title: Permease recycling and ubiquitination status reveal a particular role for Bro1 in the multivesicular body pathway.
abstract: Ubiquitination of the yeast Gap1 permease at the plasma membrane triggers its endocytosis followed by targeting to the vacuolar lumen for degradation. We previously identified Bro1 as a protein essential to this down-regulation. In this study, we show that Bro1 is essential neither to ubiquitination nor to the early steps of Gap1 endocytosis. Bro1 rather intervenes at a late step of the multivesicular body (MVB) pathway, after the core components of the endosome-associated ESCRT-III protein complex and before or in conjunction with Doa4, the ubiquitin hydrolase mediating protein deubiquitination prior to their incorporation into MVB vesicles. Bro1 markedly differs from other class E vacuolar protein sorting factors involved in MVB sorting as lack of Bro1 leads to recycling of the internalized permease back to the plasma membrane by passing through the Golgi. This recycling seems to be accompanied by deubiquitination of the permease and unexpectedly requires a normal endosome-to-vacuole transport function.
authors.affiliation: Laboratoire de Physiologie Cellulaire, Université Libre de Bruxelles, B-6041 Gosselies, Belgium.
authors.forename: Elina
authors.initials: E
authors.lastname: Nikko
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Marini
authors.forename: Bruno
authors.initials: B
authors.lastname: André
mesh_terms: D026905:Amino Acid Transport Systems; D001692:Biological Transport; D002352:Carrier Proteins / Q000737:chemistry / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D015536:Down-Regulation; D056827:Endosomal Sorting Complexes Required for Transport; D011992:Endosomes / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism; D015151:Immunoblotting; D026901:Membrane Transport Proteins / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000502:physiology*; D013869:Thiolester Hydrolases / Q000378:metabolism; D013997:Time Factors; D025801:Ubiquitin / Q000378:metabolism*; D014617:Vacuoles / Q000378:metabolism; D033921:Vesicular Transport Proteins; D020703:ras GTPase-Activating Proteins / Q000378:metabolism
chemical_list: D026905:Amino Acid Transport Systems; C480237:Bro1 protein, S cerevisiae; D002352:Carrier Proteins; D056827:Endosomal Sorting Complexes Required for Transport; C491145:GAP1 protein, S cerevisiae; D026901:Membrane Transport Proteins; D029701:Saccharomyces cerevisiae Proteins; D025801:Ubiquitin; D033921:Vesicular Transport Proteins; D020703:ras GTPase-Activating Proteins; D013869:Thiolester Hydrolases