Cloning, characterization, and functional studies of a nonintegrin platelet receptor for type I collagen

A cDNA (1.6 kb) encoding a platelet protein receptor that binds type I collagen has been isolated from a human bone marrow cDNA library by using a degenerate oligonucleotide probe derived from the amino acid sequence of a CNBr fragment of the purified receptor, Computer search revealed that this cDNA represents the coding sequence of a unique protein, Using the prokaryotic expression system pKK 223-3-65 cDNA, a 54-kD recombinant protein was obtained and purified to apparent homogeneity, In an eukaryotic expression vector (pcDNA3-65 cDNA), a 65-kD protein was identified that was recognized by monoclonal anti-65 kD antibody (anti-65m), The recombinant protein binds to type I, but not to type III collagen by affinity column chromatography, The binding of the recombinant protein to type I collagen-coated Petri dishes is inhibited by anti-65m in a dose-dependent manner, The pcDNA3-65 cDNA-transfected nonadherent T cells express the protein, allowing them to attach to a type I collagen matrix, and are inhibited by anti-65m in a dose-dependent manner, Like the receptor protein purified from platelet membranes, the recombinant protein inhibits type I collagen-induced platelet aggregation and the adhesion of [C-14]serotonin-labeled platelets to type I collagen in a dose-dependent manner, The recombinant protein neither binds to type III collagen-coated Petri dishes nor inhibits type III collagen and ADP-induced platelet aggregation, indicating specificity for type I collagen.