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Burman A, Tanjore H, Blackwell TS. Endoplasmic reticulum stress in pulmonary fibrosis. Matrix Biol 2018; 68-69:355-365. [PMID: 29567124 DOI: 10.1016/j.matbio.2018.03.015] [Citation(s) in RCA: 157] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Revised: 03/15/2018] [Accepted: 03/16/2018] [Indexed: 12/15/2022]
Abstract
Endoplasmic reticulum (ER) stress is associated with development and progression of fibrotic diseases, including idiopathic pulmonary fibrosis (IPF). ER stress was first implicated in the pathogenesis of IPF >15 years ago with the discovery of disease-causing mutations in surfactant protein C, which result in a misfolded gene product in type II alveolar epithelial cells (AECs). ER stress and the unfolded protein response (UPR) have been linked to lung fibrosis through regulation of AEC apoptosis, epithelial-mesenchymal transition, myofibroblast differentiation, and M2 macrophage polarization. Although progress has been made in understanding the causes and consequences of ER stress in IPF and a number of chronic fibrotic disorders, further studies are needed to identify key factors that induce ER stress in important cell types and define critical down-stream processes and effector molecules that mediate ER stress-related phenotypes. This review discusses potential causes of ER stress induction in the lungs and current evidence linking ER stress to fibrosis in the context of individual cell types: AECs, fibroblasts, and macrophages. As our understanding of the relationship between ER stress and lung fibrosis continues to evolve, future studies will examine new strategies to modulate UPR pathways for therapeutic benefit.
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Affiliation(s)
- Ankita Burman
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, USA
| | - Harikrishna Tanjore
- Department of Medicine, Division of Allergy, Pulmonary and Critical Care Medicine, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Timothy S Blackwell
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, USA; Department of Medicine, Division of Allergy, Pulmonary and Critical Care Medicine, Vanderbilt University School of Medicine, Nashville, TN, USA; Department of Veterans Affairs Medical Center, Nashville, TN, USA.
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102
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Tsuchiya Y, Saito M, Kadokura H, Miyazaki JI, Tashiro F, Imagawa Y, Iwawaki T, Kohno K. IRE1-XBP1 pathway regulates oxidative proinsulin folding in pancreatic β cells. J Cell Biol 2018; 217:1287-1301. [PMID: 29507125 PMCID: PMC5881499 DOI: 10.1083/jcb.201707143] [Citation(s) in RCA: 87] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 12/06/2017] [Accepted: 01/22/2018] [Indexed: 11/22/2022] Open
Abstract
In mammalian pancreatic β cells, the IRE1α-XBP1 pathway is constitutively and highly activated under physiological conditions. To elucidate the precise role of this pathway, we constructed β cell-specific Ire1α conditional knockout (CKO) mice and established insulinoma cell lines in which Ire1α was deleted using the Cre-loxP system. Ire1α CKO mice showed the typical diabetic phenotype including impaired glycemic control and defects in insulin biosynthesis postnatally at 4-20 weeks. Ire1α deletion in pancreatic β cells in mice and insulinoma cells resulted in decreased insulin secretion, decreased insulin and proinsulin contents in cells, and decreased oxidative folding of proinsulin along with decreased expression of five protein disulfide isomerases (PDIs): PDI, PDIR, P5, ERp44, and ERp46. Reconstitution of the IRE1α-XBP1 pathway restored the proinsulin and insulin contents, insulin secretion, and expression of the five PDIs, indicating that IRE1α functions as a key regulator of the induction of catalysts for the oxidative folding of proinsulin in pancreatic β cells.
