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Ernst R, Renne MF, Jain A, von der Malsburg A. Endoplasmic Reticulum Membrane Homeostasis and the Unfolded Protein Response. Cold Spring Harb Perspect Biol 2024; 16:a041400. [PMID: 38253414 PMCID: PMC11293554 DOI: 10.1101/cshperspect.a041400] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
The endoplasmic reticulum (ER) is the key organelle for membrane biogenesis. Most lipids are synthesized in the ER, and most membrane proteins are first inserted into the ER membrane before they are transported to their target organelle. The composition and properties of the ER membrane must be carefully controlled to provide a suitable environment for the insertion and folding of membrane proteins. The unfolded protein response (UPR) is a powerful signaling pathway that balances protein and lipid production in the ER. Here, we summarize our current knowledge of how aberrant compositions of the ER membrane, referred to as lipid bilayer stress, trigger the UPR.
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Affiliation(s)
- Robert Ernst
- Medical Biochemistry and Molecular Biology, Medical Faculty, Saarland University, 66421 Homburg, Germany
- Preclinical Center for Molecular Signaling (PZMS), Medical Faculty, Saarland University, 66421 Homburg, Germany
| | - Mike F Renne
- Medical Biochemistry and Molecular Biology, Medical Faculty, Saarland University, 66421 Homburg, Germany
- Preclinical Center for Molecular Signaling (PZMS), Medical Faculty, Saarland University, 66421 Homburg, Germany
| | - Aamna Jain
- Medical Biochemistry and Molecular Biology, Medical Faculty, Saarland University, 66421 Homburg, Germany
- Preclinical Center for Molecular Signaling (PZMS), Medical Faculty, Saarland University, 66421 Homburg, Germany
| | - Alexander von der Malsburg
- Medical Biochemistry and Molecular Biology, Medical Faculty, Saarland University, 66421 Homburg, Germany
- Preclinical Center for Molecular Signaling (PZMS), Medical Faculty, Saarland University, 66421 Homburg, Germany
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Liu T, Jin YQ, Wang Q, Jia CH, Ren WY, Liu JY, Yang L, Luo HM. IL-33/ST2L signaling alleviates diabetic nephropathy by regulating endoplasmic reticulum stress and apoptosis. BMC Nephrol 2023; 24:361. [PMID: 38053041 PMCID: PMC10698915 DOI: 10.1186/s12882-023-03415-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Accepted: 11/28/2023] [Indexed: 12/07/2023] Open
Abstract
OBJECTIVE Diabetic nephropathy (DN) is a serious chronic complication of diabetes mellitus (DM). Endoplasmic reticulum (ER) stress is an important factor in the regulation of pathological processes in DN, and excessive ER stress can lead to apoptosis. Although the IL-33/ST2 axis is known to be involved in diabetic kidney disease or related nephropathy, its role and molecular mechanisms remain poorly understood in terms of DN. The purpose of this study was to investigate the effects of IL-33/ST2 signaling on DN and to characterize the roles that ER stress and apoptosis play in DN. METHODS To investigate this study, mice were randomly assigned into DN (induced by 0.1% STZ) and Control groups. Biochemical indices (FBG, BUN, UPR, UCE) were measured in serum and urine samples to reflect blood glucose and kidney damage. Quantitative real-time PCR, western blot, and immunofluorescence were used to assess gene and protein expression of the IL-33/ST2 axis and ER stress relative signaling molecule. Apoptosis was analyzed by flow cytometry. RESULTS IL-33 levels are significantly increased in the kidneys of patients and mice with DN. Double immunofluorescence staining showed that IL-33 colocalized with CD31-positive endothelial cells. Treatment with IL-33 attenuated kidney injury in Streptozotocin (STZ)-treated mice. In vitro, we showed that IL-33 attenuated ER stress and apoptosis in glomerular endothelial cells. However, sST2 treatment significantly reversed these effects of IL-33. CONCLUSION Together, these data suggest that IL-33/ST2 signaling mitigates STZ-induced renal damage, partly at least, by suppressing ER stress and apoptosis. Therefore, IL-33 may be an effective therapeutic target in DN.
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Affiliation(s)
- Teng Liu
- Department of Epidemiology and Statistics, School of Public Health, Hebei Key Laboratory of Environment and Human Health, Hebei Medical University, Shijiazhuang, China
- Institute of Pediatric Research, Children's Hospital of Hebei Province, Shijiazhuang, China
| | - Yu-Qing Jin
- Department of Epidemiology and Statistics, School of Public Health, Hebei Key Laboratory of Environment and Human Health, Hebei Medical University, Shijiazhuang, China
| | - Qi Wang
- Department of Epidemiology and Statistics, School of Public Health, Hebei Key Laboratory of Environment and Human Health, Hebei Medical University, Shijiazhuang, China
| | - Cong-Hui Jia
- Department of Epidemiology and Statistics, School of Public Health, Hebei Key Laboratory of Environment and Human Health, Hebei Medical University, Shijiazhuang, China
| | - Wei-Yan Ren
- Department of Epidemiology and Statistics, School of Public Health, Hebei Key Laboratory of Environment and Human Health, Hebei Medical University, Shijiazhuang, China
| | - Jia-Yi Liu
- Department of Epidemiology and Statistics, School of Public Health, Hebei Key Laboratory of Environment and Human Health, Hebei Medical University, Shijiazhuang, China
| | - Lei Yang
- Department of Epidemiology and Statistics, School of Public Health, Hebei Key Laboratory of Environment and Human Health, Hebei Medical University, Shijiazhuang, China.
| | - Hong-Min Luo
- Department of Nephrology, Third Hospital, Hebei Medical University, Shijiazhuang, China.
