Modulatory roles of various classes of small G proteins and their regulatory proteins/factors in insulin secretion. Small G proteins, such as Rac1, Cdc42, and ARF-6 (and potentially Rho) regulate cytoskeletal remodeling and vesicular fusion in the islet. Rab3A, Rab27A, and Rap1 are implicated docking and priming of secretory vesicles at the exocytotic sites. Glucose-mediated activation of some of these signaling proteins is under the fine control of various regulatory proteins including GDIs (e.g., Rho GDI and Cav-1) and GEFs (Tiam1, ARNO, and Epac2).