Recently, we and others have reported tyrosine phosphorylation of phospholipase C-gamma 1 (PLC gamma 1) enzyme after CD3 activation of T cells, and have proposed that PLC gamma 1 mediates signal transduction through the T cell receptor (TCR/CD3). Here, using immunoblotting and immune complex PLC assays, we show that CD3 stimulation of Jurkat cells induces the association of PLC gamma 1 enzyme with CD3 complex. PLC activity is also found to co-precipitate with the CD3 zeta chain from activated cells. In addition, in vitro PLC assays show that CD3 activation leads to about 10-fold stimulation of PLC gamma 1 activity. These results, along with the observation that Jurkat cells preferentially express PLC gamma 1, indicate that PLC gamma 1 participates in CD3 signaling.

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