CONVULXIN-INDUCED PLATELET-ADHESION AND AGGREGATION - INVOLVEMENT OF GLYCOPROTEIN-VI AND GLYCOPROTEIN-IAIIA

The interaction of convulxin (Cvx), a 72-kDa glycoprotein isolated fro m the venom of Crotalus durissus terrificus with human platelets has b een studied. Cvx at low concentrations (below 100 pM) induced platelet aggregation, dense body secretion and intracellular calcium mobilizat ion which indicates that Cvx is a potent activator of human platelets. Cvx-induced platelet aggregation and secretion was inhibited by 6Fl a n anti-integrin alpha(2)beta(1) monoclonal antibody that was without e ffect on calcium mobilization. Anti-GPVI Fab fragments inhibited aggre gation, secretion and calcium mobilization triggered by Cvx, In additi on, immobilized Cvx was found to induce divalent cation-independent pl atelet adhesion in a static system. Platelet adhesion to Cvx was inhib ited by anti-GPVI Fab fragments but not by anti-integrin alpha(2)beta( 1). Cvx was shown to bind to a 57 000 Dalton protein that was identifi ed as GPVI, Altogether, these results indicate that GPVI behaves as a receptor for Cvx, while integrin alpha(2)beta(1) could play a regulato ry role in Cvx-induced platelet aggregation. Cvx and collagen interact ion with platelets, thus appears to share some characteristics but to also have specific properties.