title: Der3p/Hrd1p is required for endoplasmic reticulum-associated degradation of misfolded lumenal and integral membrane proteins.
abstract: We have studied components of the endoplasmic reticulum (ER) proofreading and degradation system in the yeast Saccharomyces cerevisiae. Using a der3-1 mutant defective in the degradation of a mutated lumenal protein, carboxypeptidase yscY (CPY*), a gene was cloned which encodes a 64-kDa protein of the ER membrane. Der3p was found to be identical with Hrd1p, a protein identified to be necessary for degradation of HMG-CoA reductase. Der3p contains five putative transmembrane domains and a long hydrophilic C-terminal tail containing a RING-H2 finger domain which is oriented to the ER lumen. Deletion of DER3 leads to an accumulation of CPY* inside the ER due to a complete block of its degradation. In addition, a DER3 null mutant allele suppresses the temperature-dependent growth phenotype of a mutant carrying the sec61-2 allele. This is accompanied by the stabilization of the Sec61-2 mutant protein. In contrast, overproduction of Der3p is lethal in a sec61-2 strain at the permissive temperature of 25 degrees C. A mutant Der3p lacking 114 amino acids of the lumenal tail including the RING-H2 finger domain is unable to mediate degradation of CPY* and Sec61-2p. We propose that Der3p acts prior to retrograde transport of ER membrane and lumenal proteins to the cytoplasm where they are subject to degradation via the ubiquitin-proteasome system. Interestingly, in ubc6-ubc7 double mutants, CPY* accumulates in the ER, indicating the necessity of an intact cytoplasmic proteolysis machinery for retrograde transport of CPY*. Der3p might serve as a component programming the translocon for retrograde transport of ER proteins, or it might be involved in recognition through its lumenal RING-H2 motif of proteins of the ER that are destined for degradation.
authors.affiliation: Institut für Biochemie, Universität Stuttgart, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Bordallo
authors.forename: R K
authors.initials: RK
authors.lastname: Plemper
authors.forename: A
authors.initials: A
authors.lastname: Finger
authors.forename: D H
authors.initials: DH
authors.lastname: Wolf
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002268:Carboxypeptidases / Q000235:genetics / Q000378:metabolism; D043402:Cathepsin A; D002455:Cell Division / Q000235:genetics; D003001:Cloning, Molecular; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology; D017353:Gene Deletion; D007425:Intracellular Membranes / Q000378:metabolism; D008025:Ligases / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D009154:Mutation; D017510:Protein Folding; D011506:Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000502:physiology*; D000069816:SEC Translocation Channels; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D044763:Ubiquitin-Conjugating Enzymes; D044767:Ubiquitin-Protein Ligases
chemical_list: D005656:Fungal Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D011506:Proteins; D000069816:SEC Translocation Channels; C499383:SEC61 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C082461:UBC6 protein, S cerevisiae; C489967:UBE2J1 protein, human; C079437:UBE2L3 protein, human; D044763:Ubiquitin-Conjugating Enzymes; C104621:HRD1 protein, S cerevisiae; D044767:Ubiquitin-Protein Ligases; D002268:Carboxypeptidases; D043402:Cathepsin A; C499283:PRC1 protein, S cerevisiae; C022633:serine carboxypeptidase; D008025:Ligases