Medical Definition of integrin
: any of various glycoproteins found on cell surfaces that are involved in the adhesion of cells (such as T cells) to other cells (such as endothelial cells) or to extracellular material (such as fibronectin or laminin) and mediate various biological processes (such as phagocytosis, wound healing, and embryogenesis) ◆Integrins are composed of two dissimilar polypeptide chains (called α and β respectively) that extend through the cell membrane and vary in composition, which can influence their biological activity (such as the specificity of the ligand that they will bind). <Through these 20 or more integrins, the [extracellular] matrix sends cells various signals that regulate what genes are active, ultimately influencing whether cells proliferate, specialize, migrate, or even kill themselves.—Richard Monastersky, Science News, 30 Aug. 1997> <Early on we understood that integrins consist of two protein chains, or subunits. The subunit designated “alpha” is today known to have about 15 variants, and the “beta” subunit has about eight variants.—Alan F. Horwitz, Scientific American, May 1997>
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