Guanine nucleotide exchange factor for the small GTPase RALA. May be involved in cytoskeletal organization. May also be involved in the stimulation of transcription in a Ras-independent fashion. Interacts with RALA (By similarity). Interacts with the SH3 domains of GRB2 and PLCG1. Associates with membranes through the PH domain. Abundant in brain and testis. The PH domain mediates binding to phosphatidylinositol 4,5-bisphosphate.