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Affiliation(s)
- Yuichi Tsuchiya
- Graduate School of Biological Sciences and Institute for Research Initiatives, Nara Institute of Science and Technology, Ikoma, Japan
| | - Michiko Saito
- Graduate School of Biological Sciences and Institute for Research Initiatives, Nara Institute of Science and Technology, Ikoma, Japan.,Bio-science Research Center, Kyoto Pharmaceutical University, Kyoto, Japan
| | - Hiroshi Kadokura
- Graduate School of Biological Sciences and Institute for Research Initiatives, Nara Institute of Science and Technology, Ikoma, Japan.,Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Japan
| | - Jun-Ichi Miyazaki
- Division of Stem Cell Regulation Research, Osaka University Graduate School of Medicine, Suita, Japan
| | - Fumi Tashiro
- Division of Stem Cell Regulation Research, Osaka University Graduate School of Medicine, Suita, Japan
| | - Yusuke Imagawa
- Graduate School of Biological Sciences and Institute for Research Initiatives, Nara Institute of Science and Technology, Ikoma, Japan.,Department of Molecular and Cellular Biology, Research Center, Osaka International Cancer Institute, Osaka, Japan
| | - Takao Iwawaki
- Division of Cell Medicine, Department of Life Science, Medical Research Institute, Kanazawa Medical University, Uchinada, Japan
| | - Kenji Kohno
- Graduate School of Biological Sciences and Institute for Research Initiatives, Nara Institute of Science and Technology, Ikoma, Japan
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103
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Smith JA. Regulation of Cytokine Production by the Unfolded Protein Response; Implications for Infection and Autoimmunity. Front Immunol 2018; 9:422. [PMID: 29556237 PMCID: PMC5844972 DOI: 10.3389/fimmu.2018.00422] [Citation(s) in RCA: 113] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Accepted: 02/16/2018] [Indexed: 12/14/2022] Open
Abstract
Protein folding in the endoplasmic reticulum (ER) is an essential cell function. To safeguard this process in the face of environmental threats and internal stressors, cells mount an evolutionarily conserved response known as the unfolded protein response (UPR). Invading pathogens induce cellular stress that impacts protein folding, thus the UPR is well situated to sense danger and contribute to immune responses. Cytokines (inflammatory cytokines and interferons) critically mediate host defense against pathogens, but when aberrantly produced, may also drive pathologic inflammation. The UPR influences cytokine production on multiple levels, from stimulation of pattern recognition receptors, to modulation of inflammatory signaling pathways, and the regulation of cytokine transcription factors. This review will focus on the mechanisms underlying cytokine regulation by the UPR, and the repercussions of this relationship for infection and autoimmune/autoinflammatory diseases. Interrogation of viral and bacterial infections has revealed increasing numbers of examples where pathogens induce or modulate the UPR and implicated UPR-modulated cytokines in host response. The flip side of this coin, the UPR/ER stress responses have been increasingly recognized in a variety of autoimmune and inflammatory diseases. Examples include monogenic disorders of ER function, diseases linked to misfolding protein (HLA-B27 and spondyloarthritis), diseases directly implicating UPR and autophagy genes (inflammatory bowel disease), and autoimmune diseases targeting highly secretory cells (e.g., diabetes). Given the burgeoning interest in pharmacologically targeting the UPR, greater discernment is needed regarding how the UPR regulates cytokine production during specific infections and autoimmune processes, and the relative place of this interaction in pathogenesis.
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Affiliation(s)
- Judith A Smith
- Department of Pediatrics, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI, United States.,Department of Medical Microbiology and Immunology, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI, United States
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104
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Adipocyte Xbp1s overexpression drives uridine production and reduces obesity. Mol Metab 2018; 11:1-17. [PMID: 29551634 PMCID: PMC6001360 DOI: 10.1016/j.molmet.2018.02.013] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Revised: 02/26/2018] [Accepted: 02/26/2018] [Indexed: 11/22/2022] Open
Abstract
Objective The spliced transcription factor Xbp1 (Xbp1s), a transducer of the unfolded protein response (UPR), regulates lipolysis. Lipolysis is stimulated by fasting when uridine synthesis is also activated in adipocytes. Methods Here we have examined the regulatory role Xbp1s in stimulation of uridine biosynthesis in adipocytes and triglyceride mobilization using inducible mouse models. Results Xbp1s is a key molecule involved in adipocyte uridine biosynthesis and release by activation of carbamoyl-phosphate synthetase 2, aspartate transcarbamylase, dihydroorotase (CAD), the rate-limiting enzyme for UMP biosynthesis. Adipocyte Xbp1s overexpression drives energy mobilization and protects mice from obesity through activation of the pyrimidine biosynthesis pathway. Conclusion These observations reveal that Xbp1s is a potent stimulator of uridine production in adipocytes, enhancing lipolysis and invoking a potential anti-obesity strategy through the induction of a futile biosynthetic cycle. ER stress is a key mechanism of obesity-related metabolic disorders. Xbp1s, a key transducer of ER stress response, stimulates uridine biosynthesis. Uridine synthesized in adipocytes is critical for plasma uridine supply. Stimulation of uridine synthesis in adipocyte by Xbp1s promotes weight loss.
