Meisenhelder J, Suh P G, Rhee S G, Hunter T
Molecular Biology and Virology Laboratory, Salk Institute, San Diego, California 92138.
Cell. 1989 Jun 30;57(7):1109-22. doi: 10.1016/0092-8674(89)90048-2.
Phospholipase C-gamma (PLC-gamma) was rapidly phosphorylated on tyrosines and serines following PDGF and EGF treatment of quiescent 3T3 mouse fibroblasts and A431 human epidermoid cells, respectively, PDGF treatment increased PLC-gamma phosphorylation within 30 sec. This lasted for up to 1 hr, and occurred at high stoichiometry. Continuous receptor occupancy was required to maintain this phosphorylation. Three major sites of tyrosine phosphorylation were detected in PLC-gamma, two of which were phosphorylated in EGF-treated A431 cells. Under certain conditions PDGF receptor coimmunoprecipitated with PLC-gamma, suggesting that PDGF receptor can phosphorylate PLC-gamma directly. Indeed, purified PDGF or EGF receptor phosphorylated purified PLC-gamma on tyrosines identical to those phosphorylated in vivo. Tyrosine phosphorylation of PLC-gamma was not induced by bombesin, TPA, or insulin. Stimulation of PLC-gamma tyrosine phosphorylation and the reported ability of PDGF and EGF to induce phosphatidylinositol turnover in different cells were strongly correlated. We propose that tyrosine phosphorylation of PLC-gamma by PDGF and EGF receptors leads to its activation, and a consequent increase in phosphatidylinositol turnover.
血小板衍生生长因子（PDGF）和表皮生长因子（EGF）分别作用于静止的3T3小鼠成纤维细胞和A431人表皮样细胞后，磷脂酶C-γ（PLC-γ）的酪氨酸和丝氨酸会迅速发生磷酸化。PDGF处理后30秒内，PLC-γ的磷酸化水平就会升高。这种升高可持续长达1小时，且化学计量比很高。需要持续的受体占据才能维持这种磷酸化。在PLC-γ中检测到三个主要的酪氨酸磷酸化位点，其中两个在EGF处理的A431细胞中发生磷酸化。在某些条件下，PDGF受体与PLC-γ共免疫沉淀，这表明PDGF受体可以直接使PLC-γ磷酸化。事实上，纯化的PDGF或EGF受体可使纯化的PLC-γ在与体内磷酸化相同的酪氨酸位点发生磷酸化。蛙皮素、佛波酯（TPA）或胰岛素不会诱导PLC-γ的酪氨酸磷酸化。PLC-γ酪氨酸磷酸化的刺激与PDGF和EGF在不同细胞中诱导磷脂酰肌醇周转的报道能力密切相关。我们认为，PDGF和EGF受体使PLC-γ酪氨酸磷酸化会导致其激活，进而使磷脂酰肌醇周转增加。
