Electroporation of pp60 super(c-src) antibodies inhibits the angiotensin II activation of phospholipase C- gamma 1 in rat aortic smooth muscle cells

Our previous study has shown that angiotensin II induces the rapid tyrosine phosphorylation and activation of phospholipase C- gamma 1 in cultured rat aortic smooth muscle. This signaling pathway is initiated by ligand binding to the AT sub(1) receptor, a cell surface G protein-coupled receptor. Antibodies to pp60 super(c-src) were introduced into RASM cells by electroporation. Angiotensin II-stimulated tyrosine phosphorylation of phospholipase C- gamma 1 was eliminated by the anti-pp60 super(c-src) antibodies but not by anti-mouse IgG or bovine serum albumin. Angiotensin II also induced the rapid tyrosine phosphorylation of pp120, a known pp60 super(c-src) kinase substrate, and this phosphorylation was also specifically inhibited by anti-pp60 super(c-src) antibodies. Electroporation of RASM cells with anti-pp60 super(c-src) antibodies had no effect on platelet-derived growth factor-stimulated tyrosine phosphorylation of PLC- gamma 1. Anti-pp60 super(c-src) also reduced the angiotensin II-stimulated inositol 1,4,5-trisphosphate production by 78%, while it had no effect on the platelet-derived growth factor-stimulated inositol 1,4,5-trisphosphate production. These data provide the first evidence for a direct involvement of pp60 super(c-src) kinase in angiotensin II-mediated PLC- gamma 1 phosphorylation and activation. Furthermore, it also describes a pathway in which a seven-transmembrane receptor can stimulate an intracellular tyrosine kinase.