Guanine nucleotide exchange factor (GEF) for Rap1A, Rap2A and M-Ras GTPases. Does not interact with cAMP.
Subcellular locations: Cytoplasm, Cell membrane
Upon binding to M-Ras, it translocates to the plasma membrane.
Isoform 3 has highest expression levels in the brain, heart, liver, lung and placenta and is barely detectable in skeletal muscle, kidney and pancreas.