Constitutive and functional association of the platelet collagen receptor glycoprotein VI–Fc receptor γ-chain complex with membrane rafts

Abstract

The platelet collagen receptor glycoprotein (GP) VI–Fc receptor γ-chain (FcRγ) complex transduces signals in an immunoreceptorlike manner. We examined a role for the Triton X-100–insoluble membrane rafts in GPVI–FcRγ complex signaling. Methyl-β-cyclodextrin (MβCD)-induced disruption of the membrane rafts inhibited not only platelet aggregation and secretion but also tyrosine phosphorylation of signaling molecules on stimulation through the GPVI–FcRγ complex. The GPVI–FcRγ complex was constitutively associated with membrane rafts wherein the Src family kinases and LAT were also present. Their association was not affected by the complex engagement but was highly sensitive to MβCD treatment. Thus, we provide the first evidence that the GPVI–FcRγ complex is constitutively and functionally associated with membrane rafts.