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Villafuerte BC, Barati MT, Rane MJ, Isaacs S, Li M, Wilkey DW, Merchant ML. Over-expression of insulin-response element binding protein-1 (IRE-BP1) in mouse pancreatic islets increases expression of RACK1 and TCTP: Beta cell markers of high glucose sensitivity. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2016; 1865:186-194. [PMID: 27816562 DOI: 10.1016/j.bbapap.2016.10.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 10/16/2016] [Accepted: 10/31/2016] [Indexed: 12/29/2022]
Abstract
BACKGROUND A targeted analysis of the 50kDa C-terminal fragment of insulin-response element binding protein-1 (IRE-BP1) activation of target genes through the insulin receptor substrate receptor/PI-3 kinase/Akt pathway has been demonstrated for the insulin growth factor-1 receptor. The broader effects of 50kDa C-terminal IRE-BP1 fragment over-expression on protein abundance in pancreatic islet beta cells have not been determined. RESULTS Liquid-chromatography coupled to tandem mass spectrometry (LC-MS/MS) analyses of replicate lysates of pancreatic islets isolated from background strain animals and transgenic animals, overexpressing IRE-BP1 in pancreatic islet beta cells, demonstrated statistically significant increases in the expression of proteins involved in protein synthesis, endoplasmic reticulum (ER) stress and scaffolding proteins important for protein kinase C signaling; some of which were confirmed by immunoblot analyses. Bioinformatic analysis of protein expression network patterns suggested IRE-BP1 over-expression leads to protein expression patterns indicative of activation of functional protein networks utilized for protein post-translational modification, protein folding, and protein synthesis. Co-immunoprecipitation experiments demonstrate a novel interaction between two differentially regulated proteins receptor for activated protein kinase C (RACK1) and translationally controlled tumor protein (TCTP). CONCLUSIONS Proteomic analysis of IRE-BP1 over-expression in pancreatic islet beta cells suggest IRE-BP1 (a) directly or indirectly through establishing hyperglycemia results in increased expression of ribosomal proteins and markers of ER stress and (b) leads to the enhanced and previously un-described interaction of RACK1 and TCTP. SIGNIFICANCE This study identified C-terminal 50kDa domain of IRE-BP1 over-expression results in increased markers of ER-stress and a novel interaction between the scaffolding proteins RACK1 and TCTP.
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Affiliation(s)
- Betty C Villafuerte
- Department of Medicine, University of Louisville, Louisville, KY, United States
| | - Michelle T Barati
- Department of Medicine, University of Louisville, Louisville, KY, United States
| | - Madhavi J Rane
- Department of Medicine, University of Louisville, Louisville, KY, United States
| | - Susan Isaacs
- Department of Medicine, University of Louisville, Louisville, KY, United States; Core Proteomics Laboratory, University of Louisville, Louisville, KY, United States
| | - Ming Li
- Department of Medicine, University of Louisville, Louisville, KY, United States; Core Proteomics Laboratory, University of Louisville, Louisville, KY, United States
| | - Daniel W Wilkey
- Department of Medicine, University of Louisville, Louisville, KY, United States; Core Proteomics Laboratory, University of Louisville, Louisville, KY, United States
| | - Michael L Merchant
- Department of Medicine, University of Louisville, Louisville, KY, United States; Core Proteomics Laboratory, University of Louisville, Louisville, KY, United States.
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52
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Hotamisligil GS, Davis RJ. Cell Signaling and Stress Responses. Cold Spring Harb Perspect Biol 2016; 8:8/10/a006072. [PMID: 27698029 DOI: 10.1101/cshperspect.a006072] [Citation(s) in RCA: 299] [Impact Index Per Article: 37.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Stress-signaling pathways are evolutionarily conserved and play an important role in the maintenance of homeostasis. These pathways are also critical for adaptation to new cellular environments. The endoplasmic reticulum (ER) unfolded protein response (UPR) is activated by biosynthetic stress and leads to a compensatory increase in ER function. The JNK and p38 MAPK signaling pathways control adaptive responses to intracellular and extracellular stresses, including environmental changes such as UV light, heat, and hyperosmotic conditions, and exposure to inflammatory cytokines. Metabolic stress caused by a high-fat diet represents an example of a stimulus that coordinately activates both the UPR and JNK/p38 signaling pathways. Chronic activation of these stress-response pathways ultimately causes metabolic changes associated with obesity and altered insulin sensitivity. Stress-signaling pathways, therefore, represent potential targets for therapeutic intervention in the metabolic stress response and other disease processes.
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Affiliation(s)
- Gökhan S Hotamisligil
- Department of Genetics and Complex Diseases, Broad Institute of Harvard-MIT, Harvard School of Public Health, Boston, Massachusetts 02115
| | - Roger J Davis
- Howard Hughes Medical Institute and Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605
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53
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Shapiro DJ, Livezey M, Yu L, Zheng X, Andruska N. Anticipatory UPR Activation: A Protective Pathway and Target in Cancer. Trends Endocrinol Metab 2016; 27:731-741. [PMID: 27354311 PMCID: PMC5035594 DOI: 10.1016/j.tem.2016.06.002] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Revised: 06/02/2016] [Accepted: 06/06/2016] [Indexed: 01/18/2023]
Abstract
The endoplasmic reticulum (EnR) stress sensor, the unfolded protein response (UPR), plays a key role in regulating intracellular protein homeostasis. The extensively studied reactive mode of UPR activation is characterized by unfolded protein, or other EnR stress, triggering UPR activation. Here we focus on the emerging anticipatory mode of UPR activation in which mitogenic steroid and peptide hormones and other effectors preactivate the UPR and anticipate a future need for increased protein folding capacity. Mild UPR activation in breast cancer can be protective and contributes to antiestrogen resistance. Hyperactivation of the anticipatory UPR pathway in cancer cells with a small molecule converts it from cytoprotective to cytotoxic, highlighting its potential as a therapeutic target in estrogen receptor-positive breast cancer.
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Affiliation(s)
- David J Shapiro
- Department of Biochemistry, University of Illinois, Urbana, IL 61801, USA.
| | - Mara Livezey
- Department of Biochemistry, University of Illinois, Urbana, IL 61801, USA
| | - Liqun Yu
- Department of Biochemistry, University of Illinois, Urbana, IL 61801, USA
| | - Xiaobin Zheng
- Department of Biochemistry, University of Illinois, Urbana, IL 61801, USA
| | - Neal Andruska
- Department of Biochemistry, University of Illinois, Urbana, IL 61801, USA; College of Medicine, University of Illinois, Urbana, IL 61801, USA
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54
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Grootjans J, Kaser A, Kaufman RJ, Blumberg RS. The unfolded protein response in immunity and inflammation. Nat Rev Immunol 2016; 16:469-84. [PMID: 27346803 DOI: 10.1038/nri.2016.62] [Citation(s) in RCA: 508] [Impact Index Per Article: 63.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The unfolded protein response (UPR) is a highly conserved pathway that allows the cell to manage endoplasmic reticulum (ER) stress that is imposed by the secretory demands associated with environmental forces. In this role, the UPR has increasingly been shown to have crucial functions in immunity and inflammation. In this Review, we discuss the importance of the UPR in the development, differentiation, function and survival of immune cells in meeting the needs of an immune response. In addition, we review current insights into how the UPR is involved in complex chronic inflammatory diseases and, through its role in immune regulation, antitumour responses.
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Affiliation(s)
- Joep Grootjans
- Division of Gastroenterology, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, Boston, Massachusetts 02115, USA
| | - Arthur Kaser
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Randal J Kaufman
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California 92037, USA
| | - Richard S Blumberg
- Division of Gastroenterology, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, Boston, Massachusetts 02115, USA
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55
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Abstract
Components of the unfolded protein response (UPR) modulate beta cell inflammation and death in early type 1 diabetes (T1D). The UPR is a mechanism by which cells react to the accumulation of misfolded proteins in the endoplasmic reticulum (ER). It aims to restore cellular homeostasis, but in case of chronic or overwhelming ER stress the persistent activation of the UPR triggers apoptosis, contributing to the loss of beta cells in both T1D and type 2 diabetes. It remains to be determined how and why the transition from 'physiological' to 'pathological' UPR takes place. A key component of the UPR is the ER transmembrane protein IRE1α (inositol-requiring enzyme 1α). IRE1α activity is modulated by both intra-ER signals and by the formation of protein complexes at its cytosolic domain. The amplitude and duration of IRE1α signaling is critical for the transition between the adaptive and cell death programs, with particular relevance for the activation of the pro-apoptotic c-Jun N-terminal kinase (JNK) in beta cells. In the present review we discuss the available information on IRE1α-regulating proteins in beta cells and their downstream targets, and the important differences observed between cytokine-induced UPR in human and rodent beta cells.
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Affiliation(s)
| | - Décio L. Eizirik
- CONTACT Decio L. Eizirik, MD, PhD ULB Center for Diabetes Research, Université Libre de Bruxelles (ULB), Route de Lennik, 808–CP618, 1070 Brussels, Belgium
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56
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Wang M, Kaufman RJ. Protein misfolding in the endoplasmic reticulum as a conduit to human disease. Nature 2016; 529:326-35. [PMID: 26791723 DOI: 10.1038/nature17041] [Citation(s) in RCA: 1053] [Impact Index Per Article: 131.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Accepted: 11/11/2015] [Indexed: 12/18/2022]
Abstract
In eukaryotic cells, the endoplasmic reticulum is essential for the folding and trafficking of proteins that enter the secretory pathway. Environmental insults or increased protein synthesis often lead to protein misfolding in the organelle, the accumulation of misfolded or unfolded proteins - known as endoplasmic reticulum stress - and the activation of the adaptive unfolded protein response to restore homeostasis. If protein misfolding is not resolved, cells die. Endoplasmic reticulum stress and activation of the unfolded protein response help to determine cell fate and function. Furthermore, endoplasmic reticulum stress contributes to the aetiology of many human diseases.
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Affiliation(s)
- Miao Wang
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, 10901 North Torrey Pines Road, La Jolla, California 92037, USA
| | - Randal J Kaufman
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, 10901 North Torrey Pines Road, La Jolla, California 92037, USA
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57
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Liu D, Liu X, Zhou T, Yao W, Zhao J, Zheng Z, Jiang W, Wang F, Aikhionbare FO, Hill DL, Emmett N, Guo Z, Wang D, Yao X, Chen Y. IRE1-RACK1 axis orchestrates ER stress preconditioning-elicited cytoprotection from ischemia/reperfusion injury in liver. J Mol Cell Biol 2015; 8:144-56. [PMID: 26711306 DOI: 10.1093/jmcb/mjv066] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2015] [Accepted: 09/22/2015] [Indexed: 12/14/2022] Open
Abstract
Endoplasmic reticulum (ER) stress is involved in ischemic preconditioning that protects various organs from ischemia/reperfusion (I/R) injury. We established an in vivo ER stress preconditioning model in which tunicamycin was injected into rats before hepatic I/R. The hepatic I/R injury, demonstrated by serum aminotransferase level and the ultra-structure of the liver, was alleviated by administration of tunicamycin, which induced ER stress in rat liver by activating inositol-requiring enzyme 1 (IRE1) and upregulating 78 kDa glucose-regulated protein (GRP78). The proteomic identification for IRE1 binders revealed interaction and cooperation among receptor for activated C kinase 1 (RACK1), phosphorylated AMPK, and IRE1 under ER stress conditions in a spatiotemporal manner. Furthermore, in vitro ER stress preconditioning was induced by thapsigargin and tunicamycin in L02 and HepG2 cells. Surprisingly, BCL2 was found to be phosphorylated by IRE1 under ER stress conditions to prevent apoptotic process by activation of autophagy. In conclusion, ER stress preconditioning protects against hepatic I/R injury, which is orchestrated by IRE1-RACK1 axis through the activation of BCL2. Our findings provide novel insights into the molecular pathways underlying ER stress preconditioning-elicited cytoprotective effect against hepatic I/R injury.
