IDENTIFICATION AND CHARACTERIZATION OF ALPHA-3-BETA-1 INTEGRIN ON PRIMARY AND TRANSFORMED RAT ISLET CELLS

Dispersed rat islet cells embedded in a matrix of collagen I are known to form aggregates in vitro reminiscent of native islets. Furthermore , it appears that islet function and survival are better maintained in vitro when cells are grown in the presence of extracellular matrix. T hese studies suggest an important role of cell-matrix interactions in the formation and maintenance of islet structure and function. The mol ecular basis of these interactions is mostly unknown. In the present s tudy, we confirm the presence of beta 1 integrins on primary and trans formed (RIN-2A line) rat islet cells. Perturbation studies in vitro sh ow that beta 1 integrins play a role in islet cell attachment and spre ading on bovine extracellular matrix and on the matrix produced by A-4 31 cells. The alpha 3 integrin subunit is coimmunoprecipitated with be ta 1 from extracts of both primary and transformed islet cells, and im munodepletion studies suggest that alpha 3 beta 1 represents nearly ha lf of the total beta 1 integrins expressed on primary islet cells. In situ, alpha 3 and beta 1 are expressed on the surface of all islet cel l types, as shown by indirect immunocytochemistry on paraformaldehyde- fixed sections of rat pancreas. In conclusion, the study demonstrates the presence of alpha 3 beta 1 on primary and transformed rat islet ce lls, and an important role of beta 1 integrins in islet cell attachmen t and spreading in vitro. (C) 1997 Academic Press.