1) Family of integral membrane proteins which serve as receptors for fibronectin, laminin, and other adhesive extracellular glycoproteins.

2) Integrins are transmembrane glycoprotein receptors that mediate cell-matrix or cell-cell adhesion, and transduce signals that regulate gene expression and cell growth. They are heterodimeric molecules consisting of noncovalently linked alpha and beta subunits. Different combinations of alpha and beta polypeptides form complexes that vary in their ligand-binding specificities. Both alpha and beta subunits display a cytoplasmic domain that interacts with the cytoskeleton (and possibly signaling molecules), a transmembrane region, and a large extracellular domain that interacts with the extracellular matrix. (from OMIM 147557)

3) Any of various glycoproteins that are found on cell surfaces (as of white blood cells or platelets), that are composed of two dissimilar polypeptide chains, that are receptors for various proteins which typically bind to the tripeptide ligand consisting of arginine, glycine, and aspartic acid, that promote adhesion of cells (as T cells) to other cells (as endothelial cells) or to extracellular material (as fibronectin or laminin), and that mediate various biological processes (as phagocytosis, wound healing, and embryogenesis).