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Affiliation(s)
- Dong Liu
- Department of Hepatobiliary Surgery, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China Present address: Department of Hepatobiliary Surgery, Navy General Hospital, Beijing 100048, China
| | - Xing Liu
- Anhui Key Laboratory of Cellular Dynamics and Hefei National Laboratory for Physical Sciences at Nanoscale, Hefei 230027, China
| | - Ti Zhou
- Department of Hepatobiliary Surgery, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China
| | - William Yao
- Atlanta Clinical & Translational Science Institute, Atlanta, GA 30310, USA
| | - Jun Zhao
- Department of Pathology, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China
| | - Zhigang Zheng
- Department of Hepatobiliary Surgery, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China
| | - Wei Jiang
- Department of Hepatobiliary Surgery, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China
| | - Fengsong Wang
- Anhui Key Laboratory of Cellular Dynamics and Hefei National Laboratory for Physical Sciences at Nanoscale, Hefei 230027, China Atlanta Clinical & Translational Science Institute, Atlanta, GA 30310, USA Department of Biochemistry, Anhui Medical University, Hefei 230027, China
| | | | - Donald L Hill
- Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Nerimah Emmett
- Atlanta Clinical & Translational Science Institute, Atlanta, GA 30310, USA
| | - Zhen Guo
- Anhui Key Laboratory of Cellular Dynamics and Hefei National Laboratory for Physical Sciences at Nanoscale, Hefei 230027, China
| | - Dongmei Wang
- Anhui Key Laboratory of Cellular Dynamics and Hefei National Laboratory for Physical Sciences at Nanoscale, Hefei 230027, China
| | - Xuebiao Yao
- Atlanta Clinical & Translational Science Institute, Atlanta, GA 30310, USA
| | - Yong Chen
- Department of Hepatobiliary Surgery, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China
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58
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Sun S, Shi G, Sha H, Ji Y, Han X, Shu X, Ma H, Inoue T, Gao B, Kim H, Bu P, Guber RD, Shen X, Lee AH, Iwawaki T, Paton AW, Paton JC, Fang D, Tsai B, Yates JR, Wu H, Kersten S, Long Q, Duhamel GE, Simpson KW, Qi L. IRE1α is an endogenous substrate of endoplasmic-reticulum-associated degradation. Nat Cell Biol 2015; 17:1546-55. [PMID: 26551274 PMCID: PMC4670240 DOI: 10.1038/ncb3266] [Citation(s) in RCA: 168] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Accepted: 10/05/2015] [Indexed: 12/13/2022]
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 IRE1α, the sensor of 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 intramembrane hydrophilic residues of IRE1α and lectin protein OS9, and is attenuated by ER stress. ERAD deficiency causes IRE1α protein stabilization, accumulation and mild activation both in vitro and in vivo. Although enterocyte-specific Sel1L-knockout mice (Sel1LΔIEC) are viable and appear normal, they are highly susceptible to experimental colitis and inflammation-associated dysbiosis, in an IRE1α-dependent but CHOP-independent manner. Hence, Sel1L-Hrd1 ERAD serves a distinct, essential function in restraint of IRE1α signaling in vivo by managing its protein turnover.
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Affiliation(s)
- Shengyi Sun
- Graduate Program in Biochemistry, Molecular and Cell Biology, Cornell University, Ithaca, New York 14853, USA
| | - Guojun Shi
- Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853, USA
| | - Haibo Sha
- Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853, USA
| | - Yewei Ji
- Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853, USA
| | - Xuemei Han
- Department of Chemical Physiology, The Scripps Research Institute, La Jolla, California 92037, USA
| | - Xin Shu
- Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853, USA
| | - Hongming Ma
- Department of Biomedical Sciences, Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center, El Paso, Texas 79905, USA
| | - Takamasa Inoue
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA
| | - Beixue Gao
- Department of Pathology, Northwestern University, Chicago, Illinois 60611, USA
| | - Hana Kim
- Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853, USA
| | - Pengcheng Bu
- Department of Electrical and Computer Engineering, Cornell University, Ithaca, New York 14853, USA.,Department of Biomedical Engineering, Cornell University, Ithaca, New York 14853, USA
| | - Robert D Guber
- Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853, USA
| | - Xiling Shen
- Department of Electrical and Computer Engineering, Cornell University, Ithaca, New York 14853, USA.,Department of Biomedical Engineering, Cornell University, Ithaca, New York 14853, USA.,Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708, USA
| | - Ann-Hwee Lee
- Department of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, New York 10021, USA
| | - Takao Iwawaki
- Education and Research Support Center, Gunma University Graduate School of Medicine, 3-39-22 Showa-machi, Maebashi, Gunma 371-8511, Japan
| | - Adrienne W Paton
- Research Centre for Infectious Diseases, School of Molecular and Biomedical Science, University of Adelaide, Adelaide, South Australia 5005, Australia
| | - James C Paton
- Research Centre for Infectious Diseases, School of Molecular and Biomedical Science, University of Adelaide, Adelaide, South Australia 5005, Australia
| | - Deyu Fang
- Department of Pathology, Northwestern University, Chicago, Illinois 60611, USA
| | - Billy Tsai
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA
| | - John R Yates
- Department of Chemical Physiology, The Scripps Research Institute, La Jolla, California 92037, USA
| | - Haoquan Wu
- Department of Biomedical Sciences, Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center, El Paso, Texas 79905, USA
| | - Sander Kersten
- Nutrition Metabolism and Genomics group, Wageningen University, Bomenweg 2, 6703HD Wageningen, The Netherlands
| | - Qiaoming Long
- Laboratory Animal Research Center, Medical College of Soochow University, Suzhou 215006, Jiangsu, China
| | - Gerald E Duhamel
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, USA
| | - Kenneth W Simpson
- Department of Clinical Science, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, USA
| | - Ling Qi
- Graduate Program in Biochemistry, Molecular and Cell Biology, Cornell University, Ithaca, New York 14853, USA.,Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853, USA
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59
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Eletto D, Eletto D, Boyle S, Argon Y. PDIA6 regulates insulin secretion by selectively inhibiting the RIDD activity of IRE1. FASEB J 2015; 30:653-65. [PMID: 26487694 DOI: 10.1096/fj.15-275883] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Accepted: 09/28/2015] [Indexed: 12/14/2022]
Abstract
Protein disulfide isomerase A6 (PDIA6) interacts with protein kinase RNA-like endoplasmic reticulum kinase (PERK) and inositol requiring enzyme (IRE)-1 and inhibits their unfolded protein response signaling. In this study, shRNA silencing of PDIA6 expression in insulin-producing mouse cells reduced insulin production (5-fold) and, consequently, glucose-stimulated insulin secretion (3-4-fold). This inhibition of insulin release was independent of the PDIA6-PERK interaction or PERK activity. Acute inhibition of PERK did not change the short-term response of β cells to glucose. Rather, PDIA6 affected insulin secretion by modulating one of the activities of IRE1. At 11 mM glucose and lower, the regulated IRE1-dependent decay (RIDD) of the mRNA activity of IRE1 was activated, but not its X-box binding protein (XBP)-1 splicing activity. In the absence of PDIA6, RIDD activity toward insulin transcripts was enhanced up to 4-fold, as shown by molecular assays in cultured cells and the use of a fluorescent reporter in intact islets. Such physiologic activation of IRE1 by glucose contrasted with IRE1 activation by chemical stress, when both IRE1 activities were induced. Thus, whereas the stimulus determines the quality of IRE1 signaling, PDIA6 attenuates multiple enzymatic activities of IRE1, maintaining its signaling within a physiologically tolerable range.
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Affiliation(s)
- Daniela Eletto
- Department of Pathology and Laboratory Medicine, The Children's Hospital of Philadelphia and Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Davide Eletto
- Department of Pathology and Laboratory Medicine, The Children's Hospital of Philadelphia and Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Sarah Boyle
- Department of Pathology and Laboratory Medicine, The Children's Hospital of Philadelphia and Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Yair Argon
- Department of Pathology and Laboratory Medicine, The Children's Hospital of Philadelphia and Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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60
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61
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Abstract
Stress induced by accumulation of misfolded proteins in the endoplasmic reticulum is observed in many physiological and pathological conditions. To cope with endoplasmic reticulum stress, cells activate the unfolded protein response, a dynamic signalling network that orchestrates the recovery of homeostasis or triggers apoptosis, depending on the level of damage. Here we provide an overview of recent insights into the mechanisms that cells employ to maintain proteostasis and how the unfolded protein response determines cell fate under endoplasmic reticulum stress.
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62
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Jia G, Xiaoxiang W, Ruijie L, Xiaoxin Z, Xiaonan Y, Qing X, Ping X. Effect of Chaiqinchengqi decoction on inositol requiring enzyme 1α in alveolar macrophages of dogs with acute necrotising pancreatitis induced by sodium taurocholate. J TRADIT CHIN MED 2015; 35:434-9. [DOI: 10.1016/s0254-6272(15)30121-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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63
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Kanekura K, Ma X, Murphy JT, Zhu LJ, Diwan A, Urano F. IRE1 prevents endoplasmic reticulum membrane permeabilization and cell death under pathological conditions. Sci Signal 2015; 8:ra62. [PMID: 26106220 DOI: 10.1126/scisignal.aaa0341] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The endoplasmic reticulum (ER) has emerged as a critical regulator of cell survival. IRE1 is a transmembrane protein with kinase and RNase activities that is localized to the ER and that promotes resistance to ER stress. We showed a mechanism by which IRE1 conferred protection against ER stress-mediated cell death. IRE1 signaling prevented ER membrane permeabilization mediated by Bax and Bak and cell death in cells experiencing ER stress. Suppression of IRE1 signaling triggered by its kinase activity led to the accumulation of the BH3 domain-containing protein Bnip3, which in turn triggered the oligomerization of Bax and Bak in the ER membrane and ER membrane permeabilization. Consequently, in response to ER stress, cells deficient in IRE1 were susceptible to leakage of ER contents, which was associated with the accumulation of calcium in mitochondria, oxidative stress in the cytosol, and ultimately cell death. Our results reveal a role for IRE1 in preventing a cell death-initializing step that emanates from the ER and provide a potential target for treating diseases characterized by ER stress, including diabetes and Wolfram syndrome.
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Affiliation(s)
- Kohsuke Kanekura
- Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA. Department of Molecular Pathology, Tokyo Medical University, Tokyo 160-8402, Japan
| | - Xiucui Ma
- Division of Cardiology, Department of Medicine, Center for Cardiovascular Research, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - John T Murphy
- Division of Cardiology, Department of Medicine, Center for Cardiovascular Research, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Lihua J Zhu
- Programs in Molecular, Cell and Cancer Biology, Molecular Medicine, and Bioinformatics and Integrative Biology, University of Massachusetts Medical School, Worcester, MA 01655, USA
| | - Abhinav Diwan
- Division of Cardiology, Department of Medicine, Center for Cardiovascular Research, Washington University School of Medicine, St. Louis, MO 63110, USA. John Cochran VA Medical Center, St. Louis, MO 63106, USA
| | - Fumihiko Urano
- Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA. Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA.
