Integrin alpha 5 beta 1 / Integrin α5β1, which is a major cellular receptor for the extracellular matrix protein fibronectin and plays a fundamental role during mammalian development., is composed of α5 (ITGA5/CD49e) and β1 (ITGB1/CD29) subunits. Integrins are adhesion receptors that transmit bidirectional signals across the plasma membrane. The Integrin alpha 5 beta 1 and its primary extracellular matrix ligand fibronectin (Fn) are of great biological importance.