Guanine nucleotide exchange factor (GEF) which may activate RAB8A and RAB8B (PubMed:12221131, PubMed:26824392). Promotes the exchange of GDP to GTP, converting inactive GDP-bound Rab proteins into their active GTP-bound form (PubMed:12221131, PubMed:26824392). Mediates the release of GDP from RAB8A and RAB8B but not from RAB3A or RAB5 (PubMed:20937701, PubMed:26824392). 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 (PubMed:20890297). Interacts with the N-terminal region of SSX2 (PubMed:12007189). Interacts with the GDP-bound forms of RAB8A and RAB8B (PubMed:26824392, PubMed:12221131). The interaction with RAB8A is prevented by phosphorylation of RAB8A at 'Thr-72' (PubMed:26824392). Interacts with the GDP-bound forms of RAB3A and RAB3D (PubMed:12221131). Interacts with DCDC1 (PubMed:22159412, PubMed:12007189, PubMed:12221131, PubMed:26824392). Interacts (via the N-terminal region) with TRAPPC14; this interaction mediates RAB3IP association with the TRAPP II complex (PubMed:31467083). 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. Expressed in brain, kidney, heart, pancreas and placenta. Not detected in skeletal muscle or liver. Belongs to the SEC2 family.