Involved in the maintenance of Golgi structure by interacting with giantin, affecting protein transport between the endoplasmic reticulum and Golgi (PubMed:11590181). Involved in hormone-induced steroid biosynthesis in testicular Leydig cells (By similarity). 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 (PubMed:27009356). (Microbial infection) Plays an essential role in Aichi virus RNA replication by recruiting PI4KB at the viral replication sites. Homodimer (PubMed:23572552). Interacts with the C-terminal cytoplasmic domain of giantin/GOLGB1 (PubMed:11590181). 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 (via Q domain) with PI4KB (via N-terminus) (PubMed:23572552, PubMed:27009356, PubMed:27989622, PubMed:22124328, PubMed:22258260). Interacts (via Q domain) with TBC1D22A AND TBC1D22B; interactions with PI4KB and with TBC1D22A and TBC1D22B are mutually exclusive (PubMed:23572552, PubMed:27009356, PubMed:27989622, PubMed:22124328). Interacts with C10ORF76 and RAB11B (PubMed:23572552). (Microbial infection) Interacts (via GOLD domain) with 3A proteins from various picornaviruses, including poliovirus, enterovirus A71, enterovirus D68, hepatitis A virus, human parechovirus 1, poliovirus, Human rhinovirus-14 (Hrv-14), coysackievirus B2, coysackievirus B3, coysackievirus B5, Aichi virus and human klassevirus (PubMed:23572552, PubMed:22258260, PubMed:31381608). Interacts (via GOLD domain) with Aichi virus protein 3A; this interaction allows the formation of a 3A/ACBD3/PI4KB complex in order to synthesize PI4P at the viral RNA replication sites (PubMed:23572552, PubMed:22124328, PubMed:27989622, PubMed:30755512) (Probable). Interacts with Aichi virus protein 2B (PubMed:22124328). Interacts with Aichi virus protein 2C (PubMed:22124328). Also mitochondrial (via its interaction with PBR). Ubiquitous, with highest expression in testis and ovary. The central Gln-rich region (Q domain) is involved in binding to PI4KB, TBC1D22A and TBC1D22B (PubMed:23572552). The C-terminal GOLD domain is essential for giantin binding. The GOLD domain is also involved in homodimerization (PubMed:23572552). (Microbial infection) The GOLD domain is involved in binding to the picornaviral protein 3A.