Promotes guanine-nucleotide exchange on ARF1, ARF5 and ARF6. Promotes the activation of ARF factors through replacement of GDP with GTP. Plays an important role in membrane trafficking, during junctional remodeling and epithelial polarization, through regulation of ARF6 activity. Interacts with TRIM23 and CYTIP (By similarity). Interacts (via coiled-coil domain) with FRMD4A (via coiled-coil domain) (By similarity). Interacts with FRMD4B (By similarity). Found in a complex with PARD3, CYTH1 and FRMD4A (By similarity). Interacts (via N-terminal domain) with INAVA (via N-terminal domain) (By similarity). Colocalized with TJP1 during epithelial polarization. Present in all tissues tested, with highest protein levels in brain and adrenal. On embryonic days 15 (E15) and E18, expression is seen in the mantle and ventricular germinal zones throughout the neuraxis. On postnatal days 0 (P0) and P7, expression is seen in the cerebral neocortex, olfactory mitral and granule cell layers, hippocampal pyramidal and dentate granule cells and the striatum. A lower expression is seen in gray matter in di-, mes- and met-encephali. In the cerebellum, the expression is evident in the external and internal granule cell layers and Purkinje cell layer. On P14, a decreased expression is seen in the di-, mes- and met-encephali. On P21 and thereafter, expression is seen in the olfactory mitral and granule cells, dentate granule cells and the cerebellar granule cells and Purkinje cells. Binds via its PH domain to the inositol head group of phosphatidylinositol 3,4,5-trisphosphate. Autoinhibited by its C-terminal basic region. Ubiquitinated by SCF(FBXW11) E3 ubiquitin-protein ligase complex. Ubiquitination induces proteasomal degradation.