Sandbox Reserved 1790: Difference between revisions
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=Introduction= | =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></font>]] | [[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></font>]] | ||
<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. | <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= | =Overall Structure= | ||
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<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. | <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== | ==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 | <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== | ==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: | <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>. | ||
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==SHOC2 and PP1C== | ==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. | <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== | ==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. | 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== | ==PP1C and MRAS== | ||
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=Signaling Pathway= | =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. | 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. | 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: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. ]] | ||
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==RASopathies== | ==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>. | 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== | ==Cancer== | ||
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=References= | =References= | ||
<references/> | <references/> | ||
Revision as of 15:39, 7 April 2023
<StructureSection load='7pui' size='350' side='right' caption='SHOC2-PP1C-MRAS (PDB entry 7upi)' scene='95/952718/Smpcomplex/2'>
SHOC2-PP1C-MRAS
Introduction
SHOC2-PP1C-MRAS (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 [1].
Overall Structure
SHOC2
SHOC2 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
PP1C 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.
MRAS
MRAS 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 GTP bound MRAS undergoes a conformational change of the switch I and switch II regions. 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 [2].
Key Ligand Interactions
SHOC2 and PP1C
PP1C binds to SHOC2 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 hydrogen bonds 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 PP1C and SHOC2. The corresponding patches interact to form a binary complex. These interactions do not result in significant conformational changes [3].
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, SHOC2-MRAS (residues) occur within the switch I and switch II regions to allow SHOC2-MRAS(full-image). These interactions include hydrogen bonds and pi stacking. The primary hydrogen bonds are R288-Q71 and R177-E47. Pi staking occurs at R104-R83 [4].
PP1C and MRAS
The interactions between PP1C and MRAS are mediated by four main hydrogen bonds: 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[5].
Disease Relevance
RASopathies
RASopathy is a broad term used to describe developmental syndromes that stem from 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 [6].
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
- ↑ Hauseman ZJ, Fodor M, Dhembi A, Viscomi J, Egli D, Bleu M, Katz S, Park E, Jang DM, Porter KA, Meili F, Guo H, Kerr G, Molle S, Velez-Vega C, Beyer KS, Galli GG, Maira SM, Stams T, Clark K, Eck MJ, Tordella L, Thoma CR, King DA. Structure of the MRAS-SHOC2-PP1C phosphatase complex. Nature. 2022 Jul 13. pii: 10.1038/s41586-022-05086-1. doi:, 10.1038/s41586-022-05086-1. PMID:35830882 doi:https://dx.doi.org/10.1038/s41586-022-05086-1
- ↑ 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. PMID:11756411 doi:10.1074/jbc.M108733200
- ↑ Kwon JJ, Hajian B, Bian Y, Young LC, Amor AJ, Fuller JR, Fraley CV, Sykes AM, So J, Pan J, Baker L, Lee SJ, Wheeler DB, Mayhew DL, Persky NS, Yang X, Root DE, Barsotti AM, Stamford AW, Perry CK, Burgin A, McCormick F, Lemke CT, Hahn WC, Aguirre AJ. Structure-function analysis of the SHOC2-MRAS-PP1C holophosphatase complex. Nature. 2022 Jul 13. pii: 10.1038/s41586-022-04928-2. doi:, 10.1038/s41586-022-04928-2. PMID:35831509 doi:https://dx.doi.org/10.1038/s41586-022-04928-2
- ↑ Lavoie H, Therrien M. Structural keys unlock RAS-MAPK cellular signalling pathway. Nature. 2022 Sep;609(7926):248-249. PMID:35970881 doi:10.1038/d41586-022-02189-7
- ↑ Liau NPD, Johnson MC, Izadi S, Gerosa L, Hammel M, Bruning JM, Wendorff TJ, Phung W, Hymowitz SG, Sudhamsu J. Structural basis for SHOC2 modulation of RAS signalling. Nature. 2022 Jun 29. pii: 10.1038/s41586-022-04838-3. doi:, 10.1038/s41586-022-04838-3. PMID:35768504 doi:https://dx.doi.org/10.1038/s41586-022-04838-3
- ↑ Rauen KA. The RASopathies. Annu Rev Genomics Hum Genet. 2013;14:355-69. PMID:23875798 doi:10.1146/annurev-genom-091212-153523
Student Contributors
Madeline Gilbert Inaya Patel Rushda Hussein
