PACS-1 (CRA_a) is a 963aa rich regulatory protein involved in protein trafficking and belongs to the PACS family. A coat protein involved in controlling the correct subcellular localization of trans-Golgi network (TGN) membrane proteins that contain acidic cluster sorting motifs, PACS-1 is also known to be involved in HIV-1 Nef-mediated removal of MHC-I from the cell surface to the TGN, thus enabling HIV-1 to escape immune surveillance. PACS-1 also 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. Usually seen in golgi apparatus, trans-Golgi network and localized in the paranuclear region, it is ubiquitously expressed in most of the tissues.