC2 at the same time <ref name="Hauseman" />.

=Signaling Pathway=
The SMP signaling pathway begins with the formation of the SMP complex. Initially, a ligand must bind to a receptor tyrosine kinase. This signals SHOC2 to bind to PP1C forming a binary complex that then binds to the membrane bound MRAS. There is some discrepancy about when the different proteins of the SMP complex come together <ref name="Liau">PMID:35768504</ref>. Some experiments indicate that the three proteins bind at the same time but the order is largely unknown. Once the SMP complex forms, its intracellular target is a key inactivation phosphorylation (Ser259) on MAPK Raf1. The serine is directly dephosphorylated by PP1C, while SHOC2 and MRAS increase PP1C’s specificity for S259 on Raf <ref name="Liau" />. When analyzing the surface structure of SHOC1-PP1C-MRAS, there was a hydrophobic groove on the SHOC2 terminus and another hydrophobic groove near the active site on PP1C <ref name="Liau" />. This region is crucial in making PP1C specific to Raf, because the NTpS region that is right next to the phosphoserine on Raf is able to bind to the hydrophobic patch on both SHOC2 and PP1C <ref name="Liau" />.
Mutations affecting SMP complex formation and stability can increase or decrease MAPK signaling, where increased stability of the complex increases MAPK signaling while decreased stability decreases signaling <ref name="Liau" />. There are a set of mutations that can happen on the SMP complex as a whole that can cause [https://www.mayoclinic.org/diseases-conditions/noonan-syndrome/symptoms-causes/syc-20354422. Noonan syndrome], a rasopathy disorder <ref name="Liau" />. On SHOC2, if the following mutations S2G, C260Y, and P510L caused differences in the complex formation with PP1C <ref name="Liau" />. On PP1C, the mutation P50R resulted in stronger ionic interactions with residues on SHOC2, resulting in a more stabilized complex <ref name="Liau" />. On MRAS, mutations such as G23V and T681I, can increase the proportion of MRAS that is GTP bound, which results in increased affinity in the SMP complex overall <ref name="Liau" />. If these mutations happen all at once, or just one or two at a time, it can still significantly alter the functionality of the SMP complex <ref name="Liau" />. This can lead to diseases like Noonan syndrome, which is where there are developmental and growth issues, and can even lead to cancers <ref name="Liau" />.

[[Image:Signal_cascade_small.jpg|800 px|thumb|center|'''Figure 3:'''Signaling cascade is shown with SHOC2 in pink, PP1C in blue, and MRAS in white. ]]

[[Image:Dephosphorylation.jpg|600 px|thumb|center|'''Figure 4:'''PP1C dephosphorylates RAF protein at serine 259 ]]
=Disease Relevance=

==RASopathies==

RASopathy is a broad term used to describe developmental syndromes that stem from [https://www.sciencedirect.com/topics/medicine-and-dentistry/germline-mutation. germline mutations] of proteins along the RAS/MAPK pathway such as SHOC2, PP1C, and MRAS. These mutations can be either gain or loss of function. Rasopathies can also lead to cancer <ref name=”Rauen”>Rauen KA. The RASopathies. Annu Rev Genomics Hum Genet. 2013;14:355-69. [http://dx.doi.org/10.1146/annurev-genom-091212-153523 doi: 10.1146/annurev-genom-091212-153523.]</ref>.

==Cancer==

Because the RAS/MAPK pathway activated by SMP regulates cell proliferation and survival, overactivity can cause tumor formation and cancer. For example, the complex has been found to play a role in the perpetuation of melanoma, leukemia, and lung cancer <ref name="Kwon" />.

=Future Studies=

Further study of the SMP complex includes clarification of the steps of the pathway. Firstly, the order of binding to form the SMP complex is unclear. Furthermore, the interaction between SMP and the Raf complex is largely unknown. Study into this step is especially important to understand how SMP activates downstream signaling.
The current knowledge of SMP can be used to study possible treatments for rasopathies and cancer. For example, the development of inhibitors that target SMP binding could prevent the effects caused by mutations that overactivate SMP. Another possible point of inhibition is the growth factor that signals SHOC2-PP1C and Raf to the cell membrane. <ref name="Liau" /> .

=References=

<references/>

==Student Contributors==
Madeline Gilbert
Inaya Patel
Rushda Hussein

[[Category:Featured in BAMBED]]
[[Category:Topic Page]]

Sandbox Reserved 1790

2023-04-20T19:27:08Z

Rushda Hussein:

<StructureSection load='7pui' size='350' side='right' caption='SHOC2-PP1C-MRAS (PDB entry [[7upi]])' scene='95/952718/Mras/2'>

=SHOC2-PP1C-MRAS=

=Introduction=
<scene name='95/952717/Zoom_out/1'>SHOC2-PP1C-MRAS</scene> (SMP) is a ternary holophosphotase complex formed by the individual proteins: SHOC2, PP1C, and MRAS. The SMP complex is involved in signaling the initiation of [https://www.nature.com/articles/7290105. MAPK pathways], which is responsible for cellular growth and development, cell proliferation, and apoptosis <ref name="Hauseman">PMID:35830882</ref>. Formation of this complex begins with an extracellular signal binding to a membrane embedded receptor [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2536775/. tyrosine kinase receptor(RTK)] <ref name="Hauseman"/>. This causes membrane-bound MRAS to exchange GDP for GTP. Initiating the SMP complex formation at the plasma membrane consists of the SHOC2 and PP1C binding first. When the MRAS exchanges GDP to GTP, it then assembles with the combined SHOC2 and PP1C. Based on MRAS targeting, PP1C catalyzes the [https://www.cell.com/fulltext/S0092-8674(00)81356-2. dephosphorylation] of the N-terminal phosphoserine (NTpS) on the [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3128629/. RAF complex] leading to the amplification of MAPK signaling <ref name="Hauseman"/>. In a normal cell, this would regulate cell proliferation but dysfunction in the ternary complex has shown signs to lead to tumor formation due to unregulated cell growth <ref name="Hauseman"/>.

=Overall Structure=

==SHOC2==
<scene name='95/952717/Shoc2/1'>SHOC2</scene> is a scaffold protein composed of 20 [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3901792/. leucine-rich repeat (LRR)] domains that form a solenoid structure <ref name="Hauseman"/>. The leucine rich region forms a concave hydrophobic core which is necessary for binding with PP1C and MRAS. SHOC2 is the crucial mediator for SHOC2-PP1C-MRAS complex formation <ref name="Hauseman"/>. The leucine rich domain is very important in creating selectivity for the PP1C protein, as that protein is used for so many other complex pathways <ref name="Hauseman"/>. The LRR domains are stabilized by an N-terminal flanking 𝝰-helix and a C-terminal helix-turn-helix <ref name="Kwon">PMID:35831509</ref>. Alongside the conserved leucine residues in the LRR domain, there is a group of conserved asparagine residues that creates a stabilizing [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7184636/. “asparagine ladder”] that is necessary for the LRR fold, giving the SHOC2 its concave structure <ref name="Kwon" />.

SHOC2 is also capable of causing various forms of cancers and rasopathies. A common one is caused by a mutation known as p.S2G <ref name="Rauen">Rauen KA. The RASopathies. Annu Rev Genomics Hum Genet. 2013;14:355-69. [http://dx.doi.org/10.1146/annurev-genom-091212-153523 doi: 10.1146/annurev-genom-091212-153523.]</ref>. This mutation causes the formation of an additional 14-carbon saturated fatty acid chain on the N-terminal glycine of SHOC2 <ref name="Rauen" />. This causes SHOC2 to become attached to the cell membrane, resulting in a prolonged dephosphorylation of RAF by PP1C <ref name="Rauen" />. With this abnormality, there is overexpression of the MAPK pathway and increased cell proliferation genes <ref name="Rauen" />. This can cause the formation of various tumors in the body. Other mutations of the SMP ternary structure as a whole can also lead to the development of Noonan syndrome <ref name="Hauseman"/>.
==PP1C==
<scene name='95/952717/Pp1c/2'>PP1C</scene> is a phosphatase. After forming a ternary complex, the hydrophobic active site on PP1C interacts with Raf and dephosphorylate Ser 259. PP1C's active site is adjacent to a hydrophobic binding pocket that binds to the C-terminal phosphoserine, located on the N-terminus of RAF, the target for dephosphorylation. PP1C can act as a phosphatase in the absence of SHOC2 but PP1C lacks intrinsic substrate selectively. The SMP complex formation endows PP1C with specificity for RAF <ref name="Hauseman" />.

The mechanism that PP1C uses to catalyze the dephosphorylation is mainly through donating a hydrogen atom to a phosphate group on the C-terminal of a phosphoserine on Raf <ref name="Kubicek"/>. This makes the phosphate group a good leaving group and it breaks off <ref name="Kubicek"/>. This catalysis is done by the serine-threonine alpha catalytic site on PP1C <ref name="Kubicek"/>. In this catalytic site, there are two Manganese ions and one calcium ion <ref name="Kubicek"/>. These metal ions are necessary in stablizing this catalytic site and there are a lot of polar negative residues in this region <ref name="Kubicek"/>.

The catalytic site is also capable of causing various rasopathies if there is a mutation present <ref name="Rauen" />. Typically the mutation is centered around the catalytic site not being able to attach to the dephosphorylation site on Ras <ref name="Rauen" />. This causes an underproduction of cell proliferation pathways and leads to Rasopathies. RASopathy is a broad term used to describe developmental syndromes that stem from germline mutations of proteins along the RAS/MAPK pathway. These mutations can be either gain or loss of function. Rasopathies can also lead to cancer <ref name="Rauen" />. The mutation in PP1C can result in damages in growth and development in multiple areas of the body .<ref name="Rauen" />

===SHOC2 and PP1C interactions===

<scene name='95/952717/Shoc2_and_pp1c/1'>PP1C binds to SHOC2</scene> on its leucine rich region(LRR). Between LRR2 and LRR5 and between LRR7 and LRR11. Mutations between SHOC2 and PP1C to the LRR were shown to completely inhibit the binding of PP1C. Five main <scene name='95/952716/Shoc2_and_pp1c/3'>hydrogen and ionic bonds</scene> are made between PP1C and SHOC2 respectively: E56-R182, E167-R203, E54-K180, R187-H178, R188-E155 <ref name="Kwon">PMID:35831509</ref>. Reflecting this ionic character, the binding regions are contained within extensive acidic and basic patches on <scene name='95/952718/Acid_base_pp1c/1'>PP1C</scene> and <scene name='95/952718/Acid_base_shoc2/2'>SHOC2</scene>. The negative acidic patches of PP1C interact with the positive basic patches of SHOC2 and vice versa to form a <scene name='95/952718/Acid_base_shoc2pp1c/1'>binary complex</scene>. These interactions do not result in significant conformational changes to PP1C in comparison to other protein interactions that can be made with PP1C <ref name="Kwon">PMID:35831509</ref>.

==MRAS==
<scene name='95/952717/Mras/2'>MRAS</scene> is a monomeric GTPase. MRAS is membrane-bound due to post-translational lipidation which allows the protein to interact with the inner membrane leaflet. <ref name="Seabra">PMID:9607139</ref> MRAS localizes the SMP complex near RAF and other components of downstream signaling. The region of MRAS not directly bound to the membrane binds SHOC2 and PP1C to orient the complex such that PP1C’s active site faces the serine that will get dephosphorylated on RAF. MRAS also controls SMP complex formation in connection with extracellular signaling based on its dualistic switching between its inactive and active state. In its inactive state, MRAS is bound to GDP. When signaled by growth factors, the GDP is exchanged for GTP when a ligand binds to the RTK <ref name="Hauseman" />. The now <scene name='95/952718/Zoom_in_gtp/1'>GTP bound MRAS</scene> undergoes a conformational change of the <scene name='95/952716/Ras-switch-zoomed/1'>switch I and switch II regions</scene>. These regions are the major binding sites with SHOC2. This conformational change activates MRAS allowing it to bind with the SHOC2-PP1C complex. In its inactive GDP-bound state, MRAS is sterically occluded from binding SHOC2. For example, R83 of GDP-bound MRAS directly clashes with SHOC2 as shown in figure 2. In comparison to other RAS proteins such as H/K/NRAS, MRAS has a greater affinity for the SHOC2-PP1C complex<ref name="Kubicek">Kubicek M, Pacher M, Abraham D, Podar K, Eulitz M, Baccarini M. Dephosphorylation of Ser-259 regulates Raf-1 membrane association. J Biol Chem. 2002 Mar 8;277(10):7913-9. [http://10.1074/jbc.M108733200 doi: 10.1074/jbc.M108733200.]</ref>. This indicates that the specific structure of MRAS is necessary for SMP function. While MRAS engages the SHOC2-PP1C complex to bring the complex to the membrane, an additional membrane-bound RAS binds RAF nearby. This binding is also stimulated by ligand binding to the RTK. This indicates that for full RAF activation and continuous signaling of Raf, two separate active RAS proteins are needed. Having two MRASs also help with the co-localization of PP1C to the NTpS region on RAF. To inactivate Raf signaling, MRAS uses its intrinsic GTPase to remove the activating gamma-phosphate on GTP. In the GDP-bound state, switch I and II move to the position shown in green in Figure 2. This inactivates SHOC2 binding due to steric clashing which causes the SMP structure to dissociate.

===SHOC2 and MRAS interactions===
[[Image:Switches.png|500 px|thumb|'''Figure 2:'''Steric clashing of Switch I and II of GDP bound MRAS, in green, with the surface of SHOC2, in magenta. GTP-bound MRAS, in white, shows no steric clashing with SHOC2s surface.</div>]]

MRAS is initially bound to GDP causing it to be in its inactive state. Inactive GDP-MRAS cannot bind to the SHOC2-PP1C complex due to steric clashing of the switch I and II regions of MRAS and its binding zone on SHOC2. Once GDP is exchanged for GTP when signaled by growth factors, MRAS is activated and conformational changes occur within the switch I and switch II regions to allow <scene name='95/952716/Scho2-mras-interactions/2'>MRAS to interact with SHOC2</scene>. These <scene name='95/952716/Scho2-mras-interactions/1'>interactions</scene> between SHOC2 and the switch I and II regions of MRAS include hydrogen bonds, ionic interactions, and π stacking. There is a hydrogen bond at R288-Q71 and ionic interaction at R177-E47. π staking occurs at R104-R83. These interactions occur between SHOC2 and MRAS respectively <ref name="Lavoie">Lavoie H, Therrien M. Structural keys unlock RAS-MAPK cellular signaling pathway. Nature. 2022 Sep;609(7926):248-249. [http://dx.doi.org/10.1038/d41586-022-02189-7 doi: 10.1038/d41586-022-02189-7. PMID: 35970881.]</ref>.

===PP1C and MRAS===

[[Image:ActiveSiteProto.png|500 px|thumb|'''Figure 1:'''Active site of PP1C on SMP.</div>]]

The interactions between <scene name='95/952718/Mras_and_pp1c/1'>PP1C and MRAS</scene> are respectively mediated by four main <scene name='95/952716/Mras_and_pp1c/3'>polar interactions</scene>: ionic interactions are between D48-R188 and H53-D197, hydrogen bonds are between K36-Q198 and Q35-M190. As the complex forms, the active site for the dephosphorylation of RAF's S259 is oriented such that it remains accessible for RAF <ref name="Hauseman" />. The relative order of complex ordering is still an area of debate. Some experiments indicate that PP1C must bind to SHOC2 before MRAS binds<ref name="Lavoie" /> but others indicated that PP1C and MRAS can bind to SHOC2 at the same time <ref name="Hauseman" />.

=Signaling Pathway=
The SMP signaling pathway begins with the formation of the SMP complex. Initially, a ligand must bind to a receptor tyrosine kinase. This signals SHOC2 to bind to PP1C forming a binary complex that then binds to the membrane bound MRAS. Some literature indicates that the three proteins bind at the same time but the order is largely unknown. Figure 2 shows the proteins binding one at a time. Once the SMP complex forms, its target is the NTpS also known as S259. The serine is directly dephosphorylated by PP1C by SHOC2 and MRAS increase its specificity for S259.
Mutations affecting SMP complex formation and stability have been shown to increase or decrease MAPK signaling. Increased stability of the complex increases MAPK signaling while decreased stability decreases signaling<ref name="Liau">PMID:35768504</ref>.

[[Image:Signal_cascade_small.jpg|800 px|thumb|center|'''Figure 3:'''Signaling cascade is shown with SHOC2 in pink, PP1C in blue, and MRAS in white. ]]

[[Image:Dephosphorylation.jpg|600 px|thumb|center|'''Figure 4:'''PP1C dephosphorylates RAF protein at serine 259 ]]
=Disease Relevance=

==RASopathies==

RASopathy is a broad term used to describe developmental syndromes that stem from [https://www.sciencedirect.com/topics/medicine-and-dentistry/germline-mutation. germline mutations] of proteins along the RAS/MAPK pathway such as SHOC2, PP1C, and MRAS. These mutations can be either gain or loss of function. Rasopathies can also lead to cancer <ref name=”Rauen”>Rauen KA. The RASopathies. Annu Rev Genomics Hum Genet. 2013;14:355-69. [http://dx.doi.org/10.1146/annurev-genom-091212-153523 doi: 10.1146/annurev-genom-091212-153523.]</ref>.

==Cancer==

Because the RAS/MAPK pathway activated by SMP regulates cell proliferation and survival, overactivity can cause tumor formation and cancer. For example, the complex has been found to play a role in the perpetuation of melanoma, leukemia, and lung cancer <ref name="Kwon" />.

=Future Studies=

Further study of the SMP complex includes clarification of the steps of the pathway. Firstly, the order of binding to form the SMP complex is unclear. Furthermore, the interaction between SMP and the Raf complex is largely unknown. Study into this step is especially important to understand how SMP activates downstream signaling.
The current knowledge of SMP can be used to study possible treatments for rasopathies and cancer. For example, the development of inhibitors that target SMP binding could prevent the effects caused by mutations that overactivate SMP. Another possible point of inhibition is the growth factor that signals SHOC2-PP1C and Raf to the cell membrane. <ref name="Liau" /> .

=References=

<references/>

==Student Contributors==
Madeline Gilbert
Inaya Patel
Rushda Hussein

[[Category:Featured in BAMBED]]
[[Category:Topic Page]]

Sandbox Reserved 1789

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{{BAMBED
|DATE=June 14, 2016
|OLDID=2607465
|BAMBEDDOI=10.1002/bmb.21026
}}

==SHOC2-PP1C-MRAS==
<StructureSection load='7UPI' size='340' side='right' caption='SHOC2-MRAS-PP1C'>

== Introduction ==

<scene name='95/952717/Zoom_out/1'>SHOC2-PP1C-MRAS</scene> (SMP) is a ternary holophosphotase complex formed by the individual proteins: SHOC2, PP1C, and MRAS. The SMP complex is involved in signaling the initiation of [https://www.nature.com/articles/7290105. MAPK pathways], which is responsible for cellular growth and development, cell proliferation, and apoptosis <ref name="Hauseman">PMID:35830882</ref>. Formation of this complex begins with an extracellular signal binding to a membrane embedded receptor [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2536775/. tyrosine kinase receptor(RTK)] <ref name="Hauseman"/>. This causes membrane-bound MRAS to exchange GDP for GTP. Initiating the SMP complex formation at the plasma membrane consists of the SHOC2 and PP1C binding first. When the MRAS exchanges GDP to GTP, it then assembles with the combined SHOC2 and PP1C. Based on MRAS targeting, PP1C catalyzes the [https://www.cell.com/fulltext/S0092-8674(00)81356-2. dephosphorylation] of the N-terminal phosphoserine (NTpS) on the [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3128629/. RAF complex] leading to the amplification of MAPK signaling <ref name="Hauseman"/>. In a normal cell, this would regulate cell proliferation but dysfunction in the ternary complex has shown signs to lead to tumor formation due to unregulated cell growth <ref name="Hauseman"/>.

[[Image:Mechanism.png|200px|center|thumb|Figure 1: Mechanism for Shoc2-MRAS-PP1C]]
[[Image:Phosphorylation.png|200px|center|thumb|Figure 2: PP1C phosphorylates Serine 259.]]