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105
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Gianfrancesco MA, Paquot N, Piette J, Legrand-Poels S. Lipid bilayer stress in obesity-linked inflammatory and metabolic disorders. Biochem Pharmacol 2018; 153:168-183. [PMID: 29462590 DOI: 10.1016/j.bcp.2018.02.022] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Accepted: 02/15/2018] [Indexed: 12/13/2022]
Abstract
The maintenance of the characteristic lipid compositions and physicochemical properties of biological membranes is essential for their proper function. Mechanisms allowing to sense and restore membrane homeostasis have been identified in prokaryotes for a long time and more recently in eukaryotes. A membrane remodeling can result from aberrant metabolism as seen in obesity. In this review, we describe how such lipid bilayer stress can account for the modulation of membrane proteins involved in the pathogenesis of obesity-linked inflammatory and metabolic disorders. We address the case of the Toll-like receptor 4 that is implicated in the obesity-related low grade inflammation and insulin resistance. The lipid raft-mediated TLR4 activation is promoted by an enrichment of the plasma membrane with saturated lipids or cholesterol increasing the lipid phase order. We discuss of the plasma membrane Na, K-ATPase that illustrates a new concept according to which direct interactions between specific residues and particular lipids determine both stability and activity of the pump in parallel with indirect effects of the lipid bilayer. The closely related sarco(endo)-plasmic Ca-ATPase embedded in the more fluid ER membrane seems to be more sensitive to a lipid bilayer stress as demonstrated by its inactivation in cholesterol-loaded macrophages or its inhibition mediated by an increased PtdCho/PtdEtn ratio in obese mice hepatocytes. Finally, we describe the model recently proposed for the activation of the conserved IRE-1 protein through alterations in the ER membrane lipid packing and thickness. Such IRE-1 activation could occur in response to abnormal lipid synthesis and membrane remodeling as observed in hepatocytes exposed to excess nutrients. Since the IRE-1/XBP1 branch also stimulates the lipid synthesis, this pathway could create a vicious cycle "lipogenesis-ER lipid bilayer stress-lipogenesis" amplifying hepatic ER pathology and the obesity-linked systemic metabolic defects.
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Affiliation(s)
- Marco A Gianfrancesco
- Laboratory of Immunometabolism and Nutrition, GIGA-I3, University of Liège, Liège, Belgium; Division of Diabetes, Nutrition and Metabolic Disorders, Department of Medicine, University Hospital of Liège, Liège, Belgium
| | - Nicolas Paquot
- Laboratory of Immunometabolism and Nutrition, GIGA-I3, University of Liège, Liège, Belgium; Division of Diabetes, Nutrition and Metabolic Disorders, Department of Medicine, University Hospital of Liège, Liège, Belgium
| | - Jacques Piette
- Laboratory of Virology and Immunology, GIGA-Molecular Biology of Diseases, University of Liège, Liège, Belgium
| | - Sylvie Legrand-Poels
- Laboratory of Immunometabolism and Nutrition, GIGA-I3, University of Liège, Liège, Belgium; Laboratory of Virology and Immunology, GIGA-Molecular Biology of Diseases, University of Liège, Liège, Belgium.
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106
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Rutkowski DT. Liver function and dysfunction - a unique window into the physiological reach of ER stress and the unfolded protein response. FEBS J 2018; 286:356-378. [PMID: 29360258 DOI: 10.1111/febs.14389] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Revised: 01/08/2018] [Accepted: 01/17/2018] [Indexed: 02/06/2023]
Abstract
The unfolded protein response (UPR) improves endoplasmic reticulum (ER) protein folding in order to alleviate stress. Yet it is becoming increasingly clear that the UPR regulates processes well beyond those directly involved in protein folding, in some cases by mechanisms that fall outside the realm of canonical UPR signaling. These pathways are highly specific from one cell type to another, implying that ER stress signaling affects each tissue in a unique way. Perhaps nowhere is this more evident than in the liver, which-beyond being a highly secretory tissue-is a key regulator of peripheral metabolism and a uniquely proliferative organ upon damage. The liver provides a powerful model system for exploring how and why the UPR extends its reach into physiological processes that occur outside the ER, and how ER stress contributes to the many systemic diseases that involve liver dysfunction. This review will highlight the ways in which the study of ER stress in the liver has expanded the view of the UPR to a response that is a key guardian of cellular homeostasis outside of just the narrow realm of ER protein folding.
