ERAD and protein import defects in a sec61 mutant lacking ER-lumenal loop 7

Tretter, Thomas; Перейра, Фернандо Лобо; Ulucan, Ozlem; Helms, Volkhard; Allan, Susanne; Kalies, Kai‐Uwe; Römisch, Karin

doi:10.1186/1471-2121-14-56

Cited by 19 publications

(26 citation statements)

References 41 publications

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“…In yeast, a gating motif that links the Sec61 lateral gate and plug domain regulates the transition from the closed to open channel conformation (Trueman et al, 2012). The sec61ΔL7 mutant lacks the entire lumenal loop 7 adjacent to the lateral gate motif, which impairs transition from the closed to the open conformation, thereby causing defective post-translational translocation, slow growth and cold sensitivity (Tretter et al, 2013). When transformed with HGT1, the sec61ΔL7 mutant accumulated GSH as Wt, which indicated correct Hgt1p plasma membrane expression, but was highly resistant to GSH-induced cell death (Fig.…”

Section: Resultsmentioning

confidence: 99%

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Endoplasmic Reticulum Transport of Glutathione by Sec61 Is Regulated by Ero1 and Bip

Ponsero¹,

Igbaria²,

Darch³

et al. 2017

Molecular Cell

106

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In the endoplasmic reticulum (ER), Ero1 catalyzes disulfide bond formation and promotes glutathione (GSH) oxidation to GSSG. Since glutathione cannot be reduced in the ER, maintenance of the ER GSH redox state and levels likely depend on ER GSH import and GSSG export. We used quantitative GSH and GSSG biosensors to monitor GSH import into the ER of yeast cells. We found that GSH enters the ER by facilitated diffusion through the Sec61 protein-conducting channel, while oxidized Bip (Kar2) inhibits transport. Increased ER GSH import triggers H2O2-dependent Bip oxidation through Ero1 reductive activation, which inhibits GSH import in a negative regulatory loop. During ER stress, transport is activated by UPR-dependent Ero1 induction and cytosolic GSH levels increase. Thus, the ER redox poise is tuned by reciprocal control of GSH import and Ero1 activation. The ER protein-conducting channel is thus permeable to small molecules, provided the driving force of a concentration gradient.

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Section: Resultsmentioning

confidence: 99%

“…Mutation in the lateral gate motif (Sec61 N302L ) (Trueman et al, 2012) and deletion of loop 7 (Sec61ΔL7) (Tretter et al, 2013), which both stabilize the closed channel conformation, almost totally inhibited GSH transport (see Fig. 4C, 4D).…”

Section: Discussionmentioning

confidence: 97%

Endoplasmic Reticulum Transport of Glutathione by Sec61 Is Regulated by Ero1 and Bip

Ponsero¹,

Igbaria²,

Darch³

et al. 2017

Molecular Cell

106

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“…The cause of apoptosis in these mice may be increased basal ER stress and reduced ER-associated degradation (ERAD), as has been demonstrated in yeast that carry this mutation, but others have documented disrupted calcium homeostasis and ER import of some substrates in cells carrying the Y344H mutation (12)(13)(14). These mice also exhibit hepatic steatosis.…”

Section: Luciferase Assaymentioning

confidence: 95%

“…Primary hepatocytes grown in 3.5 cm dishes were labeled with 150 nCi of 14 C-acetate (Perkin Elmer, Waltham, MA) for 16 h and then washed 3× with PBS, dissolved fi rst in 500 l of 0.1 M NaOH, then with 500 l of water, and combined. An aliquot was saved for protein determination.…”

Section: Lipid Synthesismentioning

confidence: 99%

Hsp90 modulates PPARγ activity in a mouse model of nonalcoholic fatty liver disease