== Overall Structure ==
=== SHOC2 ===

<scene name='95/952717/Shoc2/1'>SHOC2</scene> is a scaffold protein composed of 20 [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3901792/. leucine-rich repeat (LRR)] domains that form a solenoid structure <ref name="Hauseman"/>. The leucine rich region forms a concave hydrophobic core which is necessary for binding with PP1C and MRAS. SHOC2 is the crucial mediator for SHOC2-PP1C-MRAS complex formation <ref name="Hauseman"/>. The leucine rich domain is very important in creating selectivity for the PP1C protein, as that protein is used for so many other complex pathways <ref name="Hauseman"/>. The LRR domains are stabilized by an N-terminal flanking 𝝰-helix and a C-terminal helix-turn-helix <ref name="Kwon">PMID:35831509</ref>. Alongside the conserved leucine residues in the LRR domain, there is a group of conserved asparagine residues that creates a stabilizing [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7184636/. “asparagine ladder”] that is necessary for the LRR fold, giving the SHOC2 its concave structure <ref name="Kwon" />.

SHOC2 is also capable of causing various forms of cancers and rasopathies. A common one is caused by a mutation known as p.S2G <ref name="Rauen">Rauen KA. The RASopathies. Annu Rev Genomics Hum Genet. 2013;14:355-69. [http://dx.doi.org/10.1146/annurev-genom-091212-153523 doi: 10.1146/annurev-genom-091212-153523.]</ref>. This mutation causes the formation of an additional 14-carbon saturated fatty acid chain on the N-terminal glycine of SHOC2 <ref name="Rauen" />. This causes SHOC2 to become attached to the cell membrane, resulting in a prolonged dephosphorylation of RAF by PP1C <ref name="Rauen" />. With this abnormality, there is overexpression of the MAPK pathway and increased cell proliferation genes <ref name="Rauen" />. This can cause the formation of various tumors in the body. Other mutations of the SMP ternary structure as a whole can also lead to the development of Noonan syndrome <ref name="Hauseman"/>.

=== PP1C ===
<scene name='95/952717/Pp1c/2'>PP1C</scene> is a phosphatase. After forming a ternary complex, the hydrophobic active site on PP1C interacts with Raf and dephosphorylate Ser 259. PP1C's active site is adjacent to a hydrophobic binding pocket that binds to the C-terminal phosphoserine, located on the N-terminus of RAF, the target for dephosphorylation. PP1C can act as a phosphatase in the absence of SHOC2 but PP1C lacks intrinsic substrate selectively. The SMP complex formation endows PP1C with specificity for RAF <ref name="Hauseman" />.

The mechanism that PP1C uses to catalyze the dephosphorylation is mainly through donating a hydrogen atom to a phosphate group on the C-terminal of a phosphoserine on Raf <ref name="Kubicek"/>. This makes the phosphate group a good leaving group and it breaks off <ref name="Kubicek"/>. This catalysis is done by the serine-threonine alpha catalytic site on PP1C <ref name="Kubicek"/>. In this catalytic site, there are two Manganese ions and one calcium ion <ref name="Kubicek"/>. These metal ions are necessary in stablizing this catalytic site and there are a lot of polar negative residues in this region <ref name="Kubicek"/>.

The catalytic site is also capable of causing various rasopathies if there is a mutation present <ref name="Rauen" />. Typically the mutation is centered around the catalytic site not being able to attach to the dephosphorylation site on Ras <ref name="Rauen" />. This causes an underproduction of cell proliferation pathways and leads to Rasopathies. RASopathy is a broad term used to describe developmental syndromes that stem from germline mutations of proteins along the RAS/MAPK pathway. These mutations can be either gain or loss of function. Rasopathies can also lead to cancer <ref name="Rauen" />. The mutation in PP1C can result in damages in growth and development in multiple areas of the body .<ref name="Rauen" />

=== MRAS ===

<scene name='95/952717/Mras/2'>MRAS</scene> is a monomeric GTPase. MRAS is membrane-bound due to post-translational lipidation which allows the protein to interact with the inner membrane leaflet. <ref name="Seabra">PMID:9607139</ref> MRAS localizes the SMP complex near RAF and other components of downstream signaling. The region of MRAS not directly bound to the membrane binds SHOC2 and PP1C to orient the complex such that PP1C’s active site faces the serine that will get dephosphorylated on RAF. MRAS also controls SMP complex formation in connection with extracellular signaling based on its dualistic switching between its inactive and active state. In its inactive state, MRAS is bound to GDP. When signaled by growth factors, the GDP is exchanged for GTP when a ligand binds to the RTK <ref name="Hauseman" />. The now <scene name='95/952718/Zoom_in_gtp/1'>GTP bound MRAS</scene> undergoes a conformational change of the <scene name='95/952716/Ras-switch-zoomed/1'>switch I and switch II regions</scene>. These regions are the major binding sites with SHOC2. This conformational change activates MRAS allowing it to bind with the SHOC2-PP1C complex. In its inactive GDP-bound state, MRAS is sterically occluded from binding SHOC2. For example, R83 of GDP-bound MRAS directly clashes with SHOC2 as shown in figure 2. In comparison to other RAS proteins such as H/K/NRAS, MRAS has a greater affinity for the SHOC2-PP1C complex<ref name="Kubicek">Kubicek M, Pacher M, Abraham D, Podar K, Eulitz M, Baccarini M. Dephosphorylation of Ser-259 regulates Raf-1 membrane association. J Biol Chem. 2002 Mar 8;277(10):7913-9. [http://10.1074/jbc.M108733200 doi: 10.1074/jbc.M108733200.]</ref>. This indicates that the specific structure of MRAS is necessary for SMP function. While MRAS engages the SHOC2-PP1C complex to bring the complex to the membrane, an additional membrane-bound RAS binds RAF nearby. This binding is also stimulated by ligand binding to the RTK. This indicates that for full RAF activation and continuous signaling of Raf, two separate active RAS proteins are needed. Having two MRASs also help with the co-localization of PP1C to the NTpS region on RAF. To inactivate Raf signaling, MRAS uses its intrinsic GTPase to remove the activating gamma-phosphate on GTP. In the GDP-bound state, switch I and II move to the position shown in green in Figure 2. This inactivates SHOC2 binding due to steric clashing which causes the SMP structure to dissociate.
<scene name='95/952717/Mras/2'>MRAS</scene>
<scene name='95/952716/Gtp/1'>GTP-MRAS(full-image)</scene>
<scene name='95/952716/Gtp/1'>GTP-MRAS(zoomed-in)</scene>
<scene name='95/952716/Ras-swtich/2'>Switch I-II (full-image)</scene>
<scene name='95/952716/Ras-switch-zoomed/1'>Switch I-II (zoomed-in)</scene>

=== Key Ligand Interactions ===
[[Image:Amphbindingfinal.png|275 px|right|thumb|'''Figure 3''': Electrostatic illustration of the amphipathic binding pocket of the LPA1 receptor. This binding pocket was revealed by cutting away the exterior or the protein. This binding pocket, located in the interior of the protein, has both polar and nonpolar regions. The blue and red coloration highlight the positively and negatively charged regions, respectively, and the white color shows the nonpolar region of the binding pocket.]]

=== SHOC2 and PP1C ===
<scene name='95/952717/Shoc2_and_pp1c/1'>Shoc2-PP1C</scene>
<scene name='95/952717/Shoc2_and_pp1c/2'>SHOC2-PP1C Binding Pocket</scene>
=== SHOC2 and MRAS ===
<scene name='95/952716/Scho2-mras-interactions/2'>SHOC2-MRAS(full-image)</scene>
<scene name='95/952716/Scho2-mras-interactions/1'>SHOC2-MRAS (residues)</scene>
<scene name='95/952716/Scho2-mras-interactions/3'>SHOC2-MRAS (surface)</scene>
=== PP1C and MRAS ===
<scene name='95/952717/Mras_and_pp1c/1'>PP1C (blue) and MRAS (white)</scene>

<scene name='95/952717/Mras_and_pp1c/4'>PP1C and MRAS residue interactions</scene>

== Signaling Pathway ==

<scene name='95/952717/Pp1c_hydrophobic_patch/1'>PP1C Hydrophobic Patch and Active Site</scene>

== Disease Relevance ==

=== Cancer ===

=== RASopathies===

== Future Studies ==

==3D structures of lysophosphatidic acid receptor==

[[4z34]], [[4z35]], [[4z36]] - hLPA1 + antagonist - human 
[[2lq4]] – hLPA1 second extracellular loop – NMR 
[[4p0c]] – hLPA2/NHERF2 
[[5xsz]] – LPA6A (mutant) – zebra fish 

== References ==
<references/>
==Proteopedia Resources==
[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid_binding Category:Lysophosphatidic acid binding]

[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid Category:Lysophosphatidic acid]

[http://proteopedia.org/wiki/index.php/User:R._Jeremy_Johnson/CH462:Biochemistry_II_Butler_University Butler University Proteopedia Pages]

See also:
*[[Receptor]]
*[[Transmembrane (cell surface) receptors]]
*[[G protein-coupled receptors]]
</StructureSection>
==Student Contributors==
Madeline Gilbert
Inaya Patel
Rushda Hussein

[[Category:Featured in BAMBED]]
[[Category:Topic Page]]

Sandbox Reserved 1789

2023-04-19T19:57:23Z

Rushda Hussein:

{{BAMBED
|DATE=June 14, 2016
|OLDID=2607465
|BAMBEDDOI=10.1002/bmb.21026
}}

==SHOC2-PP1C-MRAS==
<StructureSection load='7UPI' size='340' side='right' caption='SHOC2-MRAS-PP1C'>

== Introduction ==

<scene name='95/952717/Zoom_out/1'>SHOC2-PP1C-MRAS</scene> (SMP) is a ternary holophosphotase complex formed by the individual proteins: SHOC2, PP1C, and MRAS. The SMP complex is involved in signaling the initiation of [https://www.nature.com/articles/7290105. MAPK pathways], which is responsible for cellular growth and development, cell proliferation, and apoptosis <ref name="Hauseman">PMID:35830882</ref>. Formation of this complex begins with an extracellular signal binding to a membrane embedded receptor [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2536775/. tyrosine kinase receptor(RTK)] <ref name="Hauseman"/>. This causes membrane-bound MRAS to exchange GDP for GTP. Initiating the SMP complex formation at the plasma membrane consists of the SHOC2 and PP1C binding first. When the MRAS exchanges GDP to GTP, it then assembles with the combined SHOC2 and PP1C. Based on MRAS targeting, PP1C catalyzes the [https://www.cell.com/fulltext/S0092-8674(00)81356-2. dephosphorylation] of the N-terminal phosphoserine (NTpS) on the [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3128629/. RAF complex] leading to the amplification of MAPK signaling <ref name="Hauseman"/>. In a normal cell, this would regulate cell proliferation but dysfunction in the ternary complex has shown signs to lead to tumor formation due to unregulated cell growth <ref name="Hauseman"/>.

[[Image:Mechanism.png|200px|center|thumb|Figure 1: Mechanism for Shoc2-MRAS-PP1C]]
[[Image:Phosphorylation.png|200px|center|thumb|Figure 2: PP1C phosphorylates Serine 259.]]

== Overall Structure ==
=== SHOC2 ===

<scene name='95/952717/Shoc2/1'>SHOC2</scene> is a scaffold protein composed of 20 [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3901792/. leucine-rich repeat (LRR)] domains that form a solenoid structure <ref name="Hauseman"/>. The leucine rich region forms a concave hydrophobic core which is necessary for binding with PP1C and MRAS. SHOC2 is the crucial mediator for SHOC2-PP1C-MRAS complex formation <ref name="Hauseman"/>. The leucine rich domain is very important in creating selectivity for the PP1C protein, as that protein is used for so many other complex pathways <ref name="Hauseman"/>. The LRR domains are stabilized by an N-terminal flanking 𝝰-helix and a C-terminal helix-turn-helix <ref name="Kwon">PMID:35831509</ref>. Alongside the conserved leucine residues in the LRR domain, there is a group of conserved asparagine residues that creates a stabilizing [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7184636/. “asparagine ladder”] that is necessary for the LRR fold, giving the SHOC2 its concave structure <ref name="Kwon" />.

SHOC2 is also capable of causing various forms of Rasopathies. A common one is caused by a mutation known as p.S2G <ref name="Rauen">Rauen KA. The RASopathies. Annu Rev Genomics Hum Genet. 2013;14:355-69. [http://dx.doi.org/10.1146/annurev-genom-091212-153523 doi: 10.1146/annurev-genom-091212-153523.]</ref>. This mutation causes the formation of an additional 14-carbon saturated fatty acid chain on the N-terminal glycine of SHOC2 <ref name="Rauen" />. This causes SHOC2 to become attached to the cell membrane, resulting in a prolonged dephosphorylation of RAF by PP1C <ref name="Rauen" />. With this abnormality, there is overexpression of the MAPK pathway and increased cell proliferation genes <ref name="Rauen" />

=== PP1C ===
<scene name='95/952717/Pp1c/2'>PP1C</scene> is a phosphatase. After forming a ternary complex, the hydrophobic active site on PP1C interacts with Raf and dephosphorylate Ser 259. PP1C's active site is adjacent to a hydrophobic binding pocket that binds to the C-terminal phosphoserine, located on the N-terminus of RAF, the target for dephosphorylation. PP1C can act as a phosphatase in the absence of SHOC2 but PP1C lacks intrinsic substrate selectively. The SMP complex formation endows PP1C with specificity for RAF <ref name="Hauseman" />.

The mechanism that PP1C uses to catalyze the dephosphorylation is mainly through donating a hydrogen atom to a phosphate group on the C-terminal of a [https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/phosphoserine. phosphoserine] on Raf <ref name="Kubicek"/>. This makes the phosphate group a good leaving group and it breaks off <ref name="Kubicek"/>. This catalysis is done by the serine-threonine alpha catalytic site on PP1C <ref name="Kubicek"/>. In this catalytic site, there are two Manganese ions and one calcium ion <ref name="Kubicek"/>. These metal ions are necessary in stablizing this catalytic site and there are a lot of polar negative residues in this region <ref name="Kubicek"/>

=== MRAS ===

<scene name='95/952717/Mras/2'>MRAS</scene> is a monomeric GTPase. MRAS is membrane-bound due to post-translational lipidation which allows the protein to interact with the inner membrane leaflet. <ref name="Seabra">PMID:9607139</ref> MRAS localizes the SMP complex near RAF and other components of downstream signaling. The region of MRAS not directly bound to the membrane binds SHOC2 and PP1C to orient the complex such that PP1C’s active site faces the serine that will get dephosphorylated on RAF. MRAS also controls SMP complex formation in connection with extracellular signaling based on its dualistic switching between its inactive and active state. In its inactive state, MRAS is bound to GDP. When signaled by growth factors, the GDP is exchanged for GTP when a ligand binds to the RTK <ref name="Hauseman" />. The now <scene name='95/952718/Zoom_in_gtp/1'>GTP bound MRAS</scene> undergoes a conformational change of the <scene name='95/952716/Ras-switch-zoomed/1'>switch I and switch II regions</scene>. These regions are the major binding sites with SHOC2. This conformational change activates MRAS allowing it to bind with the SHOC2-PP1C complex. In its inactive GDP-bound state, MRAS is sterically occluded from binding SHOC2. For example, R83 of GDP-bound MRAS directly clashes with SHOC2 as shown in figure 2. In comparison to other RAS proteins such as H/K/NRAS, MRAS has a greater affinity for the SHOC2-PP1C complex<ref name="Kubicek">Kubicek M, Pacher M, Abraham D, Podar K, Eulitz M, Baccarini M. Dephosphorylation of Ser-259 regulates Raf-1 membrane association. J Biol Chem. 2002 Mar 8;277(10):7913-9. [http://10.1074/jbc.M108733200 doi: 10.1074/jbc.M108733200.]</ref>. This indicates that the specific structure of MRAS is necessary for SMP function. While MRAS engages the SHOC2-PP1C complex to bring the complex to the membrane, an additional membrane-bound RAS binds RAF nearby. This binding is also stimulated by ligand binding to the RTK. This indicates that for full RAF activation and continuous signaling of Raf, two separate active RAS proteins are needed. Having two MRASs also help with the co-localization of PP1C to the NTpS region on RAF. To inactivate Raf signaling, MRAS uses its intrinsic GTPase to remove the activating gamma-phosphate on GTP. In the GDP-bound state, switch I and II move to the position shown in green in Figure 2. This inactivates SHOC2 binding due to steric clashing which causes the SMP structure to dissociate.
<scene name='95/952717/Mras/2'>MRAS</scene>
<scene name='95/952716/Gtp/1'>GTP-MRAS(full-image)</scene>
<scene name='95/952716/Gtp/1'>GTP-MRAS(zoomed-in)</scene>
<scene name='95/952716/Ras-swtich/2'>Switch I-II (full-image)</scene>
<scene name='95/952716/Ras-switch-zoomed/1'>Switch I-II (zoomed-in)</scene>

=== Key Ligand Interactions ===
[[Image:Amphbindingfinal.png|275 px|right|thumb|'''Figure 3''': Electrostatic illustration of the amphipathic binding pocket of the LPA1 receptor. This binding pocket was revealed by cutting away the exterior or the protein. This binding pocket, located in the interior of the protein, has both polar and nonpolar regions. The blue and red coloration highlight the positively and negatively charged regions, respectively, and the white color shows the nonpolar region of the binding pocket.]]

=== SHOC2 and PP1C ===
<scene name='95/952717/Shoc2_and_pp1c/1'>Shoc2-PP1C</scene>
<scene name='95/952717/Shoc2_and_pp1c/2'>SHOC2-PP1C Binding Pocket</scene>
=== SHOC2 and MRAS ===
<scene name='95/952716/Scho2-mras-interactions/2'>SHOC2-MRAS(full-image)</scene>
<scene name='95/952716/Scho2-mras-interactions/1'>SHOC2-MRAS (residues)</scene>
<scene name='95/952716/Scho2-mras-interactions/3'>SHOC2-MRAS (surface)</scene>
=== PP1C and MRAS ===
<scene name='95/952717/Mras_and_pp1c/1'>PP1C (blue) and MRAS (white)</scene>

<scene name='95/952717/Mras_and_pp1c/4'>PP1C and MRAS residue interactions</scene>

== Signaling Pathway ==

<scene name='95/952717/Pp1c_hydrophobic_patch/1'>PP1C Hydrophobic Patch and Active Site</scene>

== Disease Relevance ==

=== Cancer ===

=== RASopathies===

== Future Studies ==

==3D structures of lysophosphatidic acid receptor==

[[4z34]], [[4z35]], [[4z36]] - hLPA1 + antagonist - human 
[[2lq4]] – hLPA1 second extracellular loop – NMR 
[[4p0c]] – hLPA2/NHERF2 
[[5xsz]] – LPA6A (mutant) – zebra fish 

== References ==
<references/>
==Proteopedia Resources==
[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid_binding Category:Lysophosphatidic acid binding]

[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid Category:Lysophosphatidic acid]

[http://proteopedia.org/wiki/index.php/User:R._Jeremy_Johnson/CH462:Biochemistry_II_Butler_University Butler University Proteopedia Pages]

See also:
*[[Receptor]]
*[[Transmembrane (cell surface) receptors]]
*[[G protein-coupled receptors]]
</StructureSection>
==Student Contributors==
Madeline Gilbert
Inaya Patel
Rushda Hussein

[[Category:Featured in BAMBED]]
[[Category:Topic Page]]

Sandbox Reserved 1789

2023-04-19T19:55:58Z

Rushda Hussein:

{{BAMBED
|DATE=June 14, 2016
|OLDID=2607465
|BAMBEDDOI=10.1002/bmb.21026
}}

==SHOC2-PP1C-MRAS==
<StructureSection load='7UPI' size='340' side='right' caption='SHOC2-MRAS-PP1C'>

== Introduction ==

<scene name='95/952717/Zoom_out/1'>SHOC2-PP1C-MRAS</scene> (SMP) is a ternary holophosphotase complex formed by the individual proteins: SHOC2, PP1C, and MRAS. The SMP complex is involved in signaling the initiation of [https://www.nature.com/articles/7290105. MAPK pathways], which is responsible for cellular growth and development, cell proliferation, and apoptosis <ref name="Hauseman">PMID:35830882</ref>. Formation of this complex begins with an extracellular signal binding to a membrane embedded receptor [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2536775/. tyrosine kinase receptor(RTK)] <ref name="Hauseman"/>. This causes membrane-bound MRAS to exchange GDP for GTP. Initiating the SMP complex formation at the plasma membrane consists of the SHOC2 and PP1C binding first. When the MRAS exchanges GDP to GTP, it then assembles with the combined SHOC2 and PP1C. Based on MRAS targeting, PP1C catalyzes the [https://www.cell.com/fulltext/S0092-8674(00)81356-2. dephosphorylation] of the N-terminal phosphoserine (NTpS) on the [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3128629/. RAF complex] leading to the amplification of MAPK signaling <ref name="Hauseman"/>. In a normal cell, this would regulate cell proliferation but dysfunction in the ternary complex has shown signs to lead to tumor formation due to unregulated cell growth <ref name="Hauseman"/>.

