Coat protein that is involved in the localization of trans-Golgi network (TGN) membrane proteins that contain acidic cluster sorting motifs. Controls the endosome-to-Golgi trafficking of furin and mannose-6-phosphate receptor by connecting the acidic-cluster-containing cytoplasmic domain of these molecules with the adapter-protein complex-1 (AP-1) of endosomal clathrin-coated membrane pits. Involved in HIV-1 nef-mediated removal of MHC-I from the cell surface to the TGN. Associates with AP-1 and AP-3 but not with AP-2 complexes (PubMed:11331585). Interacts with FURIN (By similarity). Forms a ternary complex with FURIN and AP-1 (PubMed:11331585). Interacts with NPHP1; the interaction is dependent of NPHP1 phosphorylation by CK2 (PubMed:16308564). Interacts with PKD2 (via acidic region) (PubMed:15692563). Interacts with SORL1 (PubMed:17855360, PubMed:17646382). (Microbial infection) Interacts with HIV-1 Nef. (Microbial infection) Interacts with Epstein-barr virus protein BBLF1. Localizes in the perinuclear region, probably the TGN. The disease is caused by variants affecting the gene represented in this entry. Belongs to the PACS family. Extended N-terminus. Truncated N-terminus.