Promotes guanine-nucleotide exchange on ARF1. Promotes the activation of ARF factors through replacement of GDP with GTP (By similarity). Interacts with TAMALIN. Translocates from the cytosol to membranes enriched in phosphatidylinositol 3,4,5-trisphosphate. Present in all tissues tested, with highest protein levels in brain and adrenal. On embryonic days 15 (E15) and E18, expressed in the cortical plate of the cerebrum. On postnatal days 0 (P0) and P7, a moderate expression is seen in the cerebral neocortex, hippocampal pyramidal and dentate granule cell layers. In the cerebellum, expressed in the cerebellar Purkinje cells. On P14, a decreased expression is seen throughout the brain. On P21, expression is seen in the cerebellar Purkinje cells, dentate granule cells and the hippocampal pyramidal cells. Binds via its PH domain to the inositol head group of phosphatidylinositol 3,4,5-trisphosphate. Autoinhibited by its C-terminal basic region.