Expression and function of alphabeta1 integrins in pancretic beta (INS-1) cells

Integrin-extracellular matrix interactions are important determinants of beta cell behaviours. The beta1 integrin is a well-known regulator of beta cell activities; however, little is known of its associated alpha subunits. In the present study, alphabeta1 integrin expression was examined in the rat insulinoma cell line (INS-1) to identify their role in beta cell survival and function. Seven alpha subunits associated with beta1 integrin were identified, including alpha1-6 and alphaV. Among these heterodimers, alpha3beta1 was most highly expressed. Common ligands for the alpha3beta1 integrin, including fibronectin, laminin, collagen I and collagen IV were tested to identify the most suitable matrix for INS-1 cell proliferation and function. Cells exposed to collagen I and IV demonstrated significant increases in adhesion, spreading, cell viability, proliferation, and FAK phosphorylation when compared to cells cultured on fibronectin, laminin and controls. Integrin-dependent attachment also had a beneficial effect on beta cell function, increasing Pdx-1 and insulin gene and protein expression on collagens I and IV, in parallel with increased basal insulin release and enhanced insulin secretion upon high glucose challenge. Furthermore, functional blockade of alpha3beta1 integrin decreased cell adhesion, spreading and viability on both collagens and reduced Pdx-1 and insulin expression, indicating that its interactions with collagen matrices are important for beta cell survival and function. These results demonstrate that specific alphabeta1 integrin-ECM interactions are critical regulators of INS-1 beta cell survival and function and will be important in designing optimal conditions for cell-based therapies for diabetes treatment.