Function and Regulation of Selectins: A New Family of Leukocyte and Endothelial Cell Adhesion Proteins

Abstract

Three members of new family of adhesion proteins, called Selectins, have been defined: one is expressed by leukocytes (L-selectin), another by endothelial cells (E-selectin), and the third by both endothelial cells and platelets (P-selectin). L-selectin originally characterized as a 90 kD lymphocyte glycoprotein, regulates lymphocyte recirculation through peripheral lymphoid tissues by binding to specialized, postcapillary venules called high-walled endothelial venules (HEV). E-selectin, originally called endothelial-cell leukocyte adhesion molecule-1 (ELAM-I), is described as a 110 kD glycoprotein expressed on cytokine-activated, cultured endothelial cells, and on venules in sites of inflammation in vivo . P-selectin is originally isolated from activated platelets. The function of P-selectin is fully appreciated after cloning of its cDNA (see below) and determining its relationship to L- and E-selectin. The study of selectins has contributed significantly to the understanding of the extravasation process. This chapter reviews the function and regulation of selectins.