Guanine nucleotide exchange factor (GEF) for the small GTPase RALA. May be involved in cytoskeletal organization (By similarity). Guanine nucleotide exchange factor for. Interacts with the SH3 domains of GRB2, NCK1, PLCG1 and SRC. Associates with membranes through the PH domain. Widely expressed (at protein level). Isoform 2 is expressed in brain, colon, kidney, pancreas, prostate, skeletal muscle, small intestine, testis, thymus and uterus. Isoform 1 is expressed at high levels in heart and testis and at lower levels in brain, pancreas, skeletal muscle, small intestine and thymus. The PH domain mediates binding to membranes. It is required for efficient GEF activity. Extended N-terminus. Extended N-terminus.