[[Image:Mechanism.png|200px|center|thumb|Figure 1: Mechanism for Shoc2-MRAS-PP1C]]
[[Image:Phosphorylation.png|200px|center|thumb|Figure 2: PP1C phosphorylates Serine 259.]]

== Overall Structure ==
=== SHOC2 ===

<scene name='95/952717/Shoc2/1'>SHOC2</scene> is a scaffold protein composed of 20 [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3901792/. leucine-rich repeat (LRR)] domains that form a solenoid structure <ref name="Hauseman"/>. The leucine rich region forms a concave hydrophobic core which is necessary for binding with PP1C and MRAS. SHOC2 is the crucial mediator for SHOC2-PP1C-MRAS complex formation <ref name="Hauseman"/>. The leucine rich domain is very important in creating selectivity for the PP1C protein, as that protein is used for so many other complex pathways <ref name="Hauseman"/>. The LRR domains are stabilized by an N-terminal flanking 𝝰-helix and a C-terminal helix-turn-helix <ref name="Kwon">PMID:35831509</ref>. Alongside the conserved leucine residues in the LRR domain, there is a group of conserved asparagine residues that creates a stabilizing [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7184636/. “asparagine ladder”] that is necessary for the LRR fold, giving the SHOC2 its concave structure <ref name="Kwon" />.

SHOC2 is also capable of causing various forms of Rasopathies. A common one is caused by a mutation known as p.S2G <ref name="Rauen">Rauen KA. The RASopathies. Annu Rev Genomics Hum Genet. 2013;14:355-69. [http://dx.doi.org/10.1146/annurev-genom-091212-153523 doi: 10.1146/annurev-genom-091212-153523.]</ref>. This mutation causes the formation of an additional 14-carbon saturated fatty acid chain on the N-terminal glycine of SHOC2 <ref name="Rauen" />. This causes SHOC2 to become attached to the cell membrane, resulting in a prolonged dephosphorylation of RAF by PP1C <ref name="Rauen" />. With this abnormality, there is overexpression of the MAPK pathway and increased cell proliferation genes <ref name="Rauen" />

=== PP1C ===
<scene name='95/952717/Pp1c/1'>PP1C</scene> is a phosphatase. After forming a ternary complex, the hydrophobic active site on PP1C interacts with Raf and dephosphorylate Ser 259. PP1C's active site is adjacent to a hydrophobic binding pocket that binds to the C-terminal phosphoserine, located on the N-terminus of RAF, the target for dephosphorylation. PP1C can act as a phosphatase in the absence of SHOC2 but PP1C lacks intrinsic substrate selectively. The SMP complex formation endows PP1C with specificity for RAF <ref name="Hauseman" />.

The mechanism that PP1C uses to catalyze the dephosphorylation is mainly through donating a hydrogen atom to a phosphate group on the C-terminal of a [https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/phosphoserine. phosphoserine] on Raf <ref name="Kubicek"/>. This makes the phosphate group a good leaving group and it breaks off <ref name="Kubicek"/>. This catalysis is done by the serine-threonine alpha catalytic site on PP1C <ref name="Kubicek"/>. In this catalytic site, there are two Manganese ions and one calcium ion <ref name="Kubicek"/>. These metal ions are necessary in stablizing this catalytic site and there are a lot of polar negative residues in this region <ref name="Kubicek"/>

=== MRAS ===

<scene name='95/952717/Mras/2'>MRAS</scene> is a monomeric GTPase. MRAS is membrane-bound due to post-translational lipidation which allows the protein to interact with the inner membrane leaflet. <ref name="Seabra">PMID:9607139</ref> MRAS localizes the SMP complex near RAF and other components of downstream signaling. The region of MRAS not directly bound to the membrane binds SHOC2 and PP1C to orient the complex such that PP1C’s active site faces the serine that will get dephosphorylated on RAF. MRAS also controls SMP complex formation in connection with extracellular signaling based on its dualistic switching between its inactive and active state. In its inactive state, MRAS is bound to GDP. When signaled by growth factors, the GDP is exchanged for GTP when a ligand binds to the RTK <ref name="Hauseman" />. The now <scene name='95/952718/Zoom_in_gtp/1'>GTP bound MRAS</scene> undergoes a conformational change of the <scene name='95/952716/Ras-switch-zoomed/1'>switch I and switch II regions</scene>. These regions are the major binding sites with SHOC2. This conformational change activates MRAS allowing it to bind with the SHOC2-PP1C complex. In its inactive GDP-bound state, MRAS is sterically occluded from binding SHOC2. For example, R83 of GDP-bound MRAS directly clashes with SHOC2 as shown in figure 2. In comparison to other RAS proteins such as H/K/NRAS, MRAS has a greater affinity for the SHOC2-PP1C complex<ref name="Kubicek">Kubicek M, Pacher M, Abraham D, Podar K, Eulitz M, Baccarini M. Dephosphorylation of Ser-259 regulates Raf-1 membrane association. J Biol Chem. 2002 Mar 8;277(10):7913-9. [http://10.1074/jbc.M108733200 doi: 10.1074/jbc.M108733200.]</ref>. This indicates that the specific structure of MRAS is necessary for SMP function. While MRAS engages the SHOC2-PP1C complex to bring the complex to the membrane, an additional membrane-bound RAS binds RAF nearby. This binding is also stimulated by ligand binding to the RTK. This indicates that for full RAF activation and continuous signaling of Raf, two separate active RAS proteins are needed. Having two MRASs also help with the co-localization of PP1C to the NTpS region on RAF. To inactivate Raf signaling, MRAS uses its intrinsic GTPase to remove the activating gamma-phosphate on GTP. In the GDP-bound state, switch I and II move to the position shown in green in Figure 2. This inactivates SHOC2 binding due to steric clashing which causes the SMP structure to dissociate.
<scene name='95/952717/Mras/2'>MRAS</scene>
<scene name='95/952716/Gtp/1'>GTP-MRAS(full-image)</scene>
<scene name='95/952716/Gtp/1'>GTP-MRAS(zoomed-in)</scene>
<scene name='95/952716/Ras-swtich/2'>Switch I-II (full-image)</scene>
<scene name='95/952716/Ras-switch-zoomed/1'>Switch I-II (zoomed-in)</scene>

=== Key Ligand Interactions ===
[[Image:Amphbindingfinal.png|275 px|right|thumb|'''Figure 3''': Electrostatic illustration of the amphipathic binding pocket of the LPA1 receptor. This binding pocket was revealed by cutting away the exterior or the protein. This binding pocket, located in the interior of the protein, has both polar and nonpolar regions. The blue and red coloration highlight the positively and negatively charged regions, respectively, and the white color shows the nonpolar region of the binding pocket.]]

=== SHOC2 and PP1C ===
<scene name='95/952717/Shoc2_and_pp1c/1'>Shoc2-PP1C</scene>
<scene name='95/952717/Shoc2_and_pp1c/2'>SHOC2-PP1C Binding Pocket</scene>
=== SHOC2 and MRAS ===
<scene name='95/952716/Scho2-mras-interactions/2'>SHOC2-MRAS(full-image)</scene>
<scene name='95/952716/Scho2-mras-interactions/1'>SHOC2-MRAS (residues)</scene>
<scene name='95/952716/Scho2-mras-interactions/3'>SHOC2-MRAS (surface)</scene>
=== PP1C and MRAS ===
<scene name='95/952717/Mras_and_pp1c/1'>PP1C (blue) and MRAS (white)</scene>

<scene name='95/952717/Mras_and_pp1c/4'>PP1C and MRAS residue interactions</scene>

== Signaling Pathway ==

<scene name='95/952717/Pp1c_hydrophobic_patch/1'>PP1C Hydrophobic Patch and Active Site</scene>

== Disease Relevance ==

=== Cancer ===

=== RASopathies===

== Future Studies ==

==3D structures of lysophosphatidic acid receptor==

[[4z34]], [[4z35]], [[4z36]] - hLPA1 + antagonist - human 
[[2lq4]] – hLPA1 second extracellular loop – NMR 
[[4p0c]] – hLPA2/NHERF2 
[[5xsz]] – LPA6A (mutant) – zebra fish 

== References ==
<references/>
==Proteopedia Resources==
[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid_binding Category:Lysophosphatidic acid binding]

[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid Category:Lysophosphatidic acid]

[http://proteopedia.org/wiki/index.php/User:R._Jeremy_Johnson/CH462:Biochemistry_II_Butler_University Butler University Proteopedia Pages]

See also:
*[[Receptor]]
*[[Transmembrane (cell surface) receptors]]
*[[G protein-coupled receptors]]
</StructureSection>
==Student Contributors==
Madeline Gilbert
Inaya Patel
Rushda Hussein

[[Category:Featured in BAMBED]]
[[Category:Topic Page]]

Sandbox Reserved 1789

2023-04-19T19:45:42Z

Rushda Hussein:

{{BAMBED
|DATE=June 14, 2016
|OLDID=2607465
|BAMBEDDOI=10.1002/bmb.21026
}}

==SHOC2-PP1C-MRAS==
<StructureSection load='7UPI' size='340' side='right' caption='SHOC2-MRAS-PP1C'>

== Introduction ==

<scene name='95/952717/Zoom_out/1'>SHOC2-PP1C-MRAS</scene> (SMP) is a ternary holophosphotase complex formed by the individual proteins: SHOC2, PP1C, and MRAS. The SMP complex is involved in signaling the initiation of [https://www.nature.com/articles/7290105. MAPK pathways], which is responsible for cellular growth and development, cell proliferation, and apoptosis <ref name="Hauseman">PMID:35830882</ref>. Formation of this complex begins with an extracellular signal binding to a membrane embedded receptor [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2536775/. tyrosine kinase receptor(RTK)] <ref name="Hauseman"/>. This causes membrane-bound MRAS to exchange GDP for GTP. Initiating the SMP complex formation at the plasma membrane consists of the SHOC2 and PP1C binding first. When the MRAS exchanges GDP to GTP, it then assembles with the combined SHOC2 and PP1C. Based on MRAS targeting, PP1C catalyzes the [https://www.cell.com/fulltext/S0092-8674(00)81356-2. dephosphorylation] of the N-terminal phosphoserine (NTpS) on the [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3128629/. RAF complex] leading to the amplification of MAPK signaling <ref name="Hauseman"/>. In a normal cell, this would regulate cell proliferation but dysfunction in the ternary complex has shown signs to lead to tumor formation due to unregulated cell growth <ref name="Hauseman"/>.

[[Image:Mechanism.png|200px|center|thumb|Figure 1: Mechanism for Shoc2-MRAS-PP1C]]
[[Image:Phosphorylation.png|200px|center|thumb|Figure 2: PP1C phosphorylates Serine 259.]]

== Overall Structure ==
=== SHOC2 ===

<scene name='95/952717/Shoc2/1'>SHOC2</scene> is a scaffold protein composed of 20 [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3901792/. leucine-rich repeat (LRR)] domains that form a solenoid structure <ref name="Hauseman"/>. The leucine rich region forms a concave hydrophobic core which is necessary for binding with PP1C and MRAS. SHOC2 is the crucial mediator for SHOC2-PP1C-MRAS complex formation <ref name="Hauseman"/>. The leucine rich domain is very important in creating selectivity for the PP1C protein, as that protein is used for so many other complex pathways <ref name="Hauseman"/>. The LRR domains are stabilized by an N-terminal flanking 𝝰-helix and a C-terminal helix-turn-helix <ref name="Kwon">PMID:35831509</ref>. Alongside the conserved leucine residues in the LRR domain, there is a group of conserved asparagine residues that creates a stabilizing [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7184636/. “asparagine ladder”] that is necessary for the LRR fold, giving the SHOC2 its concave structure <ref name="Kwon" />.

SHOC2 is also capable of causing various forms of Rasopathies. A common one is caused by a mutation known as p.S2G <ref name="Rauen">Rauen KA. The RASopathies. Annu Rev Genomics Hum Genet. 2013;14:355-69. [http://dx.doi.org/10.1146/annurev-genom-091212-153523 doi: 10.1146/annurev-genom-091212-153523.]</ref>. This mutation causes the formation of an additional 14-carbon saturated fatty acid chain on the N-terminal glycine of SHOC2 <ref name="Rauen" />. This causes SHOC2 to become attached to the cell membrane, resulting in a prolonged dephosphorylation of RAF by PP1C <ref name="Rauen" />. With this abnormality, there is overexpression of the MAPK pathway and increased cell proliferation genes <ref name="Rauen" />

=== PP1C ===
<scene name='95/952717/Pp1c/1'>PP1C</scene> is a phosphatase. After forming a ternary complex, the hydrophobic active site on PP1C interacts with Raf and dephosphorylate Ser 259. PP1C's active site is adjacent to a hydrophobic binding pocket that binds to the C-terminal phosphoserine, located on the N-terminus of RAF, the target for dephosphorylation. PP1C can act as a phosphatase in the absence of SHOC2 but PP1C lacks intrinsic substrate selectively. The SMP complex formation endows PP1C with specificity for RAF <ref name="Hauseman" />.

The mechanism that PP1C uses to catalyze the dephosphorylation is mainly through donating a hydrogen atom to a phosphate group on the C-terminal of a [https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/phosphoserine. phosphoserine] on Raf <ref name="Kubicek"/>. This makes the phosphate group a good leaving group and it breaks off <ref name="Kubicek"/>. This catalysis is done by the serine-threonine alpha catalytic site on PP1C <ref name="Kubicek"/>. In this catalytic site, there are two Manganese ions and one calcium ion <ref name="Kubicek"/>. These metal ions are necessary in stablizing this catalytic site and there are a lot of polar negative residues in this region <ref name="Kubicek"/>

<scene name='95/952717/Pp1c/1'>PP1C</scene>
=== MRAS ===

<scene name='95/952717/Mras/2'>MRAS</scene> is a monomeric GTPase. MRAS is membrane-bound due to post-translational lipidation which allows the protein to interact with the inner membrane leaflet. <ref name="Seabra">PMID:9607139</ref> MRAS localizes the SMP complex near RAF and other components of downstream signaling. The region of MRAS not directly bound to the membrane binds SHOC2 and PP1C to orient the complex such that PP1C’s active site faces the serine that will get dephosphorylated on RAF. MRAS also controls SMP complex formation in connection with extracellular signaling based on its dualistic switching between its inactive and active state. In its inactive state, MRAS is bound to GDP. When signaled by growth factors, the GDP is exchanged for GTP when a ligand binds to the RTK <ref name="Hauseman" />. The now <scene name='95/952718/Zoom_in_gtp/1'>GTP bound MRAS</scene> undergoes a conformational change of the <scene name='95/952716/Ras-switch-zoomed/1'>switch I and switch II regions</scene>. These regions are the major binding sites with SHOC2. This conformational change activates MRAS allowing it to bind with the SHOC2-PP1C complex. In its inactive GDP-bound state, MRAS is sterically occluded from binding SHOC2. For example, R83 of GDP-bound MRAS directly clashes with SHOC2 as shown in figure 2. In comparison to other RAS proteins such as H/K/NRAS, MRAS has a greater affinity for the SHOC2-PP1C complex<ref name="Kubicek">Kubicek M, Pacher M, Abraham D, Podar K, Eulitz M, Baccarini M. Dephosphorylation of Ser-259 regulates Raf-1 membrane association. J Biol Chem. 2002 Mar 8;277(10):7913-9. [http://10.1074/jbc.M108733200 doi: 10.1074/jbc.M108733200.]</ref>. This indicates that the specific structure of MRAS is necessary for SMP function. While MRAS engages the SHOC2-PP1C complex to bring the complex to the membrane, an additional membrane-bound RAS binds RAF nearby. This binding is also stimulated by ligand binding to the RTK. This indicates that for full RAF activation and continuous signaling of Raf, two separate active RAS proteins are needed. Having two MRASs also help with the co-localization of PP1C to the NTpS region on RAF. To inactivate Raf signaling, MRAS uses its intrinsic GTPase to remove the activating gamma-phosphate on GTP. In the GDP-bound state, switch I and II move to the position shown in green in Figure 2. This inactivates SHOC2 binding due to steric clashing which causes the SMP structure to dissociate.
<scene name='95/952717/Mras/2'>MRAS</scene>
<scene name='95/952716/Gtp/1'>GTP-MRAS(full-image)</scene>
<scene name='95/952716/Gtp/1'>GTP-MRAS(zoomed-in)</scene>
<scene name='95/952716/Ras-swtich/2'>Switch I-II (full-image)</scene>
<scene name='95/952716/Ras-switch-zoomed/1'>Switch I-II (zoomed-in)</scene>

=== Key Ligand Interactions ===
[[Image:Amphbindingfinal.png|275 px|right|thumb|'''Figure 3''': Electrostatic illustration of the amphipathic binding pocket of the LPA1 receptor. This binding pocket was revealed by cutting away the exterior or the protein. This binding pocket, located in the interior of the protein, has both polar and nonpolar regions. The blue and red coloration highlight the positively and negatively charged regions, respectively, and the white color shows the nonpolar region of the binding pocket.]]

=== SHOC2 and PP1C ===
<scene name='95/952717/Shoc2_and_pp1c/1'>Shoc2-PP1C</scene>
<scene name='95/952717/Shoc2_and_pp1c/2'>SHOC2-PP1C Binding Pocket</scene>
=== SHOC2 and MRAS ===
<scene name='95/952716/Scho2-mras-interactions/2'>SHOC2-MRAS(full-image)</scene>
<scene name='95/952716/Scho2-mras-interactions/1'>SHOC2-MRAS (residues)</scene>
<scene name='95/952716/Scho2-mras-interactions/3'>SHOC2-MRAS (surface)</scene>
=== PP1C and MRAS ===
<scene name='95/952717/Mras_and_pp1c/1'>PP1C (blue) and MRAS (white)</scene>

<scene name='95/952717/Mras_and_pp1c/4'>PP1C and MRAS residue interactions</scene>

== Signaling Pathway ==

<scene name='95/952717/Pp1c_hydrophobic_patch/1'>PP1C Hydrophobic Patch and Active Site</scene>

== Disease Relevance ==

=== Cancer ===

=== RASopathies===

== Future Studies ==

==3D structures of lysophosphatidic acid receptor==

[[4z34]], [[4z35]], [[4z36]] - hLPA1 + antagonist - human 
[[2lq4]] – hLPA1 second extracellular loop – NMR 
[[4p0c]] – hLPA2/NHERF2 
[[5xsz]] – LPA6A (mutant) – zebra fish 

== References ==
<references/>
==Proteopedia Resources==
[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid_binding Category:Lysophosphatidic acid binding]

[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid Category:Lysophosphatidic acid]

[http://proteopedia.org/wiki/index.php/User:R._Jeremy_Johnson/CH462:Biochemistry_II_Butler_University Butler University Proteopedia Pages]

See also:
*[[Receptor]]
*[[Transmembrane (cell surface) receptors]]
*[[G protein-coupled receptors]]
</StructureSection>
==Student Contributors==
Madeline Gilbert
Inaya Patel
Rushda Hussein

[[Category:Featured in BAMBED]]
[[Category:Topic Page]]

Sandbox Reserved 1789

2023-04-19T19:12:53Z

Rushda Hussein:

{{BAMBED
|DATE=June 14, 2016
|OLDID=2607465
|BAMBEDDOI=10.1002/bmb.21026
}}

==SHOC2-PP1C-MRAS==
<StructureSection load='7UPI' size='340' side='right' caption='SHOC2-MRAS-PP1C'>

== Introduction ==

<scene name='95/952718/Zoom_out/1'>SHOC2-PP1C-MRAS</scene> (SMP) is a ternary holophosphotase complex formed by the individual proteins: SHOC2, PP1C, and MRAS. The SMP complex is involved in signaling the initiation of [https://www.nature.com/articles/7290105. MAPK pathways], which is responsible for cellular growth and development, cell proliferation, and apoptosis <ref name="Hauseman">PMID:35830882</ref>. Formation of this complex begins with an extracellular signal binding to a membrane embedded receptor [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2536775/. tyrosine kinase receptor(RTK)] <ref name="Hauseman"/>. This causes membrane-bound MRAS to exchange GDP for GTP. Initiating the SMP complex formation at the plasma membrane consists of the SHOC2 and PP1C binding first. When the MRAS exchanges GDP to GTP, it then assembles with the combined SHOC2 and PP1C. Based on MRAS targeting, PP1C catalyzes the [https://www.cell.com/fulltext/S0092-8674(00)81356-2. dephosphorylation] of the N-terminal phosphoserine (NTpS) on the [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3128629/. RAF complex] leading to the amplification of MAPK signaling <ref name="Hauseman"/>. In a normal cell, this would regulate cell proliferation but dysfunction in the ternary complex has shown signs to lead to tumor formation due to unregulated cell growth <ref name="Hauseman"/>.

