The Rab3-interacting molecule RIM is expressed in pancreatic β-cells and is implicated in insulin exocytosis

The putative Rab3 effector RIM (Rab3-interacting molecule) was detected by Northern blotting, RT-PCR and Western blotting in native pancreatic beta-cells as well as in the derived cell lines INS-1E and HIT-TIS. RIM was localized on the plasma membrane of INS-1E cells and beta-cells, An involvement of RIM in insulin exocytosis was indicated by transfection experiments of INS-1E cells with the Rab3 binding domain of RTM, This domain enhanced glucose-stimulated secretion in intact cells and Ca2+-stimulated exocytosis in permeabilized cells. Go-expression of Rab3A reversed the effect of RIM on exocytosis. These results suggest an implication of RIM in the control of insulin secretion. (C) 2000 Federation of European Biochemical Societies.