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The adhesion of cells to each other and to the proteins of the extracellular matrix provides a stable environment for cell growth, differentiation, and migration. This is a prerequisite for the normal function of all components of the cardiovascular system. Adhesive interactions, however, are also involved in the pathogenesis of cardiovascular disease, regulating thrombus formation, facilitating leucocyte infiltration, mediating the migration and proliferation of smooth muscle cells, and enabling the deposition of fibrotic tissue. There is, therefore, increasing interest in the receptors that determine these processes—cell adhesion molecules.
Three main groups of adhesion molecules have been implicated in cardiovascular pathology: integrins, selectins, and members of the immunoglobulin superfamily. The structure and function of these molecules is outlined briefly, followed by an assessment of their importance in cardiac disease.
Structure and function of cell adhesion molecules
INTEGRINS
Integrins are glycoproteins composed of two subunits, the α and β chains (fig 1). As their name suggests they mediate the adhesion of cells to each other and to surrounding substrates, “integrating” the cell with its environment.1 In addition, they straddle the cell membrane and play an important role in initiating intracellular events in response to extracellular stimuli.2 The most widely distributed integrins belong to the β1 subfamily, which mainly influence the adhesion of cells to extracellular matrix proteins such as fibronectin, collagens, and laminin (table 1). The β2 integrins are expressed solely by white cells and principally interact with members of the immunoglobulin superfamily promoting leucocyte adhesion and infiltration. The β3 family has two principal members (table 1) with differing, but important, functions. Activation of the αIIbβ3 or glycoprotein IIb/IIIa receptor is the final step in platelet aggregation and determines the adhesion of platelets to other matrix and plasma proteins. This allows them to bind to vascular endothelium and exposed subendothelial proteins. The …