[[Image:Mechanism.png|200px|center|thumb|Figure 1: Mechanism for Shoc2-MRAS-PP1C]]
[[Image:Phosphorylation.png|200px|center|thumb|Figure 2: PP1C phosphorylates Serine 259.]]

== Overall Structure ==
=== SHOC2 ===

<scene name='95/952717/Shoc2/1'>SHOC2</scene> is a scaffold protein composed of 20 [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3901792/. leucine-rich repeat (LRR)] domains that form a solenoid structure <ref name="Hauseman"/>. The leucine rich region forms a concave hydrophobic core which is necessary for binding with PP1C and MRAS. SHOC2 is the crucial mediator for SHOC2-PP1C-MRAS complex formation <ref name="Hauseman"/>. The leucine rich domain is very important in creating selectivity for the PP1C protein, as that protein is used for so many other complex pathways <ref name="Hauseman"/>. The LRR domains are stabilized by an N-terminal flanking 𝝰-helix and a C-terminal helix-turn-helix <ref name="Kwon">PMID:35831509</ref>. Alongside the conserved leucine residues in the LRR domain, there is a group of conserved asparagine residues that creates a stabilizing [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7184636/. “asparagine ladder”] that is necessary for the LRR fold, giving the SHOC2 its concave structure <ref name="Kwon" />.

SHOC2 is also capable of causing various forms of Rasopathies. A common one is caused by a mutation known as p.S2G <ref name="Rauen">Rauen KA. The RASopathies. Annu Rev Genomics Hum Genet. 2013;14:355-69. [http://dx.doi.org/10.1146/annurev-genom-091212-153523 doi: 10.1146/annurev-genom-091212-153523.]</ref>. This mutation causes the formation of an additional 14-carbon saturated fatty acid chain on the N-terminal glycine of SHOC2 <ref name="Rauen" />. This causes SHOC2 to become attached to the cell membrane, resulting in a prolonged dephosphorylation of RAF by PP1C <ref name="Rauen" />. With this abnormality, there is overexpression of the MAPK pathway and increased cell proliferation genes <ref name="Rauen" />

=== PP1C ===
<scene name='95/952717/Pp1c/1'>PP1C</scene> is a phosphatase. After forming a ternary complex, the hydrophobic active site on PP1C interacts with Raf and dephosphorylate Ser 259. PP1C's active site is adjacent to a hydrophobic binding pocket that binds to the C-terminal phosphoserine, located on the N-terminus of RAF, the target for dephosphorylation. PP1C can act as a phosphatase in the absence of SHOC2 but PP1C lacks intrinsic substrate selectively. The SMP complex formation endows PP1C with specificity for RAF <ref name="Hauseman" />.

The mechanism that PP1C uses to catalyze the dephosphorylation is mainly through donating a hydrogen atom to a phosphate group on the C-terminal of a [https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/phosphoserine. phosphoserine] on Raf <ref name="Kubicek"/>. This makes the phosphate group a good leaving group and it breaks off <ref name="Kubicek"/>. This catalysis is done by the serine-threonine alpha catalytic site on PP1C <ref name="Kubicek"/>. In this catalytic site, there are two Manganese ions and one calcium ion <ref name="Kubicek"/>. These metal ions are necessary in stablizing this catalytic site and there are a lot of polar negative residues in this region <ref name="Kubicek"/>

<scene name='95/952717/Pp1c/1'>PP1C</scene>
=== MRAS ===

<scene name='95/952717/Mras/2'>MRAS</scene> is a monomeric GTPase. MRAS is membrane-bound due to post-translational lipidation which allows the protein to interact with the inner membrane leaflet. <ref name="Seabra">PMID:9607139</ref> MRAS localizes the SMP complex near RAF and other components of downstream signaling. The region of MRAS not directly bound to the membrane binds SHOC2 and PP1C to orient the complex such that PP1C’s active site faces the serine that will get dephosphorylated on RAF. MRAS also controls SMP complex formation in connection with extracellular signaling based on its dualistic switching between its inactive and active state. In its inactive state, MRAS is bound to GDP. When signaled by growth factors, the GDP is exchanged for GTP when a ligand binds to the RTK <ref name="Hauseman" />. The now <scene name='95/952718/Zoom_in_gtp/1'>GTP bound MRAS</scene> undergoes a conformational change of the <scene name='95/952716/Ras-switch-zoomed/1'>switch I and switch II regions</scene>. These regions are the major binding sites with SHOC2. This conformational change activates MRAS allowing it to bind with the SHOC2-PP1C complex. In its inactive GDP-bound state, MRAS is sterically occluded from binding SHOC2. For example, R83 of GDP-bound MRAS directly clashes with SHOC2 as shown in figure 2. In comparison to other RAS proteins such as H/K/NRAS, MRAS has a greater affinity for the SHOC2-PP1C complex<ref name="Kubicek">Kubicek M, Pacher M, Abraham D, Podar K, Eulitz M, Baccarini M. Dephosphorylation of Ser-259 regulates Raf-1 membrane association. J Biol Chem. 2002 Mar 8;277(10):7913-9. [http://10.1074/jbc.M108733200 doi: 10.1074/jbc.M108733200.]</ref>. This indicates that the specific structure of MRAS is necessary for SMP function. While MRAS engages the SHOC2-PP1C complex to bring the complex to the membrane, an additional membrane-bound RAS binds RAF nearby. This binding is also stimulated by ligand binding to the RTK. This indicates that for full RAF activation and continuous signaling of Raf, two separate active RAS proteins are needed. Having two MRASs also help with the co-localization of PP1C to the NTpS region on RAF. To inactivate Raf signaling, MRAS uses its intrinsic GTPase to remove the activating gamma-phosphate on GTP. In the GDP-bound state, switch I and II move to the position shown in green in Figure 2. This inactivates SHOC2 binding due to steric clashing which causes the SMP structure to dissociate.
<scene name='95/952717/Mras/2'>MRAS</scene>
<scene name='95/952716/Gtp/1'>GTP-MRAS(full-image)</scene>
<scene name='95/952716/Gtp/1'>GTP-MRAS(zoomed-in)</scene>
<scene name='95/952716/Ras-swtich/2'>Switch I-II (full-image)</scene>
<scene name='95/952716/Ras-switch-zoomed/1'>Switch I-II (zoomed-in)</scene>

=== Key Ligand Interactions ===
[[Image:Amphbindingfinal.png|275 px|right|thumb|'''Figure 3''': Electrostatic illustration of the amphipathic binding pocket of the LPA1 receptor. This binding pocket was revealed by cutting away the exterior or the protein. This binding pocket, located in the interior of the protein, has both polar and nonpolar regions. The blue and red coloration highlight the positively and negatively charged regions, respectively, and the white color shows the nonpolar region of the binding pocket.]]

=== SHOC2 and PP1C ===
<scene name='95/952717/Shoc2_and_pp1c/1'>Shoc2-PP1C</scene>
<scene name='95/952717/Shoc2_and_pp1c/2'>SHOC2-PP1C Binding Pocket</scene>
=== SHOC2 and MRAS ===
<scene name='95/952716/Scho2-mras-interactions/2'>SHOC2-MRAS(full-image)</scene>
<scene name='95/952716/Scho2-mras-interactions/1'>SHOC2-MRAS (residues)</scene>
<scene name='95/952716/Scho2-mras-interactions/3'>SHOC2-MRAS (surface)</scene>
=== PP1C and MRAS ===
<scene name='95/952717/Mras_and_pp1c/1'>PP1C (blue) and MRAS (white)</scene>

<scene name='95/952717/Mras_and_pp1c/4'>PP1C and MRAS residue interactions</scene>

== Signaling Pathway ==

<scene name='95/952717/Pp1c_hydrophobic_patch/1'>PP1C Hydrophobic Patch and Active Site</scene>

== Disease Relevance ==

=== Cancer ===

=== RASopathies===

== Future Studies ==

==3D structures of lysophosphatidic acid receptor==

[[4z34]], [[4z35]], [[4z36]] - hLPA1 + antagonist - human 
[[2lq4]] – hLPA1 second extracellular loop – NMR 
[[4p0c]] – hLPA2/NHERF2 
[[5xsz]] – LPA6A (mutant) – zebra fish 

== References ==
<references/>
==Proteopedia Resources==
[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid_binding Category:Lysophosphatidic acid binding]

[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid Category:Lysophosphatidic acid]

[http://proteopedia.org/wiki/index.php/User:R._Jeremy_Johnson/CH462:Biochemistry_II_Butler_University Butler University Proteopedia Pages]

See also:
*[[Receptor]]
*[[Transmembrane (cell surface) receptors]]
*[[G protein-coupled receptors]]
</StructureSection>
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<StructureSection load='7pui' size='350' side='right' caption='SHOC2-PP1C-MRAS (PDB entry [[7upi]])' scene='95/952718/Mras/2'>>

=SHOC2-PP1C-MRAS=

=Introduction=
<scene name='95/952718/Zoom_out/1'>SHOC2-PP1C-MRAS</scene> (SMP) is a ternary holophosphotase complex formed by the individual proteins: SHOC2, PP1C, and MRAS. Formation of this complex begins with a signal binding to a receptor [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2536775/. tyrosine kinase receptor(RTK)]. This causes membrane-bound MRAS to exchange GDP for GTP. From here the complex comes together in the plasma membrane. Its role in MAPK signaling is the dephosphorylation of the N-terminal phosphoserine (NTpS) on the [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3128629/. RAF complex] leading to further downstream signaling effects <ref name=”Hauseman”>PMID:35830882</ref>.

=Overall Structure=

==SHOC2==
<scene name='95/952717/Shoc2/1'>SHOC2</scene> is a scaffold protein that is composed of 20 leucine-rich repeat domains that form a solenoid structure. The leucine rich region forms a concave hydrophobic core which is necessary for binding with PP1C and MRAS. SHOC2 is the crucial mediator for SHOC2-PP1C-MRAS complex formation.
==PP1C==
<scene name='95/952717/Pp1c/1'>PP1C</scene> is a catalytic protein. After forming a ternary complex, the hydrophobic active site on the protein interacts with Raf to act as a phosphatase and dephosphorylate Ser 259. PP1C's active site is adjacent to a hydrophobic patch. It's theorized that the hydrophobic patch binds to the C-terminal of N-terminal phosphoserine of RAF, the target for dephosphorylation. PP1C can act as a phosphatase in the absence of SHOC2 but PP1C lasks intrinsic substrate selectively. So SMP complex formation is necessary for PP1C specificity to RAF.
[[Image:ActiveSiteProto.png|500 px|thumb|'''Figure 2:'''Active site of PP1C on SMP.</div>]]
==MRAS==
<scene name='95/952717/Mras/2'>MRAS</scene> is a membrane-bound structure that aids the complex in localizing near other structures such as the RAS-RAF-MAPK complex in order to initiate downstream signaling. In its inactive state, MRAS is bound to GDP. When signaled by growth factors, the GDP is exchanged for GTP. The now <scene name='95/952718/Zoom_in_gtp/1'>GTP bound MRAS</scene> undergoes a conformational change of the <scene name='95/952716/Ras-switch-zoomed/1'>switch I and switch II regions</scene>. This conformational change activates the protein allowing it to bind with the SHOC2-PP1C complex. Without the conformational change when GDP is exchanged to GTP, the GDP-MRAS wouldn't be able to bind to SHOC2 because of steric clashing. In comparison to other RAS proteins, MRAS has a greater affinity for the SHOC2-PP1C complex<ref name=”Kubicek”>Kubicek M, Pacher M, Abraham D, Podar K, Eulitz M, Baccarini M. Dephosphorylation of Ser-259 regulates Raf-1 membrane association. J Biol Chem. 2002 Mar 8;277(10):7913-9. [http://10.1074/jbc.M108733200 doi: 10.1074/jbc.M108733200.]</ref>. MRAS engages the SHOC2-PP1C complex and RAF on the same surface indicating that for RAF signaling two separate active MRASs are needed. Having two MRASs also help with the co-localization of PP1C to the NTpS region on RAF.

[[Image:Switches.png|500 px|thumb|'''Figure 2:'''Steric clashing of Switch I and II of GDP bound MRAS, in green, with the surface of SHOC2, in magenta. GTP-bound MRAS, in white, shows no steric clashing with SHOC2s surface.</div>]]

=Key Ligand Interactions=

==SHOC2 and PP1C==

<scene name='95/952717/Shoc2_and_pp1c/1'>PP1C binds to SHOC2</scene> on its leucine rich region(LRR). Specifically, on two broad surfaces between LRR2 and LRR5 and between LRR7 and LRR11. Mutations made to the LRR were shown to completely inhibit the binding of PP1C. Five main <scene name='95/952717/Shoc2_and_pp1c/2'>hydrogen bonds</scene> are made: E56-R182, E167-R203, E54-K180, R187-H178, R188-E155. The binding regions can also be shown as acidic and basic patches on <scene name='95/952718/Acid_base_pp1c/1'>PP1C</scene> and <scene name='95/952718/Acid_base_shoc2/1'>SHOC2</scene>. The corresponding patches interact to form a <scene name='95/952718/Acid_base_shoc2pp1c/1'>binary complex</scene>. These interactions do not result in significant conformational changes <ref name=”Kwon”>PMID:35831509</ref>.

==SHOC2 and MRAS==
MRAS is initially bound to GDP causing it to be in its inactive state. This form cannot bind to the SHOC2-PP1C complex due to steric clashing. Once GDP is exchanged for GTP to activate the protein, <scene name='95/952716/conformational changes/1'>SHOC2-MRAS (residues)</scene> occur within the switch I and switch II regions to allow <scene name='95/952716/MRAS to interact with SHOC2/2'>SHOC2-MRAS(full-image)</scene>. These <scene name='95/952716/Scho2-mras-interactions/1'>interactions</scene> include hydrogen bonds and pi stacking. The primary hydrogen bonds are R288-Q71 and R177-E47. Pi staking occurs at R104-R83 <ref name=”Lavoie”>Lavoie H, Therrien M. Structural keys unlock RAS-MAPK cellular signalling pathway. Nature. 2022 Sep;609(7926):248-249. [http://dx.doi.org/10.1038/d41586-022-02189-7 doi: 10.1038/d41586-022-02189-7. PMID: 35970881.]</ref>.

==PP1C and MRAS==
The interactions between <scene name='95/952717/Mras_and_pp1c/1'>PP1C and MRAS</scene> are mediated by four main <scene name='95/952717/Mras_and_pp1c/4'>hydrogen bonds</scene>: R188-D48, M190-Q35, D197-H53, Q198-K36. It is unclear whether PP1C must bind to SHOC2 before MRAS binds or if PP1C and MRAS can bind to SHOC2 at the same time.
=Signaling Pathway=
The SMP signaling pathway begins with the formation of the SMP complex. Initially, a ligand must bind to a receptor tyrosine kinase. This signals SHOC2 to bind to PP1C forming a binary complex that then binds to the membrane bound MRAS. Some literature indicates that the three proteins bind at the same time but the order is largely unknown. Figure 2 shows the proteins binding one at a time. Once the SMP complex forms, its target is the N-terminal phosphoserine (NTpS) also known as S259. The serine is directly dephosphorylated by PP1C by SHOC2 and MRAS increase its specificity for S259.
Mutations affecting SMP complex formation and stability have been shown to increase or decrease MAPK signaling. Increased stability of the complex increases MAPK signaling while decreased stability decreases signaling<ref name="Liau">PMID:35768504</ref>.

[[Image:Signal_cascade_small.jpg|800 px|thumb|center|'''Figure 2:'''Signaling cascade is shown with SHOC2 in pink, PP1C in blue, and MRAs in white. ]]

[[Image:Dephosphorylation.jpg|600 px|thumb|center|'''Figure 3:'''PP1C dephosphorylates RAF protein at serine 259 ]]
=Disease Relevance=

==RASopathies==

RASopathy is a broad term used to describe developmental syndromes that stem from [https://www.sciencedirect.com/topics/medicine-and-dentistry/germline-mutation. germline mutations] of proteins along the RAS/MAPK pathway such as SHOC2, PP1C, and MRAS. These mutations can be either gain or loss of function. Rasopathies can also lead to cancer <ref name=”Rauen”>Rauen KA. The RASopathies. Annu Rev Genomics Hum Genet. 2013;14:355-69. [http://dx.doi.org/10.1146/annurev-genom-091212-153523 doi: 10.1146/annurev-genom-091212-153523.]</ref>.

==Cancer==

Because the RAS/MAPK pathway activated by SMP regulates cell proliferation and survival, overactivity can cause tumor formation and cancer. For example, the complex has been found to play a role in the perpetuation of melanoma, leukemia, and lung cancer.

=Future Studies=

Further study of the SMP complex includes clarification of the steps of the pathway. Firstly, the order of binding to form the SMP complex is unclear. Furthermore, the interaction between SMP and the Raf complex is largely unknown. Study into this step is especially important to understand how SMP activates downstream signaling.
The current knowledge of SMP can be used to study possible treatments for rasopathies and cancer. For example, the development of inhibitors that target SMP binding could prevent the effects caused by mutations that overactivate SMP. Another possible point of inhibition is the growth factor that signals SHOC2-PP1C and Raf to the cell membrane. <ref name="Liau" /> .

=References=

<references/>

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<StructureSection load='7pui' size='350' side='right' caption='SHOC2-PP1C-MRAS (PDB entry [[7upi]])' scene='95/952718/Mras/2'>>

=SHOC2-PP1C-MRAS=

=Introduction=
<scene name='95/952718/Zoom_out/1'>SHOC2-PP1C-MRAS</scene> (SMP) is a ternary holophosphotase complex formed by the individual proteins: SHOC2, PP1C, and MRAS. Formation of this complex begins with a signal binding to a receptor [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2536775/. tyrosine kinase receptor(RTK)]. This causes membrane-bound MRAS to exchange GDP for GTP. From here the complex comes together in the plasma membrane. Its role in MAPK signaling is the dephosphorylation of the N-terminal phosphoserine (NTpS) on the [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3128629/. RAF complex] leading to further downstream signaling effects.

=Overall Structure=

==SHOC2==
<scene name='95/952717/Shoc2/1'>SHOC2</scene> is a scaffold protein that is composed of 20 leucine-rich repeat domains that form a solenoid structure. The leucine rich region forms a concave hydrophobic core which is necessary for binding with PP1C and MRAS. SHOC2 is the crucial mediator for SHOC2-PP1C-MRAS complex formation.
==PP1C==
<scene name='95/952717/Pp1c/1'>PP1C</scene> is a catalytic protein. After forming a ternary complex, the hydrophobic active site on the protein interacts with Raf to act as a phosphatase and dephosphorylate Ser 259. PP1C's active site is adjacent to a hydrophobic patch. It's theorized that the hydrophobic patch binds to the C-terminal of N-terminal phosphoserine of RAF, the target for dephosphorylation. PP1C can act as a phosphatase in the absence of SHOC2 but PP1C lasks intrinsic substrate selectively. So SMP complex formation is necessary for PP1C specificity to RAF.
[[Image:ActiveSiteProto.png|500 px|thumb|'''Figure 2:'''Active site of PP1C on SMP.</div>]]
==MRAS==
<scene name='95/952717/Mras/2'>MRAS</scene> is a membrane-bound structure that aids the complex in localizing near other structures such as the RAS-RAF-MAPK complex in order to initiate downstream signaling. In its inactive state, MRAS is bound to GDP. When signaled by growth factors, the GDP is exchanged for GTP. The now <scene name='95/952718/Zoom_in_gtp/1'>GTP bound MRAS</scene> undergoes a conformational change of the <scene name='95/952716/Ras-switch-zoomed/1'>switch I and switch II regions</scene>. This conformational change activates the protein allowing it to bind with the SHOC2-PP1C complex. Without the conformational change when GDP is exchanged to GTP, the GDP-MRAS wouldn't be able to bind to SHOC2 because of steric clashing. In comparison to other RAS proteins, MRAS has a greater affinity for the SHOC2-PP1C complex<ref name=”Kubicek”>PMID:11756411</ref>. MRAS engages the SHOC2-PP1C complex and RAF on the same surface indicating that for RAF signaling two separate active MRASs are needed. Having two MRASs also help with the co-localization of PP1C to the NTpS region on RAF.