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Affiliation(s)
- D Thomas Rutkowski
- Department of Anatomy and Cell Biology, University of Iowa Carver College of Medicine, IA, USA.,Department of Internal Medicine, University of Iowa Carver College of Medicine, IA, USA
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107
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Yonekura S, Tsuchiya M, Tokutake Y, Mizusawa M, Nakano M, Miyaji M, Ishizaki H, Haga S. The unfolded protein response is involved in both differentiation and apoptosis of bovine mammary epithelial cells. J Dairy Sci 2018; 101:3568-3578. [PMID: 29428758 DOI: 10.3168/jds.2017-13718] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Accepted: 12/20/2017] [Indexed: 12/29/2022]
Abstract
The unfolded protein response (UPR) describes a process involved in the homeostasis of endoplasmic reticulum (ER) and the differentiation of secretory cells. At present, the roles of UPR in the mammary gland tissue of dairy cattle are unknown. In the current study, we investigated the expression of UPR-related genes in Holstein cows during the developmental and lactating stages of the mammary gland tissue. To investigate the roles of UPR during the differentiation of mammary epithelial cells (MEC), we used MAC-T cells, a line of MEC. We collected samples of mammary gland tissue in dairy cows by biopsy during the late gestation and lactation periods and examined the expression of UPR-related genes by quantitative real-time PCR. Expression levels of the spliced X-box binding protein 1 (XBP1) and activating transcription factor 4 (ATF4) were found to be significantly higher in the mammary gland tissue 10 d before delivery compared with 40 d before delivery. An investigation before and after differentiation in MAC-T cells showed that the expression of ATF4 increased after differentiation of MEC, whereas that of the spliced XBP1 did not significantly change. Western blot analysis revealed that the differentiation-inducing stimulus induced phosphorylation of eukaryotic initiation factor 2α (eIF2α) but reduced that of protein kinase RNA-like endoplasmic reticulum kinase (PERK). Additionally, in ATF4-knockdown bovine MEC, differentiation was significantly suppressed; ATF4 knockdown also significantly suppressed the expression of glucocorticoid and insulin receptors. These results revealed that ER stress-independent ATF4 is involved in the cell differentiation mechanism, either directly or indirectly, via the control of the expression of lactogenic hormone receptors in bovine MEC. Immediately after parturition, gene expression levels of the spliced XBP1, ATF4, and C/EBP homologous protein (CHOP) markedly increased in mammary gland tissue, with a strong negative correlation between expression of CHOP and initial milk yield; CHOP is an apoptosis-related protein induced by ER stress. The above findings indicate that UPR is intrinsically associated with apoptosis of MEC, thus affecting the differentiation of these cells, as well as milk yield.
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Affiliation(s)
- Shinichi Yonekura
- Department of Interdisciplinary Genome Sciences and Cell Metabolism, Institute for Biomedical Sciences, Interdisciplinary Cluster for Cutting Edge Research, Shinshu University, 8304 Minamiminowa, Kamiina, Nagano 399-4598, Japan; Graduate School of Agriculture, Shinshu University, 8304 Minamiminowa, Kamiina, Nagano 399-4598, Japan; Interdisciplinary Graduate School of Science and Technology, Shinshu University, 8304 Minamiminowa, Kamiina, Nagano 399-4598, Japan.
