PACS1 or phosphofurin acidic cluster sorting protein 1 belongs to the PACS familyof proteins and is involved in protein trafficking. PACS1 contains an acidic cluster sorting motifs and plays an important role in the localization of trans-Golgi network (TGN) membrane proteins. It has also been implicated in secretory granule biogenesis. In order to enable HIV-1 to escape immune surveillance, PACS-1 is also reported to be involved in HIV-1 Nef-mediated removal of MHC-I from the cell surface to the trans-golgi network. Diseases caused by mutation in this gene include mental retardation (MRD17) and AIDS. PACS1 has expression in adipose tissue, liver, spleen, bone, blood, brain. It has 2 isoforms produced by alternative splicing.