Cytochalasin D stimulation of tyrosine phosphorylation and phosphotyrosine-associated kinase activity in vascular smooth muscle cells

The actin filament-disrupting agent cytochalasin D strikingly increased tyrosine phosphorylation of a 75 kDa protein (p75) in rabbit aortic vascular smooth muscle cells. The microtubule-disrupting agent, colchicine had no effect on p75 tyrosine phosphorylation. Cytochalasin D also stimulated p75-directed kinase activity as determined by kinase assays of anti-Tyr(P) immunoprecipitates, Cytochalasin D stimulated tyrosine phosphorylation of the F-actin-binding protein, p80/85 cortactin, but p75 was not immunologically related either to cortactin, the phosphatidylinositol 3'-kinase p85 alpha subunit, or the 80 kDa isoform of caldesmon. These results suggest that p75 may represent a cytochalasin D-inducible kinase or kinase-associated component and provide evidence for the existence of a potentially novel kinase pathway regulated by disruption of the actin cytoskeleton. (C) 1998 Academic Press.