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Mechanism of tyrosine phosphorylation and activation of phospholipase c-γ1. Tyrosine 783 phosphorylation is not sufficient for lipase activation
- Mechanism of tyrosine phosphorylation and activation of phospholipase c-γ1. Tyrosine 783 phosphorylation is not sufficient for lipase activation
- Sekiya F.; Poulin B.; Kim Y.J.; Rhee S.G.
- Ewha Authors
- SCOPUS Author ID
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- Journal Title
- Journal of Biological Chemistry
- Journal of Biological Chemistry vol. 279, no. 31, pp. 32181 - 32190
- SCI; SCIE; SCOPUS
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- Phospholipase C-γ1 (PLC-γ1) is phosphorylated on three tyrosine residues: Tyr-771, Tyr-783, and Tyr-1253. With the use of antibodies specific for each of these phosphorylation sites, we have now determined the kinetics and magnitude of phosphorylation at each site. Phosphorylation of Tyr-783, which is essential for lipase activation, was observed in all stimulated cell types examined. The extent of phosphorylation of Tyr-1253 was ∼50 to 70% of that of Tyr-783 in cells stimulated with platelet-derived growth factor (PDGF) or epidermal growth factor (EGF), but Tyr-1253 phosphorylation was not detected in B or T cell lines stimulated through B- and T-cell antigen receptors, respectively. Tyr-771 was phosphorylated only at a low level in all cells studied. In cells stimulated with PDGF, phosphorylation and dephosphorylaiion of Tyr-783 and of Tyr-1253 occurred with similar kinetics; the receptor kinase appeared to phosphorylate both sites, albeit with Tyr-783 favored over Tyr-1253, before the bound PLC-γ1 was released, and phosphorylation at the two sites occurred independently. PDGF and EGF induced similar levels of phosphorylation of Tyr-783 and of Tyr-1253 in a cell line that expressed receptors for both growth factors. However, only PDGF, not EGF, elicited substantial PLC activity, suggesting that Tyr-783 phosphorylation was not sufficient for enzyme activation. Finally, concurrent production of phosphatidylinositol 3,4,5-trisphosphate was found to contribute to the activation of phosphorylated PLC-γ1.
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