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gp78 functions downstream of Hrd1 to promote degradation of misfolded proteins of the endoplasmic reticulum

Eukaryotic cells eliminate misfolded proteins from the endoplasmic reticulum (ER) via a conserved process termed ER-associated degradation (ERAD). Central regulators of the ERAD system are membrane-bound ubiquitin ligases, which are thought to channel misfolded proteins through the ER membrane durin...

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Detalles Bibliográficos
Autores principales: Zhang, Ting, Xu, Yue, Liu, Yanfen, Ye, Yihong
Formato: Online Artículo Texto
Lenguaje:English
Publicado: The American Society for Cell Biology 2015
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4666138/
https://www.ncbi.nlm.nih.gov/pubmed/26424800
http://dx.doi.org/10.1091/mbc.E15-06-0354
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author Zhang, Ting
Xu, Yue
Liu, Yanfen
Ye, Yihong
author_facet Zhang, Ting
Xu, Yue
Liu, Yanfen
Ye, Yihong
author_sort Zhang, Ting
collection PubMed
description Eukaryotic cells eliminate misfolded proteins from the endoplasmic reticulum (ER) via a conserved process termed ER-associated degradation (ERAD). Central regulators of the ERAD system are membrane-bound ubiquitin ligases, which are thought to channel misfolded proteins through the ER membrane during retrotranslocation. Hrd1 and gp78 are mammalian ubiquitin ligases homologous to Hrd1p, an ubiquitin ligase essential for ERAD in Saccharomyces cerevisiae. However, the functional relevance of these proteins to Hrd1p is unclear. In this paper, we characterize the gp78-containing ubiquitin ligase complex and define its functional interplay with Hrd1 using biochemical and recently developed CRISPR-based genetic tools. Our data show that transient inactivation of the gp78 complex by short hairpin RNA–mediated gene silencing causes significant stabilization of both luminal and membrane ERAD substrates, but unlike Hrd1, which plays an essential role in retrotranslocation and ubiquitination of these ERAD substrates, knockdown of gp78 does not affect either of these processes. Instead, gp78 appears to act downstream of Hrd1 to promote ERAD via cooperation with the BAG6 chaperone complex. We conclude that the Hrd1 complex forms an essential retrotranslocation module that is evolutionarily conserved, but the mammalian ERAD system uses additional ubiquitin ligases to assist Hrd1 during retrotranslocation.
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spelling pubmed-46661382016-02-16 gp78 functions downstream of Hrd1 to promote degradation of misfolded proteins of the endoplasmic reticulum Zhang, Ting Xu, Yue Liu, Yanfen Ye, Yihong Mol Biol Cell Articles Eukaryotic cells eliminate misfolded proteins from the endoplasmic reticulum (ER) via a conserved process termed ER-associated degradation (ERAD). Central regulators of the ERAD system are membrane-bound ubiquitin ligases, which are thought to channel misfolded proteins through the ER membrane during retrotranslocation. Hrd1 and gp78 are mammalian ubiquitin ligases homologous to Hrd1p, an ubiquitin ligase essential for ERAD in Saccharomyces cerevisiae. However, the functional relevance of these proteins to Hrd1p is unclear. In this paper, we characterize the gp78-containing ubiquitin ligase complex and define its functional interplay with Hrd1 using biochemical and recently developed CRISPR-based genetic tools. Our data show that transient inactivation of the gp78 complex by short hairpin RNA–mediated gene silencing causes significant stabilization of both luminal and membrane ERAD substrates, but unlike Hrd1, which plays an essential role in retrotranslocation and ubiquitination of these ERAD substrates, knockdown of gp78 does not affect either of these processes. Instead, gp78 appears to act downstream of Hrd1 to promote ERAD via cooperation with the BAG6 chaperone complex. We conclude that the Hrd1 complex forms an essential retrotranslocation module that is evolutionarily conserved, but the mammalian ERAD system uses additional ubiquitin ligases to assist Hrd1 during retrotranslocation. The American Society for Cell Biology 2015-12-01 /pmc/articles/PMC4666138/ /pubmed/26424800 http://dx.doi.org/10.1091/mbc.E15-06-0354 Text en © 2015 Zhang et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0). “ASCB®,” “The American Society for Cell Biology®,” and “Molecular Biology of the Cell®” are registered trademarks of The American Society for Cell Biology.
spellingShingle Articles
Zhang, Ting
Xu, Yue
Liu, Yanfen
Ye, Yihong
gp78 functions downstream of Hrd1 to promote degradation of misfolded proteins of the endoplasmic reticulum
title gp78 functions downstream of Hrd1 to promote degradation of misfolded proteins of the endoplasmic reticulum
title_full gp78 functions downstream of Hrd1 to promote degradation of misfolded proteins of the endoplasmic reticulum
title_fullStr gp78 functions downstream of Hrd1 to promote degradation of misfolded proteins of the endoplasmic reticulum
title_full_unstemmed gp78 functions downstream of Hrd1 to promote degradation of misfolded proteins of the endoplasmic reticulum
title_short gp78 functions downstream of Hrd1 to promote degradation of misfolded proteins of the endoplasmic reticulum
title_sort gp78 functions downstream of hrd1 to promote degradation of misfolded proteins of the endoplasmic reticulum
topic Articles
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4666138/
https://www.ncbi.nlm.nih.gov/pubmed/26424800
http://dx.doi.org/10.1091/mbc.E15-06-0354
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