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64
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Hiramatsu N, Chiang WC, Kurt TD, Sigurdson CJ, Lin JH. Multiple Mechanisms of Unfolded Protein Response-Induced Cell Death. THE AMERICAN JOURNAL OF PATHOLOGY 2015; 185:1800-8. [PMID: 25956028 DOI: 10.1016/j.ajpath.2015.03.009] [Citation(s) in RCA: 122] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Revised: 02/09/2015] [Accepted: 03/26/2015] [Indexed: 12/12/2022]
Abstract
Eukaryotic cells fold and assemble membrane and secreted proteins in the endoplasmic reticulum (ER), before delivery to other cellular compartments or the extracellular environment. Correctly folded proteins are released from the ER, and poorly folded proteins are retained until they achieve stable conformations; irreparably misfolded proteins are targeted for degradation. Diverse pathological insults, such as amino acid mutations, hypoxia, or infection, can overwhelm ER protein quality control, leading to misfolded protein buildup, causing ER stress. To cope with ER stress, eukaryotic cells activate the unfolded protein response (UPR) by increasing levels of ER protein-folding enzymes and chaperones, enhancing the degradation of misfolded proteins, and reducing protein translation. In mammalian cells, three ER transmembrane proteins, inositol-requiring enzyme-1 (IRE1; official name ERN1), PKR-like ER kinase (PERK; official name EIF2AK3), and activating transcription factor-6, control the UPR. The UPR signaling triggers a set of prodeath programs when the cells fail to successfully adapt to ER stress or restore homeostasis. ER stress and UPR signaling are implicated in the pathogenesis of diverse diseases, including neurodegeneration, cancer, diabetes, and inflammation. This review discusses the current understanding in both adaptive and apoptotic responses as well as the molecular mechanisms instigating apoptosis via IRE1 and PERK signaling. We also examine how IRE1 and PERK signaling may be differentially used during neurodegeneration arising in retinitis pigmentosa and prion infection.
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Affiliation(s)
- Nobuhiko Hiramatsu
- Department of Pathology, University of California-San Diego, La Jolla, California
| | - Wei-Chieh Chiang
- Department of Pathology, University of California-San Diego, La Jolla, California
| | - Timothy D Kurt
- Department of Pathology, University of California-San Diego, La Jolla, California
| | | | - Jonathan H Lin
- Department of Pathology, University of California-San Diego, La Jolla, California.
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65
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Zhou T, Lv X, Guo X, Ruan B, Liu D, Ding R, Gao Y, Ding J, Dou K, Chen Y. RACK1 modulates apoptosis induced by sorafenib in HCC cells by interfering with the IRE1/XBP1 axis. Oncol Rep 2015; 33:3006-14. [PMID: 25901709 DOI: 10.3892/or.2015.3920] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2014] [Accepted: 03/24/2015] [Indexed: 11/06/2022] Open
Abstract
Sorafenib is one of the preferred drugs for the treatment of advanced primary hepatocellular carcinoma (HCC). However, its side-effects and acquired resistance limit its use. The unfolded protein response (UPR) induced by chemotherapeutics has been demonstrated to be required for tumor cells to maintain malignancy and therapy resistance. Activation of the IRE1/XBP1 pathway during the UPR is important for tumor survival under pathophysiological conditions. In the present study, we found that the UPR was activated and RACK1 was overexpressed in three human HCC cell lines and in HCC samples. Activation of the IRE1/XBP1 signaling pathway plays a protective role when HCC cells encounter endoplasmic reticulum (ER) stress due to in vitro sorafenib treatment. We then found that the interaction between IRE1 and RACK1 was essential for the activation of IRE1 signaling in sorafenib-treated cells. Exogenous overexpression of RACK1 enhanced the phosphorylation level of IRE1 and increased XBP1 mRNA splicing activity, which protected the HCC cells from sorafenib-induced apoptosis. However, the re-expression of RACK1 led HCC cells to regain susceptibility to sorafenib-induced apoptosis. Taken together, the present study suggests that the RACK1/IRE1 complex may contribute to activation of the UPR in HCC cells. Targeting RACK1 in combination with sorafenib administration is a potential strategy for clinical trials of advanced HCC treatment.
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Affiliation(s)
- Ti Zhou
- Department of Hepatobiliary Surgery, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
| | - Xing Lv
- Department of Hepatobiliary Surgery, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
| | - Xin Guo
- Department of Hepatobiliary Surgery, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
| | - Bai Ruan
- Department of Hepatobiliary Surgery, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
| | - Dong Liu
- Department of Hepatobiliary Surgery, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
| | - Rui Ding
- Department of Hepatobiliary Surgery, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
| | - Yuan Gao
- Department of Hepatobiliary Surgery, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
| | - Jie Ding
- Department of Pharmacy, Xi'an Central Hospital, Xi'an, Shaanxi 710032, P.R. China
| | - Kefeng Dou
- Department of Hepatobiliary Surgery, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
| | - Yong Chen
- Department of Hepatobiliary Surgery, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
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Pieper R, Martin L, Schunter N, Villodre Tudela C, Weise C, Klopfleisch R, Zentek J, Einspanier R, Bondzio A. Impact of high dietary zinc on zinc accumulation, enzyme activity and proteomic profiles in the pancreas of piglets. J Trace Elem Med Biol 2015; 30:30-6. [PMID: 25744507 DOI: 10.1016/j.jtemb.2015.01.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Revised: 01/13/2015] [Accepted: 01/14/2015] [Indexed: 12/26/2022]
Abstract
The exocrine pancreas plays an important role in zinc homeostasis. Feeding very high (2000-3000mgzinc/kg diet) levels of zinc oxide to piglets for short periods is a common practice in the swine industry to improve performance and prevent diseases. The impact on pancreatic function and possible side effects during long-term feeding of high dietary zinc levels are still poorly understood. A total of 54 weaned piglets were either fed with low (57mg/kg, LZn), normal (164mg/kg, NZn) or high (2425mg/kg, HZn) zinc concentration in the diets. After 4 weeks of feeding, ten piglets per treatment were euthanized and pancreas samples were taken. Tissue zinc concentration and metallothionein abundance was greater with HZn compared with NZn and LZn (P<0.05). Similarly, activity of α-amylase, lipase, trypsin and chymotrypsin was higher with HZn as compared with NZn and LZn diets (P<0.05), whereas elastase activity was unchanged. Total trolox equivalent antioxidative capacity of pancreas tissue was higher with HZn diets compared with the other treatments (P<0.05). Pancreatic protein profiles of NZn and HZn fed piglets were obtained by 2D-DIGE technique and revealed 15 differentially expressed proteins out of 2100 detected spots (P<0.05). The differentially expressed proteins aldose reductase, eukaryotic elongation factor II and peroxiredoxin III were confirmed by immunoblotting. Identified proteins include zinc finger-containing transcription factors and proteins mainly associated with oxidative stress response and signal transduction in HZn compared with NZn pigs. Histologic examination however showed no morphologic changes. The results suggest that long-term supply of very high dietary zinc increases zinc and metallothionein concentration, and digestive enzyme activity, but also triggers oxidative stress reactions in the pancreas of young pigs. The data provide new insights into pancreatic function under outbalanced zinc homeostasis.
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Affiliation(s)
- R Pieper
- Institute of Animal Nutrition, Department of Veterinary Medicine, Freie Universität Berlin, Königin-Luise-Strasse 49, D-14195 Berlin, Germany.
| | - L Martin
- Institute of Animal Nutrition, Department of Veterinary Medicine, Freie Universität Berlin, Königin-Luise-Strasse 49, D-14195 Berlin, Germany
| | - N Schunter
- Institute of Animal Nutrition, Department of Veterinary Medicine, Freie Universität Berlin, Königin-Luise-Strasse 49, D-14195 Berlin, Germany
| | - C Villodre Tudela
- Institute of Animal Nutrition, Department of Veterinary Medicine, Freie Universität Berlin, Königin-Luise-Strasse 49, D-14195 Berlin, Germany
| | - C Weise
- Institute of Chemistry and Biochemistry, Department of Biology, Chemistry and Pharmacy, Freie Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany
| | - R Klopfleisch
- Institute of Veterinary Pathology, Department of Veterinary Medicine, Freie Universität Berlin, Robert-von-Ostertag-Strasse 15, D-14163 Berlin, Germany
| | - J Zentek
- Institute of Animal Nutrition, Department of Veterinary Medicine, Freie Universität Berlin, Königin-Luise-Strasse 49, D-14195 Berlin, Germany
| | - R Einspanier
- Institute of Veterinary Biochemistry, Department of Veterinary Medicine, Freie Universität Berlin, Oertzenweg 19b, D-14163 Berlin, Germany
| | - A Bondzio
- Institute of Veterinary Biochemistry, Department of Veterinary Medicine, Freie Universität Berlin, Oertzenweg 19b, D-14163 Berlin, Germany
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Liu Y, Shao M, Wu Y, Yan C, Jiang S, Liu J, Dai J, Yang L, Li J, Jia W, Rui L, Liu Y. Role for the endoplasmic reticulum stress sensor IRE1α in liver regenerative responses. J Hepatol 2015; 62:590-8. [PMID: 25457211 DOI: 10.1016/j.jhep.2014.10.022] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Revised: 09/14/2014] [Accepted: 10/09/2014] [Indexed: 12/22/2022]
Abstract
BACKGROUND & AIMS As the main detoxifying organ of the body, the liver possesses a remarkable ability to regenerate after toxic injury, tissue resection or viral infection. A growing number of cellular signaling pathways have been implicated in orchestrating the process of liver regeneration. Here we investigated the role of inositol-requiring enzyme-1α (IRE1α), a key signal transducer of the unfolded protein response (UPR), in liver regeneration. METHODS Using mice with hepatocyte-specific deletion of IRE1α, we examined the role of IRE1α in liver regeneration after challenges with carbon tetrachloride (CCl4) or hepatic surgery. We also investigated if IRE1α deficiency could affect the activation state of signal transducer and activator of transcription 3 (STAT3) in hepatocytes. Using co-immunoprecipitation and glutathione S-transferase (GST) pull-down assays, we analyzed whether IRE1α could interact with STAT3 to regulate its phosphorylation. RESULTS We found that in response to CCl4-induced liver damage or after two-thirds partial hepatectomy (PH), abrogation of IRE1α caused marked exacerbation of liver injury and impairment in regenerative proliferation of hepatocytes in mice. Furthermore, IRE1α deficiency resulted in dampened STAT3 activation, and restoration of IRE1α expression led to sustained phosphorylation of STAT3 in IRE1α-null hepatocytes. Additionally, IRE1α could directly and constitutively associate with STAT3, leading to elevated phosphorylation when stimulated by IL-6. CONCLUSIONS These results suggest that IRE1α may promote liver regeneration through acting as a signaling platform to regulate the STAT3 pathway.
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Affiliation(s)
- Yang Liu
- Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of the Chinese Academy of Sciences, Shanghai 200031, China
| | - Mengle Shao
- Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of the Chinese Academy of Sciences, Shanghai 200031, China
| | - Ying Wu
- Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of the Chinese Academy of Sciences, Shanghai 200031, China
| | - Cheng Yan
- Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of the Chinese Academy of Sciences, Shanghai 200031, China
| | - Shan Jiang
- Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Clinical Center for Diabetes, Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai 200233, China
| | - Jingnan Liu
- Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of the Chinese Academy of Sciences, Shanghai 200031, China
| | - Jianli Dai
- School of Life Science and Technology, ShanghaiTech University, Shanghai 200031, China
| | - Liu Yang
- Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of the Chinese Academy of Sciences, Shanghai 200031, China
| | - Jia Li
- National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Weiping Jia
- Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Clinical Center for Diabetes, Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai 200233, China
| | - Liangyou Rui
- Department of Molecular and Integrative Physiology, The University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Yong Liu
- Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of the Chinese Academy of Sciences, Shanghai 200031, China; School of Life Science and Technology, ShanghaiTech University, Shanghai 200031, China.
