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).
Subcellular locations: Cytoplasm, Membrane
Predominantly expressed in brain and adrenal gland. Isoform 2 is expressed in liver. Isoform 1 is expressed in liver at very low levels.