The content of phosphatidylinositol 3,5-bisphosphate (PtdIns(3,5)P2) in endosomal membranes changes dynamically with fission and fusion events that generate or absorb intracellular transport vesicles. VAC14 is a component of a trimolecular complex that tightly regulates the level of PtdIns(3,5)P2. Other components of this complex are the PtdIns(3,5)P2-synthesizing enzyme PIKFYVE (MIM 609414) and the PtdIns(3,5)P2 phosphatase FIG4 (MIM 609390). VAC14 functions as an activator of PIKFYVE (Sbrissa et al., 2007 [PubMed 17556371]).[supplied by OMIM, Feb 2010]