title: The phosphorylation state of an autoregulatory domain controls PACS-1-directed protein traffic.
abstract: PACS-1 is a cytosolic sorting protein that directs the localization of membrane proteins in the trans-Golgi network (TGN)/endosomal system. PACS-1 connects the clathrin adaptor AP-1 to acidic cluster sorting motifs contained in the cytoplasmic domain of cargo proteins such as furin, the cation-independent mannose-6-phosphate receptor and in viral proteins such as human immunodeficiency virus type 1 Nef. Here we show that an acidic cluster on PACS-1, which is highly similar to acidic cluster sorting motifs on cargo molecules, acts as an autoregulatory domain that controls PACS-1-directed sorting. Biochemical studies show that Ser278 adjacent to the acidic cluster is phosphorylated by CK2 and dephosphorylated by PP2A. Phosphorylation of Ser278 by CK2 or a Ser278-->Asp mutation increased the interaction between PACS-1 and cargo, whereas a Ser278-->Ala substitution decreased this interaction. Moreover, the Ser278-->Ala mutation yields a dominant-negative PACS-1 molecule that selectively blocks retrieval of PACS-1-regulated cargo molecules to the TGN. These results suggest that coordinated signaling events regulate transport within the TGN/endosomal system through the phosphorylation state of both cargo and the sorting machinery.
authors.affiliation: Vollum Institute, L-474, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA.
authors.forename: Gregory K
authors.initials: GK
authors.lastname: Scott
authors.forename: Feng
authors.initials: F
authors.lastname: Gu
authors.forename: Colin M
authors.initials: CM
authors.lastname: Crump
authors.forename: Laurel
authors.initials: L
authors.lastname: Thomas
authors.forename: Lei
authors.initials: L
authors.lastname: Wan
authors.forename: Yang
authors.initials: Y
authors.lastname: Xiang
authors.forename: Gary
authors.initials: G
authors.lastname: Thomas
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism*; D002460:Cell Line; D015693:Gene Products, nef / Q000378:metabolism; D015497:HIV-1 / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry; D010750:Phosphoproteins / Q000737:chemistry*; D010766:Phosphorylation; D021381:Protein Transport; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012694:Serine; D014162:Transfection; D014407:Tumor Cells, Cultured; D033921:Vesicular Transport Proteins; D054311:nef Gene Products, Human Immunodeficiency Virus
chemical_list: D002352:Carrier Proteins; D015693:Gene Products, nef; C491914:PACS1 protein, human; D010446:Peptide Fragments; D010750:Phosphoproteins; D011994:Recombinant Proteins; D033921:Vesicular Transport Proteins; D054311:nef Gene Products, Human Immunodeficiency Virus; D012694:Serine