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Ishiwata-Kimata Y, Kimata Y. Fundamental and Applicative Aspects of the Unfolded Protein Response in Yeasts. J Fungi (Basel) 2023; 9:989. [PMID: 37888245 PMCID: PMC10608004 DOI: 10.3390/jof9100989] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Revised: 10/03/2023] [Accepted: 10/04/2023] [Indexed: 10/28/2023] Open
Abstract
Upon the dysfunction or functional shortage of the endoplasmic reticulum (ER), namely, ER stress, eukaryotic cells commonly provoke a protective gene expression program called the unfolded protein response (UPR). The molecular mechanism of UPR has been uncovered through frontier genetic studies using Saccharomyces cerevisiae as a model organism. Ire1 is an ER-located transmembrane protein that directly senses ER stress and is activated as an RNase. During ER stress, Ire1 promotes the splicing of HAC1 mRNA, which is then translated into a transcription factor that induces the expression of various genes, including those encoding ER-located molecular chaperones and protein modification enzymes. While this mainstream intracellular UPR signaling pathway was elucidated in the 1990s, new intriguing insights have been gained up to now. For instance, various additional factors allow UPR evocation strictly in response to ER stress. The UPR machineries in other yeasts and fungi, including pathogenic species, are another important research topic. Moreover, industrially beneficial yeast strains carrying an enforced and enlarged ER have been produced through the artificial and constitutive induction of the UPR. In this article, we review canonical and up-to-date insights concerning the yeast UPR, mainly from the viewpoint of the functions and regulation of Ire1 and HAC1.
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Affiliation(s)
| | - Yukio Kimata
- Division of Biological Science, Graduate School of Science and Technology, Nara Institute of Science and Technology, Nara 630-0192, Japan
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Fauzee YNBM, Yoshida Y, Kimata Y. Endoplasmic stress sensor Ire1 is involved in cytosolic/nuclear protein quality control in Pichia pastoris cells independent of HAC1. Front Microbiol 2023; 14:1157146. [PMID: 37415818 PMCID: PMC10321714 DOI: 10.3389/fmicb.2023.1157146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Accepted: 05/31/2023] [Indexed: 07/08/2023] Open
Abstract
In eukaryotic species, dysfunction of the endoplasmic reticulum (ER), namely, ER stress, provokes a cytoprotective transcription program called the unfolded protein response (UPR). The UPR is triggered by transmembrane ER-stress sensors, including Ire1, which acts as an endoribonuclease to splice and mature the mRNA encoding the transcription factor Hac1 in many fungal species. Through analyses of the methylotrophic yeast Pichia pastoris (syn. Komagataella phaffii), we revealed a previously unknown function of Ire1. In P. pastoris cells, the IRE1 knockout mutation (ire1Δ) and HAC1 knockout mutation (hac1Δ) caused only partially overlapping gene expression changes. Protein aggregation and the heat shock response (HSR) were induced in ire1Δ cells but not in hac1Δ cells even under non-stress conditions. Moreover, Ire1 was further activated upon high-temperature culturing and conferred heat stress resistance to P. pastoris cells. Our findings cumulatively demonstrate an intriguing case in which the UPR machinery controls cytosolic protein folding status and the HSR, which is known to be activated upon the accumulation of unfolded proteins in the cytosol and/or nuclei.
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Phuong HT, Ishiwata-Kimata Y, Kimata Y. An ER-accumulated mutant of yeast Pma1 causes membrane-related stress to induce the unfolded protein response. Biochem Biophys Res Commun 2023; 667:58-63. [PMID: 37209563 DOI: 10.1016/j.bbrc.2023.05.044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Accepted: 05/13/2023] [Indexed: 05/22/2023]
Abstract
Upon dysfunction of the endoplasmic reticulum (ER), namely ER stress, eukaryotic cells provoke the unfolded protein response (UPR), which is triggered by ER stress sensors including Ire1. While the ER luminal domain of Ire1 is known to directly recognize misfolded soluble proteins accumulated in the ER, the transmembrane domain of Ire1 is involved in its self-association and activation upon membrane lipid-related abnormalities, which are so-called lipid bilayer stress (LBS). Here we inquired how the ER accumulation of misfolded transmembrane proteins induces the UPR. In yeast Saccharomyces cerevisiae cells, a multi-transmembrane protein, Pma1, is not transported to the cell surface but aggregates on the ER membrane when carrying a point mutation (Pma1-2308). Here, we show that GFP-tagged Ire1 co-localized with the Pma1-2308-mCherry puncta. This co-localization and the UPR induced by Pma1-2308-mCherry were compromised by a point mutation in Ire1 that specifically impairs its activation upon LBS. We presume that Pma1-2308-mCherry locally affects the properties (probably the thickness) of the ER membrane at its aggregation sites, where Ire1 is then recruited, self-associated, and then activated.
