Identification of a Functional Site on CD36 Involved in the Interaction Between Platelets and Collagen

Adhesion of platelets to collagen, exposed on the subendothelium as a result of vessel wall injury, is a vital step in the formation of a haemostatic plug. Glycoprotein CD36, also known as GPIIIb/GPIV, is one of the platelet glycoproteins known to interact with collagen. The aim of this work was to identify structural/functional sites on CD36 interacting with collagen. Eight peptides, corresponding to sites presumed to be hydrophylic, were synthesized by Fmoc (Fluorenylmethoxycarbonyl) chemistry. Peptides were tested for their ability to inhibit platelet aggregation induced by type I collagen. Peptide E5 (WLNETGTIGDEKA; 415-427), but not the other peptides, inhibited aggregation and secretion of washed platelets induced by collagen but had no effect on thrombin or ADP induced aggregation. Moreover, peptide E5 was shown to interfere with the binding of (125)I-labelled CD36 to collagen. Peptide E5 had little or no effect on collagen-induced platelet aggregation performed in platelet rich plasma (PRP), as previously described in the cases of monoclonal antibodies directed against α(2)or β(1). These results indicate that peptide E5 represents a site on CD36 that interacts with collagen and is involved in platelet functions.