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Brozzi F, Gerlo S, Grieco FA, Nardelli TR, Lievens S, Gysemans C, Marselli L, Marchetti P, Mathieu C, Tavernier J, Eizirik DL. A combined "omics" approach identifies N-Myc interactor as a novel cytokine-induced regulator of IRE1 protein and c-Jun N-terminal kinase in pancreatic beta cells. J Biol Chem 2015; 289:20677-93. [PMID: 24936061 DOI: 10.1074/jbc.m114.568808] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Type 1 diabetes is an autoimmune disease with a strong inflammatory component. The cytokines interleukin-1β and interferon-γ contribute to beta cell apoptosis in type 1 diabetes. These cytokines induce endoplasmic reticulum stress and the unfolded protein response (UPR), contributing to the loss of beta cells. IRE1α, one of the UPR mediators, triggers insulin degradation and inflammation in beta cells and is critical for the transition from "physiological" to "pathological" UPR. The mechanisms regulating inositol-requiring protein 1α (IRE1α) activation and its signaling for beta cell "adaptation," "stress response," or "apoptosis" remain to be clarified. To address these questions, we combined mammalian protein-protein interaction trap-based IRE1α interactome and functional genomic analysis of human and rodent beta cells exposed to pro-inflammatory cytokines to identify novel cytokine-induced regulators of IRE1α. Based on this approach, we identified N-Myc interactor (NMI) as an IRE1α-interacting/modulator protein in rodent and human pancreatic beta cells. An increased expression of NMI was detected in islets from nonobese diabetic mice with insulitis and in rodent or human beta cells exposed in vitro to the pro-inflammatory cytokines interleukin-1β and interferon-γ. Detailed mechanistic studies demonstrated that NMI negatively modulates IRE1α-dependent activation of JNK and apoptosis in rodent and human pancreatic beta cells. In conclusion, by using a combined omics approach, we identified NMI induction as a novel negative feedback mechanism that decreases IRE1α-dependent activation of JNK and apoptosis in cytokine-exposed beta cells
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69
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Identification of small molecules that protect pancreatic β cells against endoplasmic reticulum stress-induced cell death. ACS Chem Biol 2014; 9:2796-806. [PMID: 25279668 PMCID: PMC4273981 DOI: 10.1021/cb500740d] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
![]()
Endoplasmic
reticulum (ER) stress plays an important role in the
decline in pancreatic β cell function and mass observed in type
2 diabetes. Here, we developed a novel β cell-based high-throughput
screening assay to identify small molecules that protect β cells
against ER stress-induced cell death. Mouse βTC6 cells were
treated with the ER stressor tunicamycin to induce ER stress, and
cell death was measured as a reduction in cellular ATP. A collection
of 17600 compounds was screened for molecules that promote β
cell survival. Of the approximately 80 positive hits, two selected
compounds were able to increase the survival of human primary β
cells and rodent β cell lines subjected to ER stressors including
palmitate, a free fatty acid of pathological relevance to diabetes.
These compounds also restored ER stress-impaired glucose-stimulated
insulin secretion responses. We show that the compounds promote β
cell survival by reducing the expression of key genes of the unfolded
protein response and apoptosis, thus alleviating ER stress. Identification
of small molecules that prevent ER stress-induced β cell dysfunction
and death may provide a new modality for the treatment of diabetes.
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70
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Wang M, Kaufman RJ. The impact of the endoplasmic reticulum protein-folding environment on cancer development. Nat Rev Cancer 2014; 14:581-97. [PMID: 25145482 DOI: 10.1038/nrc3800] [Citation(s) in RCA: 771] [Impact Index Per Article: 77.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The endoplasmic reticulum (ER) is an essential organelle in eukaryotic cells for the storage and regulated release of calcium and as the entrance to the secretory pathway. Protein misfolding in the ER causes accumulation of misfolded proteins (ER stress) and activation of the unfolded protein response (UPR), which has evolved to maintain a productive ER protein-folding environment. Both ER stress and UPR activation are documented in many different human cancers. In this Review, we summarize the impact of ER stress and UPR activation on every aspect of cancer and discuss outstanding questions for which answers will pave the way for therapeutics.
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Affiliation(s)
- Miao Wang
- Degenerative Diseases Program, Center for Cancer Research, Sanford-Burnham Medical Research Institute, 10901 N. Torrey Pines Rd, La Jolla, California 92037, USA
| | - Randal J Kaufman
- Degenerative Diseases Program, Center for Cancer Research, Sanford-Burnham Medical Research Institute, 10901 N. Torrey Pines Rd, La Jolla, California 92037, USA
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71
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Biden TJ, Boslem E, Chu KY, Sue N. Lipotoxic endoplasmic reticulum stress, β cell failure, and type 2 diabetes mellitus. Trends Endocrinol Metab 2014; 25:389-98. [PMID: 24656915 DOI: 10.1016/j.tem.2014.02.003] [Citation(s) in RCA: 155] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2013] [Revised: 02/12/2014] [Accepted: 02/19/2014] [Indexed: 02/06/2023]
Abstract
Failure of the unfolded protein response (UPR) to maintain optimal folding of pro-insulin in the endoplasmic reticulum (ER) leads to unresolved ER stress and β cell death. This contributes not only to some rare forms of diabetes, but also to type 2 diabetes mellitus (T2DM). Many key findings, elaborated over the past decade, are based on the lipotoxicity model, entailing chronic exposure of β cells to elevated levels of fatty acids (FAs). Here, we update recent progress on how FAs initiate ER stress, particularly via disruption of protein trafficking, and how this leads to apoptosis. We also highlight differences in how β cells are impacted by the classic UPR, versus the more selective UPR that arises as part of a broader response to lipotoxicity.
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Affiliation(s)
- Trevor J Biden
- Diabetes and Obesity Program, Garvan Institute of Medical Research, Sydney, NSW 2010, Australia.
| | - Ebru Boslem
- Diabetes and Obesity Program, Garvan Institute of Medical Research, Sydney, NSW 2010, Australia
| | - Kwan Yi Chu
- Diabetes and Obesity Program, Garvan Institute of Medical Research, Sydney, NSW 2010, Australia
| | - Nancy Sue
- Diabetes and Obesity Program, Garvan Institute of Medical Research, Sydney, NSW 2010, Australia
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Rodríguez M, Domingo E, Alonso S, Frade JG, Eiros J, Crespo MS, Fernández N. The unfolded protein response and the phosphorylations of activating transcription factor 2 in the trans-activation of il23a promoter produced by β-glucans. J Biol Chem 2014; 289:22942-22957. [PMID: 24982422 DOI: 10.1074/jbc.m113.522656] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Current views on the control of IL-23 production focus on the regulation of il23a, the gene encoding IL-23 p19, by NF-κB in combination with other transcription factors. C/EBP homologous protein (CHOP), X2-Box-binding protein 1 (XBP1), activator protein 1 (AP1), SMAD, CCAAT/enhancer-binding protein (C/EBPβ), and cAMP-response element-binding protein (CREB) have been involved in response to LPS, but no data are available regarding the mechanism triggered by the fungal mimic and β-glucan-containing stimulus zymosan, which produces IL-23 and to a low extent the related cytokine IL-12 p70. Zymosan induced the mobilization of CHOP from the nuclear fractions to phagocytic vesicles. Hypha-forming Candida also induced the nuclear disappearance of CHOP. Assay of transcription factor binding to the il23a promoter showed an increase of Thr(P)-71-Thr(P)-69-activating transcription factor 2 (ATF2) binding in response to zymosan. PKC and PKA/mitogen- and stress-activated kinase inhibitors down-regulated Thr(P)-71-ATF2 binding to the il23a promoter and il23a mRNA expression. Consistent with the current concept of complementary phosphorylations on N-terminal Thr-71 and Thr-69 of ATF2 by ERK and p38 MAPK, MEK, and p38 MAPK inhibitors blunted Thr(P)-69-ATF2 binding. Knockdown of atf2 mRNA with siRNA correlated with inhibition of il23a mRNA, but it did not affect the expression of il12/23b and il10 mRNA. These data indicate the following: (i) zymosan decreases nuclear proapoptotic CHOP, most likely by promoting its accumulation in phagocytic vesicles; (ii) zymosan-induced il23a mRNA expression is best explained through coordinated κB- and ATF2-dependent transcription; and (iii) il23a expression relies on complementary phosphorylation of ATF2 on Thr-69 and Thr-71 dependent on PKC and MAPK activities.
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Affiliation(s)
- Mario Rodríguez
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad de Valladolid, 47005-Valladolid
| | - Esther Domingo
- Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, 47003-Valladolid
| | - Sara Alonso
- Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, 47003-Valladolid
| | - Javier García Frade
- Division of Hematology, Hospital Universitario Rio Hortega, 47012-Valladolid, and
| | - José Eiros
- Division of Microbiology, Hospital Universitario Rio Hortega, 47012-Valladolid, Spain
| | - Mariano Sánchez Crespo
- Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, 47003-Valladolid,.
| | - Nieves Fernández
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad de Valladolid, 47005-Valladolid
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The IRE1α-XBP1 pathway regulates metabolic stress-induced compensatory proliferation of pancreatic β-cells. Cell Res 2014; 24:1137-40. [PMID: 24797433 DOI: 10.1038/cr.2014.55] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
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74
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Long L, Deng Y, Yao F, Guan D, Feng Y, Jiang H, Li X, Hu P, Lu X, Wang H, Li J, Gao X, Xie D. Recruitment of Phosphatase PP2A by RACK1 Adaptor Protein Deactivates Transcription Factor IRF3 and Limits Type I Interferon Signaling. Immunity 2014; 40:515-29. [DOI: 10.1016/j.immuni.2014.01.015] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Accepted: 01/24/2014] [Indexed: 01/19/2023]
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75
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Hepatic IRE1α regulates fasting-induced metabolic adaptive programs through the XBP1s-PPARα axis signalling. Nat Commun 2014; 5:3528. [PMID: 24670948 DOI: 10.1038/ncomms4528] [Citation(s) in RCA: 124] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Accepted: 02/28/2014] [Indexed: 01/19/2023] Open
Abstract
Although the mammalian IRE1α-XBP1 branch of the cellular unfolded protein response has been implicated in glucose and lipid metabolism, the exact metabolic role of IRE1α signalling in vivo remains poorly understood. Here we show that hepatic IRE1α functions as a nutrient sensor that regulates the metabolic adaptation to fasting. We find that prolonged deprivation of food or consumption of a ketogenic diet activates the IRE1α-XBP1 pathway in mouse livers. Hepatocyte-specific abrogation of Ire1α results in impairment of fatty acid β-oxidation and ketogenesis in the liver under chronic fasting or ketogenic conditions, leading to hepatosteatosis; liver-specific restoration of XBP1s reverses the defects in IRE1α null mice. XBP1s directly binds to and activates the promoter of PPARα, the master regulator of starvation responses. Hence, our results demonstrate that hepatic IRE1α promotes the adaptive shift of fuel utilization during starvation by stimulating mitochondrial β-oxidation and ketogenesis through the XBP1s-PPARα axis.
