Collagen-platelet interaction: Separate receptor sites for types I and III collagen

Abstract

We have isolated a platelet membrane protein of M r47 kDa which is responsible for the interaction of platelets with type III collagen. The 47 kDa protein was purified to apparent homogeneity by type III collagen-Sepharose 2B column chromatography and preparative slab gel electrophoreses. The 47 kDa protein blocked the adhesion of platelets to type III but not to type I collagen. Polyclonal antibodies were obtained from rabbits immunized with the purified 47 kDa protein emulsified in complete Freund's adjuvant. The polyclonal antibodies inhibited the type III collagen but not type I collagen-induced platelet aggregation. The inhibitory effect of the antibodies on type III collagen-induced platelet aggregation was dose-dependent. Cross-inhibition on platelet aggregation studies showed that type I collagen receptor antibodies (M r65 kDa) did not inhibit type III collagen-induced platelet aggregation and type III collagen receptor antibodies did not inhibit type I collagen induced platelet aggregation. These results suggest that type I and type III collagens interact with platelets at separate sites.