Wheeler

Gekakis²

2014

Journal of Lipid Research

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This article is available online at http://www.jlr.org the molecular and cellular levels can have a signifi cant effect on treatment of this disease and its comorbidities.Different cellular and molecular mechanisms are hypothesized to play a role in the development of steatosis. The liver plays a key role in lipid metabolism. It must balance secretion of VLDL, which requires uptake of dietary lipids or de novo synthesis, with oxidation of fatty acids to fuel its own anabolic programs, such as gluconeogenesis ( 1 ). A disturbance in this balance can lead to a deleterious accumulation of excess lipids. Increases in synthesis, via constitutively active sterol-regulatory element binding protein (SREBP) 1c, for example, or increases in uptake, via overexpression of the fatty acid transporter CD36, are suffi cient to induce steatosis ( 4, 5 ). On the other hand, reductions in fatty acid oxidation or VLDL secretion increase fatty acid accumulation ( 6, 7 ). Furthermore, insulin resistance is thought to exacerbate steatosis, as higher levels of insulin can drive increased lipogenesis in the liver ( 8 ).With respect to rodent models, both dietary manipulations (e.g., high-fat or methionine-and-choline-defi cient diet) and genetic obesity (e.g., the ob/ob mouse) model aspects of NAFLD ( 9 ). These models suggest many possible mechanisms for steatosis, such as infl ammation, endoplasmic reticulum (ER) stress, and lipotoxic stress. Investigation in mouse models that are independent of dietary manipulation, obesity, or insulin resistance can therefore be helpful in describing primary etiological factors involved in the pathogenesis of NAFLD.Previously, we have shown that mice homozygous for an ethylnitrosourea-induced point mutation in the Sec61a1 gene ( Sec61a1 Y344H/Y344H) develop diabetes due to ␤ -cell apoptosis ( 10 ). Sec61a1 encodes Sec61 ␣ , a 10-pass transmembrane Abstract Nonalcoholic fatty liver disease (NAFLD) is a highly prevalent complication of obesity, yet cellular mechanisms that lead to its development are not well defi ned. Previously, we have documented hepatic steatosis in mice carrying a mutation in the Sec61a1 gene. Here we examined the mechanism behind NAFLD in Sec61a1 mutant mice. Livers of mutant mice exhibited upregulation of Pparg and its target genes Cd36 , Cidec , and Lpl , correlating with increased uptake of fatty acid. Interestingly, these mice also displayed activation of the heat shock response (HSR), with elevated levels of heat shock protein (

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“…was predominantly from yeast Sec61 mutants that are defective in both import of secretory proteins and export of ERAD substrates (6). Furthermore, a Sec61 mutant without defects in protein import but with reduced ability to bind to the 19S proteasome regulatory particle (RP) showed decreased ER export of a 19S proteasome RP-dependent substrate when proteasomes were limiting, providing a functional link between Sec61 and retrotranslocation (7).…”

Section: Significancementioning

confidence: 99%

Sec61 blockade by mycolactone inhibits antigen cross-presentation independently of endosome-to-cytosol export

Grotzke

Kozik

Morel

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Although antigen cross-presentation in dendritic cells (DCs) is critical to the initiation of most cytotoxic immune responses, the intracellular mechanisms and traffic pathways involved are still unclear. One of the most critical steps in this process, the export of internalized antigen to the cytosol, has been suggested to be mediated by Sec61. Sec61 is the channel that translocates signal peptide-bearing nascent polypeptides into the endoplasmic reticulum (ER), and it was also proposed to mediate protein retrotranslocation during ER-associated degradation (a process called ERAD). Here, we used a newly identified Sec61 blocker, mycolactone, to analyze Sec61's contribution to antigen cross-presentation, ERAD, and transport of internalized antigens into the cytosol. As shown previously in other cell types, mycolactone prevented protein import into the ER of DCs. Mycolactone-mediated Sec61 blockade also potently suppressed both antigen cross-presentation and direct presentation of synthetic peptides to CD8 + T cells. In contrast, it did not affect protein export from the ER lumen or from endosomes into the cytosol, suggesting that the inhibition of cross-presentation was not related to either of these trafficking pathways. Proteomic profiling of mycolactoneexposed DCs showed that expression of mediators of antigen presentation, including MHC class I and β2 microglobulin, were highly susceptible to mycolactone treatment, indicating that Sec61 blockade affects antigen cross-presentation indirectly. Together, our data suggest that the defective translocation and subsequent degradation of Sec61 substrates is the cause of altered antigen cross-presentation in Sec61-blocked DCs.Sec61 | cross-presentation | ERAD | mycolactone

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ERAD and protein import defects in a sec61 mutant lacking ER-lumenal loop 7

Cited by 19 publications

References 41 publications

Endoplasmic Reticulum Transport of Glutathione by Sec61 Is Regulated by Ero1 and Bip

Endoplasmic Reticulum Transport of Glutathione by Sec61 Is Regulated by Ero1 and Bip

Hsp90 modulates PPARγ activity in a mouse model of nonalcoholic fatty liver disease

Sec61 blockade by mycolactone inhibits antigen cross-presentation independently of endosome-to-cytosol export

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