Lipid Rafts Facilitate the Interaction of PECAM-1 with the Glycoprotein VI-FcR γ-Chain Complex in Human Platelets

• Published in: The Journal of biological chemistry 2006-12, Vol.281 (51), p.39330-39338
• Main Authors: Lee, Fiona A., van Lier, Marjolijn, Relou, Ingrid A.M., Foley, Loraine, Akkerman, Jan-Willem N., Heijnen, Harry F.G., Farndale, Richard W.
• Format: Article
• Language: English
• Subjects: Amino Acid Motifs; Animals; Blood Platelets - metabolism; Cattle; Cell Membrane - metabolism; Cholera Toxin - chemistry; Cholera Toxin - pharmacology; Down-Regulation; Humans; Membrane Microdomains - chemistry; Membrane Microdomains - metabolism; Microscopy, Confocal; Phosphorylation; Platelet Endothelial Cell Adhesion Molecule-1 - chemistry; Platelet Membrane Glycoproteins - chemistry; Receptors, IgG - chemistry; Tyrosine - chemistry
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M607930200

Glycoprotein (GP) VI, the main signaling receptor for collagen on platelets, is expressed in complex with the FcR γ-chain. The latter contains an immunoreceptor tyrosine-based activation motif, which becomes phosphorylated, initiating a signaling cascade leading to the rapid activation and aggregation of platelets. Previous studies have shown that signaling by immunoreceptor tyrosine-based activation motif-containing receptors is counteracted by signals from receptors with immunoreceptor tyrosine-based inhibitory motifs. Here we show, by immunoprecipitation, that the GPVI-FcR γ-chain complex associates with the immunoreceptor tyrosine-based inhibitory motif-containing receptor, PECAM-1. In platelets stimulated with collagen-related peptide (CRP-XL), tyrosine phosphorylation of PECAM-1 precedes that of the FcR γ-chain, implying direct regulation of the former. The GPVI-FcR γ-chain complex and PECAM-1 were present in both lipid raft and soluble fractions in human platelets; this distribution was unaltered by activation with CRP-XL. Their association occurred in lipid rafts and was lost after lipid raft depletion using methyl-β-cyclodextrin. We propose that lipid raft clustering facilitates the interaction of PECAM-1 with the GPVI-FcR γ-chain complex, leading to the down-regulation of the latter.