Guanine nucleotide exchange factor (GEF) for RAP1A, RAP1B and RAP2A small GTPases that is activated by binding cAMP. Seems not to activate RAB3A. Involved in cAMP-dependent, PKA-independent exocytosis through interaction with RIMS2 (By similarity). Interacts with RIMS1 and RIMS2. Probably part of a complex with RIMS2 and GTP-activated RAB3A (By similarity).