title: Substrate- and ubiquitin-dependent trafficking of the yeast siderophore transporter Sit1.
abstract: Eukaryotic plasma membrane transporters are subjected to a tightly regulated intracellular trafficking. The yeast siderophore iron transporter1 (Sit1) displays substrate-regulated trafficking. It is targeted to the plasma membrane or to a vacuolar degradative pathway when synthesized in the presence or absence of external substrate, respectively. Sorting of Sit1 to the vacuolar pathway is dependent on the clathrin adaptor Gga2, and more specifically on its C-GAT subdomain. Plasma membrane undergoes substrate-induced ubiquitylation dependent on the Rsp5 ubiquitin protein ligase. Sit1 is also ubiquitylated in an Rsp5-dependent manner in internal compartments when expressed in the absence of substrate. In several rsp5 mutants including cells deleted for RSP5, Sit1 expressed in the absence of substrate is correctly targeted to the endosomal pathway but its sorting to multivesicular bodies (MVBs) is impaired. Consequently, it displays endosome to plasma membrane targeting, with kinetics similar to those observed in vps mutants defective for MVB sorting. Plasma membrane Sit1 is modified by Lys63-linked ubiquitin chains. We also show for the first time in yeast that modification by this latter type of ubiquitin chains is required directly or indirectly for efficient MVB sorting, as it is for efficient internalization at the plasma membrane.
authors.affiliation: Département de Biologie Cellulaire, Laboratoire Trafic Intracellulaire des Protéines dans la Levure, Institut Jacques Monod, UMR 7592 CNRS-Universités Paris 6 et 7, 75251 Paris cedex 05, France.
authors.forename: Zoi
authors.initials: Z
authors.lastname: Erpapazoglou
authors.forename: Marine
authors.initials: M
authors.lastname: Froissard
authors.forename: Isabelle
authors.initials: I
authors.lastname: Nondier
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Lesuisse
authors.forename: Rosine
authors.initials: R
authors.lastname: Haguenauer-Tsapis
authors.forename: Naïma
authors.initials: N
authors.lastname: Belgareh-Touzé
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D004705:Endocytosis; D056827:Endosomal Sorting Complexes Required for Transport; D049452:Green Fluorescent Proteins / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D008954:Models, Biological; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D017262:Siderophores / Q000378:metabolism*; D013379:Substrate Specificity; D025801:Ubiquitin / Q000737:chemistry* / Q000378:metabolism; D043743:Ubiquitin-Protein Ligase Complexes / Q000378:metabolism
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D056827:Endosomal Sorting Complexes Required for Transport; C497361:Gga2 protein, S cerevisiae; D026901:Membrane Transport Proteins; C118510:SIT1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D017262:Siderophores; D025801:Ubiquitin; D049452:Green Fluorescent Proteins; D043743:Ubiquitin-Protein Ligase Complexes; C469287:RSP5 protein, S cerevisiae