Src Homology Domains of Phospholipase C γ1 Inhibit Nerve Growth Factor‐Induced Differentiation of PC12 Cells

Abstract

Phospholipase C γ1 (PLC‐γ1) is phosphorylated on treatment of cells with nerve growth factor (NGF). To assess the role of PLC‐γ1 in mediating the neuronal differentiation induced by NGF treatment, we established PC12 cells that overexpress whole PLC‐γ1 (PLC‐γ1PC12), the SH2‐SH2‐SH3 domain (PLC‐γ1SH223PC12), SH2‐SH2‐deleted mutants (PLC‐γ1ΔSH22PC12), and SH3‐deleted mutants (PLC‐γ1ΔSH3PC12). Overexpressed whole PLC‐γ1 or the SH2‐SH2‐SH3 domain of PLC‐γ1 stimulated cell growth and inhibited NGF‐induced neurite outgrowth of PC12 cells. However, cells expressing PLC‐γ1 lacking the SH2‐SH2 domain or the SH3 domain had no effect on NGF‐induced neuronal differentiation. Overexpression of intact PLC‐γ1 resulted in a threefold increase in total inositol phosphate accumulation on treatment with NGF. However, overexpression of the SH2‐SH2‐SH3 domain of PLC‐γ1 did not alter total inositol phosphate accumulation. To investigate whether the SH2‐SH2‐SH3 domain of PLC‐γ1 can mediate the NGF‐induced signal, tyrosine phosphorylation of the SH2‐SH2‐SH3 domain of PLC‐γ1 on NGF treatment was examined. The SH2‐SH2‐SH3 domain of PLC‐γ1 as well as intact PLC‐γ1 could be tyrosine‐phosphorylated on NGF treatment. These results indicate that the overexpressed SH2‐SH2‐SH3 domain of PLC‐γ1 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‐γ1 but to the SH2‐SH2‐SH3 domain of PLC‐γ1.