Cargo transport protein that is required for apical transport from the trans-Golgi network (TGN). Transports AQP2 from the trans-Golgi network (TGN) to sites of AQP2 phosphorylation. Mediates the non-vesicular transport of glucosylceramide (GlcCer) from the trans-Golgi network (TGN) to the plasma membrane and plays a pivotal role in the synthesis of complex glycosphingolipids. Binding of both phosphatidylinositol 4-phosphate (PIP) and ARF1 are essential for the GlcCer transfer ability. Also required for primary cilium formation, possibly by being involved in the transport of raft lipids to the apical membrane, and for membrane tubulation (By similarity). Homodimer. Interacts with ARF1; the interaction together with phosphatidylinositol 4-phosphate binding is required for FAPP2 GlcCer transfer ability. Binds through its PH domain to PtdIns(4)P and ARF1, and subsequently localizes to TGN exit sites. The PH domain of FAPPS binds the small GTPase ARF1 and phosphatidylinositol-4-phosphate (PtdIns4P) with high selectivity, and is required for recruitment of FAPPs to the trans-Golgi network (TGN).