title: Molecular chaperones in the yeast endoplasmic reticulum maintain the solubility of proteins for retrotranslocation and degradation.
abstract: Endoplasmic reticulum (ER)-associated degradation (ERAD) is the process by which aberrant proteins in the ER lumen are exported back to the cytosol and degraded by the proteasome. Although ER molecular chaperones are required for ERAD, their specific role(s) in this process have been ill defined. To understand how one group of interacting lumenal chaperones facilitates ERAD, the fates of pro-alpha-factor and a mutant form of carboxypeptidase Y were examined both in vivo and in vitro. We found that these ERAD substrates are stabilized and aggregate in the ER at elevated temperatures when BiP, the lumenal Hsp70 molecular chaperone, is mutated, or when the genes encoding the J domain-containing proteins Jem1p and Scj1p are deleted. In contrast, deletion of JEM1 and SCJ1 had little effect on the ERAD of a membrane protein. These results suggest that one role of the BiP, Jem1p, and Scj1p chaperones is to maintain lumenal ERAD substrates in a retrotranslocation-competent state.
authors.affiliation: Department of Chemistry, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan.
authors.forename: S I
authors.initials: SI
authors.lastname: Nishikawa
authors.forename: S W
authors.initials: SW
authors.lastname: Fewell
authors.forename: Y
authors.initials: Y
authors.lastname: Kato
authors.forename: J L
authors.initials: JL
authors.lastname: Brodsky
authors.forename: T
authors.initials: T
authors.lastname: Endo
mesh_terms: D002268:Carboxypeptidases / Q000235:genetics / Q000378:metabolism; D043402:Cathepsin A; D004721:Endoplasmic Reticulum / Q000201:enzymology / Q000378:metabolism*; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000072235:Mating Factor; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins; D018832:Molecular Chaperones; D009154:Mutation / Q000235:genetics; D010455:Peptides / Q000378:metabolism; D011485:Protein Binding; D011498:Protein Precursors / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D000069816:SEC Translocation Channels; D029701:Saccharomyces cerevisiae Proteins; D012995:Solubility; D013696:Temperature; D013816:Thermodynamics; D015003:Yeasts / Q000166:cytology* / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C106168:JEM1 protein, S cerevisiae; C060153:KAR2 protein, yeast; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D018832:Molecular Chaperones; D010455:Peptides; D011498:Protein Precursors; C067634:SCJ1 protein, S cerevisiae; D000069816:SEC Translocation Channels; C074215:SEC63 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D000072235:Mating Factor; D002268:Carboxypeptidases; D043402:Cathepsin A