Acts as a guanine-nucleotide exchange factor (GEF). Promotes guanine-nucleotide exchange on ARF1, ARF3 and ARF6. Promotes the activation of ARF factors through replacement of GDP with GTP. The cell membrane form, in association with ARL4 proteins, recruits ARF6 to the plasma membrane (By similarity). Involved in neurite growth (By similarity). Heteromer. Composed of TAMALIN, CYTH2 and at least one GRM1. Interacts with ARRB1. Interacts with ARL4D; the interaction is direct (By similarity). Directly interacts with CCDC120 through the coiled coil domain; this interaction stabilizes CCDC120, possibly by preventing its ubiquitination, and is required for neurite growth in a neuroblastoma cell line. Interacts with FRMD4A (By similarity). Interacts (via N-terminal domain) with INAVA (via N-terminal domain) (By similarity). Recruited to the cell membrane through its association with ARL4A, ARL4C and ARL4D. Requires also interaction with phosphoinositides for targeting to plasma membrane (By similarity). In differentiating neuroblastoma cells, colocalizes with CCDC120 in both neurite shaft and growth cone areas (By similarity). Present in all tissues tested, with highest protein levels in brain and adrenal. On embryonic days 15 (E15) and E18, a weak expression is seen in the mantle and ventricular germinal zones throughout the neuraxis. On postnatal days 0 (P0) and P7, weakly expressed in the gray matter, but not in the white matter, throughout the brain. In the cerebellum, the expression is seen in the external granule cell layer. Binds via its PH domain to the inositol head group of phosphatidylinositol 3,4,5-trisphosphate. The PH domain is necessary and sufficient for plasma membrane relocalization (By similarity). Autoinhibited by its C-terminal basic region. The coiled coil domain is involved in interaction with CCDC120.