| | - Megumi Tsuchiya
- Graduate School of Agriculture, Shinshu University, 8304 Minamiminowa, Kamiina, Nagano 399-4598, Japan
| | - Yukako Tokutake
- Interdisciplinary Graduate School of Science and Technology, Shinshu University, 8304 Minamiminowa, Kamiina, Nagano 399-4598, Japan
| | - Moeko Mizusawa
- Graduate School of Agriculture, Shinshu University, 8304 Minamiminowa, Kamiina, Nagano 399-4598, Japan
| | - Miwa Nakano
- Grazing Animal Unit, Division of Grassland Farming, Institute of Livestock and Grassland Science, NARO, 768 Senbonmatsu, Nasushiobara, Tochigi 329-2793, Japan
| | - Makoto Miyaji
- Feed Production and Utilization Group, Division of Dairy Production Research, Hokkaido Agricultural Research Center, NARO, 1 Hitsujigaoka, Toyohira, Sapporo, Hokkaido 062-8555, Japan
| | - Hiroshi Ishizaki
- Grazing Animal Unit, Division of Grassland Farming, Institute of Livestock and Grassland Science, NARO, 768 Senbonmatsu, Nasushiobara, Tochigi 329-2793, Japan
| | - Satoshi Haga
- Grazing Animal Unit, Division of Grassland Farming, Institute of Livestock and Grassland Science, NARO, 768 Senbonmatsu, Nasushiobara, Tochigi 329-2793, Japan
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108
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Kong B, Bruns P, Behler NA, Chang L, Schlitter AM, Cao J, Gewies A, Ruland J, Fritzsche S, Valkovskaya N, Jian Z, Regel I, Raulefs S, Irmler M, Beckers J, Friess H, Erkan M, Mueller NS, Roth S, Hackert T, Esposito I, Theis FJ, Kleeff J, Michalski CW. Dynamic landscape of pancreatic carcinogenesis reveals early molecular networks of malignancy. Gut 2018; 67:146-156. [PMID: 27646934 DOI: 10.1136/gutjnl-2015-310913] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Revised: 08/15/2016] [Accepted: 08/23/2016] [Indexed: 12/12/2022]
Abstract
OBJECTIVE The initial steps of pancreatic regeneration versus carcinogenesis are insufficiently understood. Although a combination of oncogenic Kras and inflammation has been shown to induce malignancy, molecular networks of early carcinogenesis remain poorly defined. DESIGN We compared early events during inflammation, regeneration and carcinogenesis on histological and transcriptional levels with a high temporal resolution using a well-established mouse model of pancreatitis and of inflammation-accelerated KrasG12D-driven pancreatic ductal adenocarcinoma. Quantitative expression data were analysed and extensively modelled in silico. RESULTS We defined three distinctive phases-termed inflammation, regeneration and refinement-following induction of moderate acute pancreatitis in wild-type mice. These corresponded to different waves of proliferation of mesenchymal, progenitor-like and acinar cells. Pancreas regeneration required a coordinated transition of proliferation between progenitor-like and acinar cells. In mice harbouring an oncogenic Kras mutation and challenged with pancreatitis, there was an extended inflammatory phase and a parallel, continuous proliferation of mesenchymal, progenitor-like and acinar cells. Analysis of high-resolution transcriptional data from wild-type animals revealed that organ regeneration relied on a complex interaction of a gene network that normally governs acinar cell homeostasis, exocrine specification and intercellular signalling. In mice with oncogenic Kras, a specific carcinogenic signature was found, which was preserved in full-blown mouse pancreas cancer. CONCLUSIONS These data define a transcriptional signature of early pancreatic carcinogenesis and a molecular network driving formation of preneoplastic lesions, which allows for more targeted biomarker development in order to detect cancer earlier in patients with pancreatitis.
