[Integrins: a family of cell adhesion receptors]

Integrins are a family of cell adhesion molecules (CAM's) that mediate the communication between the intracellular and the extracellular compartments. The growing interest in CAM's is due to the essential role they play in cell-cell and cell-matrix recognition processes. These receptors are formed by a non-covalently associated glycoprotein complex of two distinct polypeptide chains, called, alpha and beta. The association of different subunits results in the formation of, at least, 16 different integrins that provide cells with a great versatility in their adhesion properties. An integrin molecule comprises a cytoplasmic domain that interacts with the cytoskeleton, a transmembranous domain and an extracellular domain that binds to one or more ligands. beta 1, beta 2 and beta 3, are the best characterized integrin subfamilies; they are expressed, in different amounts, in epithelial and endothelial cells, leukocytes, fibroblasts and platelets. b1 integrins are essentially involved in cell-extracellular matrix interactions and beta 2 subfamily in leukocyte-leukocyte and leukocyte-endothelial cell communications. The integrin subfamily beta 3 mediates the adhesion of platelets with fibrinogen and other ligands. During embryonic development, integrins in association with other CAM's, play an essential role in cell migration and morphogenesis. Moreover, in processes like inflammation, wound healing and thrombosis, integrins and other CAM's mediate the interactions among the injured tissue and circulating cells. In two genetic diseases like the leukocyte adhesion deficiency and the Glanzmann's thrombasthenia an impairment in leukocyte-endothelial cell interactions and platelet aggregation is detected, due to deficiencies or abnormalities in beta 2 or beta 3 integrin subfamilies, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)