ELECTROPORATION OF PP60(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 (RASM) cells (Marrero, M. B,, Paxton, W, G,, Duff, J, L,, Berk, B, C,, and Bernstein, K, E, (1994) J, Biol, Chem, 269, 10935-10939), This signaling pathway is initiated by ligand binding to the AT(1) receptor, a cell surface G protein-coupled receptor, Antibodies to pp60(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(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(c-src) kinase substrate, and this phosphorylation was also specifically inhibited by anti-pp60(c-src) antibodies, Electroporation of RASM cells with anti-pp60(c-src) antibodies had no effect on platelet-derived growth factor-stimulated tyrosine phosphorylation of PLC-gamma 1, Anti-pp60(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(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.