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Platelet adhesion and signaling induced by the octapeptide primary binding sequence (KOGEOGPK) from type III collagen

U553 INSERM: Hémostase, Endothélium et Angiogénèse, Institut d’Hématologie, Université Paris VII-Denis Diderot, IFR Saint-Louis, Hôpital Saint-Louis, Paris Cedex, France

¹Correspondence: U 553 INSERM, Hôpital Saint-Louis, 1 Avenue Claude Vellefaux, 75475 Paris-cedex 10, France. E-mail: f.lafeve{at}chu-stlouis.fr

Platelet adhesion to vascular collagens is an essential step in the initiation of hemostasis and thrombosis. Several platelet receptors interact with type I and type III collagens, including GP Ia/IIa and GP VI. We recently described a new platelet receptor (TIIICBP) specific for a type III collagen-related primary binding sequence, the KOGEOGPK octapeptide. Here, we characterize platelet adhesion to the immobilized octapeptide and demonstrate that this adhesion 1) is Ca²⁺ and Mg²⁺ independent, suggesting a noninvolvement of GP Ia/IIa; 2) is not inhibited by an antibody against GP VI; and 3) triggers platelet protein tyrosine phosphorylation. Whereas TXA₂ has minimal effects, released ADP via only P2Y₁₂ potentiates platelet adhesion to the octapeptide. Octapeptide-induced platelet adhesion triggers platelet signaling through tyrosine phosphorylation of the 68 kDa subunit of TIIICBP, Syk, PLCgamma2, and FAK. Tyrosine phosphorylation of the FcR gamma-chain and LAT is also observed but to a lesser extent than with type III collagen, suggesting the requirement of GP VI for full tyrosine phosphorylation of FcR gamma-chain and LAT. The present study provides evidence for a critical role for the type III collagen-related KOGEOGPK octapeptide in mediating platelet adhesion and signaling, and consequently in platelet-collagen interactions.—Maurice, P., Legrand, C., Fauvel-Lafève, F. Platelet adhesion and signaling induced by the octapeptide primary binding sequence (KOGEOGPK) from type III collagen.

Key Words: platelet aggregation • glycoprotein • platelet-collagen interaction