[[Image:Switches.png|500 px|thumb|'''Figure 2:'''Steric clashing of Switch I and II of GDP bound MRAS, in green, with the surface of SHOC2, in magenta. GTP-bound MRAS, in white, shows no steric clashing with SHOC2s surface.</div>]]

=Key Ligand Interactions=

==SHOC2 and PP1C==

<scene name='95/952717/Shoc2_and_pp1c/1'>PP1C binds to SHOC2</scene> on its leucine rich region(LRR). Specifically, on two broad surfaces between LRR2 and LRR5 and between LRR7 and LRR11. Mutations made to the LRR were shown to completely inhibit the binding of PP1C. Five main <scene name='95/952717/Shoc2_and_pp1c/2'>hydrogen bonds</scene> are made: E56-R182, E167-R203, E54-K180, R187-H178, R188-E155. The binding regions can also be shown as acidic and basic patches on <scene name='95/952718/Acid_base_pp1c/1'>PP1C</scene> and <scene name='95/952718/Acid_base_shoc2/1'>SHOC2</scene>. The corresponding patches interact to form a <scene name='95/952718/Acid_base_shoc2pp1c/1'>binary complex</scene>. These interactions do not result in significant conformational changes <ref name=”Kwon”>PMID:35831509</ref>.

==SHOC2 and MRAS==
MRAS is initially bound to GDP causing it to be in its inactive state. This form cannot bind to the SHOC2-PP1C complex due to steric clashing. Once GDP is exchanged for GTP to activate the protein, <scene name='95/952716/conformational changes/1'>SHOC2-MRAS (residues)</scene> occur within the switch I and switch II regions to allow <scene name='95/952716/MRAS to interact with SHOC2/2'>SHOC2-MRAS(full-image)</scene>. These <scene name='95/952716/Scho2-mras-interactions/1'>interactions</scene> include hydrogen bonds and pi stacking. The primary hydrogen bonds are R288-Q71 and R177-E47. Pi staking occurs at R104-R83 <ref name=”Lavoie”>PMID:35970881</ref>.

==PP1C and MRAS==
The interactions between <scene name='95/952717/Mras_and_pp1c/1'>PP1C and MRAS</scene> are mediated by four main <scene name='95/952717/Mras_and_pp1c/4'>hydrogen bonds</scene>: R188-D48, M190-Q35, D197-H53, Q198-K36. It is unclear whether PP1C must bind to SHOC2 before MRAS binds or if PP1C and MRAS can bind to SHOC2 at the same time.
=Signaling Pathway=
The SMP signaling pathway begins with the formation of the SMP complex. Initially, a ligand must bind to a receptor tyrosine kinase. This signals SHOC2 to bind to PP1C forming a binary complex that then binds to the membrane bound MRAS. Some literature indicates that the three proteins bind at the same time but the order is largely unknown. Figure 2 shows the proteins binding one at a time. Once the SMP complex forms, its target is the N-terminal phosphoserine (NTpS) also known as S259. The serine is directly dephosphorylated by PP1C by SHOC2 and MRAS increase its specificity for S259.
Mutations affecting SMP complex formation and stability have been shown to increase or decrease MAPK signaling. Increased stability of the complex increases MAPK signaling while decreased stability decreases signaling<ref name="Liau">PMID:35768504</ref>.

[[Image:Signal_cascade_small.jpg|800 px|thumb|center|'''Figure 2:'''Signaling cascade is shown with SHOC2 in pink, PP1C in blue, and MRAs in white. ]]

[[Image:Dephosphorylation.jpg|600 px|thumb|center|'''Figure 3:'''PP1C dephosphorylates RAF protein at serine 259 ]]
=Disease Relevance=

==RASopathies==

RASopathy is a broad term used to describe developmental syndromes that stem from [https://www.sciencedirect.com/topics/medicine-and-dentistry/germline-mutation. germline mutations] of proteins along the RAS/MAPK pathway such as SHOC2, PP1C, and MRAS. These mutations can be either gain or loss of function. Rasopathies can also lead to cancer <ref name=”Rauen”>Rauen KA. The RASopathies. Annu Rev Genomics Hum Genet. 2013;14:355-69. [http://dx.doi.org/10.1146/annurev-genom-091212-153523 doi: 10.1146/annurev-genom-091212-153523.]</ref>.

==Cancer==

Because the RAS/MAPK pathway activated by SMP regulates cell proliferation and survival, overactivity can cause tumor formation and cancer. For example, the complex has been found to play a role in the perpetuation of melanoma, leukemia, and lung cancer.

=Future Studies=

Further study of the SMP complex includes clarification of the steps of the pathway. Firstly, the order of binding to form the SMP complex is unclear. Furthermore, the interaction between SMP and the Raf complex is largely unknown. Study into this step is especially important to understand how SMP activates downstream signaling.
The current knowledge of SMP can be used to study possible treatments for rasopathies and cancer. For example, the development of inhibitors that target SMP binding could prevent the effects caused by mutations that overactivate SMP. Another possible point of inhibition is the growth factor that signals SHOC2-PP1C and Raf to the cell membrane. <ref name="Liau" /> .

=References=

<references/>

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Madeline Gilbert
Inaya Patel
Rushda Hussein

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<StructureSection load='7pui' size='350' side='right' caption='SHOC2-PP1C-MRAS (PDB entry [[7upi]])' scene='95/952718/Mras/2'>>

=SHOC2-PP1C-MRAS=

=Introduction=
[[Image:SMP complex.jpg|300 px|right|thumb|'''Figure 1:'''Overall cartoon of SHOC2-PP1C-MRAS structure with SHOC2 in pink, PP1C in blue, and MRAs in white.</div>]]
<scene name='95/952718/Zoom_out/1'>SHOC2-PP1C-MRAS</scene> (SMP) is a ternary complex formed by the individual proteins: SHOC2, PP1C, and MRAS. Formation of this complex begins with a signal binding to a receptor tyrosine kinase receptor(RTK). This causes membrane bound MRAS to exchange GDP for GTP. From here the complex comes together and is able to dephosphorylate the RAF complex leading to further downstream signaling effects <ref name=”Hauseman”>PMID:35830882</ref>.

=Overall Structure=

==SHOC2==
<scene name='95/952717/Shoc2/1'>SHOC2</scene> is a scaffold protein that is composed of 20 leucine-rich repeat domains that form a solenoid structure. The leucine rich region forms a concave hydrophobic core which is necessary for binding with PP1C and MRAS.
==PP1C==
<scene name='95/952717/Pp1c/1'>PP1C</scene> is a catalytic protein. After forming a ternary complex, the <scene name='95/952717/Pp1c_hydrophobic_patch/1'>hydrophobic active site</scene> on the protein interacts with Raf to act as a phosphatase and dephosphorylate Ser 259.
[[Image:ActiveSiteProto.png|500 px|thumb|'''Figure 2:'''Active site of PP1C on SMP.</div>]]
==MRAS==
<scene name='95/952717/Mras/2'>MRAS</scene> is a membrane bound structure that aids the complex in localizing near other structures such as the RAS-RAF-MAPK complex in order to initiate downstream signaling. In its inactive state, MRAS is bound to GDP. When signaled by [https://www.ncbi.nlm.nih.gov/books/NBK442024/. growth factors], the GDP is exchanged for GTP. The now <scene name='95/952718/Zoom_in_gtp/1'>GTP bound MRAS</scene> undergoes a conformational change of the <scene name='95/952716/Ras-switch-zoomed/1'>switch I and switch II regions</scene>. This conformational change activates the protein allowing it to bind more easily with the SHOC2-PP1C complex. In comparison to other RAS proteins, MRAS has a greater affinity for the SHOC2-PP1C complex <ref name=”Kubicek”>PMID:11756411</ref>.
[[Image:Switches.png|500 px|thumb|'''Figure 2:'''Steric clashing of Switch I and II of GDP bound MRAS, in green, with the surface of SHOC2, in magenta. GTP-bound MRAS, in white, shows no steric clashing with SHOC2s surface.</div>]]

=Key Ligand Interactions=

==SHOC2 and PP1C==

<scene name='95/952717/Shoc2_and_pp1c/1'>PP1C binds to SHOC2</scene> on its leucine rich region(LRR). Specifically, on two broad surfaces between LRR2 and LRR5 and between LRR7 and LRR11. Mutations made to the LRR were shown to completely inhibit the binding of PP1C. Five main <scene name='95/952717/Shoc2_and_pp1c/2'>hydrogen bonds</scene> are made: E56-R182, E167-R203, E54-K180, R187-H178, R188-E155. The binding regions can also be shown as acidic and basic patches on <scene name='95/952718/Acid_base_pp1c/1'>PP1C</scene> and <scene name='95/952718/Acid_base_shoc2/1'>SHOC2</scene>. The corresponding patches interact to form a <scene name='95/952718/Acid_base_shoc2pp1c/1'>binary complex</scene>. These interactions do not result in significant conformational changes <ref name=”Kwon”>PMID:35831509</ref>.

==SHOC2 and MRAS==
MRAS is initially bound to GDP causing it to be in its inactive state. This form cannot bind to the SHOC2-PP1C complex due to steric clashing. Once GDP is exchanged for GTP to activate the protein, <scene name='95/952716/conformational changes/1'>SHOC2-MRAS (residues)</scene> occur within the switch I and switch II regions to allow <scene name='95/952716/MRAS to interact with SHOC2/2'>SHOC2-MRAS(full-image)</scene>. These <scene name='95/952716/Scho2-mras-interactions/1'>interactions</scene> include hydrogen bonds and pi stacking. The primary hydrogen bonds are R288-Q71 and R177-E47. Pi staking occurs at R104-R83 <ref name=”Lavoie”>PMID:35970881</ref>.

==PP1C and MRAS==
The interactions between <scene name='95/952717/Mras_and_pp1c/1'>PP1C and MRAS</scene> are mediated by four main <scene name='95/952717/Mras_and_pp1c/4'>hydrogen bonds</scene>: R188-D48, M190-Q35, D197-H53, Q198-K36. It is unclear whether PP1C must bind to SHOC2 before MRAS binds or if PP1C and MRAS can bind to SHOC2 at the same time.
=Signaling Pathway=
The SMP signaling pathway begins with the formation of the SMP complex. Initially, a ligand must bind to a receptor tyrosine kinase. This signals SHOC2 to bind to PP1C forming a binary complex that then binds to the membrane bound MRAS. Some literature indicates that the three proteins bind at the same time but the order is largely unknown. Figure 2 shows the proteins binding one at a time. Once the SMP complex forms, its target is the N-terminal phosphoserine (NTpS) also known as S259. The serine is directly dephosphorylated by PP1C by SHOC2 and MRAS increase its specificity for S259.
Mutations affecting SMP complex formation and stability have been shown to increase or decrease MAPK signaling. Increased stability of the complex increases MAPK signaling while decreased stability decreases signaling<ref name=”Liau”>PMID:35768504</ref>.

[[Image:Signal_cascade_small.jpg|800 px|thumb|center|'''Figure 2:'''Signaling cascade is shown with SHOC2 in pink, PP1C in blue, and MRAs in white. ]]

[[Image:Dephosphorylation.jpg|600 px|thumb|center|'''Figure 3:'''PP1C dephosphorylates RAF protein at serine 259 ]]
=Disease Relevance=

==RASopathies==

RASopathy is a broad term used to describe developmental syndromes that stem from [https://www.sciencedirect.com/topics/medicine-and-dentistry/germline-mutation. germline mutations] of proteins along the RAS/MAPK pathway such as SHOC2, PP1C, and MRAS. These mutations can be either gain or loss of function. Rasopathies can also lead to cancer <ref name=”Rauen”>PMID:23875798</ref>.

==Cancer==

Because the RAS/MAPK pathway activated by SMP regulates cell proliferation and survival, overactivity can cause tumor formation and cancer. For example, the complex has been found to play a role in the perpetuation of melanoma, leukemia, and lung cancer.

=Future Studies=

Further study of the SMP complex includes clarification of the steps of the pathway. Firstly, the order of binding to form the SMP complex is unclear. Furthermore, the interaction between SMP and the Raf complex is largely unknown. Study into this step is especially important to understand how SMP activates downstream signaling.
The current knowledge of SMP can be used to study possible treatments for rasopathies and cancer. For example, the development of inhibitors that target SMP binding could prevent the effects caused by mutations that overactivate SMP. Another possible point of inhibition is the growth factor that signals SHOC2-PP1C and Raf to the cell membrane.

=References=

<references/>

==Student Contributors==
Madeline Gilbert
Inaya Patel
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2023-04-07T15:58:24Z

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<StructureSection load='7pui' size='350' side='right' caption='SHOC2-PP1C-MRAS (PDB entry [[7upi]])' scene='95/952718/Mras/2'>>

=SHOC2-PP1C-MRAS=

=Introduction=
[[Image:SMP complex.jpg|300 px|right|thumb|'''Figure 1:'''Overall cartoon of SHOC2-PP1C-MRAS structure with SHOC2 in pink, PP1C in blue, and MRAs in white.</div>]]
<scene name='95/952718/Zoom_out/1'>SHOC2-PP1C-MRAS</scene> (SMP) is a ternary complex formed by the individual proteins: SHOC2, PP1C, and MRAS. Formation of this complex begins with a signal binding to a receptor tyrosine kinase receptor(RTK). This causes membrane bound MRAS to exchange GDP for GTP. From here the complex comes together and is able to dephosphorylate the RAF complex leading to further downstream signaling effects <ref name=”Hauseman”>PMID:35830882</ref>.

=Overall Structure=

==SHOC2==
<scene name='95/952717/Shoc2/1'>SHOC2</scene> is a scaffold protein that is composed of 20 leucine-rich repeat domains that form a solenoid structure. The leucine rich region forms a concave hydrophobic core which is necessary for binding with PP1C and MRAS.
==PP1C==
<scene name='95/952717/Pp1c/1'>PP1C</scene> is a catalytic protein. After forming a ternary complex, the <scene name='95/952717/Pp1c_hydrophobic_patch/1'>hydrophobic active site</scene> on the protein interacts with Raf to act as a phosphatase and dephosphorylate Ser 259.
==MRAS==
<scene name='95/952717/Mras/2'>MRAS</scene> is a membrane bound structure that aids the complex in localizing near other structures such as the RAS-RAF-MAPK complex in order to initiate downstream signaling. In its inactive state, MRAS is bound to GDP. When signaled by [https://www.ncbi.nlm.nih.gov/books/NBK442024/. growth factors], the GDP is exchanged for GTP. The now <scene name='95/952718/Zoom_in_gtp/1'>GTP bound MRAS</scene> undergoes a conformational change of the <scene name='95/952716/Ras-switch-zoomed/1'>switch I and switch II regions</scene>. This conformational change activates the protein allowing it to bind more easily with the SHOC2-PP1C complex. In comparison to other RAS proteins, MRAS has a greater affinity for the SHOC2-PP1C complex <ref name=”Kubicek”>PMID:11756411</ref>.

=Key Ligand Interactions=

==SHOC2 and PP1C==

<scene name='95/952717/Shoc2_and_pp1c/1'>PP1C binds to SHOC2</scene> on its leucine rich region(LRR). Specifically, on two broad surfaces between LRR2 and LRR5 and between LRR7 and LRR11. Mutations made to the LRR were shown to completely inhibit the binding of PP1C. Five main <scene name='95/952717/Shoc2_and_pp1c/2'>hydrogen bonds</scene> are made: E56-R182, E167-R203, E54-K180, R187-H178, R188-E155. The binding regions can also be shown as acidic and basic patches on <scene name='95/952718/Acid_base_pp1c/1'>PP1C</scene> and <scene name='95/952718/Acid_base_shoc2/1'>SHOC2</scene>. The corresponding patches interact to form a <scene name='95/952718/Acid_base_shoc2pp1c/1'>binary complex</scene>. These interactions do not result in significant conformational changes <ref name=”Kwon”>PMID:35831509</ref>.

==SHOC2 and MRAS==
MRAS is initially bound to GDP causing it to be in its inactive state. This form cannot bind to the SHOC2-PP1C complex due to steric clashing. Once GDP is exchanged for GTP to activate the protein, <scene name='95/952716/conformational changes/1'>SHOC2-MRAS (residues)</scene> occur within the switch I and switch II regions to allow <scene name='95/952716/MRAS to interact with SHOC2/2'>SHOC2-MRAS(full-image)</scene>. These <scene name='95/952716/Scho2-mras-interactions/1'>interactions</scene> include hydrogen bonds and pi stacking. The primary hydrogen bonds are R288-Q71 and R177-E47. Pi staking occurs at R104-R83 <ref name=”Lavoie”>PMID:35970881</ref>.

==PP1C and MRAS==
The interactions between <scene name='95/952717/Mras_and_pp1c/1'>PP1C and MRAS</scene> are mediated by four main <scene name='95/952717/Mras_and_pp1c/4'>hydrogen bonds</scene>: R188-D48, M190-Q35, D197-H53, Q198-K36. It is unclear whether PP1C must bind to SHOC2 before MRAS binds or if PP1C and MRAS can bind to SHOC2 at the same time.
=Signaling Pathway=
The SMP signaling pathway begins with the formation of the SMP complex. Initially, a ligand must bind to a receptor tyrosine kinase. This signals SHOC2 to bind to PP1C forming a binary complex that then binds to the membrane bound MRAS. Some literature indicates that the three proteins bind at the same time but the order is largely unknown. Figure 2 shows the proteins binding one at a time. Once the SMP complex forms, its target is the N-terminal phosphoserine (NTpS) also known as S259. The serine is directly dephosphorylated by PP1C by SHOC2 and MRAS increase its specificity for S259.
Mutations affecting SMP complex formation and stability have been shown to increase or decrease MAPK signaling. Increased stability of the complex increases MAPK signaling while decreased stability decreases signaling<ref name=”Liau”>PMID:35768504</ref>.

[[Image:Signal_cascade_small.jpg|800 px|thumb|center|'''Figure 2:'''Signaling cascade is shown with SHOC2 in pink, PP1C in blue, and MRAs in white. ]]

[[Image:Dephosphorylation.jpg|600 px|thumb|center|'''Figure 3:'''PP1C dephosphorylates RAF protein at serine 259 ]]
=Disease Relevance=

==RASopathies==

RASopathy is a broad term used to describe developmental syndromes that stem from [https://www.sciencedirect.com/topics/medicine-and-dentistry/germline-mutation. germline mutations] of proteins along the RAS/MAPK pathway such as SHOC2, PP1C, and MRAS. These mutations can be either gain or loss of function. Rasopathies can also lead to cancer <ref name=”Rauen”>PMID:23875798</ref>.

==Cancer==

Because the RAS/MAPK pathway activated by SMP regulates cell proliferation and survival, overactivity can cause tumor formation and cancer. For example, the complex has been found to play a role in the perpetuation of melanoma, leukemia, and lung cancer.

=Future Studies=

Further study of the SMP complex includes clarification of the steps of the pathway. Firstly, the order of binding to form the SMP complex is unclear. Furthermore, the interaction between SMP and the Raf complex is largely unknown. Study into this step is especially important to understand how SMP activates downstream signaling.
The current knowledge of SMP can be used to study possible treatments for rasopathies and cancer. For example, the development of inhibitors that target SMP binding could prevent the effects caused by mutations that overactivate SMP. Another possible point of inhibition is the growth factor that signals SHOC2-PP1C and Raf to the cell membrane.

=References=

<references/>

==Student Contributors==
Madeline Gilbert
Inaya Patel
Rushda Hussein

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2023-04-07T15:39:02Z

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<StructureSection load='7pui' size='350' side='right' caption='SHOC2-PP1C-MRAS (PDB entry [[7upi]])' scene='95/952718/Smpcomplex/2'>

=SHOC2-PP1C-MRAS=

=Introduction=
[[Image:SMP complex.jpg|300 px|right|thumb|'''Figure 1:'''Overall cartoon of SHOC2-PP1C-MRAS structure with SHOC2 in pink, PP1C in blue, and MRAs in white.</div>]]
<scene name='95/952718/Zoom_out/1'>SHOC2-PP1C-MRAS</scene> (SMP) is a ternary complex formed by the individual proteins: SHOC2, PP1C, and MRAS. Formation of this complex begins with a signal binding to a receptor tyrosine kinase receptor(RTK). This causes membrane bound MRAS to exchange GDP for GTP. From here the complex comes together and is able to dephosphorylate the RAF complex leading to further downstream signaling effects <ref name=”Hauseman”>PMID:35830882</ref>.

