The platelet collagen receptor glycoprotein VI is a member of the immunoglobulin superfamily closely related to Fc alpha R and the natural killer receptors

We have cloned the platelet collagen receptor glycoprotein (GP) VI from a h uman bone marrow cDNA library using rapid amplification of cDNA ends with p latelet mRNA to complete the 5' end sequence. GPVI was isolated from platel ets using affinity chromatography on the snake C-type lectin, convulxin, as a critical step. Internal peptide sequences were obtained, and degenerate primers were designed to amplify a fragment of the GPVI cDNA, which was the n used as a probe to screen the library. Purified GPVI, as well as Fab frag ments of polyclonal antibodies made against the receptor, inhibited collage n-induced platelet aggregation. The GPVI receptor cDNA has an open reading frame of 1017 base pairs coding for a protein of 339 amino acids including a putative 23-amino acid signal sequence and a 19-amino acid transmembrane domain between residues 247 and 265, GPVI belongs to the immunoglobulin sup erfamily, and its sequence is closely related to Fc alpha R and to the natu ral killer receptors, Its extracellular chain has two Ig-C2-like domains fo rmed by disulfide bridges. An arginine residue is found in position 3 of th e transmembrane portion, which should permit association with Fc gamma and its immunoreceptor tyrosine based activation motif via a salt bridge. With 51 amino acids, the cytoplasmic tail is relatively long and shows little ho mology to the C-terminal part of the other family members. The ability of t he cloned GPVI cDNA to code for a functional platelet collagen receptor was demonstrated in the megakaryocytic cell line Dami, Dami cells transfected with GPVI cDNA mobilized intracellular Ca2+ in response to collagen, unlike the nontransfected or mock transfected Dami cells, which do not respond to collagen.