Glycoprotein VI

Glycoprotein VI (GPVI) is a membrane glycoprotein unique to platelets and has been identified as a physiological receptor for collagen. Damage to a vessel wall exposes the subendothelial component collagen to platelets in the blood flow. Interaction of platelets with collagen via the receptor GPVI results in platelet activation and adhesion--the processes that are essential for thrombus formation. On the platelet surface, GPVI is present as a complex with the homodimeric Fc receptor y-chain (FcRgamma with a possible stoichiometry of two GPVI molecules and one FcRgamma dimer). When collagen binds to GPVI, a platelet activation cascade is initiated by tyrosine phosphorylation of the immunoreceptor tyrosine-based activation motif of FcRgamma and this phosphorylation induces the formation of a large complex composed from many signal-transducing proteins. In flow adhesion experiments that closely approximate physiological conditions, GPVI is essential for the formation of large platelet aggregates on collagen.