Guanine nucleotide exchange factor (GEF) which may activate RAB8A and RAB8B (PubMed:12221131). Promotes the exchange of GDP to GTP, converting inactive GDP-bound Rab proteins into their active GTP-bound form (PubMed:12221131). Mediates the release of GDP from RAB8A and RAB8B but not from RAB3A or RAB5 (By similarity). Modulates actin organization and promotes polarized transport of RAB8A-specific vesicles to the cell surface (PubMed:12221131). Together with RAB11A, RAB8A, the exocyst complex, PARD3, PRKCI, ANXA2, CDC42 and DNMBP promotes transcytosis of PODXL to the apical membrane initiation sites (AMIS), apical surface formation and lumenogenesis (By similarity). Interacts with the N-terminal region of SSX2 (By similarity). Interacts with the GDP-bound forms of RAB8A and RAB8B (By similarity). The interaction with RAB8A is prevented by phosphorylation of RAB8A at 'Thr-72' (By similarity). Interacts with the GDP-bound forms of RAB3A and RAB3D (PubMed:7532276). Interacts with DCDC1 (By similarity) (PubMed:7532276). Interacts (via the N-terminal region) with TRAPPC14; this interaction mediates RAB3IP association with the TRAPP II complex (By similarity). Predominantly cytoplasmic but a small proportion colocalizes with SSX2 in the nucleus. Activation of protein kinase C results in redistribution to the periphery of lamellipodia. In the cytoskeleton, localizes to cortical actin (By similarity). Ubiquitously expressed. Expressed at highest level in testis. Belongs to the SEC2 family.