Granja C, Lin L L, Yunis E J, Relias V, Dasgupta J D
Division of Immunogenetics, Dana-Farber Cancer Institute, Boston, Massachusetts 02115.
J Biol Chem. 1991 Sep 5;266(25):16277-80.
Stimulation of T cell antigen receptor (TCR/CD3) following the recognition of peptide-major histocompatibility antigen complex induces phosphatidylinositol 4,5-bisphosphate (PIP2) hydrolysis. However, the phospholipase C (PLC) enzyme mediating this process has not been identified. We report that PLC gamma 1 protein is expressed in human T cells. It is a phosphoprotein, and the activation of cyclic AMP-dependent protein kinase (PKA) or of protein kinase C (PKC) with forskolin or phorbol ester, respectively, increases the level of phosphorylation. CD3 stimulation of T cells induces tyrosine phosphorylation of PLC gamma 1 and causes 8-10-fold higher yield of PLC activity with anti-phosphotyrosine antibody (APTyr Ab) from activated cells than from non-activated cells. Genistein, an inhibitor of protein tyrosine kinase, decreases this yield of AP-Tyr Ab-bound PLC activity from activated cells and lowers the level of Ca2+ mobilization. Furthermore, phorbol ester and forskolin treatment of cells before CD3 stimulation reduces the level of tyrosine phosphorylation of PLC gamma 1 and the PLC activity associated with APTyr Ab. These results suggest that CD3 stimulation activates PIP2 hydrolysis by inducing tyrosine phosphorylation of PLC gamma 1, which is regulated negatively by PKC and PKA.
在识别肽 - 主要组织相容性抗原复合物后，T细胞抗原受体（TCR/CD3）的刺激会诱导磷脂酰肌醇4,5 - 二磷酸（PIP2）水解。然而，介导这一过程的磷脂酶C（PLC）酶尚未被鉴定出来。我们报告称PLCγ1蛋白在人T细胞中表达。它是一种磷蛋白，分别用福斯高林或佛波酯激活环磷酸腺苷依赖性蛋白激酶（PKA）或蛋白激酶C（PKC），会增加其磷酸化水平。T细胞的CD3刺激会诱导PLCγ1的酪氨酸磷酸化，并导致用抗磷酸酪氨酸抗体（APTyr Ab）从活化细胞中获得的PLC活性比未活化细胞高8 - 10倍。蛋白酪氨酸激酶抑制剂染料木黄酮会降低活化细胞中与APTyr Ab结合的PLC活性产量，并降低Ca2+动员水平。此外，在CD3刺激之前用佛波酯和福斯高林处理细胞会降低PLCγ1的酪氨酸磷酸化水平以及与APTyr Ab相关的PLC活性。这些结果表明，CD3刺激通过诱导PLCγ1的酪氨酸磷酸化来激活PIP2水解，而PKC和PKA对其具有负调控作用。