=Overall Structure=

==SHOC2==
<scene name='95/952717/Shoc2/1'>SHOC2</scene> is a scaffold protein that is composed of 20 leucine-rich repeat domains that form a solenoid structure. The leucine rich region forms a concave hydrophobic core which is necessary for binding with PP1C and MRAS.
==PP1C==
<scene name='95/952717/Pp1c/1'>PP1C</scene> is a catalytic protein. After forming a ternary complex, the <scene name='95/952717/Pp1c_hydrophobic_patch/1'>hydrophobic active site</scene> on the protein interacts with Raf to act as a phosphatase and dephosphorylate Ser 259.
==MRAS==
<scene name='95/952717/Mras/2'>MRAS</scene> is a membrane bound structure that aids the complex in localizing near other structures such as the RAS-RAF-MAPK complex in order to initiate downstream signaling. In its inactive state, MRAS is bound to GDP. When signaled by [https://www.ncbi.nlm.nih.gov/books/NBK442024/. growth factors], the GDP is exchanged for GTP. The now <scene name='95/952718/Zoom_in_gtp/1'>GTP bound MRAS</scene> undergoes a conformational change of the <scene name='95/952716/Ras-switch-zoomed/1'>switch I and switch II regions</scene>. This conformational change activates the protein allowing it to bind more easily with the SHOC2-PP1C complex. In comparison to other RAS proteins, MRAS has a greater affinity for the SHOC2-PP1C complex <ref name=”Kubicek”>PMID:11756411</ref>.

=Key Ligand Interactions=

==SHOC2 and PP1C==

<scene name='95/952717/Shoc2_and_pp1c/1'>PP1C binds to SHOC2</scene> on its leucine rich region(LRR). Specifically, on two broad surfaces between LRR2 and LRR5 and between LRR7 and LRR11. Mutations made to the LRR were shown to completely inhibit the binding of PP1C. Five main <scene name='95/952717/Shoc2_and_pp1c/2'>hydrogen bonds</scene> are made: E56-R182, E167-R203, E54-K180, R187-H178, R188-E155. The binding regions can also be shown as acidic and basic patches on <scene name='95/952718/Acid_base_pp1c/1'>PP1C</scene> and <scene name='95/952718/Acid_base_shoc2/1'>SHOC2</scene>. The corresponding patches interact to form a <scene name='95/952718/Acid_base_shoc2pp1c/1'>binary complex</scene>. These interactions do not result in significant conformational changes <ref name=”Kwon”>PMID:35831509</ref>.

==SHOC2 and MRAS==
MRAS is initially bound to GDP causing it to be in its inactive state. This form cannot bind to the SHOC2-PP1C complex due to steric clashing. Once GDP is exchanged for GTP to activate the protein, <scene name='95/952716/conformational changes/1'>SHOC2-MRAS (residues)</scene> occur within the switch I and switch II regions to allow <scene name='95/952716/MRAS to interact with SHOC2/2'>SHOC2-MRAS(full-image)</scene>. These <scene name='95/952716/Scho2-mras-interactions/1'>interactions</scene> include hydrogen bonds and pi stacking. The primary hydrogen bonds are R288-Q71 and R177-E47. Pi staking occurs at R104-R83 <ref name=”Lavoie”>PMID:35970881</ref>.

==PP1C and MRAS==
The interactions between <scene name='95/952717/Mras_and_pp1c/1'>PP1C and MRAS</scene> are mediated by four main <scene name='95/952717/Mras_and_pp1c/4'>hydrogen bonds</scene>: R188-D48, M190-Q35, D197-H53, Q198-K36. It is unclear whether PP1C must bind to SHOC2 before MRAS binds or if PP1C and MRAS can bind to SHOC2 at the same time.
=Signaling Pathway=
The SMP signaling pathway begins with the formation of the SMP complex. Initially, a ligand must bind to a receptor tyrosine kinase. This signals SHOC2 to bind to PP1C forming a binary complex that then binds to the membrane bound MRAS. Some literature indicates that the three proteins bind at the same time but the order is largely unknown. Figure 2 shows the proteins binding one at a time. Once the SMP complex forms, its target is the N-terminal phosphoserine (NTpS) also known as S259. The serine is directly dephosphorylated by PP1C by SHOC2 and MRAS increase its specificity for S259.
Mutations affecting SMP complex formation and stability have been shown to increase or decrease MAPK signaling. Increased stability of the complex increases MAPK signaling while decreased stability decreases signaling<ref name=”Liau”>PMID:35768504</ref>.

[[Image:Signal_cascade_small.jpg|800 px|thumb|center|'''Figure 2:'''Signaling cascade is shown with SHOC2 in pink, PP1C in blue, and MRAs in white. ]]

[[Image:Dephosphorylation.jpg|600 px|thumb|center|'''Figure 3:'''PP1C dephosphorylates RAF protein at serine 259 ]]
=Disease Relevance=

==RASopathies==

RASopathy is a broad term used to describe developmental syndromes that stem from [https://www.sciencedirect.com/topics/medicine-and-dentistry/germline-mutation. germline mutations] of proteins along the RAS/MAPK pathway such as SHOC2, PP1C, and MRAS. These mutations can be either gain or loss of function. Rasopathies can also lead to cancer <ref name=”Rauen”>PMID:23875798</ref>.

==Cancer==

Because the RAS/MAPK pathway activated by SMP regulates cell proliferation and survival, overactivity can cause tumor formation and cancer. For example, the complex has been found to play a role in the perpetuation of melanoma, leukemia, and lung cancer.

=Future Studies=

Further study of the SMP complex includes clarification of the steps of the pathway. Firstly, the order of binding to form the SMP complex is unclear. Furthermore, the interaction between SMP and the Raf complex is largely unknown. Study into this step is especially important to understand how SMP activates downstream signaling.
The current knowledge of SMP can be used to study possible treatments for rasopathies and cancer. For example, the development of inhibitors that target SMP binding could prevent the effects caused by mutations that overactivate SMP. Another possible point of inhibition is the growth factor that signals SHOC2-PP1C and Raf to the cell membrane.

=References=

<references/>

==Student Contributors==
Madeline Gilbert
Inaya Patel
Rushda Hussein

[[Category:Featured in BAMBED]]
[[Category:Topic Page]]

Sandbox Reserved 1790

2023-04-07T15:18:32Z

Rushda Hussein:

<StructureSection load='7pui' size='350' side='right' caption='SHOC2-PP1C-MRAS (PDB entry [[7upi]])' scene='95/952718/Smpcomplex/2'>

=SHOC2-PP1C-MRAS=

=Introduction=
[[Image:SMP complex.jpg|300 px|right|thumb|'''Figure 1:'''Overall cartoon of SHOC2-PP1C-MRAS structure with SHOC2 in pink, PP1C in blue, and MRAs in white.</div>]]
<scene name='95/952718/Zoom_out/1'>SHOC2-PP1C-MRAS</scene> (SMP) is a ternary complex formed by the individual proteins: SHOC2, PP1C, and MRAS. Formation of this complex begins with a signal binding to a receptor tyrosine kinase receptor(RTK). This causes membrane bound MRAS to exchange GDP for GTP. From here the complex comes together and is able to dephosphorylate the RAF complex leading to further downstream signaling effects.

=Overall Structure=

==SHOC2==
<scene name='95/952717/Shoc2/1'>SHOC2</scene> is a scaffold protein that is composed of 20 leucine-rich repeat domains that form a solenoid structure. The leucine rich region forms a concave hydrophobic core which is necessary for binding with PP1C and MRAS.
==PP1C==
<scene name='95/952717/Pp1c/1'>PP1C</scene> is a catalytic protein. After forming a ternary complex, the <scene name='95/952717/Pp1c_hydrophobic_patch/1'>hydrophobic active site</scene> on the protein interacts with Raf to act as a phosphatase and dephosphorylate Ser 259<ref>PMID:35830882</ref>..
==MRAS==
<scene name='95/952717/Mras/2'>MRAS</scene> is a membrane bound structure that aids the complex in localizing near other structures such as the RAS-RAF-MAPK complex in order to initiate downstream signaling. In its inactive state, MRAS is bound to GDP. When signaled by [https://www.ncbi.nlm.nih.gov/books/NBK442024/. growth factors], the GDP is exchanged for GTP. The now <scene name='95/952718/Zoom_in_gtp/1'>GTP bound MRAS</scene> undergoes a conformational change of the <scene name='95/952716/Ras-switch-zoomed/1'>switch I and switch II regions</scene>. This conformational change activates the protein allowing it to bind more easily with the SHOC2-PP1C complex. In comparison to other RAS proteins, MRAS has a greater affinity for the SHOC2-PP1C complex<ref>PMID:35970881</ref>.

=Key Ligand Interactions=

==SHOC2 and PP1C==

<scene name='95/952717/Shoc2_and_pp1c/1'>PP1C binds to SHOC2</scene> on its leucine rich region(LRR). Specifically, on two broad surfaces between LRR2 and LRR5 and between LRR7 and LRR11. Mutations made to the LRR were shown to completely inhibit the binding of PP1C. Five main <scene name='95/952717/Shoc2_and_pp1c/2'>hydrogen bonds</scene> are made: E56-R182, E167-R203, E54-K180, R187-H178, R188-E155. The binding regions can also be shown as acidic and basic patches on <scene name='95/952718/Acid_base_pp1c/1'>PP1C</scene> and <scene name='95/952718/Acid_base_shoc2/1'>SHOC2</scene>. The corresponding patches interact to form a <scene name='95/952718/Acid_base_shoc2pp1c/1'>binary complex</scene>. These interactions do not result in significant conformational changes.

==SHOC2 and MRAS==
MRAS is initially bound to GDP causing it to be in its inactive state. This form cannot bind to the SHOC2-PP1C complex due to steric clashing. Once GDP is exchanged for GTP to activate the protein, <scene name='95/952716/conformational changes/1'>SHOC2-MRAS (residues)</scene> occur within the switch I and switch II regions to allow <scene name='95/952716/MRAS to interact with SHOC2/2'>SHOC2-MRAS(full-image)</scene>. These <scene name='95/952716/Scho2-mras-interactions/1'>interactions</scene> include hydrogen bonds and pi stacking. The primary hydrogen bonds are R288-Q71 and R177-E47. Pi staking occurs at R104-R83.

==PP1C and MRAS==
The interactions between <scene name='95/952717/Mras_and_pp1c/1'>PP1C and MRAS</scene> are mediated by four main <scene name='95/952717/Mras_and_pp1c/4'>hydrogen bonds</scene>: R188-D48, M190-Q35, D197-H53, Q198-K36. It is unclear whether PP1C must bind to SHOC2 before MRAS binds or if PP1C and MRAS can bind to SHOC2 at the same time.
=Signaling Pathway=
The SMP signaling pathway begins with the formation of the SMP complex. Initially, a ligand must bind to a receptor tyrosine kinase. This signals SHOC2 to bind to PP1C forming a binary complex that then binds to the membrane bound MRAS. Some literature indicates that the three proteins bind at the same time but the order is largely unknown. Figure 2 shows the proteins binding one at a time. Once the SMP complex forms, its target is the N-terminal phosphoserine (NTpS) also known as S259. The serine is directly dephosphorylated by PP1C by SHOC2 and MRAS increase its specificity for S259.
Mutations affecting SMP complex formation and stability have been shown to increase or decrease MAPK signaling. Increased stability of the complex increases MAPK signaling while decreased stability decreases signaling.

[[Image:Signal_cascade_small.jpg|800 px|thumb|center|'''Figure 2:'''Signaling cascade is shown with SHOC2 in pink, PP1C in blue, and MRAs in white. ]]

[[Image:Dephosphorylation.jpg|600 px|thumb|center|'''Figure 3:'''PP1C dephosphorylates RAF protein at serine 259 ]]
=Disease Relevance=

==RASopathies==

RASopathy is a broad term used to describe developmental syndromes that stem from [https://www.sciencedirect.com/topics/medicine-and-dentistry/germline-mutation. germline mutations] of proteins along the RAS/MAPK pathway such as SHOC2, PP1C, and MRAS. These mutations can be either gain or loss of function. Rasopathies can also lead to cancer<ref>PMID:23875798</ref>.

==Cancer==

Because the RAS/MAPK pathway activated by SMP regulates cell proliferation and survival, overactivity can cause tumor formation and cancer. For example, the complex has been found to play a role in the perpetuation of melanoma, leukemia, and lung cancer.

=Future Studies=

Further study of the SMP complex includes clarification of the steps of the pathway. Firstly, the order of binding to form the SMP complex is unclear. Furthermore, the interaction between SMP and the Raf complex is largely unknown. Study into this step is especially important to understand how SMP activates downstream signaling.
The current knowledge of SMP can be used to study possible treatments for rasopathies and cancer. For example, the development of inhibitors that target SMP binding could prevent the effects caused by mutations that overactivate SMP. Another possible point of inhibition is the growth factor that signals SHOC2-PP1C and Raf to the cell membrane.

=References=

<ref name=”Hauseman”>PMID:35830882</ref>.
<ref name=”Kubicek”>PMID:11756411</ref>.
<ref name=”Kwon”>PMID:35831509</ref>.
<ref name=”Lavoie”>PMID:35970881</ref>.
<ref name=”Liau”>PMID:35768504</ref>.
<ref name=”Rauen”>PMID:23875798</ref>.

<references/>

==Student Contributors==
Madeline Gilbert
Inaya Patel
Rushda Hussein

[[Category:Featured in BAMBED]]
[[Category:Topic Page]]

Sandbox Reserved 1789

2023-04-07T14:40:15Z

Rushda Hussein:

{{BAMBED
|DATE=June 14, 2016
|OLDID=2607465
|BAMBEDDOI=10.1002/bmb.21026
}}

==SHOC2-PP1C-MRAS==
<StructureSection load='7UPI' size='340' side='right' caption='SHOC2-MRAS-PP1C'>

== Introduction ==
'''Receptor Tyrosine Kinase Receptor'''
*[[Lipid signaling]]
*[[Transmembrane (cell surface) receptors]]

[[Image:Mechanism.png|200px|center|thumb|Figure 1: Mechanism for Shoc2-MRAS-PP1C]]
[[Image:Phosphorylation.png|200px|center|thumb|Figure 2: PP1C phosphorylates Serine 259.]]

== Overall Structure ==
=== SHOC2 ===
<scene name='95/952717/Shoc2/1'>SHOC2</scene>
=== PP1C ===
<scene name='95/952717/Pp1c/1'>PP1C</scene>
=== MRAS ===
<scene name='95/952717/Mras/2'>MRAS</scene>
<scene name='95/952716/Gtp/1'>GTP-MRAS(full-image)</scene>
<scene name='95/952716/Gtp/1'>GTP-MRAS(zoomed-in)</scene>
<scene name='95/952716/Ras-swtich/2'>Switch I-II (full-image)</scene>
<scene name='95/952716/Ras-switch-zoomed/1'>Switch I-II (zoomed-in)</scene>
=== Key Ligand Interactions ===
[[Image:Amphbindingfinal.png|275 px|right|thumb|'''Figure 3''': Electrostatic illustration of the amphipathic binding pocket of the LPA1 receptor. This binding pocket was revealed by cutting away the exterior or the protein. This binding pocket, located in the interior of the protein, has both polar and nonpolar regions. The blue and red coloration highlight the positively and negatively charged regions, respectively, and the white color shows the nonpolar region of the binding pocket.]]

=== SHOC2 and PP1C ===
<scene name='95/952717/Shoc2_and_pp1c/1'>Shoc2-PP1C</scene>
<scene name='95/952717/Shoc2_and_pp1c/2'>SHOC2-PP1C Binding Pocket</scene>
=== SHOC2 and MRAS ===
<scene name='95/952716/Scho2-mras-interactions/2'>SHOC2-MRAS(full-image)</scene>
<scene name='95/952716/Scho2-mras-interactions/1'>SHOC2-MRAS (residues)</scene>
<scene name='95/952716/Scho2-mras-interactions/3'>SHOC2-MRAS (surface)</scene>
=== PP1C and MRAS ===
<scene name='95/952717/Mras_and_pp1c/1'>PP1C (blue) and MRAS (white)</scene>

<scene name='95/952717/Mras_and_pp1c/4'>PP1C and MRAS residue interactions</scene>

== Signaling Pathway ==

<scene name='95/952717/Pp1c_hydrophobic_patch/1'>PP1C Hydrophobic Patch and Active Site</scene>

== Disease Relevance ==

=== Cancer ===

=== RASopathies===

== Future Studies ==

==3D structures of lysophosphatidic acid receptor==

[[4z34]], [[4z35]], [[4z36]] - hLPA1 + antagonist - human 
[[2lq4]] – hLPA1 second extracellular loop – NMR 
[[4p0c]] – hLPA2/NHERF2 
[[5xsz]] – LPA6A (mutant) – zebra fish 

== References ==
<references/>
==Proteopedia Resources==
[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid_binding Category:Lysophosphatidic acid binding]

[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid Category:Lysophosphatidic acid]

[http://proteopedia.org/wiki/index.php/User:R._Jeremy_Johnson/CH462:Biochemistry_II_Butler_University Butler University Proteopedia Pages]

See also:
*[[Receptor]]
*[[Transmembrane (cell surface) receptors]]
*[[G protein-coupled receptors]]
</StructureSection>
==Student Contributors==
Madeline Gilbert
Inaya Patel
Rushda Hussein

[[Category:Featured in BAMBED]]
[[Category:Topic Page]]

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{{BAMBED
|DATE=June 14, 2016
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}}

==SHOC2-PP1C-MRAS==
<StructureSection load='7UPI' size='340' side='right' caption='SHOC2-MRAS-PP1C'>

== Introduction ==
'''Receptor Tyrosine Kinase Receptor'''
*[[Lipid signaling]]
*[[Transmembrane (cell surface) receptors]]

[[Image:Mechanism.png|200px|center|thumb|Figure 1: Mechanism for Shoc2-MRAS-PP1C]]
[[Image:Phosphorylation.png|200px|center|thumb|Figure 2: PP1C phosphorylates Serine 259.]]

== Overall Structure ==
=== SHOC2 ===
<scene name='95/952717/Shoc2/1'>SHOC2</scene>
=== PP1C ===
<scene name='95/952717/Pp1c/1'>PP1C</scene>
=== MRAS ===
<scene name='95/952717/Mras/2'>MRAS</scene>

=== Key Ligand Interactions ===
[[Image:Amphbindingfinal.png|275 px|right|thumb|'''Figure 3''': Electrostatic illustration of the amphipathic binding pocket of the LPA1 receptor. This binding pocket was revealed by cutting away the exterior or the protein. This binding pocket, located in the interior of the protein, has both polar and nonpolar regions. The blue and red coloration highlight the positively and negatively charged regions, respectively, and the white color shows the nonpolar region of the binding pocket.]]

=== SHOC2 and PP1C ===
<scene name='95/952717/Shoc2_and_pp1c/1'>Shoc2-PP1C</scene>
<scene name='95/952717/Shoc2_and_pp1c/2'>SHOC2-PP1C Binding Pocket</scene>
=== SHOC2 and MRAS ===

=== PP1C and MRAS ===

== Signaling Pathway ==

<scene name='95/952717/Pp1c_hydrophobic_patch/1'>PP1C Hydrophobic Patch and Active Site</scene>

== Disease Relevance ==

=== Cancer ===

=== RASopathies===

== Future Studies ==

==3D structures of lysophosphatidic acid receptor==

[[4z34]], [[4z35]], [[4z36]] - hLPA1 + antagonist - human 
[[2lq4]] – hLPA1 second extracellular loop – NMR 
[[4p0c]] – hLPA2/NHERF2 
[[5xsz]] – LPA6A (mutant) – zebra fish 

== References ==
<references/>
==Proteopedia Resources==
[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid_binding Category:Lysophosphatidic acid binding]

[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid Category:Lysophosphatidic acid]

[http://proteopedia.org/wiki/index.php/User:R._Jeremy_Johnson/CH462:Biochemistry_II_Butler_University Butler University Proteopedia Pages]

See also:
*[[Receptor]]
*[[Transmembrane (cell surface) receptors]]
*[[G protein-coupled receptors]]
</StructureSection>
==Student Contributors==
Madeline Gilbert
Inaya Patel
Rushda Hussein

[[Category:Featured in BAMBED]]
[[Category:Topic Page]]

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}}

==SHOC2-PP1C-MRAS==
<StructureSection load='7UPI' size='340' side='right' caption='SHOC2-MRAS-PP1C'>

== Introduction ==
'''Receptor Tyrosine Kinase Receptor'''
*[[Lipid signaling]]
*[[Transmembrane (cell surface) receptors]]

[[Image:Mechanism.png|200px|center|thumb|Figure 1: Mechanism for Shoc2-MRAS-PP1C]]
[[Image:Phosphorylation.png|200px|center|thumb|Figure 2: PP1C phosphorylates Serine 259.]]

