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. Interacts with RIMS1 and RIMS2. Probably part of a complex with RIMS2 and GTP-activated RAB3A. Predominantly expressed in brain and adrenal gland. Isoform 2 is expressed in liver. Isoform 1 is expressed in liver at very low levels. 3 isoforms of the human protein are produced by alternative promoter. Note: This description may include information from UniProtKB.
Biological Process: calcium ion-dependent exocytosis; cAMP-mediated signaling; insulin secretion; negative regulation of synaptic transmission; positive regulation of protein secretion; positive regulation of smooth muscle cell migration; regulation of dendrite development; regulation of exocytosis; signal transduction