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Affiliation(s)
- Bo Kong
- Department of Surgery, Technische Universität München (TUM), Munich, Germany.,Department of Gastroenterology, Nanjing Drum Tower Hospital, Nanjing University, Nanjing, China
| | - Philipp Bruns
- Department of Surgery, Technische Universität München (TUM), Munich, Germany.,Institute of Computational Biology, Helmholtz-Zentrum München GmbH, Neuherberg, Germany
| | - Nora A Behler
- Department of Surgery, Technische Universität München (TUM), Munich, Germany
| | - Ligong Chang
- Department of Surgery, Technische Universität München (TUM), Munich, Germany
| | | | - Jing Cao
- Department of Surgery, Technische Universität München (TUM), Munich, Germany
| | - Andreas Gewies
- Institute für Klinische Chemie und Pathobiochemie, TUM, Munich, Germany.,Research Unit Cellular Signal Integration, Institute of Molecular Toxicology and Pharmacology, Helmholtz Zentrum München, Neuherberg, Germany.,German Cancer Consortium (DKTK) at the partner site Munich and German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Jürgen Ruland
- Institute für Klinische Chemie und Pathobiochemie, TUM, Munich, Germany.,German Cancer Consortium (DKTK) at the partner site Munich and German Cancer Research Center (DKFZ), Heidelberg, Germany.,German Center for Infection Research (DZIF), Partner Site Munich, Munich, Germany
| | - Sina Fritzsche
- Department of Surgery, Technische Universität München (TUM), Munich, Germany
| | | | - Ziying Jian
- Department of Surgery, Technische Universität München (TUM), Munich, Germany
| | - Ivonne Regel
- Institute of Pathology, Heinrich-Heine University, Duesseldorf, Germany
| | - Susanne Raulefs
- Department of Surgery, Technische Universität München (TUM), Munich, Germany
| | - Martin Irmler
- Institute of Experimental Genetics, Helmholtz Zentrum München GmbH, Neuherberg, Germany
| | - Johannes Beckers
- Institute of Experimental Genetics, Helmholtz Zentrum München GmbH, Neuherberg, Germany.,Chair of Experimental Genetics, Technische Universität München, Freising, Germany.,Deutsches Zentrum für Diabetesforschung, Neuherberg, Germany
| | - Helmut Friess
- Department of Surgery, Technische Universität München (TUM), Munich, Germany
| | - Mert Erkan
- Department of Surgery, Koc University, Istanbul, Turkey
| | - Nikola S Mueller
- Institute of Computational Biology, Helmholtz-Zentrum München GmbH, Neuherberg, Germany
| | - Susanne Roth
- Department of Surgery, University of Heidelberg, Heidelberg, Germany
| | - Thilo Hackert
- Department of Surgery, University of Heidelberg, Heidelberg, Germany
| | - Irene Esposito
- Institute of Pathology, Heinrich-Heine University, Duesseldorf, Germany
| | - Fabian J Theis
- Institute of Computational Biology, Helmholtz-Zentrum München GmbH, Neuherberg, Germany.,Department of Mathematics, TUM, Munich, Germany
| | - Jörg Kleeff
- Department of Surgery, Technische Universität München (TUM), Munich, Germany.,NIHR Pancreas Biomedical Research Unit, Department of Molecular and Clinical Cancer Medicine, University of Liverpool, Liverpool, UK
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109
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Smith MD, Harley ME, Kemp AJ, Wills J, Lee M, Arends M, von Kriegsheim A, Behrends C, Wilkinson S. CCPG1 Is a Non-canonical Autophagy Cargo Receptor Essential for ER-Phagy and Pancreatic ER Proteostasis. Dev Cell 2017; 44:217-232.e11. [PMID: 29290589 PMCID: PMC5791736 DOI: 10.1016/j.devcel.2017.11.024] [Citation(s) in RCA: 309] [Impact Index Per Article: 44.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Revised: 11/02/2017] [Accepted: 11/29/2017] [Indexed: 12/11/2022]
Abstract
Mechanisms of selective autophagy of the ER, known as ER-phagy, require molecular delineation, particularly in vivo. It is unclear how these events control ER proteostasis and cellular health. Here, we identify cell-cycle progression gene 1 (CCPG1), an ER-resident protein with no known physiological role, as a non-canonical cargo receptor that directly binds to core autophagy proteins via an LIR motif to mammalian ATG8 proteins and, independently and via a discrete motif, to FIP200. These interactions facilitate ER-phagy. The CCPG1 gene is inducible by the unfolded protein response and thus directly links ER stress to ER-phagy. In vivo, CCPG1 protects against ER luminal protein aggregation and consequent unfolded protein response hyperactivation and tissue injury of the exocrine pancreas. Thus, via identification of this autophagy protein, we describe an unexpected molecular mechanism of ER-phagy and provide evidence that this may be physiologically relevant in ER luminal proteostasis. CCPG1 is an ER stress-inducible ER-phagy cargo receptor in mammals CCPG1 binds directly to ATG8 proteins and FIP200 via distinct peptide motifs CCPG1 lysosomal degradation and ER-phagy both require these interactions CCPG1 maintains normal ER luminal proteostasis in pancreatic acinar cells in vivo
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Affiliation(s)
- Matthew D Smith
- Edinburgh Cancer Research UK Centre, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XR, UK
| | - Margaret E Harley
- Edinburgh Cancer Research UK Centre, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XR, UK
| | - Alain J Kemp
- Edinburgh Cancer Research UK Centre, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XR, UK
| | - Jimi Wills
- Edinburgh Cancer Research UK Centre, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XR, UK
| | - Martin Lee
- Edinburgh Cancer Research UK Centre, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XR, UK
| | - Mark Arends
- Edinburgh Cancer Research UK Centre, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XR, UK
| | - Alex von Kriegsheim
- Edinburgh Cancer Research UK Centre, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XR, UK
| | - Christian Behrends
- Munich Cluster for Systems Neurology (SyNergy), Ludwig-Maximilians-University Munich, München, Germany
| | - Simon Wilkinson
- Edinburgh Cancer Research UK Centre, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XR, UK.