== Overall Structure ==
=== SHOC2 ===
<scene name='95/952717/Shoc2/1'>SHOC2</scene>
=== PP1C ===
<scene name='95/952717/Pp1c/1'>PP1C</scene>
=== MRAS ===
<scene name='95/952717/Mras/2'>MRAS</scene>

=== Key Ligand Interactions ===
[[Image:Amphbindingfinal.png|275 px|right|thumb|'''Figure 3''': Electrostatic illustration of the amphipathic binding pocket of the LPA1 receptor. This binding pocket was revealed by cutting away the exterior or the protein. This binding pocket, located in the interior of the protein, has both polar and nonpolar regions. The blue and red coloration highlight the positively and negatively charged regions, respectively, and the white color shows the nonpolar region of the binding pocket.]]

=== SHOC2 and PP1C ===
<scene name='95/952717/Shoc2_and_pp1c/1'>Shoc2-PP1C</scene>
<scene name='95/952717/Shoc2_and_pp1c/2'>SHOC2-PP1C Binding Pocket</scene>
=== SHOC2 and MRAS ===

=== PP1C and MRAS ===

== Signaling Pathway ==

== Disease Relevance ==

=== Cancer ===

=== RASopathies===

== Future Studies ==

==3D structures of lysophosphatidic acid receptor==

[[4z34]], [[4z35]], [[4z36]] - hLPA1 + antagonist - human 
[[2lq4]] – hLPA1 second extracellular loop – NMR 
[[4p0c]] – hLPA2/NHERF2 
[[5xsz]] – LPA6A (mutant) – zebra fish 

== References ==
<references/>
==Proteopedia Resources==
[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid_binding Category:Lysophosphatidic acid binding]

[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid Category:Lysophosphatidic acid]

[http://proteopedia.org/wiki/index.php/User:R._Jeremy_Johnson/CH462:Biochemistry_II_Butler_University Butler University Proteopedia Pages]

See also:
*[[Receptor]]
*[[Transmembrane (cell surface) receptors]]
*[[G protein-coupled receptors]]
</StructureSection>
==Student Contributors==
Madeline Gilbert
Inaya Patel
Rushda Hussein

[[Category:Featured in BAMBED]]
[[Category:Topic Page]]

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{{Sandbox_Reserved_Santoro_2013}}


----

== Background ==

[[Image:MyJak2.jpg|thumb|250px|left|Not, "just another kinase". Picture from Protein Data Bank.]]
Janus Kinase 2 is a non-receptor janus kinase, a protein which is part of the tyrosine kinases. These group of kinases are the primary intracellular mediators of cytokine signaling and are involved in the control of cellular growth. As a non-receptor kinase, Jak 2 has a cytoplasmic enzyme which catalyzes the transfer of a phosphate group through phosphorylation to the tyrosine residue in the protein. Such an enzyme plays a crucial role in regulating various cellular functions by switching on or off additional enzymes within the cell. <ref> Hanks, SK., Quinn, AM., Hunter, T. (1988). The protein kinase family: conserved features and deduced phylogeny of the catalytic domains. Science 241 (4861): 42–52. doi:10.1126/science.3291115. PMID 3291115. </ref> Such phosphorylation is a reversible process, and used in many different pathways as a method to control cellular activity. However kinases like Jak2, have enzymes which add phosphate groups to hydroxyl side chains as can be seen in the diagram. <ref> Hudel, H. [Internet]. Irvine [CA]. Center for Biomembrane Systems at UC Irvine; c2013. [Updated 2013 Jan 3; cited 2013 March 23]. Available from: http://bass.bio.uci.edu </ref>

Jak2 was given its name "Janus" after the two-faced Roman God "Janus" who was known as the custodian of the universe and the God of new beginnings. <ref> Janus incarnate [Internet]. Kirwan Studios; c2011. [Updated 2011 Feb 3; cited 2013 March 23' Retrieved from http://rense.com/general92/janus.htm http://rense.com/general92/janus.htm </ref> The abbreviation 'Jak' is commonly referred to as 'just another kinase' as, when it was first discovered, the kinase's role was not yet fully understood. <ref> Weinberg, I. (April 2010). Janus Kinase (Jak2)”. Vascular Medicind; Angiolgist http://www.angiologist.com/general-medicine/janus-kinase-2-jak2/ </ref>

== Analyzing and Discovering Jak2 Structure ==

In determining the three-dimensional structure of the Jak2 protein, three primary methods of analysis were used; protein expression and purification, crystallization, and x-ray data collection. <ref> Lucet, I., Fantino, E., & Styles, M. (2005). The structural basis of janus kinase 2 inhibition by a potent and specific pan-janus kinase inhibitor. Blood, 107, 176-183. doi: 10.1182/blood-2005-06-2413 http://bloodjournal.hematologylibrary.org/content/107/1/176.full.pdf </ref> In the protein expression and purification the Jak2 residue was cloned using pFastBac which uses “two promoters in a single vector for expression of two proteins simultaneously in insect cells”. <ref> pFastbac Duo [Internet]. Life Technologies Corporation; c2013. [Updated 2013; cited 2013 March 23]. Available from: http://www.invitrogen.com/1/1/14896-pfastbac-dual.html </ref> The bacmid DNA with the kinase insert was then isolated and put into cells of insect army worms. The cells were then grown, lysed and centrifuged after which the protein was then incubated, separated with gel filtration and fractions were taken for crystallization trials. In these crystallization trials, the protein residue was used to grow crystals via hanging drop vapor-diffusion. The purified protein complex was then mixed with solutions which subsequently formed crystals after one to three days. The crystalized protein was then flash frozen and the structure determined via molecular replacement and the AmoRe program. <ref> ) Lucet, I., Fantino, E., & Styles, M. (2005). The structural basis of janus kinase 2 inhibition by a potent and specific pan-janus kinase inhibitor. Blood, 107, 176-183. doi: 10.1182/blood-2005-06-2413 http://bloodjournal.hematologylibrary.org/content/107/1/176.full.pdf </ref>

<Structure load='2b7a' size='350' frame='true' align='right' caption='3-D Structure of Jak2 as created in Protein Data Bank' scene='Insert optional scene name here' />

[[Image:Jak2structure.png|thumb|300px|left|Ribbon representation of Jak2 structure as determined by Dr. Isabelle S. Lucet et al]]
The structure of Jak 2 can be broken down into seven separate components, as seen in the pictured diagram to the left. The top, gray, portion of the protein was found to be the N-terminal lobe (residues 840-931). This loop is comprised of a 5-stranded anti-parallel beta-sheet (Beta1 - 5) and one alpha-helix (alpha C). The large dark green portion seen on the bottom is the COOH-terminal lobe. This carboxylic acid lobe is comprised of 8 alpha-helices (alpha D-alpha K), and 3 3/10 helices (3/10B, 3/10C, 3/10D), and 3 pairs of anti-parallel Beta-strands (Beta7-8, 6-9, and 10-11). The orange portion in the middle-right of the protein is the glycine loop which makes contacts with the activation loop and catalytic loop. This glycine loop, while small, is of great importance, as it is known to be essential in substrate and nucleotide binding. In yellow, to the top-left, there is a hinge region present which aids in molecule interactions. The blue section in the low middle is the catalytic loop, the red loop to the right is the activation loop and finally the dark blue section towards the bottom-right is the JAK2 lip which contains one 3/10C helix and one alpha-helix connected by a short linker. <ref> ) Lucet, I., Fantino, E., & Styles, M. (2005). The structural basis of janus kinase 2 inhibition by a potent and specific pan-janus kinase inhibitor. Blood, 107, 176-183. doi: 10.1182/blood-2005-06-2413 http://bloodjournal.hematologylibrary.org/content/107/1/176.full.pdf </ref>

== Function ==

There are four members of the janus kinase family, Jak1, Jak2, Jak3, and Jak4. Each kinase has unique functions based on their respective abilities to bind to different cytokine receptors. Out of those four janus kinases, Jak2 is responsible for erythropoietin and thrombopoietin signaling which then causes the proliferation, activation and transcription of blood cells. <ref> Weinberg, I. (April 2010). Janus Kinase (Jak2)”. Vascular Medicind; Angiolgist http://www.angiologist.com/general-medicine/janus-kinase-2-jak2/</ref> The Jak2 Signal Transducers and Activators of Transcription (STAT) pathway is what influences the kinase ability. The janus kinase-STAT pathway is the central path taken for such cell signal transcription though the erythropoietin receptor. <ref> O'Shea, J., Gadina, M., & Chen, X. (2005). Structure of a janus kinase: molecular insights and prospects for optimizing a new class of immunosuppressants. The Journal of the American Society of Hematology, 106(3), 765-766. doi: 10.1182/blood-2005-05-1947 http://bloodjournal.hematologylibrary.org/content/106/3/765.full </ref> Under normal conditions, various levels of regulation maintain Jak2 in its inactive form until receptor activation occurs and involve interactions of the pseudokinase domain (JH2) and FERM domain (JH4 to -7) with the kinase domain (JH1). <ref> Funakoshi-Tago, M., Pelletier, S., & Moritake, H. (2008). Jak2 ferm domain interaction with the erythropoietin receptor regulates jak2 kinase activity. Molecular and Cellular Biology, 28(5), 1792-1801. doi: 10.1128/MCB.01447-07 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2258779/ </ref>
[[Image:Jak2A.png|thumb|250px|left|Figure 1]]
[[Image:Jak2B.png|thumb|200px|center|Figure 2]]
[[Image:Jak2C.png|thumb|200px|right|Figure 3]]
In the unbound and inactive state of Jak2, the FERM (JH4-7), JH1 (kinase domain) and JH2 (pseduokinase domain) domains of are tightly folded together preventing the catalytic domain from being active. (Figure 1) However, the first activation step of Jak2 is the displacement of the FERM domain by its interaction with the receptor which begins the unfolding of domains within the protein to allow access to the various binding domains. (Figure 2). In the presence of a ligand, receptor aggregation occurs. As a result of this aggregation, the tyrosine within the Jak2 active loop is phosphorylated and then induces changes in both JH2 and JH1 domains. Once phosphorylation occurs within the activation loop, the kinase is fully activated. (Figure 3) {Figures 1-3 from (Funakoshi-Tago, 2008)} Under normal conditions, Jak2 is not associated with a receptor and is locked into an inactive state. Receptor binding through the FERM domain relieves steric constraints, and allows Jak2 to be activated once it is engaged with its erythropoietin receptor. Activation of Jak2 by erythropoietin receptor engagement leads to the tyrosine phosphorylation of the receptor and Jak2. <ref> Funakoshi-Tago, M., Pelletier, S., & Moritake, H. (2008). Jak2 ferm domain interaction with the erythropoietin receptor regulates jak2 kinase activity. Molecular and Cellular Biology, 28(5), 1792-1801. doi: 10.1128/MCB.01447-07 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2258779/ </ref>
[[Image:Jak2Mutation.png|thumb|250px|left|Figure 4, (Gnanasambandan, 2011)]]
Mutations in Jak2 can result in the erythropoietin receptor being activated all the time. Due to lack of auto-inhibition of the JAK2 enzyme because of this activating mutation the receptor is effectively switched to the ‘on’ position indefinitely, constantly over-produce cells. This type of mutation has been found to occur in a nucleotide substitution of valine to phenylalanine and is therefore termed, V617F. The active conformation of Jak2 is likely to be mimicked by the Jak2-V617F mutant and this thereby results in either oncogenesis, polycythemia or other hematopoietic disorders. <ref>Gnanasambandan, K., & Sayeski, P. (2011). A structure-function perspective of jak2 mutations and implications for alternate drug design strategies: the road not taken. Department of Physiology and Functional Genomics, University of Florida College of Medicine, 18(30), 59-73. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/21864276 http://www.ncbi.nlm.nih.gov/pubmed/21864276 </ref> Other mutant conformations, such as the Y613E mutant, failed to undergo complete conformational changes leading to its activation. <ref> Funakoshi-Tago, M., Pelletier, S., & Moritake, H. (2008). Jak2 ferm domain interaction with the erythropoietin receptor regulates jak2 kinase activity. Molecular and Cellular Biology, 28(5), 1792-1801. doi: 10.1128/MCB.01447-07 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2258779/
(7) Kirwan, J. (02, 2011 03). Janus incarnate. Retrieved from http://rense.com/general92/janus.htm </ref> A diagramed example of how normal Jak2 receptors work, as well as how this mutation works mechanically can be seen on figure 4.
[[Image:Jak2DNA.png|thumb|250px|left|Figure 5, (Lucet, 2005)]] Figure 5 shows the amino acid sequence alignment of JAK2 along with the other members of the JAK family TYK2, JAK3, and JAK1 and the kinase domain of FAK and LCK around the Lip region. Cylinders show alpha-helices, the residues conserved among the JAK kinases sequence are highlighted in red. The dark gray boxes indicate which residues are conserved to at least 75% within the janus kinase family and finally the light gray boxes indicate conservatively substituted residues. <ref> ) Lucet, I., Fantino, E., & Styles, M. (2005). The structural basis of janus kinase 2 inhibition by a potent and specific pan-janus kinase inhibitor. Blood, 107, 176-183. doi: 10.1182/blood-2005-06-2413 http://bloodjournal.hematologylibrary.org/content/107/1/176.full.pdf </ref>

== Conditions Associated with Jak2 Mutations ==
As Janus Kinase 2 has a significant role in hematopoiesis, the formation and development of blood cells, mutations in the protein most commonly result in constitutive kinase activation which lead to oncogenesis. Some of the cancers associated with such mutations have been found to be myeloid leukemia, lymphoid leukemia, polycythemia vera, along with other myeloproliferative neoplasms. <ref> Funakoshi-Tago, M., Pelletier, S., & Moritake, H. (2008). Jak2 ferm domain interaction with the erythropoietin receptor regulates jak2 kinase activity. Molecular and Cellular Biology, 28(5), 1792-1801. doi: 10.1128/MCB.01447-07 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2258779/ </ref> While there are many different genetic mutations which are resultant of leukemias, 85% of patients diagnosed with polycythemia vera are found to have the mutation in their Jak2 protein. <ref> Polycythemia Vera [Internet]. Rochester [Mn]. The Mayo Clinic; c2011. [Updated 2011 Apr 7; cited 2013 March 23]. Available from: http://www.mayoclinic.com/health/polycythemia-vera/DS00919 </ref>

== Current and Future Therapies ==

There are currently many therapies for differing forms of leukemia, some of which include cytoreductive medications such as hydroxyurea or agrylin, to suppress the bone marrow’s ability to make blood cells, cell destructive medications like cytoxin which act as oral chemotheraputic agents, interferon treatments to stimulate the patient's immune response to fight and kill overproduction or white and red blood cells. Finally traditional chemotherapy is commonly used, as well, for both leukemias as well as progressive polycythemia vera. <ref> Acute Myeloid Leukemia [Internet]. Bethesda [MD]. The National Cancer Institute; c2013. [Updated 2013 March 06; cited 2013 March 23]. Available from: http://m.cancer.gov/topics/treatment/bycancer/adultAML/Patient </ref> <ref> Chronic Lymphocytic Leukemia [Internet]. Rochester [Mn]. The Mayo Clinic; c2011. [Updated 2011 Apr 7; cited 2013 March 23]. Available from: http://www.mayoclinic.com/health/chronic-lymphocytic-leukemia/DS00565 </ref> <ref> Polycythemia Vera [Internet]. Rochester [Mn]. The Mayo Clinic; c2011. [Updated 2011 Apr 7; cited 2013 March 23]. Available from: http://www.mayoclinic.com/health/polycythemia-vera/DS00919 </ref> <ref> Polycythemia Treatment and Management [Internet]. Medscape; 2012. [Updated 2012 Jan 10; cited 2013 March 23]. Available from: http://emedicine.medscape.com/article/205114-treatment </ref> While there are a few Jak2 inhibitors already in use which use competitive inhibition for ATP binding pockets, they are not extremely effective due to non-specificity. Due to this issue with specificity, the current therapies for Jak2 mutations are being more focused on allosteric inhibition designs. This research is believed to be hopeful due to the successes it has had with other, different, kinase inhibition. Possible sites which scientists are targeting for such inhibition include, the type II Inhibitor pocket, substrate binding sites, kinase pseudo kinase domain interface, SH2JK2 Linker Region, and the FERM Domain. Currently many of these are in both pre and post clinical trials. <ref> Gnanasambandan, K., & Sayeski, P. (2011). A structure-function perspective of jak2 mutations and implications for alternate drug design strategies: the road not taken. Department of Physiology and Functional Genomics, University of Florida College of Medicine, 18(30), 59-73. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/21864276 http://www.ncbi.nlm.nih.gov/pubmed/21864276 </ref> A brief discussion on diseases associated with Jak2, as well as the function of the protein can be found on an already established Proteopedia page found at [[2b7a]].

==References==

<references />

File:Phosphorylation.png

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|DATE=June 14, 2016
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}}

==SHOC2-PP1C-MRAS==
<StructureSection load='7UPI' size='340' side='right' caption='SHOC2-MRAS-PP1C'>

== Introduction ==
'''Receptor Tyrosine Kinase Receptor'''
*[[Lipid signaling]]
*[[Transmembrane (cell surface) receptors]]

[[Image:Mechanism.png|200px|center|thumb|Figure 1: Mechanism for Shoc2-MRAS-PP1C]]
[[Image:Phosphorylation.jpg|200px|center|thumb|Figure 2: PP1C phosphorylates Serine 259.]]

== Overall Structure ==
=== SHOC2 ===
<scene name='95/952717/Shoc2/1'>SHOC2</scene>
=== PP1C ===
<scene name='95/952717/Pp1c/1'>PP1C</scene>
=== MRAS ===
<scene name='95/952717/Mras/2'>MRAS</scene>

=== Key Ligand Interactions ===
[[Image:Amphbindingfinal.png|275 px|right|thumb|'''Figure 3''': Electrostatic illustration of the amphipathic binding pocket of the LPA1 receptor. This binding pocket was revealed by cutting away the exterior or the protein. This binding pocket, located in the interior of the protein, has both polar and nonpolar regions. The blue and red coloration highlight the positively and negatively charged regions, respectively, and the white color shows the nonpolar region of the binding pocket.]]

=== SHOC2 and PP1C ===
<scene name='95/952717/Shoc2_and_pp1c/1'>Shoc2-PP1C</scene>
<scene name='95/952717/Shoc2_and_pp1c/2'>SHOC2-PP1C Binding Pocket</scene>
=== SHOC2 and MRAS ===

=== PP1C and MRAS ===

== Signaling Pathway ==

== Disease Relevance ==

=== Cancer ===

=== RASopathies===

== Future Studies ==

==3D structures of lysophosphatidic acid receptor==

[[4z34]], [[4z35]], [[4z36]] - hLPA1 + antagonist - human 
[[2lq4]] – hLPA1 second extracellular loop – NMR 
[[4p0c]] – hLPA2/NHERF2 
[[5xsz]] – LPA6A (mutant) – zebra fish 

== References ==
<references/>
==Proteopedia Resources==
[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid_binding Category:Lysophosphatidic acid binding]

[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid Category:Lysophosphatidic acid]

[http://proteopedia.org/wiki/index.php/User:R._Jeremy_Johnson/CH462:Biochemistry_II_Butler_University Butler University Proteopedia Pages]

See also:
*[[Receptor]]
*[[Transmembrane (cell surface) receptors]]
*[[G protein-coupled receptors]]
</StructureSection>
==Student Contributors==
Madeline Gilbert
Inaya Patel
Rushda Hussein

[[Category:Featured in BAMBED]]
[[Category:Topic Page]]

File:Mechanism.png

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==SHOC2-PP1C-MRAS==
<StructureSection load='7UPI' size='340' side='right' caption='SHOC2-MRAS-PP1C'>

== Introduction ==
'''Receptor Tyrosine Kinase Receptor'''
*[[Lipid signaling]]
*[[Transmembrane (cell surface) receptors]]

[[Image: Mechanism.png |200px|center|thumb|Figure 1: Mechanism for Shoc2-MRAS-PP1C]]
[[Image:Phosphorylation.jpg|200px|center|thumb|Figure 2: PP1C phosphorylates Serine 259.]]

