Phosphatidylinositol-4-phosphate-binding protein that links Golgi membranes to the cytoskeleton and may participate in the tensile force required for vesicle budding from the Golgi (PubMed:19837035, PubMed:24786584). Thereby, may play a role in Golgi membrane trafficking and could indirectly give its flattened shape to the Golgi apparatus (By similarity). May also bind to the coatomer to regulate Golgi membrane trafficking (PubMed:23720043, PubMed:24786584). May play a role in anterograde transport from the Golgi to the plasma membrane and regulate secretion (By similarity). Also involved in the control of the localization of Golgi enzymes through interaction with their cytoplasmic part (By similarity). Functions in cytokinesis by regulating contractile ring formation and vesicle trafficking during cleavage furrow ingression (PubMed:24786584). May also have a role in the intital steps of central spindle formation (PubMed:24786584). Can also bind phosphatidylinositol-3-phosphate and phosphatidylinositol-5-phosphate in vitro (PubMed:24786584). Homooligomer (By similarity). Interacts with botv, Ext2 and ttv (PubMed:23720043). Interacts with Vti1 (PubMed:23720043). Interacts with Vps35, Rab5, Chc, Rab11, zip, Pav and Sep1 (PubMed:24786584). Phosphatidylinositol 4-phosphate-binding and oligomerization participate in the recruitment onto Golgi membranes (PubMed:23720043). In dividing cells associates with vesicles in polar regions of the cells during metaphase and anaphase, and localizes to the cleavage furrow during telophase (PubMed:24786584). Lethal (PubMed:23720043, PubMed:24786584). Embryos display an aberrant pattern of denticles with some additional dorsalization and twisting (PubMed:23720043). It is associated with a defect in heparan sulfate proteoglycan synthesis which in turn alters hedgehog signaling (PubMed:23720043). Belongs to the GOLPH3/VPS74 family.