title: Inhibition of p97-dependent protein degradation by Eeyarestatin I.
abstract: Elimination of misfolded proteins from the endoplasmic reticulum (ER) by ER-associated degradation involves substrate retrotranslocation from the ER lumen into the cytosol for degradation by the proteasome. For many substrates, retrotranslocation requires the action of ubiquitinating enzymes, which polyubiquitinate substrates emerging from the ER lumen, and of the p97-Ufd1-Npl4 ATPase complex, which hydrolyzes ATP to dislocate polyubiquitinated substrates into the cytosol. Polypeptides extracted by p97 are eventually transferred to the proteasome for destruction. In mammalian cells, ERAD can be blocked by a chemical inhibitor termed Eeyarestatin I, but the mechanism of EerI action is unclear. Here we report that EerI can associate with a p97 complex to inhibit ERAD. The interaction of EerI with the p97 complex appears to negatively influence a deubiquitinating process that is mediated by p97-associated deubiquitinating enzymes. We further show that ataxin-3, a p97-associated deubiquitinating enzyme previously implicated in ER-associated degradation, is among those affected. Interestingly, p97-associated deubiquitination is also involved in degradation of a soluble substrate. Our analyses establish a role for a novel deubiquitinating process in proteasome-dependent protein turnover.
authors.affiliation: Laboratory of Molecular Biology, NIDDK, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Qiuyan
authors.initials: Q
authors.lastname: Wang
authors.forename: Lianyun
authors.initials: L
authors.lastname: Li
authors.forename: Yihong
authors.initials: Y
authors.lastname: Ye
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport; D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D000067699:Ataxin-3; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D006835:Hydrazones / Q000494:pharmacology*; D006918:Hydroxyurea / Q000031:analogs & derivatives* / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism*; D017510:Protein Folding; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D025801:Ubiquitin / Q000235:genetics / Q000378:metabolism; D054875:Ubiquitination / Q000187:drug effects* / Q000502:physiology; D000074405:Valosin Containing Protein
chemical_list: C492847:1-(4-chlorophenyl)-3-(3-(4-chlorophenyl)-5,5-dimethyl-1-(3-(5-nitrofuran-2-yl)allyldienehydrazinocarbonylmethyl)-2-oxoimidazolidin-4-yl)-1-hydroxyurea; D033942:Adaptor Proteins, Vesicular Transport; D018797:Cell Cycle Proteins; D006835:Hydrazones; D047908:Intracellular Signaling Peptides and Proteins; C514112:NPLOC4 protein, human; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D011506:Proteins; D012097:Repressor Proteins; C491497:UFD1 protein, human; D025801:Ubiquitin; C092341:ATXN3 protein, human; D000067699:Ataxin-3; D046988:Proteasome Endopeptidase Complex; D000251:Adenosine Triphosphatases; D000074405:Valosin Containing Protein; D006918:Hydroxyurea