title: The Sec63p J-domain is required for ERAD of soluble proteins in yeast.
abstract: How misfolded proteins are exported from the ER to the cytosol for degradation (ER-associated Degradation, ERAD) and which proteins are participating in this process is not understood. Several studies using a single, leaky mutant indicated that Sec63p might be involved in ERAD. More recently, Sec63p was also found strongly associated with proteasomes attached to the protein-conducting channel in the ER membrane which presumably form part of the export machinery. These observations prompted us to reinvestigate the role of Sec63p in ERAD by generating new mutants which were selected in a screen monitoring the intracellular accumulation of the ERAD substrate CPY*. We show that a mutation in the DnaJ-domain of Sec63p causes a defect in ERAD, whereas mutations in the Brl, acidic, and transmembrane domains only affect protein import into the ER. Unexpectedly, mutations in the acidic domain which mediates interaction of Sec63p with Sec62p also caused defects in cotranslational import. In contrast to mammalian cells where SEC63 expression levels affect steady-state levels of multi-spanning transmembrane proteins, the sec63 J-domain mutant was only defective in ERAD of soluble substrates.
authors: Department of Microbiology, Faculty of Natural Sciences and Technology VIII, Saarland University, Saarbrücken, Germany.
authors: Christina
authors: C
authors: Servas
authors: Karin
authors: K
authors: Römisch
mesh_terms: D043402:Cathepsin A / Q000378:metabolism; D060746:Endoplasmic Reticulum-Associated Degradation / Q000187:drug effects; D004795:Enzyme Stability / Q000187:drug effects; D006360:Heat-Shock Proteins / Q000737:chemistry* / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000378:metabolism*; D050505:Mutant Proteins / Q000302:isolation & purification / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000187:drug effects; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000378:metabolism*; D012995:Solubility; D013329:Structure-Activity Relationship; D013379:Substrate Specificity / Q000187:drug effects; D013696:Temperature; D014415:Tunicamycin / Q000494:pharmacology
chemical_list: D006360:Heat-Shock Proteins; D026901:Membrane Transport Proteins; D050505:Mutant Proteins; C074215:SEC63 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014415:Tunicamycin; D043402:Cathepsin A