title: Human HRD1 protects against ER stress-induced apoptosis through ER-associated degradation.
abstract: Stresses that impair the function of the endoplasmic reticulum (ER) lead to an accumulation of unfolded protein in the ER. Under these conditions, the expression of a variety of genes involved in preventing the accumulation of the unfolded proteins is induced. Yeast Hrd1p is an ER stress-inducible ER membrane protein that acts as a ubiquitin ligase (E3) with a RING finger motif and plays a role in the ubiquitination of proteins in the ER. We report here the identification and characterization of a human homolog to yeast Hrd1p. The predicted structures are highly conserved from yeast to humans. Indeed, human HRD1 was localized to the ER and ubiquitinated its substrates. Furthermore, it was found that human HRD1 was up-regulated by ER stress via IRE1 and ATF6, which are ER stress transducers. Interestingly, 293 cells stably expressing wild-type HRD1, but not the C329S mutant, afforded resistance to ER stress-induced apoptosis. These results suggest that the production of HRD1 is up-regulated to protect against ER stress-induced apoptosis by degrading unfolded proteins accumulated in the ER.
authors.affiliation: Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Kaneko
authors.forename: Masataro
authors.initials: M
authors.lastname: Ishiguro
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Niinuma
authors.forename: Mai
authors.initials: M
authors.lastname: Uesugi
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Nomura
mesh_terms: D000595:Amino Acid Sequence; D017209:Apoptosis; D002460:Cell Line; D019610:Cytoprotection; D004721:Endoplasmic Reticulum / Q000201:enzymology* / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008025:Ligases / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D017510:Protein Folding; D011506:Proteins / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D016415:Sequence Alignment; D044767:Ubiquitin-Protein Ligases; D015854:Up-Regulation
chemical_list: D011506:Proteins; D029701:Saccharomyces cerevisiae Proteins; C104621:HRD1 protein, S cerevisiae; D044767:Ubiquitin-Protein Ligases; D008025:Ligases