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110
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Abstract
The endoplasmic reticulum (ER) is a key site for lipid biosynthesis and folding of nascent transmembrane and secretory proteins. These processes are maintained by careful homeostatic control of the environment within the ER lumen. Signalling sensors within the ER detect perturbations within the lumen (ER stress) and employ downstream signalling cascades that engage effector mechanisms to restore homeostasis. The most studied signalling mechanism that the ER employs is the unfolded protein response (UPR), which is known to increase a number of effector mechanisms, including autophagy. In this chapter, we will discuss the emerging role of autophagy as a UPR effector pathway. We will focus on the recently discovered selective autophagy pathway for ER, ER-phagy, with particular emphasis on the structure and function of known mammalian ER-phagy receptors, namely FAM134B, SEC62, RTN3 and CCPG1. Finally, we conclude with our view of where the future of this field can lead our understanding of the involvement of ER-phagy in ER homeostasis.
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111
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Lugea A, Gerloff A, Su HY, Xu Z, Go A, Hu C, French SW, Wilson JS, Apte MV, Waldron RT, Pandol SJ. The Combination of Alcohol and Cigarette Smoke Induces Endoplasmic Reticulum Stress and Cell Death in Pancreatic Acinar Cells. Gastroenterology 2017; 153:1674-1686. [PMID: 28847752 PMCID: PMC5705421 DOI: 10.1053/j.gastro.2017.08.036] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Revised: 08/11/2017] [Accepted: 08/21/2017] [Indexed: 01/11/2023]
Abstract
BACKGROUND & AIMS Smoking, an independent risk factor for pancreatitis, accelerates the development of alcoholic pancreatitis. Alcohol feeding of mice induces up-regulation of spliced X-box binding protein 1 (XBP1s), which regulates the endoplasmic reticulum (ER) unfolded protein response and promotes cell survival upon ER stress. We examined whether smoking affects the adaptive mechanisms induced by alcohol and accelerates disorders of the ER in pancreatic acinar cells. METHODS We studied the combined effects of ethanol (EtOH) and cigarette smoke extract (CSE) on ER stress and cell death responses in mouse and human primary acini and the acinar cell line AR42J. Cells were incubated with EtOH (50 mmol/L), CSE (20-40 μg/mL), or both (CSE+EtOH), and analyzed by immunoblotting, quantitative reverse-transcription polymerase chain reaction, and cell death assays. Some cells were incubated with MKC-3946, an inhibitor of endoplasmic reticulum to nucleus signaling 1 (ERN1, also called IRE1) that blocks XBP1s formation. Male Sprague-Dawley rats were fed isocaloric amounts of an EtOH-containing (Lieber-DeCarli) or control diet for 11 weeks and exposed to cigarette smoke or room air in an exposure chamber for 2 hours each day. During the last 3 weeks, a subset of rats received intravenous injections of lipopolysaccharide (LPS, 3 mg/kg per week) to induce pancreatitis or saline (control). Pancreatic tissues were collected and analyzed by histology and immunostaining techniques. RESULTS In AR42J and primary acini, CSE+EtOH induced cell death (necrosis and apoptosis), but neither agent alone had this effect. Cell death was associated with a significant decrease in expression of XBP1s. CSE+EtOH, but neither agent alone, slightly decreased adenosine triphosphate levels in AR42J cells, but induced oxidative stress and sustained activation (phosphorylation) of eukaryotic translation initiation factor 2 alpha kinase 3 (EIF2AK3, also called PERK) and increased protein levels of DNA damage inducible transcript 3 (DDIT3, also called CHOP). CHOP regulates transcription to promote apoptosis. Incubation of AR42J or primary mouse or human acinar cells with MKC-3946 reduced expression of XBP1s, increased levels of CHOP, and induced cell death. In rats fed an EtOH diet, exposure to cigarette smoke increased ER stress in acinar cells and sensitized the pancreas to LPS-induced pathology. CONCLUSIONS Cigarette smoke promotes cell death and features of pancreatitis in EtOH-sensitized acinar cells by suppressing the adaptive unfolded protein response signaling pathway. It also activates ER stress pathways that promote acinar cell death.
