Promotes guanine-nucleotide exchange on ARF1. Promotes the activation of ARF factors through replacement of GDP with GTP (PubMed:18042453). Plays a role in the epithelial polarization (PubMed:20080746). Interacts with TAMALIN. Interacts with FRMD4A (PubMed:20080746). Interacts with FRMD4B (PubMed:20080746). Translocates from the cytosol to membranes enriched in phosphatidylinositol 3,4,5-trisphosphate. Binds via its PH domain to the inositol head group of phosphatidylinositol 3,4,5-trisphosphate. Autoinhibited by its C-terminal basic region.