Differential regulation of phosphoinositide metabolism by alpha(V)beta(3) and alpha(V)beta(5) integrins upon smooth muscle cell migration

Smooth muscle cell migration is a key step of atherosclerosis and angiogene sis. We demonstrate that alpha (V)beta (3) and alpha (V)beta (5) integrins synergistically regulate smooth muscle cell migration onto vitronectin. Usi ng an original haptotactic cell migration assay, we measured a strong stimu lation of phosphoinositide metabolism in migrating vascular smooth muscle c ells. Phosphatidic acid production and phosphoinositide 3-kinase IA activat ion were triggered only upon alpha (V)beta (3) engagement. Blockade of alph a (V)beta (3) engagement or phospholipase C activity resulted in a strong i nhibition of smooth muscle cell spreading on vitronectin. By contrast, bloc kade of alpha (V)beta (5) reinforced elongation and polarization of cell sh ape. Moreover, Pyk2-associated tyrosine kinase and phosphoinositide 4-kinas e activities measured in Pyk2 immunoprecipitates were stimulated upon cell migration. Blockade of either alpha (V)beta (3) or alpha (V)beta (5) functi on, as well as inhibition of phospholipase C activity, decreased both Pyk2- associated activities. We demonstrated that the Pyk2-associated phosphoinos itide 4-kinase corresponded to the beta isoform. Our data point to the meta bolism of phosphoinositides as a regulatory pathway for the differential ro les played by alpha (V)beta (3) and alpha (V)beta (5) upon cell migration a nd identify the Pyk2-associated phosphoinositide 4-kinase beta as a common target for both integrins.