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76
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Parmar JH, Cook KL, Shajahan-Haq AN, Clarke PAG, Tavassoly I, Clarke R, Tyson JJ, Baumann WT. Modelling the effect of GRP78 on anti-oestrogen sensitivity and resistance in breast cancer. Interface Focus 2014; 3:20130012. [PMID: 24511377 DOI: 10.1098/rsfs.2013.0012] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Understanding the origins of resistance to anti-oestrogen drugs is of critical importance to many breast cancer patients. Recent experiments show that knockdown of GRP78, a key gene in the unfolded protein response (UPR), can re-sensitize resistant cells to anti-oestrogens, and overexpression of GRP78 in sensitive cells can cause them to become resistant. These results appear to arise from the operation and interaction of three cellular systems: the UPR, autophagy and apoptosis. To determine whether our current mechanistic understanding of these systems is sufficient to explain the experimental results, we built a mathematical model of the three systems and their interactions. We show that the model is capable of reproducing previously published experimental results and some new data gathered specifically for this paper. The model provides us with a tool to better understand the interactions that bring about anti-oestrogen resistance and the effects of GRP78 on both sensitive and resistant breast cancer cells.
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Affiliation(s)
- Jignesh H Parmar
- Department of Biological Sciences , Virginia Polytechnic Institute and State University , Blacksburg, VA 24061 , USA
| | - Katherine L Cook
- Department of Oncology, Lombardi Comprehensive Cancer Center , Georgetown University Medical Center , Washington, DC 20057 , USA
| | - Ayesha N Shajahan-Haq
- Department of Oncology, Lombardi Comprehensive Cancer Center , Georgetown University Medical Center , Washington, DC 20057 , USA
| | - Pamela A G Clarke
- Department of Oncology, Lombardi Comprehensive Cancer Center , Georgetown University Medical Center , Washington, DC 20057 , USA
| | - Iman Tavassoly
- Department of Biological Sciences , Virginia Polytechnic Institute and State University , Blacksburg, VA 24061 , USA
| | - Robert Clarke
- Department of Oncology, Lombardi Comprehensive Cancer Center , Georgetown University Medical Center , Washington, DC 20057 , USA
| | - John J Tyson
- Department of Biological Sciences , Virginia Polytechnic Institute and State University , Blacksburg, VA 24061 , USA
| | - William T Baumann
- Bradley Department of Electrical and Computer Engineering , Virginia Polytechnic Institute and State University , Blacksburg, VA 24061 , USA
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77
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Eletto D, Eletto D, Dersh D, Gidalevitz T, Argon Y. Protein disulfide isomerase A6 controls the decay of IRE1α signaling via disulfide-dependent association. Mol Cell 2014; 53:562-576. [PMID: 24508390 DOI: 10.1016/j.molcel.2014.01.004] [Citation(s) in RCA: 171] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2013] [Revised: 11/25/2013] [Accepted: 01/03/2014] [Indexed: 11/29/2022]
Abstract
The response to endoplasmic reticulum (ER) stress relies on activation of unfolded protein response (UPR) sensors, and the outcome of the UPR depends on the duration and strength of signal. Here, we demonstrate a mechanism that attenuates the activity of the UPR sensor inositol-requiring enzyme 1α (IRE1α). A resident ER protein disulfide isomerase, PDIA6, limits the duration of IRE1α activity by direct binding to cysteine 148 in the lumenal domain of the sensor, which is oxidized when IRE1 is activated. PDIA6-deficient cells hyperrespond to ER stress with sustained autophosphorylation of IRE1α and splicing of XBP1 mRNA, resulting in exaggerated upregulation of UPR target genes and increased apoptosis. In vivo, PDIA6-deficient C. elegans exhibits constitutive UPR and fails to complete larval development, a program that normally requires the UPR. Thus, PDIA6 activity provides a mechanism that limits UPR signaling and maintains it within a physiologically appropriate range.
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Affiliation(s)
- Davide Eletto
- Department of Pathology and Laboratory Medicine, The Children's Hospital of Philadelphia and The University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Daniela Eletto
- Department of Pathology and Laboratory Medicine, The Children's Hospital of Philadelphia and The University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Devin Dersh
- Department of Pathology and Laboratory Medicine, The Children's Hospital of Philadelphia and The University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Tali Gidalevitz
- Department of Biology, Drexel University, Philadelphia, PA 19104, USA
| | - Yair Argon
- Department of Pathology and Laboratory Medicine, The Children's Hospital of Philadelphia and The University of Pennsylvania, Philadelphia, PA 19104, USA
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LIN YANG, CUI MANHUA, TENG HONG, WANG FENGWEN, YU WEI, XU TIANMIN. Silencing the receptor of activated C-kinase 1 (RACK1) suppresses tumorigenicity in epithelial ovarian cancer in vitro and in vivo. Int J Oncol 2014; 44:1252-8. [DOI: 10.3892/ijo.2014.2274] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2013] [Accepted: 12/18/2013] [Indexed: 11/05/2022] Open
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Rabhi N, Salas E, Froguel P, Annicotte JS. Role of the unfolded protein response in β cell compensation and failure during diabetes. J Diabetes Res 2014; 2014:795171. [PMID: 24812634 PMCID: PMC4000654 DOI: 10.1155/2014/795171] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Revised: 03/12/2014] [Accepted: 03/13/2014] [Indexed: 02/06/2023] Open
Abstract
Pancreatic β cell failure leads to diabetes development. During disease progression, β cells adapt their secretory capacity to compensate the elevated glycaemia and the peripheral insulin resistance. This compensatory mechanism involves a fine-tuned regulation to modulate the endoplasmic reticulum (ER) capacity and quality control to prevent unfolded proinsulin accumulation, a major protein synthetized within the β cell. These signalling pathways are collectively termed unfolded protein response (UPR). The UPR machinery is required to preserve ER homeostasis and β cell integrity. Moreover, UPR actors play a key role by regulating ER folding capacity, increasing the degradation of misfolded proteins, and limiting the mRNA translation rate. Recent genetic and biochemical studies on mouse models and human UPR sensor mutations demonstrate a clear requirement of the UPR machinery to prevent β cell failure and increase β cell mass and adaptation throughout the progression of diabetes. In this review we will highlight the specific role of UPR actors in β cell compensation and failure during diabetes.
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Affiliation(s)
- Nabil Rabhi
- European Genomic Institute for Diabetes (EGID), CNRS UMR 8199, Lille 2 University of Health and Law, 59000 Lille, France
| | - Elisabet Salas
- European Genomic Institute for Diabetes (EGID), CNRS UMR 8199, Lille 2 University of Health and Law, 59000 Lille, France
| | - Philippe Froguel
- European Genomic Institute for Diabetes (EGID), CNRS UMR 8199, Lille 2 University of Health and Law, 59000 Lille, France
- Departments of Genomics of Common Disease, Hammersmith Hospital, Imperial College London, London, UK
| | - Jean-Sébastien Annicotte
- European Genomic Institute for Diabetes (EGID), CNRS UMR 8199, Lille 2 University of Health and Law, 59000 Lille, France
- Laboratoire Bases Moléculaires et Modélisation du Diabète et de l'Obésité, Faculté de Médecine, Pôle Recherche, 59045 Lille, France
- *Jean-Sébastien Annicotte:
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80
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Zhao M, Zang B, Cheng M, Ma Y, Yang Y, Yang N. Differential responses of hepatic endoplasmic reticulum stress and inflammation in diet-induced obese rats with high-fat diet rich in lard oil or soybean oil. PLoS One 2013; 8:e78620. [PMID: 24223162 PMCID: PMC3819370 DOI: 10.1371/journal.pone.0078620] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2013] [Accepted: 09/13/2013] [Indexed: 02/06/2023] Open
Abstract
Scopes To investigate the effects of high-fat diet enriched with lard oil or soybean oil on liver endoplasmic reticulum (ER) stress and inflammation markers in diet-induced obese (DIO) rats and estimate the influence of following low-fat diet feeding. Methods and Results Male SD rats were fed with standard low-fat diet (LF, n = 10) and two isoenergentic high-fat diets enriched with lard (HL, n = 45) or soybean oil (HS, n = 45) respectively for 10 weeks. Then DIO rats from HL and HS were fed either high-fat diet continuously (HL/HL, HS/HS) or switched to low-fat diet (HL/LF, HS/LF) for another 8 weeks. Rats in control group were maintained with low-fat diet. Body fat, serum insulin level, HOMA-IR and ectopic lipid deposition in liver were increased in HL/HL and HS/HS compared to control, but increased to a greater extent in HL/HL compared to HS/HS. Markers of ER stress including PERK and CHOP protein expression and phosphorylation of eIF2α were significantly elevated in HL/HL group while phosphorylation of IRE1α and GRP78 protein expression were suppressed in both HL/HL and HS/HS. Besides, inflammatory signals (OPN, TLR2, TLR4 and TNF-α) expressions significantly increased in HL/HL compared to others. Switching to low-fat diet reduced liver fat deposition, HOMA-IR, mRNA expression of TLR4, TNF-α, PERK in both HL/LF and HS/LF, but only decreased protein expression of OPN, PERK and CHOP in HL/LF group. In addition, HL/LF and HS/LF exhibited decreased phosphorylation of eIF2α and increased phosphorylation of IRE1α and GRP78 protein expression when compared with HL/HL and HS/HS respectively. Conclusions Lard oil was more deleterious in insulin resistance and hepatic steatosis via promoting ER stress and inflammation responses in DIO rats, which may be attributed to the enrichment of saturated fatty acid. Low-fat diet was confirmed to be useful in recovering from impaired insulin sensitivity and liver fat deposition in this study.
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Affiliation(s)
- Min Zhao
- Department of Nutrition and Food Hygiene, Hubei Key Laboratory of Food Nutrition and Safety, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, People's Republic of China
- Ministry of Education Key Lab of Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, People's Republic of China
| | - Baocai Zang
- Department of Nutrition and Food Hygiene, Hubei Key Laboratory of Food Nutrition and Safety, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, People's Republic of China
- Ministry of Education Key Lab of Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, People's Republic of China
| | - Mengjie Cheng
- Department of Nutrition and Food Hygiene, Hubei Key Laboratory of Food Nutrition and Safety, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, People's Republic of China
| | - Yan Ma
- Department of Nutrition and Food Hygiene, Hubei Key Laboratory of Food Nutrition and Safety, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, People's Republic of China
| | - Yanhong Yang
- Department of Nutrition and Food Hygiene, Hubei Key Laboratory of Food Nutrition and Safety, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, People's Republic of China
| | - Nianhong Yang
- Department of Nutrition and Food Hygiene, Hubei Key Laboratory of Food Nutrition and Safety, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, People's Republic of China
- Ministry of Education Key Lab of Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, People's Republic of China
- * E-mail:
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81
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Kedersha N, Ivanov P, Anderson P. Stress granules and cell signaling: more than just a passing phase? Trends Biochem Sci 2013; 38:494-506. [PMID: 24029419 DOI: 10.1016/j.tibs.2013.07.004] [Citation(s) in RCA: 454] [Impact Index Per Article: 41.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Revised: 07/23/2013] [Accepted: 07/29/2013] [Indexed: 12/27/2022]
Abstract
Stress granules (SGs) contain translationally-stalled mRNAs, associated preinitiation factors, and specific RNA-binding proteins. In addition, many signaling proteins are recruited to SGs and/or influence their assembly, which is transient, lasting only until the cells adapt to stress or die. Beyond their role as mRNA triage centers, we posit that SGs constitute RNA-centric signaling hubs analogous to classical multiprotein signaling domains such as transmembrane receptor complexes. As signaling centers, SG formation communicates a 'state of emergency', and their transient existence alters multiple signaling pathways by intercepting and sequestering signaling components. SG assembly and downstream signaling functions may require a cytosolic phase transition facilitated by intrinsically disordered, aggregation-prone protein regions shared by RNA-binding and signaling proteins.
