Dataset Information

IRE1? is an endogenous substrate of endoplasmic-reticulum-associated degradation.

ABSTRACT: Endoplasmic reticulum (ER)-associated degradation (ERAD) represents a principle quality control mechanism to clear misfolded proteins in the ER; however, its physiological significance and the nature of endogenous ERAD substrates remain largely unexplored. Here we discover that IRE1?, the sensor of the unfolded protein response (UPR), is a bona fide substrate of the Sel1L-Hrd1 ERAD complex. ERAD-mediated IRE1? degradation occurs under basal conditions in a BiP-dependent manner, requires both the intramembrane hydrophilic residues of IRE1? and the lectin protein OS9, and is attenuated by ER stress. ERAD deficiency causes IRE1? protein stabilization, accumulation and mild activation both in vitro and in vivo. Although enterocyte-specific Sel1L-knockout mice (Sel1L(?IEC)) are viable and seem normal, they are highly susceptible to experimental colitis and inflammation-associated dysbiosis, in an IRE1?-dependent but CHOP-independent manner. Hence, Sel1L-Hrd1 ERAD serves a distinct, essential function in restraint of IRE1? signalling in vivo by managing its protein turnover.

SUBMITTER: Sun S

PROVIDER: S-EPMC4670240 | biostudies-literature | 2015 Dec

REPOSITORIES: biostudies-literature

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IRE1α is an endogenous substrate of endoplasmic-reticulum-associated degradation.

Sun Shengyi S Shi Guojun G Sha Haibo H Ji Yewei Y Han Xuemei X Shu Xin X Ma Hongming H Inoue Takamasa T Gao Beixue B Kim Hana H Bu Pengcheng P Guber Robert D RD Shen Xiling X Lee Ann-Hwee AH Iwawaki Takao T Paton Adrienne W AW Paton James C JC Fang Deyu D Tsai Billy B Yates John R JR Wu Haoquan H Kersten Sander S Long Qiaoming Q Duhamel Gerald E GE Simpson Kenneth W KW Qi Ling L

Nature cell biology 20151109 12

Endoplasmic reticulum (ER)-associated degradation (ERAD) represents a principle quality control mechanism to clear misfolded proteins in the ER; however, its physiological significance and the nature of endogenous ERAD substrates remain largely unexplored. Here we discover that IRE1α, the sensor of the unfolded protein response (UPR), is a bona fide substrate of the Sel1L-Hrd1 ERAD complex. ERAD-mediated IRE1α degradation occurs under basal conditions in a BiP-dependent manner, requires both the ...[more]

PMID: 26551274

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Project description:Studies in the yeast Saccharomyces cerevisiae have helped define mechanisms underlying the activity of the ubiquitin-proteasome system (UPS), uncover the proteasome assembly pathway, and link the UPS to the maintenance of cellular homeostasis. However, the spectrum of UPS substrates is incompletely defined, even though multiple techniques-including MS-have been used. Therefore, we developed a substrate trapping proteomics workflow to identify previously unknown UPS substrates. We first generated a yeast strain with an epitope tagged proteasome subunit to which a proteasome inhibitor could be applied. Parallel experiments utilized inhibitor insensitive strains or strains lacking the tagged subunit. After affinity isolation, enriched proteins were resolved, in-gel digested, and analyzed by high resolution liquid chromatography-tandem MS. A total of 149 proteasome partners were identified, including all 33 proteasome subunits. When we next compared data between inhibitor sensitive and resistant cells, 27 proteasome partners were significantly enriched. Among these proteins were known UPS substrates and proteins that escort ubiquitinated substrates to the proteasome. We also detected Erg25 as a high-confidence partner. Erg25 is a methyl oxidase that converts dimethylzymosterol to zymosterol, a precursor of the plasma membrane sterol, ergosterol. Because Erg25 is a resident of the endoplasmic reticulum (ER) and had not previously been directly characterized as a UPS substrate, we asked whether Erg25 is a target of the ER associated degradation (ERAD) pathway, which most commonly mediates proteasome-dependent destruction of aberrant proteins. As anticipated, Erg25 was ubiquitinated and associated with stalled proteasomes. Further, Erg25 degradation depended on ERAD-associated ubiquitin ligases and was regulated by sterol synthesis. These data expand the cohort of lipid biosynthetic enzymes targeted for ERAD, highlight the role of the UPS in maintaining ER function, and provide a novel tool to uncover other UPS substrates via manipulations of our engineered strain.

Dataset Information

IRE1? is an endogenous substrate of endoplasmic-reticulum-associated degradation.

Publications

IRE1α is an endogenous substrate of endoplasmic-reticulum-associated degradation.

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