Platelet Membrane Glycoprotein IIb/IIIa: Member of a Family of Arg-Gly-Asp—Specific Adhesion Receptors

TLDR

Platelet surface adhesion to fibrinogen and fibronectin, key to thrombosis and hemostasis, is blocked by synthetic RGD peptides that mimic the cell‑adhesion motif. An insolubilized heptapeptide RGD affinity matrix selectively isolates platelet membrane glycoprotein IIb/IIIa from detergent extracts. The isolated IIb/IIIa confers liposomes binding to fibrinogen, fibronectin, and vitronectin but not thrombospondin or albumin, demonstrating that this RGD‑recognizing receptor has broader specificity and confirming a family of such adhesion receptors.

Abstract

Adhesive interactions of the platelet surface with plasma proteins such as fibrinogen and fibronectin play an important role in thrombosis and hemostasis. The binding of both of these proteins to platelets is inhibited by synthetic peptides containing the sequence Arg-Gly-Asp, which corresponds to the cell adhesion site in fibronectin and is also present in the alpha chain of fibrinogen. An affinity matrix made of an insolubilized heptapeptide containing the Arg-Gly-Asp sequence selectively binds the platelet membrane glycoprotein IIb/IIIa from detergent extracts of platelets. When incorporated into liposome membranes, the isolated protein confers to the liposomes the ability to bind to surfaces coated with fibrinogen, fibronectin, and vitronectin but not to surfaces coated with thrombospondin or albumin. This platelet receptor is related to the previously identified fibronectin and vitronectin receptors in that it recognizes an Arg-Gly-Asp sequence but differs from the other receptors in its wider specificity toward various adhesive proteins. These results establish the existence of a family of adhesion receptors that recognize the sequence Arg-Gly-Asp.