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Affiliation(s)
- Nancy Kedersha
- Division of Rheumatology, Immunology and Allergy, Brigham and Women's Hospital, Smith 652, One Jimmy Fund Way, Boston, MA 02115, USA
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82
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Qiu Q, Zheng Z, Chang L, Zhao YS, Tan C, Dandekar A, Zhang Z, Lin Z, Gui M, Li X, Zhang T, Kong Q, Li H, Chen S, Chen A, Kaufman RJ, Yang WL, Lin HK, Zhang D, Perlman H, Thorp E, Zhang K, Fang D. Toll-like receptor-mediated IRE1α activation as a therapeutic target for inflammatory arthritis. EMBO J 2013; 32:2477-90. [PMID: 23942232 DOI: 10.1038/emboj.2013.183] [Citation(s) in RCA: 148] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Accepted: 07/15/2013] [Indexed: 01/27/2023] Open
Abstract
In rheumatoid arthritis (RA), macrophage is one of the major sources of inflammatory mediators. Macrophages produce inflammatory cytokines through toll-like receptor (TLR)-mediated signalling during RA. Herein, we studied macrophages from the synovial fluid of RA patients and observed a significant increase in activation of inositol-requiring enzyme 1α (IRE1α), a primary unfolded protein response (UPR) transducer. Myeloid-specific deletion of the IRE1α gene protected mice from inflammatory arthritis, and treatment with the IRE1α-specific inhibitor 4U8C attenuated joint inflammation in mice. IRE1α was required for optimal production of pro-inflammatory cytokines as evidenced by impaired TLR-induced cytokine production in IRE1α-null macrophages and neutrophils. Further analyses demonstrated that tumour necrosis factor (TNF) receptor-associated factor 6 (TRAF6) plays a key role in TLR-mediated IRE1α activation by catalysing IRE1α ubiquitination and blocking the recruitment of protein phosphatase 2A (PP2A), a phosphatase that inhibits IRE1α phosphorylation. In summary, we discovered a novel regulatory axis through TRAF6-mediated IRE1α ubiquitination in regulating TLR-induced IRE1α activation in pro-inflammatory cytokine production, and demonstrated that IRE1α is a potential therapeutic target for inflammatory arthritis.
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Affiliation(s)
- Quan Qiu
- Department of Pathology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
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83
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IRE1: ER stress sensor and cell fate executor. Trends Cell Biol 2013; 23:547-55. [PMID: 23880584 DOI: 10.1016/j.tcb.2013.06.005] [Citation(s) in RCA: 390] [Impact Index Per Article: 35.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Revised: 05/31/2013] [Accepted: 06/19/2013] [Indexed: 12/20/2022]
Abstract
Cells operate a signaling network termed the unfolded protein response (UPR) to monitor protein-folding capacity in the endoplasmic reticulum (ER). Inositol-requiring enzyme 1 (IRE1) is an ER transmembrane sensor that activates the UPR to maintain the ER and cellular function. Although mammalian IRE1 promotes cell survival, it can initiate apoptosis via decay of antiapoptotic miRNAs. Convergent and divergent IRE1 characteristics between plants and animals underscore its significance in cellular homeostasis. This review provides an updated scenario of the IRE1 signaling model, discusses emerging IRE1 sensing mechanisms, compares IRE1 features among species, and outlines exciting future directions in UPR research.
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84
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Mao X, Jia X, Qiu F. Enantioselective pharmacodynamics of propranolol in HUVEC cells: a study using chiral 2D gel electrophoresis and mass spectrometry. Mol Med Rep 2013; 8:128-32. [PMID: 23660645 DOI: 10.3892/mmr.2013.1464] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2013] [Accepted: 04/24/2013] [Indexed: 11/06/2022] Open
Abstract
Propranolol (PRO), a nonselective β-adrenergic receptor (β-AR) antagonist, has two enantiomers, R(+)-PRO and S(-)-PRO, which have diverse biological effects. For example, S(-)-PRO blocks the β-receptor ~100 times more strongly than R(+)-PRO. However, the signaling pathway that causes this difference remains unclear. This pathway may affect the expression of numerous proteins, some of which play key roles during the drug action process. Therefore, we treated human umbilical vein endothelial cells (HUVECs) with R(+)-PRO and S(-)-PRO in order to identify differentially expressed proteins and to determine their functions in the drug action process. Of the 22 differentially expressed protein spots investigated, 14 demonstrated higher expression levels in the R(+)-PRO-treated cells, while 8 demonstrated lower expression levels in the same cells. Mass spectrometry identified 10 of the differentially expressed proteins: 4 signaling molecules, 2 metabolic enzymes, 3 heat shock proteins and 1 cytoskeleton protein. Our results suggest that these differentially expressed proteins, particularly guanine nucleotide-binding protein subunit β-2-like 1 (GBLP), are the key biomacromolecules underlying the mechanism by which PRO enantiomers induce stereoselective cellular responses. The results aid in clarifying the role of PRO in the treatment of arrhythmia and angina.
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Affiliation(s)
- Xiaoqin Mao
- Department of Clinical Laboratory, The First People's Hospital of Yunnan Province, Kunming, Yunnan 650032, PR China
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85
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Mutoh S, Sobhany M, Moore R, Perera L, Pedersen L, Sueyoshi T, Negishi M. Phenobarbital indirectly activates the constitutive active androstane receptor (CAR) by inhibition of epidermal growth factor receptor signaling. Sci Signal 2013; 6:ra31. [PMID: 23652203 DOI: 10.1126/scisignal.2003705] [Citation(s) in RCA: 142] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Phenobarbital is a central nervous system depressant that also indirectly activates nuclear receptor constitutive active androstane receptor (CAR), which promotes drug and energy metabolism, as well as cell growth (and death), in the liver. We found that phenobarbital activated CAR by inhibiting epidermal growth factor receptor (EGFR) signaling. Phenobarbital bound to EGFR and potently inhibited the binding of EGF, which prevented the activation of EGFR. This abrogation of EGFR signaling induced the dephosphorylation of receptor for activated C kinase 1 (RACK1) at Tyr(52), which then promoted the dephosphorylation of CAR at Thr(38) by the catalytic core subunit of protein phosphatase 2A. The findings demonstrated that the phenobarbital-induced mechanism of CAR dephosphorylation and activation is mediated through its direct interaction with and inhibition of EGFR.
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Affiliation(s)
- Shingo Mutoh
- Pharmacogenetics Section, Laboratory of Reproductive and Developmental Toxicology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
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86
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Abstract
Post-translational modifications in TRPV1 (transient receptor potential vanilloid 1) play a critical role in channel activity. Phosphorylation of serine/threonine residues within the N- and C-termini of TRPV1 are implicated in receptor sensitization and activation. Conversely, TRPV1 desensitization occurs via a calcium-dependent mechanism and leads to receptor de-phosphorylation. Importantly, we recently demonstrated that TRPV1 association with β-arrestin-2 is critical to receptor desensitization via its ability to scaffold the phosphodiesterase PDE4D5 to the receptor, regulating TRPV1 phosphorylation. In the present study, we demonstrate that phosphorylation of TRPV1 and β-arrestin-2 regulates this association at the membrane. Under serum-free media conditions, we observed a significant decrease in TRPV1 and β-arrestin-2 association in transfected CHO (Chinese-hamster ovary) cells. Pharmacological activation of the kinases PKA (protein kinase A) and PKC (protein kinase C) led to a robust increase in TRPV1 and β-arrestin-2 association, whereas inhibition of PKA and PKC decreased association. Previously, we identified potential PKA residues (Ser(116), Thr(370)) in the N-terminus of TRPV1 modulated by β-arrestin-2. In the present study we reveal that the phosphorylation status of Thr(370) dictates the β-arrestin-2 and TRPV1 association. Furthermore, we demonstrate that CK2 (casein kinase 2)-mediated phosphorylation of β-arrestin-2 at Thr(382) is critical for its association with TRPV1. Taken together, the findings of the present study suggest that phosphorylation controls the association of TRPV1 with β-arrestin-2.
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87
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Deng Y, Srivastava R, Howell SH. Endoplasmic reticulum (ER) stress response and its physiological roles in plants. Int J Mol Sci 2013; 14:8188-212. [PMID: 23591838 PMCID: PMC3645738 DOI: 10.3390/ijms14048188] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2013] [Revised: 03/19/2013] [Accepted: 04/01/2013] [Indexed: 01/29/2023] Open
Abstract
The endoplasmic reticulum (ER) stress response is a highly conserved mechanism that results from the accumulation of unfolded or misfolded proteins in the ER. The response plays an important role in allowing plants to sense and respond to adverse environmental conditions, such as heat stress, salt stress and pathogen infection. Since the ER is a well-controlled microenvironment for proper protein synthesis and folding, it is highly susceptible to stress conditions. Accumulation of unfolded or misfolded proteins activates a signaling pathway, called the unfolded protein response (UPR), which acts to relieve ER stress and, if unsuccessful, leads to cell death. Plants have two arms of the UPR signaling pathway, an arm involving the proteolytic processing of membrane-associated basic leucine zipper domain (bZIP) transcription factors and an arm involving RNA splicing factor, IRE1, and its mRNA target. These signaling pathways play an important role in determining the cell's fate in response to stress conditions.
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Affiliation(s)
- Yan Deng
- Plant Sciences Institute and Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA 50011, USA; E-Mails: (Y.D.); (R.S.)
| | - Renu Srivastava
- Plant Sciences Institute and Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA 50011, USA; E-Mails: (Y.D.); (R.S.)
| | - Stephen H. Howell
- Plant Sciences Institute and Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA 50011, USA; E-Mails: (Y.D.); (R.S.)
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88
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The role of the unfolded protein response in diabetes mellitus. Semin Immunopathol 2013; 35:333-50. [PMID: 23529219 DOI: 10.1007/s00281-013-0369-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Accepted: 03/13/2013] [Indexed: 12/13/2022]
Abstract
The endoplasmic reticulum (ER) plays a key role in the synthesis and modification of secretory and membrane proteins in all eukaryotic cells. Under normal conditions, these proteins are correctly folded and assembled in the ER. However, when cells are exposed to environmental factors such as overproduction of ER proteins, viral infections, or glucose deprivation, the secretory and membrane proteins can accumulate in unfolded or misfolded forms in the lumen of the ER, and consequently, cause stress in the ER. To maintain cellular homeostasis, cells induce several responses to ER stress. In mammalian cells, ER stress responses are induced by a diversity of signal pathways. There are three ER-located transmembrane proteins that play important roles in mammalian ER stress responses: activating transcription factor 6, inositol-requiring protein 1, and protein kinase RNA-like endoplasmic reticulum kinase. ER stress is linked to various diseases, including diabetes. This review highlights the particular importance of ER stress-responsive molecules in insulin biosynthesis, glyconeogenesis, insulin resistance, glucose intolerance, and pancreatic β-cell apoptosis. An understanding of the pathogenic mechanism of diabetes from the aspect of ER stress is crucial in formulating therapeutic strategies.
