Platelet adhesion to collagen via the alpha 2 beta 1 integrin under arterial flow conditions causes rapid tyrosine phosphorylation of pp125FAK.

Adhesion of human platelets to collagen under arterial flow conditions mediated by the alpha 2 beta 1 integrin increased tyrosine phosphorylation of several proteins, one of which was the focal adhesion tyrosine kinase, pp125FAK. Tyrosine phosphorylation of pp125FAK did not occur in non-adherent flowing platelets or in platelets attached to poly(L-lysine). Neither adhesion nor tyrosine phosphorylation was affected by pretreatment of platelets with GRGDSP peptide or by anti-alpha IIb beta 3 monoclonal antibody P2. Adherent platelets retained their discoid shape, suggesting that induction of pp125FAK precedes platelet spreading. The tyrosine kinase inhibitor erbstatin decreased tyrosine phosphorylation in non-stimulated platelets and blocked platelet adhesion. These results suggest that pp125FAK plays an important role in platelet adhesion to collagen via the alpha 2 beta 1 integrin.