Platelet Adhesion to Collagen and Collagen-Related Peptide Under Flow: Roles of the 2 1 Integrin, GPVI, and Src Tyrosine Kinases

R. Polanowska-Grabowska
2003 Arteriosclerosis, Thrombosis and Vascular Biology  
Objective-Platelet stimulation by collagen and collagen-related peptides (CRPs) is associated with activation of protein tyrosine kinases. In the present study, we investigated the role of Src family tyrosine kinases in the initial adhesion events of human platelets to collagen and cross-linked CRP. Methods and Results-Under arterial flow conditions, a glycoprotein VI-specific substrate, cross-linked CRP, caused rapid (Ͻ2 second) platelet retention and protein tyrosine phosphorylation that were
more » ... markedly decreased by the Src family kinase inhibitor pyrozolopyrimidine (PP2) or by aggregation inhibitor GRGDSP. CRP-induced platelet retention was transient, and 90% of single platelets or aggregates detached within seconds. PP2, although having no effect on RGD peptide-binding to CRP, completely blocked aggregation and tyrosine phosphorylation of Syk and phospholipase C␥2 (PLC␥2). In contrast, PP2 weakly (Ͻ30%) suppressed firm adhesion to collagen mediated primarily by the ␣ 2 ␤ 1 integrin. Although PP2 prevented activation of Syk and PLC␥2 in collagen-adherent platelets, tyrosine phosphorylation of several unidentified protein bands persisted, as did autophosphorylation of pp125 FAK . Conclusions-These findings indicate that activation of Src-tyrosine kinases Syk and PLC␥2 is not required for the initial stable attachment of human platelets to collagen and for FAK autophosphorylation. However, Src-tyrosine kinases are critical for glycoprotein VI-mediated signaling leading to platelet aggregation. (Arterioscler Thromb Vasc Biol. 2003; 23:1934-1940
doi:10.1161/01.atv.0000086937.46974.70 pmid:12869350 fatcat:u4nikn57u5g3lkarargrtft7ci