== Overall Structure ==
=== SHOC2 ===
<scene name='95/952717/Shoc2/1'>SHOC2</scene>
=== PP1C ===
<scene name='95/952717/Pp1c/1'>PP1C</scene>
=== MRAS ===
<scene name='95/952717/Mras/2'>MRAS</scene>

=== Key Ligand Interactions ===
[[Image:Amphbindingfinal.png|275 px|right|thumb|'''Figure 3''': Electrostatic illustration of the amphipathic binding pocket of the LPA1 receptor. This binding pocket was revealed by cutting away the exterior or the protein. This binding pocket, located in the interior of the protein, has both polar and nonpolar regions. The blue and red coloration highlight the positively and negatively charged regions, respectively, and the white color shows the nonpolar region of the binding pocket.]]

=== SHOC2 and PP1C ===
<scene name='95/952717/Shoc2_and_pp1c/1'>Shoc2-PP1C</scene>
<scene name='95/952717/Shoc2_and_pp1c/2'>SHOC2-PP1C Binding Pocket</scene>
=== SHOC2 and MRAS ===

=== PP1C and MRAS ===

== Signaling Pathway ==

== Disease Relevance ==

=== Cancer ===

=== RASopathies===

== Future Studies ==

==3D structures of lysophosphatidic acid receptor==

[[4z34]], [[4z35]], [[4z36]] - hLPA1 + antagonist - human 
[[2lq4]] – hLPA1 second extracellular loop – NMR 
[[4p0c]] – hLPA2/NHERF2 
[[5xsz]] – LPA6A (mutant) – zebra fish 

== References ==
<references/>
==Proteopedia Resources==
[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid_binding Category:Lysophosphatidic acid binding]

[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid Category:Lysophosphatidic acid]

[http://proteopedia.org/wiki/index.php/User:R._Jeremy_Johnson/CH462:Biochemistry_II_Butler_University Butler University Proteopedia Pages]

See also:
*[[Receptor]]
*[[Transmembrane (cell surface) receptors]]
*[[G protein-coupled receptors]]
</StructureSection>
==Student Contributors==
Madeline Gilbert
Inaya Patel
Rushda Hussein

[[Category:Featured in BAMBED]]
[[Category:Topic Page]]

File:Mechanism.png

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{{BAMBED
|DATE=June 14, 2016
|OLDID=2607465
|BAMBEDDOI=10.1002/bmb.21026
}}

==SHOC2-PP1C-MRAS==
<StructureSection load='7UPI' size='340' side='right' caption='SHOC2-MRAS-PP1C'>

== Introduction ==
'''Receptor Tyrosine Kinase Receptor'''
*[[Lipid signaling]]
*[[Transmembrane (cell surface) receptors]]

[[Image: Mechanism.jpg|200px|center|thumb|Figure 1: Mechanism for Shoc2-MRAS-PP1C]]
[[Image:Phosphorylation.jpg|200px|center|thumb|Figure 2: PP1C phosphorylates Serine 259.]]

== Overall Structure ==
=== SHOC2 ===
<scene name='95/952717/Shoc2/1'>SHOC2</scene>
=== PP1C ===
<scene name='95/952717/Pp1c/1'>PP1C</scene>
=== MRAS ===
<scene name='95/952717/Mras/2'>MRAS</scene>

=== Key Ligand Interactions ===
[[Image:Amphbindingfinal.png|275 px|right|thumb|'''Figure 3''': Electrostatic illustration of the amphipathic binding pocket of the LPA1 receptor. This binding pocket was revealed by cutting away the exterior or the protein. This binding pocket, located in the interior of the protein, has both polar and nonpolar regions. The blue and red coloration highlight the positively and negatively charged regions, respectively, and the white color shows the nonpolar region of the binding pocket.]]

=== SHOC2 and PP1C ===
<scene name='95/952717/Shoc2_and_pp1c/1'>Shoc2-PP1C</scene>
<scene name='95/952717/Shoc2_and_pp1c/2'>SHOC2-PP1C Binding Pocket</scene>
=== SHOC2 and MRAS ===

=== PP1C and MRAS ===

== Signaling Pathway ==

== Disease Relevance ==

=== Cancer ===

=== RASopathies===

== Future Studies ==

==3D structures of lysophosphatidic acid receptor==

[[4z34]], [[4z35]], [[4z36]] - hLPA1 + antagonist - human 
[[2lq4]] – hLPA1 second extracellular loop – NMR 
[[4p0c]] – hLPA2/NHERF2 
[[5xsz]] – LPA6A (mutant) – zebra fish 

== References ==
<references/>
==Proteopedia Resources==
[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid_binding Category:Lysophosphatidic acid binding]

[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid Category:Lysophosphatidic acid]

[http://proteopedia.org/wiki/index.php/User:R._Jeremy_Johnson/CH462:Biochemistry_II_Butler_University Butler University Proteopedia Pages]

See also:
*[[Receptor]]
*[[Transmembrane (cell surface) receptors]]
*[[G protein-coupled receptors]]
</StructureSection>
==Student Contributors==
Madeline Gilbert
Inaya Patel
Rushda Hussein

[[Category:Featured in BAMBED]]
[[Category:Topic Page]]

Sandbox Reserved 1789

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Rushda Hussein:

{{BAMBED
|DATE=June 14, 2016
|OLDID=2607465
|BAMBEDDOI=10.1002/bmb.21026
}}

==SHOC2-PP1C-MRAS==
<StructureSection load='7UPI' size='340' side='right' caption='SHOC2-MRAS-PP1C'>

== Introduction ==
'''Receptor Tyrosine Kinase Receptor'''
*[[Lipid signaling]]
*[[Transmembrane (cell surface) receptors]]

[[Image: Mechanism.jpg|200px|center|thumb|Figure 1: Mechanism for Shoc2-MRAS-PP1C]]
[[Image:Phosphorylation.jpg|200px|center|thumb|Figure 2: PP1C phosphorylates Serine 259. ]]

== Overall Structure ==
=== SHOC2 ===
<scene name='95/952717/Shoc2/1'>SHOC2</scene>
=== PP1C ===
<scene name='95/952717/Pp1c/1'>PP1C</scene>
=== MRAS ===
<scene name='95/952717/Mras/2'>MRAS</scene>

=== Key Ligand Interactions ===
[[Image:Amphbindingfinal.png|275 px|right|thumb|'''Figure 3''': Electrostatic illustration of the amphipathic binding pocket of the LPA1 receptor. This binding pocket was revealed by cutting away the exterior or the protein. This binding pocket, located in the interior of the protein, has both polar and nonpolar regions. The blue and red coloration highlight the positively and negatively charged regions, respectively, and the white color shows the nonpolar region of the binding pocket.]]

=== SHOC2 and PP1C ===
<scene name='95/952717/Shoc2_and_pp1c/1'>Shoc2-PP1C</scene>
<scene name='95/952717/Shoc2_and_pp1c/2'>SHOC2-PP1C Binding Pocket</scene>
=== SHOC2 and MRAS ===

=== PP1C and MRAS ===

== Signaling Pathway ==

== Disease Relevance ==

=== Cancer ===

=== RASopathies===

== Future Studies ==

==3D structures of lysophosphatidic acid receptor==

[[4z34]], [[4z35]], [[4z36]] - hLPA1 + antagonist - human 
[[2lq4]] – hLPA1 second extracellular loop – NMR 
[[4p0c]] – hLPA2/NHERF2 
[[5xsz]] – LPA6A (mutant) – zebra fish 

== References ==
<references/>
==Proteopedia Resources==
[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid_binding Category:Lysophosphatidic acid binding]

[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid Category:Lysophosphatidic acid]

[http://proteopedia.org/wiki/index.php/User:R._Jeremy_Johnson/CH462:Biochemistry_II_Butler_University Butler University Proteopedia Pages]

See also:
*[[Receptor]]
*[[Transmembrane (cell surface) receptors]]
*[[G protein-coupled receptors]]
</StructureSection>
==Student Contributors==
Madeline Gilbert
Inaya Patel
Rushda Hussein

[[Category:Featured in BAMBED]]
[[Category:Topic Page]]

Sandbox Reserved 1789

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Rushda Hussein:

{{BAMBED
|DATE=June 14, 2016
|OLDID=2607465
|BAMBEDDOI=10.1002/bmb.21026
}}

==SHOC2-PP1C-MRAS==
<StructureSection load='7UPI' size='340' side='right' caption='SHOC2-MRAS-PP1C'>

== Introduction ==
'''Receptor Tyrosine Kinase Receptor'''
*[[Lipid signaling]]
*[[Transmembrane (cell surface) receptors]]

[[Image: Mechanism.jpg|1500px|center|thumb|'''Figure 1:''' Mechanism for Shoc2-MRAS-PP1C]]
[[Image:Phosphorylation.jpg|1500px|center|thumb|'''Figure 2:''' PP1C phosphorylates Serine 259. ]]

== Overall Structure ==
=== SHOC2 ===
<scene name='95/952717/Shoc2/1'>SHOC2</scene>
=== PP1C ===
<scene name='95/952717/Pp1c/1'>PP1C</scene>
=== MRAS ===
<scene name='95/952717/Mras/2'>MRAS</scene>

=== Key Ligand Interactions ===
[[Image:Amphbindingfinal.png|275 px|right|thumb|'''Figure 3''': Electrostatic illustration of the amphipathic binding pocket of the LPA1 receptor. This binding pocket was revealed by cutting away the exterior or the protein. This binding pocket, located in the interior of the protein, has both polar and nonpolar regions. The blue and red coloration highlight the positively and negatively charged regions, respectively, and the white color shows the nonpolar region of the binding pocket.]]

=== SHOC2 and PP1C ===
<scene name='95/952717/Shoc2_and_pp1c/1'>Shoc2-PP1C</scene>
<scene name='95/952717/Shoc2_and_pp1c/2'>SHOC2-PP1C Binding Pocket</scene>
=== SHOC2 and MRAS ===

=== PP1C and MRAS ===

== Signaling Pathway ==

== Disease Relevance ==

=== Cancer ===

=== RASopathies===

== Future Studies ==

==3D structures of lysophosphatidic acid receptor==

[[4z34]], [[4z35]], [[4z36]] - hLPA1 + antagonist - human 
[[2lq4]] – hLPA1 second extracellular loop – NMR 
[[4p0c]] – hLPA2/NHERF2 
[[5xsz]] – LPA6A (mutant) – zebra fish 

== References ==
<references/>
==Proteopedia Resources==
[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid_binding Category:Lysophosphatidic acid binding]

[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid Category:Lysophosphatidic acid]

[http://proteopedia.org/wiki/index.php/User:R._Jeremy_Johnson/CH462:Biochemistry_II_Butler_University Butler University Proteopedia Pages]

See also:
*[[Receptor]]
*[[Transmembrane (cell surface) receptors]]
*[[G protein-coupled receptors]]
</StructureSection>
==Student Contributors==
Madeline Gilbert
Inaya Patel
Rushda Hussein

[[Category:Featured in BAMBED]]
[[Category:Topic Page]]

Sandbox Reserved 1789

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Rushda Hussein:

{{BAMBED
|DATE=June 14, 2016
|OLDID=2607465
|BAMBEDDOI=10.1002/bmb.21026
}}

==SHOC2-PP1C-MRAS==
<StructureSection load='7UPI' size='340' side='right' caption='SHOC2-MRAS-PP1C'>

== Introduction ==
'''Receptor Tyrosine Kinase Receptor'''
*[[Lipid signaling]]
*[[Transmembrane (cell surface) receptors]]

[[Image: Mechanism.jpg|1000px|center|thumb|'''Figure 1:''' Mechanism for Shoc2-MRAS-PP1C]]
[[Image:Phosphorylation.jpg|1000px|center|thumb|'''Figure 2:''' PP1C phosphorylates Serine 259. ]]

== Overall Structure ==
=== SHOC2 ===
<scene name='95/952717/Shoc2/1'>SHOC2</scene>
=== PP1C ===
<scene name='95/952717/Pp1c/1'>PP1C</scene>
=== MRAS ===
<scene name='95/952717/Mras/2'>MRAS</scene>

=== Key Ligand Interactions ===
[[Image:Amphbindingfinal.png|275 px|right|thumb|'''Figure 3''': Electrostatic illustration of the amphipathic binding pocket of the LPA1 receptor. This binding pocket was revealed by cutting away the exterior or the protein. This binding pocket, located in the interior of the protein, has both polar and nonpolar regions. The blue and red coloration highlight the positively and negatively charged regions, respectively, and the white color shows the nonpolar region of the binding pocket.]]

=== SHOC2 and PP1C ===
<scene name='95/952717/Shoc2_and_pp1c/1'>Shoc2-PP1C</scene>
<scene name='95/952717/Shoc2_and_pp1c/2'>SHOC2-PP1C Binding Pocket</scene>
=== SHOC2 and MRAS ===

=== PP1C and MRAS ===

== Signaling Pathway ==

== Disease Relevance ==

=== Cancer ===

=== RASopathies===

== Future Studies ==

==3D structures of lysophosphatidic acid receptor==

[[4z34]], [[4z35]], [[4z36]] - hLPA1 + antagonist - human 
[[2lq4]] – hLPA1 second extracellular loop – NMR 
[[4p0c]] – hLPA2/NHERF2 
[[5xsz]] – LPA6A (mutant) – zebra fish 

== References ==
<references/>
==Proteopedia Resources==
[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid_binding Category:Lysophosphatidic acid binding]

[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid Category:Lysophosphatidic acid]

[http://proteopedia.org/wiki/index.php/User:R._Jeremy_Johnson/CH462:Biochemistry_II_Butler_University Butler University Proteopedia Pages]

See also:
*[[Receptor]]
*[[Transmembrane (cell surface) receptors]]
*[[G protein-coupled receptors]]
</StructureSection>
==Student Contributors==
Madeline Gilbert
Inaya Patel
Rushda Hussein

[[Category:Featured in BAMBED]]
[[Category:Topic Page]]

Sandbox Reserved 1789

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Rushda Hussein:

{{BAMBED
|DATE=June 14, 2016
|OLDID=2607465
|BAMBEDDOI=10.1002/bmb.21026
}}

==SHOC2-PP1C-MRAS==
<StructureSection load='7UPI' size='340' side='right' caption='SHOC2-MRAS-PP1C'>

== Introduction ==
'''Receptor Tyrosine Kinase Receptor'''
*[[Lipid signaling]]
*[[Transmembrane (cell surface) receptors]]

[[Image:LPA_in_membrane4.fw.png|200px|center|thumb|'''Figure 1:''' LPA receptor (blue) bound to the cell membrane. The binding pocket is highlighted in red. The added bRIL protein is highlighted in orange.]]

[[Image: Mechanism.jpg|200px|center|thumb|'''Figure 1:''' Mechanism for Shoc2-MRAS-PP1C]]
[[Image:Phosphorylation.jpg|200px|center|thumb|'''Figure 2:''' PP1C phosphorylates Serine 259. ]]

== Overall Structure ==
=== SHOC2 ===
<scene name='95/952717/Shoc2/1'>SHOC2</scene>
=== PP1C ===
<scene name='95/952717/Pp1c/1'>PP1C</scene>
=== MRAS ===
<scene name='95/952717/Mras/2'>MRAS</scene>

=== Key Ligand Interactions ===
[[Image:Amphbindingfinal.png|275 px|right|thumb|'''Figure 3''': Electrostatic illustration of the amphipathic binding pocket of the LPA1 receptor. This binding pocket was revealed by cutting away the exterior or the protein. This binding pocket, located in the interior of the protein, has both polar and nonpolar regions. The blue and red coloration highlight the positively and negatively charged regions, respectively, and the white color shows the nonpolar region of the binding pocket.]]

=== SHOC2 and PP1C ===
<scene name='95/952717/Shoc2_and_pp1c/1'>Shoc2-PP1C</scene>
<scene name='95/952717/Shoc2_and_pp1c/2'>SHOC2-PP1C Binding Pocket</scene>
=== SHOC2 and MRAS ===

=== PP1C and MRAS ===

== Signaling Pathway ==

== Disease Relevance ==

=== Cancer ===

=== RASopathies===

== Future Studies ==

==3D structures of lysophosphatidic acid receptor==

[[4z34]], [[4z35]], [[4z36]] - hLPA1 + antagonist - human 
[[2lq4]] – hLPA1 second extracellular loop – NMR 
[[4p0c]] – hLPA2/NHERF2 
[[5xsz]] – LPA6A (mutant) – zebra fish 

== References ==
<references/>
==Proteopedia Resources==
[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid_binding Category:Lysophosphatidic acid binding]

[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid Category:Lysophosphatidic acid]

[http://proteopedia.org/wiki/index.php/User:R._Jeremy_Johnson/CH462:Biochemistry_II_Butler_University Butler University Proteopedia Pages]

See also:
*[[Receptor]]
*[[Transmembrane (cell surface) receptors]]
*[[G protein-coupled receptors]]
</StructureSection>
==Student Contributors==
Madeline Gilbert
Inaya Patel
Rushda Hussein

[[Category:Featured in BAMBED]]
[[Category:Topic Page]]

Sandbox Reserved 1789

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Rushda Hussein:

{{BAMBED
|DATE=June 14, 2016
|OLDID=2607465
|BAMBEDDOI=10.1002/bmb.21026
}}

==SHOC2-PP1C-MRAS==
<StructureSection load='7UPI' size='340' side='right' caption='SHOC2-MRAS-PP1C'>

== Introduction ==
'''Receptor Tyrosine Kinase Receptor'''
*[[Lipid signaling]]
*[[Transmembrane (cell surface) receptors]]

[[Image:LPA_in_membrane4.fw.png|200px|center|thumb|'''Figure 1:''' LPA receptor (blue) bound to the cell membrane. The binding pocket is highlighted in red. The added bRIL protein is highlighted in orange.]]

[[Image: Mechanism.jpg]]
[[Image:Phosphorylation.jpg]]
== Overall Structure ==
=== SHOC2 ===
<scene name='95/952717/Shoc2/1'>SHOC2</scene>
=== PP1C ===
<scene name='95/952717/Pp1c/1'>PP1C</scene>
=== MRAS ===
<scene name='95/952717/Mras/2'>MRAS</scene>

=== Key Ligand Interactions ===
[[Image:Amphbindingfinal.png|275 px|right|thumb|'''Figure 3''': Electrostatic illustration of the amphipathic binding pocket of the LPA1 receptor. This binding pocket was revealed by cutting away the exterior or the protein. This binding pocket, located in the interior of the protein, has both polar and nonpolar regions. The blue and red coloration highlight the positively and negatively charged regions, respectively, and the white color shows the nonpolar region of the binding pocket.]]

=== SHOC2 and PP1C ===
<scene name='95/952717/Shoc2_and_pp1c/1'>Shoc2-PP1C</scene>
<scene name='95/952717/Shoc2_and_pp1c/2'>SHOC2-PP1C Binding Pocket</scene>
=== SHOC2 and MRAS ===

=== PP1C and MRAS ===

== Signaling Pathway ==

== Disease Relevance ==

=== Cancer ===

=== RASopathies===

== Future Studies ==

==3D structures of lysophosphatidic acid receptor==

[[4z34]], [[4z35]], [[4z36]] - hLPA1 + antagonist - human 
[[2lq4]] – hLPA1 second extracellular loop – NMR 
[[4p0c]] – hLPA2/NHERF2 
[[5xsz]] – LPA6A (mutant) – zebra fish 

== References ==
<references/>
==Proteopedia Resources==
[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid_binding Category:Lysophosphatidic acid binding]

[http://proteopedia.org/wiki/index.php/Category:Lysophosphatidic_acid Category:Lysophosphatidic acid]

[http://proteopedia.org/wiki/index.php/User:R._Jeremy_Johnson/CH462:Biochemistry_II_Butler_University Butler University Proteopedia Pages]

See also:
*[[Receptor]]
*[[Transmembrane (cell surface) receptors]]
*[[G protein-coupled receptors]]
</StructureSection>
==Student Contributors==
Madeline Gilbert
Inaya Patel
Rushda Hussein

[[Category:Featured in BAMBED]]
[[Category:Topic Page]]

File:Phosphorylation.jpg

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Rushda Hussein:

File:Mechanism.jpg

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Rushda Hussein: uploaded a new version of "Image:Mechanism.jpg"