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Substrate‐ and Ubiquitin‐Dependent Trafficking of the Yeast Siderophore Transporter Sit1
Author(s) -
Erpapazoglou Zoi,
Froissard Marine,
dier Isabelle,
Lesuisse Emmanuel,
HaguenauerTsapis Rosine,
BelgarehTouzé Naïma
Publication year - 2008
Publication title -
traffic
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.677
H-Index - 130
eISSN - 1600-0854
pISSN - 1398-9219
DOI - 10.1111/j.1600-0854.2008.00766.x
Subject(s) - endosome , ubiquitin , microbiology and biotechnology , ubiquitin ligase , biology , internalization , vacuolar protein sorting , transport protein , signal transducing adaptor protein , clathrin , endocytosis , intracellular , biochemistry , signal transduction , cell , gene
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.