Involved in the maintenance of Golgi structure by interacting with giantin, affecting protein transport between the endoplasmic reticulum and Golgi. Involved in hormone-induced steroid biosynthesis in testicular Leydig cells. Recruits PI4KB to the Golgi apparatus membrane; enhances the enzyme activity of PI4KB activity via its membrane recruitment thereby increasing the local concentration of the substrate in the vicinity of the kinase. Interacts with the C-terminal cytoplasmic domain of giantin/GOLGB1 (By similarity). Interacts with PBR and PKA regulatory subunit RI-alpha. Does not interact with PKA regulatory subunit RI-beta nor PKA regulatory subunit RII-alpha (By similarity). Interacts with PI4KB, TBC1D22A AND TBC1D22B; interactions with PI4KB and with TBC1D22A and TBC1D22B are mutually exclusive. Interacts with C10ORF76 and RAB11B (By similarity). Also mitochondrial (via its interaction with PBR). The GOLD domain is essential for giantin binding.