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.
Molecular Function: protein binding; Ras GTPase binding; guanyl-nucleotide exchange factor activity; protein complex binding; nucleotide binding; cAMP-dependent protein kinase regulator activity; cAMP binding; Ras guanyl-nucleotide exchange factor activity
Biological Process: regulation of protein amino acid phosphorylation; exocytosis; regulation of dendrite development; positive regulation of smooth muscle cell migration; signal transduction; negative regulation of synaptic transmission; calcium ion-dependent exocytosis; regulation of exocytosis; regulation of small GTPase mediated signal transduction; cAMP-mediated signaling; positive regulation of Ras GTPase activity; insulin secretion; small GTPase mediated signal transduction; positive regulation of GTPase activity
SS: The number of records in which this modification site was determined using site-specific methods. SS methods include amino acid sequencing, site-directed mutagenesis, modification site-specific antibodies, specific MS strategies, etc.