PLC gamma 1, a possible mediator of T cell receptor function.
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.
Granja
C
C
Division of Immunogenetics, Dana-Farber Cancer Institute, Boston, Massachusetts 02115.
Lin
L L
LL
Yunis
E J
EJ
Relias
V
V
Dasgupta
J D
JD
D000945:Antigens, Differentiation, T-Lymphocyte / Q000378:metabolism*; D015153:Blotting, Western; D017252:CD3 Complex; D005576:Colforsin / Q000494:pharmacology; D004789:Enzyme Activation; D006801:Humans; D007938:Leukemia; D010766:Phosphorylation; D011233:Precipitin Tests; D011493:Protein Kinase C / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000201:enzymology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism
D000945:Antigens, Differentiation, T-Lymphocyte; D017252:CD3 Complex; D011948:Receptors, Antigen, T-Cell; D005576:Colforsin; D014443:Tyrosine; D011494:Protein Kinases; D011493:Protein Kinase C; D010738:Type C Phospholipases; D013755:Tetradecanoylphorbol Acetate