Sandbox Reserved 1490: Difference between revisions
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The activation of the receptor is due to a ligand-induced dimerization : the extracellular receptor domain dimerization brings the cytosolic kinase domains next to each other for intermolecular autophosphorylation. The latter occurs when one subunit of the dimeric receptor phosphorylates tyrosine residues on the other subunit. It happens in a sequential manner : Tyr-992 in the kinase activation loop is phosphorylated first, followed by autophosphorylation at Tyr-1108 and at additional tyrosine residues. Autophosphorylation also has multiple functions including recruitment of downstream signaling molecules.<ref name="Mechanistic effects of autophosphorylation" /> | The activation of the receptor is due to a ligand-induced dimerization : the extracellular receptor domain dimerization brings the cytosolic kinase domains next to each other for intermolecular autophosphorylation. The latter occurs when one subunit of the dimeric receptor phosphorylates tyrosine residues on the other subunit. It happens in a sequential manner : Tyr-992 in the kinase activation loop is phosphorylated first, followed by autophosphorylation at Tyr-1108 and at additional tyrosine residues. Autophosphorylation also has multiple functions including recruitment of downstream signaling molecules.<ref name="Mechanistic effects of autophosphorylation" /> | ||
Looking more closely at the TIE2 intracellular domain, 1106 is found at the base of a loop formed between the C-terminus tail and the C-terminus lobe of the kinase. The OH group of Tyr-1106 is thus directly into the solvent and accessible to phosphorylation. However, Tyr-1100 is not solvent exposed : thereby implying that the carboxy-terminal tail must undergo a conformational change upon activation of the receptor to expose this tyrosine residue for phosphorylation.<ref>PMID:12665569</ref> | Looking more closely at the TIE2 intracellular domain, 1106 is found at the base of a loop formed between the C-terminus tail and the C-terminus lobe of the kinase. The OH group of Tyr-1106 is thus directly into the solvent and accessible to phosphorylation. However, Tyr-1100 is not solvent exposed : thereby implying that the carboxy-terminal tail must undergo a conformational change upon activation of the receptor to expose this tyrosine residue for phosphorylation.<ref name="A unique autophosphorylation">PMID: 12665569</ref> | ||
Consequent to ANGPT1 stimulation, the SH2 domain-containing p85 subunit of [[2pna|phosphatidylinositol (PI) 3-kinase]] is recruited to TIE via tyrosine residue 1100 in the C-end tail of the receptor, leading to activation of the enzyme.<ref | Consequent to ANGPT1 stimulation, the SH2 domain-containing p85 subunit of [[2pna|phosphatidylinositol (PI) 3-kinase]] is recruited to TIE via tyrosine residue 1100 in the C-end tail of the receptor, leading to activation of the enzyme.<ref name="A unique autophosphorylation"/> | ||
Interestingly, inhibition of PI 3′ kinase activity can only partially inhibit the chemotactic effect of ANGPT1 on endothelial cells, thereby implying that additional TIE2 binding partners may also contribute to ANGPT1-mediated endothelial cell migration. Phosphorylation of TIE2 further results in its association with a docking protein related to downstream of kinase (Dok), known as Dok-R, it allows Dok-R to serve as a substrate of TIE2 and thereby become tyrosine phosphorylated.<ref | Interestingly, inhibition of PI 3′ kinase activity can only partially inhibit the chemotactic effect of ANGPT1 on endothelial cells, thereby implying that additional TIE2 binding partners may also contribute to ANGPT1-mediated endothelial cell migration. Phosphorylation of TIE2 further results in its association with a docking protein related to downstream of kinase (Dok), known as Dok-R, it allows Dok-R to serve as a substrate of TIE2 and thereby become tyrosine phosphorylated.<ref name="A unique autophosphorylation"/> | ||