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Affiliation(s)
- Huong Thi Phuong
- Division of Biological Science, Graduate School of Science and Technology, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara, 630-0192, Japan; Institute of Biotechnology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet road, Cau Giay, Ha Noi, Viet Nam
| | - Yuki Ishiwata-Kimata
- Division of Biological Science, Graduate School of Science and Technology, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara, 630-0192, Japan
| | - Yukio Kimata
- Division of Biological Science, Graduate School of Science and Technology, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara, 630-0192, Japan.
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Fast-Growing Saccharomyces cerevisiae Cells with a Constitutive Unfolded Protein Response and Their Potential for Lipidic Molecule Production. Appl Environ Microbiol 2022; 88:e0108322. [PMID: 36255243 PMCID: PMC9642017 DOI: 10.1128/aem.01083-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Saccharomyces cerevisiae cells, dysfunction of the endoplasmic reticulum (ER), so-called ER stress, leads to conversion of HAC1 mRNA to the spliced form (HAC1i), which is translated into a transcription factor that drastically changes the gene expression profile. This cellular response ultimately enhances ER functions and is named the unfolded protein response (UPR). Artificial evocation of the UPR is therefore anticipated to increase productivity of beneficial materials on and in the ER. However, as demonstrated here, cells constitutively expressing HAC1i mRNA (HAC1i cells), which exhibited a strong UPR even under nonstress conditions, grew considerably slowly and frequently yielded fast-growing and low-UPR progeny. Intriguingly, growth of HAC1i cells was faster in the presence of weak ER stress that was induced by low concentrations of the ER stressor tunicamycin or by cellular expression of the ER-located version of green fluorescent protein (GFP). HAC1i cells producing ER-localized GFP stably exhibited a strong UPR activity, carried a highly expanded ER, and abundantly produced triglycerides and heterogenous carotenoids. We therefore propose that our findings provide a basis for metabolic engineering to generate cells producing valuable lipidic molecules. IMPORTANCE The UPR is thought to be a cellular response to cope with the accumulation of unfolded proteins in the ER. In S. cerevisiae cells, the UPR is severely repressed under nonstress conditions. The findings of this study shed light on the physiological significance of the tight regulation of the UPR. Constitutive UPR induction caused considerable growth retardation, which was partly rescued by the induction of weak ER stress. Therefore, we speculate that when the UPR is inappropriately induced in unstressed cells lacking aberrant ER client proteins, the UPR improperly impairs normal cellular functions. Another important point of this study was the generation of S. cerevisiae strains stably exhibiting a strong UPR activity and abundantly producing triglycerides and heterogenous carotenoids. We anticipate that our findings may be applied to produce valuable lipidic molecules using yeast cells as a potential next-generation technique.
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Ishiwata-Kimata Y, Hata T, Kimata Y. Self-association status-dependent inactivation of the endoplasmic reticulum stress sensor Ire1 by C-terminal tagging with artificial peptides. Biosci Biotechnol Biochem 2022; 86:739-746. [PMID: 35285870 DOI: 10.1093/bbb/zbac038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Accepted: 03/08/2022] [Indexed: 11/14/2022]
Abstract
Upon endoplasmic reticulum (ER) stress, eukaryotic cells commonly induce unfolded protein response (UPR), which is triggered, at least partly, by the ER stress sensor Ire1. Upon ER stress, Ire1 is dimerized or forms oligomeric clusters, resulting in the activation of Ire1 as an endoribonuclease. In ER-stressed Saccharomyces cerevisiae cells, HAC1 mRNA is spliced by Ire1 and then translated into a transcription factor that promotes the UPR. Herein, we report that Ire1 tagged artificially with irrelevant peptides at the C terminus is almost completely inactive when only dimerized, while it induced the UPR as well as untagged Ire1 when clustered. This finding suggests a fundamental difference between the dimeric and clustered forms of Ire1. By comparing UPR levels in S. cerevisiae cells carrying artificially peptide-tagged Ire1 to that in cells carrying untagged Ire1, we estimated the self-association status of Ire1 under various ER stress conditions.
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Affiliation(s)
- Yuki Ishiwata-Kimata
- Division of Biological Science, Graduate School of Science and Technology, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara, Japan
| | - Tatsuya Hata
- Division of Biological Science, Graduate School of Science and Technology, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara, Japan
| | - Yukio Kimata
- Division of Biological Science, Graduate School of Science and Technology, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara, Japan
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