Collagen-mimetic peptides mediate flow-dependent thrombus formation by high- or low-affinity binding of integrin α2β1 and glycoprotein VI

Abstract

Background: Collagen acts as a potent surface for platelet adhesion and thrombus formation under conditions of blood flow. Studies using collagen-derived triple-helical peptides have identified the GXX' GER motif as an adhesive ligand for platelet integrin α2β1, and (GPO) n as a binding sequence for the signaling collagen receptor, glycoprotein VI (GPVI). Objective: The potency was investigated of triple-helical peptides, consisting of GXX' GER sequences within (GPO)n or (GPP)n motifs, to support flow-dependent thrombus formation. Results: At a high-shear rate, immobilized peptides containing both thehigh-affinity α2β1-binding motif GFOGER and the (GPO)n motif supported platelet aggregation and procoagulant activity, even in the absence of von Willebrand factor (VWF). With peptides containing only one of these motifs, co-immobilized VWF was needed for thrombus formation. The (GPO)n but not the (GPP)n sequence induced GPVI-dependent platelet aggregation and procoagulant activity. Peptides with intermediate affinity (GLSGER, GMOGER) or low-affinity (GASGER, GAOGER) α2β1-binding motifs formed procoagulant thrombi only if both (GPO)n and VWF were present. At a low-shear rate, immobilized peptides with high- or low-affinity α2β1-binding motifs mediated formation of thrombi with procoagulant platelets only in combination with (GPO)n. Conclusions: Triple-helical peptides with specific receptor-binding motifs mimic the properties of native collagen I in thrombus formation by binding to both platelet collagen receptors. At a high-shear rate, either GPIb or high-affinity (but not low-affinity) GXX'GER mediates GPVI-dependent formation of procoagulant thrombi. By extension, high-affinity binding for α2β1 can control the overall platelet-adhesive activity of native collagens. © 2008 International Society on Thrombosis and Haemostasis.