Role of the recombinant non-integrin platelet collagen receptor P65 on platelet activation induced by convulxin

Convulxin (Cvx) isolated from Crotalus durissus terrificus venom selectivel y binds with a high affinity to platelets and induces platelet aggregation by a mechanism that resembles that induced by collagen. Taking advantage th at P65 has been recently cloned and expressed as a recombinant soluble prot ein (rec-P65), we examined the role of this non-integrin collagen receptor in platelet activation induced by Cvx. Rec-P65 blocked platelet adhesion to collagen-coated surfaces and inhibited platelet aggregation and ATP secret ion induced by type I collagen. On the other hand, rec-P65 did not inhibit platelet aggregation and ATP secretion induced by Cvx, and it did not affec t platelet adhesion to Cvx. In addition, ligand-blotting indicated that the Cvx binding to the collagen receptor GPVI was preserved in the presence of rec-P65. These observations indicate that P65 does not play a significant role in platelet activation by Cvx; in contrast, platelet response to colla gen involves multiple receptors, (C) 2000 Academic Press.