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89
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He Y, Beatty A, Han X, Ji Y, Ma X, Adelstein RS, Yates JR, Kemphues K, Qi L. Nonmuscle myosin IIB links cytoskeleton to IRE1α signaling during ER stress. Dev Cell 2013; 23:1141-52. [PMID: 23237951 DOI: 10.1016/j.devcel.2012.11.006] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Revised: 09/19/2012] [Accepted: 11/12/2012] [Indexed: 01/05/2023]
Abstract
Here we identify and characterize a cytoskeletal myosin protein required for IRE1α oligomerization, activation, and signaling. Proteomic screening identified nonmuscle myosin heavy chain IIB (NMHCIIB), a subunit of nonmuscle myosin IIB (NMIIB), as an ER stress-dependent interacting protein specific to IRE1α. Loss of NMIIB compromises XBP1s and UPR target gene expression with no effect on the PERK pathway. Mechanistically, NMIIB is required for IRE1α aggregation and foci formation under ER stress. The NMIIB-mediated effect on IRE1α signaling is in part dependent on the phosphorylation of myosin regulatory light chain and the actomyosin contractility of NMIIB. Biologically, the function of NMIIB in ER stress response is conserved as both mammalian cells and C. elegans lacking NMIIB exhibit hypersensitivity to ER stress. Thus, optimal IRE1α activation and signaling require concerted coordination between the ER and cytoskeleton.
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Affiliation(s)
- Yin He
- Graduate Program in Genetics, Genomics, and Development, Cornell University, Ithaca, NY 14853, USA
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90
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Lafleur MA, Stevens JL, Lawrence JW. Xenobiotic perturbation of ER stress and the unfolded protein response. Toxicol Pathol 2013; 41:235-62. [PMID: 23334697 DOI: 10.1177/0192623312470764] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The proper folding, assembly, and maintenance of cellular proteins is a highly regulated process and is critical for cellular homeostasis. Multiple cellular compartments have adapted their own systems to ensure proper protein folding, and quality control mechanisms are in place to manage stress due to the accumulation of unfolded proteins. When the accumulation of unfolded proteins exceeds the capacity to restore homeostasis, these systems can result in a cell death response. Unfolded protein accumulation in the endoplasmic reticulum (ER) leads to ER stress with activation of the unfolded protein response (UPR) governed by the activating transcription factor 6 (ATF6), inositol requiring enzyme-1 (IRE1), and PKR-like endoplasmic reticulum kinase (PERK) signaling pathways. Many xenobiotics have been shown to influence ER stress and UPR signaling with either pro-survival or pro-death features. The ultimate outcome is dependent on many factors including the mechanism of action of the xenobiotic, concentration of xenobiotic, duration of exposure (acute vs. chronic), cell type affected, nutrient levels, oxidative stress, state of differentiation, and others. Assessing perturbations in activation or inhibition of ER stress and UPR signaling pathways are likely to be informative parameters to measure when analyzing mechanisms of action of xenobiotic-induced toxicity.
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Affiliation(s)
- Marc A Lafleur
- Comparative Biology and Safety Sciences, Amgen Inc., Thousand Oaks, California 91320, USA.
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91
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Oikawa D, Kitamura A, Kinjo M, Iwawaki T. Direct association of unfolded proteins with mammalian ER stress sensor, IRE1β. PLoS One 2012; 7:e51290. [PMID: 23236464 PMCID: PMC3517461 DOI: 10.1371/journal.pone.0051290] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2012] [Accepted: 11/01/2012] [Indexed: 12/13/2022] Open
Abstract
IRE1, an ER-localized transmembrane protein, plays a central role in the unfolded protein response (UPR). IRE1 senses the accumulation of unfolded proteins in its luminal domain and transmits a signal to the cytosolic side through its kinase and RNase domains. Although the downstream pathways mediated by two mammalian IRE1s, IRE1α and IRE1β, are well documented, their luminal events have not been fully elucidated. In particular, there have been no reports on how IRE1β senses the unfolded proteins. In this study, we performed a comparative analysis to clarify the luminal event mediated by the mammalian IRE1s. Confocal fluorescent microscopy using GFP-fused IRE1s revealed that IRE1β clustered into discrete foci upon ER stress. Also, fluorescence correlation spectroscopy (FCS) analysis in living cells indicated that the size of the IRE1β complex is robustly increased upon ER stress. Moreover, unlike IRE1α, the luminal domain of IRE1β showed anti-aggregation activity in vitro, and IRE1β was coprecipitated with the model unfolded proteins in cells. Strikingly, association with BiP was drastically reduced in IRE1β, while IRE1α was associated with BiP and dissociated upon ER stress. This is the first report indicating that, differently from IRE1α, the luminal event mediated by IRE1β involves direct interaction with unfolded proteins rather than association/dissociation with BiP, implying an intrinsic diversity in the sensing mechanism of mammalian sensors.
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Affiliation(s)
- Daisuke Oikawa
- Iwawaki lab, Advanced Scientific Research Leaders Development Unit, Gunma University, Maebashi, Gunma, Japan
- Research Fellow of the Japan Society for the Promotion of Science, Chiyoda-ku, Tokyo, Japan
- Iwawaki Initiative Research Unit, Advanced Science Institute, RIKEN, Wako, Saitama, Japan
- * E-mail: (DO); (TI)
| | - Akira Kitamura
- Laboratory of Molecular Cell Dynamics, Faculty of Advanced Life Science, Hokkaido University, Kita-ku, Sapporo, Japan
| | - Masataka Kinjo
- Laboratory of Molecular Cell Dynamics, Faculty of Advanced Life Science, Hokkaido University, Kita-ku, Sapporo, Japan
| | - Takao Iwawaki
- Iwawaki lab, Advanced Scientific Research Leaders Development Unit, Gunma University, Maebashi, Gunma, Japan
- Iwawaki Initiative Research Unit, Advanced Science Institute, RIKEN, Wako, Saitama, Japan
- PRESTO, Japan Science and Technology Agency, Kawaguchi, Saitama, Japan
- * E-mail: (DO); (TI)
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92
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Zhang Y, Gan Z, Huang P, Zhou L, Mao T, Shao M, Jiang X, Chen Y, Ying H, Cao M, Li J, Li J, Zhang WJ, Yang L, Liu Y. A role for protein inhibitor of activated STAT1 (PIAS1) in lipogenic regulation through SUMOylation-independent suppression of liver X receptors. J Biol Chem 2012; 287:37973-85. [PMID: 22969086 DOI: 10.1074/jbc.m112.403139] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Liver X receptors (LXRs) are nuclear receptors that function to modulate lipid metabolism as well as immune and inflammatory responses. Upon activation by their ligands, LXRs up-regulate a spectrum of gene transcription programs involved in cholesterol and fatty acid homeostasis. However, the mechanisms by which LXR-mediated transcriptional activation is regulated remain incompletely understood. Here, we show that PIAS1, a member of the protein inhibitor of the activated STAT family of proteins with small ubiquitin-like modifier (SUMO) E3 ligase activity, acts to suppress LXR ligand-dependent transcriptional activation of the lipogenic program in hepatocytes. We found that liver mRNA expression levels of Pias1 and Pias3 were inversely associated with those of genes involved in lipogenesis in mouse models with diet-induced or genetic obesity. Overexpression of PIAS1 in primary hepatocytes resulted in a reduction of LXR ligand-induced fatty acid synthesis and suppression of the expression of lipogenic genes, including Srebp1c and Fas. Moreover, PIAS1 was able to interact with LXRβ and repress its transcriptional activity upon ligand stimulation, which did not require PIAS1-promoted SUMO modification of LXRβ. In addition, PIAS1 could also interact with PGC-1β and attenuate its association with LXRβ, blunting the ability of PGC-1β to co-activate LXRβ. Importantly, PIAS1 impaired LXRβ binding to its target DNA sequence. Taken together, our results suggest that PIAS1 may serve as a lipogenic regulator by negatively modulating LXRs in a SUMOylation-independent manner.
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Affiliation(s)
- Yongliang Zhang
- Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Graduate School of the Chinese Academy of Sciences, Shanghai 200031, China
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93
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Abstract
The endoplasmic reticulum (ER) controls many important aspects of cellular function, including processing of secreted and membrane proteins, synthesis of membranes, and calcium storage. Maintenance of ER function is controlled through a network of signaling pathways collectively known as the unfolded protein response (UPR). The UPR balances the load of incoming proteins with the folding capacity of the ER and allows cells to adapt to situations that disrupt this balance. This disruption is referred to as ER stress. Although ER stress often arises in pathological situations, the UPR plays a central role in the normal development and function of cells specializing in secretion. Many aspects of this response are conserved broadly across eukaryotes; most organisms use some subset of a group of ER transmembrane proteins to signal to the nucleus and induce a broad transcriptional upregulation of genes involved in ER function. However, new developments in metazoans, plants, and fungi illustrate interesting variations on this theme. Here, we summarize mechanisms for detecting and counteracting ER stress, the role of the UPR in normal secretory cell function, and how these pathways vary across organisms and among different tissues and cell types.
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Affiliation(s)
- Kristin A Moore
- Department of Biology and the Center for Cell and Genome Science, University of Utah, Salt Lake City, Utah 84112-0840, USA
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94
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Neuronal Cbl controls biosynthesis of insulin-like peptides in Drosophila melanogaster. Mol Cell Biol 2012; 32:3610-23. [PMID: 22778134 DOI: 10.1128/mcb.00592-12] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Cbl family proteins function as both E3 ubiquitin ligases and adaptor proteins to regulate various cellular signaling events, including the insulin/insulin-like growth factor 1 (IGF1) and epidermal growth factor (EGF) pathways. These pathways play essential roles in growth, development, metabolism, and survival. Here we show that in Drosophila melanogaster, Drosophila Cbl (dCbl) regulates longevity and carbohydrate metabolism through downregulating the production of Drosophila insulin-like peptides (dILPs) in the brain. We found that dCbl was highly expressed in the brain and knockdown of the expression of dCbl specifically in neurons by RNA interference increased sensitivity to oxidative stress or starvation, decreased carbohydrate levels, and shortened life span. Insulin-producing neuron-specific knockdown of dCbl resulted in similar phenotypes. dCbl deficiency in either the brain or insulin-producing cells upregulated the expression of dilp genes, resulting in elevated activation of the dILP pathway, including phosphorylation of Drosophila Akt and Drosophila extracellular signal-regulated kinase (dERK). Genetic interaction analyses revealed that blocking Drosophila epidermal growth factor receptor (dEGFR)-dERK signaling in pan-neurons or insulin-producing cells by overexpressing a dominant-negative form of dEGFR abolished the effect of dCbl deficiency on the upregulation of dilp genes. Furthermore, knockdown of c-Cbl in INS-1 cells, a rat β-cell line, also increased insulin biosynthesis and glucose-stimulated secretion in an ERK-dependent manner. Collectively, these results suggest that neuronal dCbl regulates life span, stress responses, and metabolism by suppressing dILP production and the EGFR-ERK pathway mediates the dCbl action. Cbl suppression of insulin biosynthesis is evolutionarily conserved, raising the possibility that Cbl may similarly exert its physiological actions through regulating insulin production in β cells.
