Platelet/Endothelial Cell Adhesion Molecule-1 (PECAM-1, CD31): The All-Purpose Adhesion Molecule

Abstract

Platelet/endothelial cell adhesion molecule-1 (PECAM-1, CD31, and henceforth in this review referred to as “PECAM”) is a member of the immunoglobulin gene superfamily. This 130kDa glycoprotein is concentrated in the junctions between vascular endothelial cells and expressed diffusely on the surfaces of platelets and many types of circulating leukocytes. In addition to being expressed on multiple cell types that interact within the bone marrow and vascular system, it is capable of mediating several different adhesion reactions. It can bind like cells to each other (homotypic adhesion), such as at the endothelial junction. It can bind different cells together (heterotypic adhesion), such as leukocyte to endothelium. On a molecular level, PECAM is capable of homophilic (PECAM binding to PECAM) as well as heterophilic adhesion, (for which certain sulfated glycosaminoglycans may be ligands), depending upon the experimental conditions. Moreover, on leukocytes, ligation of PECAM has been shown to activate adhesion molecules of the integrin family on the same cell. PECAM is thus in a position to play many different roles in the physiology and pathophysiology of the vascular system.