Src homology domains of phospholipase C γ1 inhibit nerve growth factor-induced differentiation of PC12 cells

Phospholipase C gamma 1 (PLC-gamma 1) is phosphorylated on treatment of cells with nerve growth factor (NGF).To assess the role of PLC-gamma 1 in mediating the neuronal differentiation induced by NGF treatment, we established PC12 cells that overexpress whole PLC-gamma 1 (PLC-gamma 1PC12), the SH2-SH2-SH3 domain (PLC-gamma 1SH223PC12), SH2-SH2-deleted mutants (PLC-gamma 1 Delta SH22PC12), and SH3-deleted mutants (PLC-gamma 1 Delta SH3PC12). Overexpressed whole PLC-yl or the SH2-SH2-SH3 domain of PLC-gamma 1 stimulated cell growth and inhibited NGF-induced neurite outgrowth of PC12 cells. However, cells expressing PLC-yl lacking the SH2-SH2 domain or the SH3 domain had no effect on NGF-induced neuronal differentiation. Overexpression of intact PLC-gamma 1 resulted in a threefold increase in total inositol phosphate accumulation on treatment with NGF. However, overexpression of the SH2-SH2-SH3 domain of PLC-gamma 1 did not alter total inositol phosphate accumulation. To investigate whether the SH2-SH2-SH3 domain of PLC-gamma 1 can mediate the NGF-induced signal, tyrosine phosphorylation of the SH2-SH2-SH3 domain of PLC-gamma 1 on NGF treatment was examined. The SH2-SH2-SH3 domain of PLC-gamma 1 as well as intact PLC-gamma 1 could be tyrosine-phosphorylated on NGF treatment. These results indicate that the overexpressed SH2-SH2-SH3 domain of PLC-gamma 1 can block the differentiation of PC12 cells induced by NGF and that the inhibition appears not to be related to the lipase activity of PLC-gamma 1 but to the SH2-SH2-SH3 domain of PLC-gamma 1.