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95
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Wang G, Liu G, Wang X, Sethi S, Ali-Fehmi R, Abrams J, Zheng Z, Zhang K, Ethier S, Yang ZQ. ERLIN2 promotes breast cancer cell survival by modulating endoplasmic reticulum stress pathways. BMC Cancer 2012; 12:225. [PMID: 22681620 PMCID: PMC3732090 DOI: 10.1186/1471-2407-12-225] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Accepted: 05/14/2012] [Indexed: 11/10/2022] Open
Abstract
Background Amplification of the 8p11-12 region has been found in approximately 15% of human breast cancer and is associated with poor prognosis. Previous genomic analysis has led us to identify the endoplasmic reticulum (ER) lipid raft-associated 2 (ERLIN2) gene as one of the candidate oncogenes within the 8p11-12 amplicon in human breast cancer, particularly in the luminal subtype. ERLIN2, an ER membrane protein, has recently been identified as a novel mediator of ER-associated degradation. Yet, the biological roles of ERLIN2 and molecular mechanisms by which ERLIN2 coordinates ER pathways in breast carcinogenesis remain unclear. Methods We established the MCF10A-ERLIN2 cell line, which stably over expresses ERLIN2 in human nontransformed mammary epithelial cells (MCF10A) using the pLenti6/V5-ERLIN2 construct. ERLIN2 over expressing cells and their respective parental cell lines were assayed for in vitro transforming phenotypes. Next, we knocked down the ERLIN2 as well as the ER stress sensor IRE1α activity in the breast cancer cell lines to characterize the biological roles and molecular basis of the ERLIN2 in carcinogenesis. Finally, immunohistochemical staining was performed to detect ERLIN2 expression in normal and cancerous human breast tissues Results We found that amplification of the ERLIN2 gene and over expression of the ERLIN2 protein occurs in both luminal and Her2 subtypes of breast cancer. Gain- and loss-of-function approaches demonstrated that ERLIN2 is a novel oncogenic factor associated with the ER stress response pathway. The IRE1α/XBP1 axis in the ER stress pathway modulated expression of ERLIN2 protein levels in breast cancer cells. We also showed that over expression of ERLIN2 facilitated the adaptation of breast epithelial cells to ER stress by supporting cell growth and protecting the cells from ER stress-induced cell death. Conclusions ERLIN2 may confer a selective growth advantage for breast cancer cells by facilitating a cytoprotective response to various cellular stresses associated with oncogenesis. The information provided here sheds new light on the mechanism of breast cancer malignancy
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Affiliation(s)
- Guohui Wang
- Karmanos Cancer Institute, Wayne State University, Detroit, MI 48201, USA
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96
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Li X, Zhu H, Huang H, Jiang R, Zhao W, Liu Y, Zhou J, Guo FJ. Study on the effect of IRE1a on cell growth and apoptosis via modulation PLK1 in ER stress response. Mol Cell Biochem 2012; 365:99-108. [PMID: 22314839 DOI: 10.1007/s11010-012-1248-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Accepted: 01/14/2012] [Indexed: 11/27/2022]
Abstract
The mammalian unfolded protein response (UPR) protects the cell against the stress of misfolded proteins in the endoplasmic reticulum (ER). Failure to adapt to ER stress causes the UPR to trigger apoptosis. Inositol-requiring enzyme-1a (IRE1a), as one of three unfolded protein sensors in UPR signaling pathways, senses ER unfolded proteins through an ER lumenal domain that becomes oligomerized during ER stress. It is known to be important for ER stress-mediated apoptosis and cell growth, but the exact molecular mechanism underlying these processes remains unexplored. In this study, we report that knockdown of IRE1a by an siRNA silencing approach enhanced, whereas its overexpression inhibited, cell proliferation in Hepatoma cells. Besides, overexpression of IRE1a induced, while its repression inhibited, ER stress-mediated apoptosis in Hepatomas cells. Furthermore, we found that overexpressed IRE1a can down-regulate Polo-like kinase 1(PLK1) from mRNA and protein two levels. IRE1a-mediated induction of apoptosis and inhibition of proliferation in response to ER stress is through downregulation PLK1, an early trigger for G2/M transition known to be participated in regulating cell proliferation and cell apoptosis. Collectively, these findings reveal a novel critical role of IRE1a in ER stress-mediated apoptosis and the molecular mechanisms involved. IRE1a may be a useful molecular target for the development of novel predictive and therapeutic strategies in cancer.
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Affiliation(s)
- Xiangzhu Li
- Department of Cell Biology and Genetics, ChongQing Medical University, ChongQing 400016, China
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97
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Tang C, Koulajian K, Schuiki I, Zhang L, Desai T, Ivovic A, Wang P, Robson-Doucette C, Wheeler MB, Minassian B, Volchuk A, Giacca A. Glucose-induced beta cell dysfunction in vivo in rats: link between oxidative stress and endoplasmic reticulum stress. Diabetologia 2012; 55:1366-79. [PMID: 22396011 DOI: 10.1007/s00125-012-2474-8] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Accepted: 12/07/2011] [Indexed: 11/29/2022]
Abstract
AIMS/HYPOTHESIS Endoplasmic reticulum (ER) stress has been implicated in glucose-induced beta cell dysfunction. However, its causal role has not been established in vivo. Our objective was to determine the causal role of ER stress and its link to oxidative stress in glucose-induced beta cell dysfunction in vivo. METHODS Healthy Wistar rats were infused i.v. with glucose for 48 h to achieve 20 mmol/l hyperglycaemia with or without the co-infusion of the superoxide dismutase mimetic tempol (TPO), or the chemical chaperones 4-phenylbutyrate (PBA) or tauroursodeoxycholic acid (TUDCA). This was followed by assessment of beta cell function and measurement of ER stress markers and superoxide in islets. RESULTS Glucose infusion for 48 h increased mitochondrial superoxide and ER stress markers and impaired beta cell function. Co-infusion of TPO, which we previously found to reduce mitochondrial superoxide and prevent glucose-induced beta cell dysfunction, reduced ER stress markers. Similar to findings with TPO, co-infusion of PBA, which decreases mitochondrial superoxide, prevented glucose-induced beta cell dysfunction in isolated islets. TUDCA was also effective. Also similar to findings with TPO, PBA prevented beta cell dysfunction during hyperglycaemic clamps in vivo and after hyperglycaemia (15 mmol/l) for 96 h. CONCLUSIONS/INTERPRETATION Here, we causally implicate ER stress in hyperglycaemia-induced beta cell dysfunction in vivo. We show that: (1) there is a positive feedback cycle between oxidative stress and ER stress in glucose-induced beta cell dysfunction, which involves mitochondrial superoxide; and (2) this cycle can be interrupted by superoxide dismutase mimetics as well as chemical chaperones, which are of potential interest to preserve beta cell function in type 2 diabetes.
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Affiliation(s)
- C Tang
- Department of Physiology, University of Toronto, Medical Science Building, Room 3336, 1 King's College Circle, Toronto, ON, Canada M5S 1A8
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98
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BH3-only proteins are part of a regulatory network that control the sustained signalling of the unfolded protein response sensor IRE1α. EMBO J 2012; 31:2322-35. [PMID: 22510886 DOI: 10.1038/emboj.2012.84] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Accepted: 03/13/2012] [Indexed: 12/12/2022] Open
Abstract
Adaptation to endoplasmic reticulum (ER) stress depends on the activation of the unfolded protein response (UPR) stress sensor inositol-requiring enzyme 1α (IRE1α), which functions as an endoribonuclease that splices the mRNA of the transcription factor XBP-1 (X-box-binding protein-1). Through a global proteomic approach we identified the BCL-2 family member PUMA as a novel IRE1α interactor. Immun oprecipitation experiments confirmed this interaction and further detected the association of IRE1α with BIM, another BH3-only protein. BIM and PUMA double-knockout cells failed to maintain sustained XBP-1 mRNA splicing after prolonged ER stress, resulting in early inactivation. Mutation in the BH3 domain of BIM abrogated the physical interaction with IRE1α, inhibiting its effects on XBP-1 mRNA splicing. Unexpectedly, this regulation required BCL-2 and was antagonized by BAD or the BH3 domain mimetic ABT-737. The modulation of IRE1α RNAse activity by BH3-only proteins was recapitulated in a cell-free system suggesting a direct regulation. Moreover, BH3-only proteins controlled XBP-1 mRNA splicing in vivo and affected the ER stress-regulated secretion of antibodies by primary B cells. We conclude that a subset of BCL-2 family members participates in a new UPR-regulatory network, thus assuming apoptosis-unrelated functions.
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Kang JH, Chang YC, Maurizi MR. 4-O-carboxymethyl ascochlorin causes ER stress and induced autophagy in human hepatocellular carcinoma cells. J Biol Chem 2012; 287:15661-71. [PMID: 22433868 DOI: 10.1074/jbc.m112.358473] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The synthetic derivative of ascochlorin, 4-O-carboxymethyl ascochlorin (AS-6) is an agonist of the nuclear hormone receptor PPARγ and has been shown to induce differentiation in mouse pre-adipocytes and to ameliorate type II diabetes in a murine model. AS-6 was cytotoxic when added at micromolar concentrations to cultures of three different human cancer cell lines. We used gel electrophoresis and mass spectrometry to identify proteins with altered expression in human hepatocarcinoma cells (HepG2) cells after 12 h in the presence of AS-6 and found 58 proteins that were differentially expressed. Many of the proteins showing increased expression in cells treated with AS-6 are involved in protein quality control, including glucose-regulated protein 78 (GRP78/BiP), a regulator of ER stress responses, and the transcriptional regulator CHOP, which mediates ER stress-induced apoptosis. Cells treated with AS-6 undergo an autophagic response accompanied by increased expression of beclin1, ATG5, and LC3-II and autophagosome formation marked by the appearance of large vesicles containing LC3-II. Grp78 induction was inhibited when the PPARγ antagonist, GW9662, was added together with AS-6, and autophagy and cell death were partially blocked. 3-methyl-adenine (3-MA), an inhibitor of phosphatidyl inositol 3-kinase (PI3-kinase) prevented induction of ATG5 and activation of LC3-II and blocked autophagosome formation. 3-MA also blocked induction of GRP78 and CHOP, suggesting that PI3-kinase, which is known to mediate ER stress-induced autophagy, also plays a role in initiating apoptosis in response to ER stress. Together these data establish that the cytotoxicity of AS-6 operates by a mechanism dependent on ER stress-induced autophagy and apoptosis.
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Affiliation(s)
- Jeong Han Kang
- Laboratory of Cell Biology, NCI, National Institutes of Health, Bethesda, Maryland 20892, USA
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Jäger R, Bertrand MJM, Gorman AM, Vandenabeele P, Samali A. The unfolded protein response at the crossroads of cellular life and death during endoplasmic reticulum stress. Biol Cell 2012; 104:259-70. [PMID: 22268789 DOI: 10.1111/boc.201100055] [Citation(s) in RCA: 155] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2011] [Accepted: 01/18/2012] [Indexed: 12/14/2022]
Abstract
One of the early cellular responses to endoplasmic reticulum (ER) stress is the activation of the unfolded protein response (UPR). ER stress and the UPR are both implicated in numerous human diseases and pathologies. In spite of this, our knowledge of the molecular mechanisms that regulate cell fate following ER stress is limited. The UPR is initiated by three ER transmembrane receptors: PKR-like ER kinase (PERK), activating transcription factor (ATF) 6 and inositol-requiring enzyme 1 (IRE1). These proteins sense the accumulation of unfolded proteins and their activation triggers specific adaptive responses to resolve the stress. Intriguingly, the very same receptors can initiate signalling pathways that lead to apoptosis when the attempts to resolve the ER stress fail. In this review, we describe the known pro-apoptotic signalling pathways emanating from activated PERK, ATF6 and IRE1 and discuss how their signalling switches from an adaptive to a pro-apoptotic response.
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Affiliation(s)
- Richard Jäger
- Apoptosis Research Centre, National University of Ireland Galway, Galway, Ireland
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