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Affiliation(s)
- Aurelia Lugea
- Cedars-Sinai Medical Center, Los Angeles, California; VA Greater Los Angeles Healthcare System/University of California, Los Angeles, California.
| | - Andreas Gerloff
- VA Greater Los Angeles Healthcare System/University of California, Los Angeles, CA
| | | | - Zhihong Xu
- University of New South Wales, Liverpool, Australia and Ingham Institute for Applied Medical Research, Liverpool, Australia
| | - Ariel Go
- Cedars-Sinai Medical Center, Los Angeles, CA
| | - Cheng Hu
- Cedars-Sinai Medical Center, Los Angeles, CA
| | | | - Jeremy S. Wilson
- University of New South Wales, Liverpool, Australia and Ingham Institute for Applied Medical Research, Liverpool, Australia
| | - Minoti V. Apte
- University of New South Wales, Liverpool, Australia and Ingham Institute for Applied Medical Research, Liverpool, Australia
| | - Richard T. Waldron
- Cedars-Sinai Medical Center, Los Angeles, CA,VA Greater Los Angeles Healthcare System/University of California, Los Angeles, CA
| | - Stephen J. Pandol
- Cedars-Sinai Medical Center, Los Angeles, CA,VA Greater Los Angeles Healthcare System/University of California, Los Angeles, CA
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112
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Jacquemyn J, Cascalho A, Goodchild RE. The ins and outs of endoplasmic reticulum-controlled lipid biosynthesis. EMBO Rep 2017; 18:1905-1921. [PMID: 29074503 DOI: 10.15252/embr.201643426] [Citation(s) in RCA: 154] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Revised: 08/18/2017] [Accepted: 09/18/2017] [Indexed: 12/21/2022] Open
Abstract
Endoplasmic reticulum (ER)-localized enzymes synthesize the vast majority of cellular lipids. The ER therefore has a major influence on cellular lipid biomass and balances the production of different lipid categories, classes, and species. Signals from outside and inside the cell are directed to ER-localized enzymes, and lipid enzyme activities are defined by the integration of internal, homeostatic, and external information. This allows ER-localized lipid synthesis to provide the cell with membrane lipids for growth, proliferation, and differentiation-based changes in morphology and structure, and to maintain membrane homeostasis across the cell. ER enzymes also respond to physiological signals to drive carbohydrates and nutritionally derived lipids into energy-storing triglycerides. In this review, we highlight some key regulatory mechanisms that control ER-localized enzyme activities in animal cells. We also discuss how they act in concert to maintain cellular lipid homeostasis, as well as how their dysregulation contributes to human disease.
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Affiliation(s)
- Julie Jacquemyn
- VIB-KU Leuven Center for Brain & Disease Research, Leuven, Belgium.,Department of Neurosciences, KU Leuven, Leuven, Belgium
| | - Ana Cascalho
- VIB-KU Leuven Center for Brain & Disease Research, Leuven, Belgium.,Department of Neurosciences, KU Leuven, Leuven, Belgium
| | - Rose E Goodchild
- VIB-KU Leuven Center for Brain & Disease Research, Leuven, Belgium .,Department of Neurosciences, KU Leuven, Leuven, Belgium
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113
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Rouzier C, Moore D, Delorme C, Lacas-Gervais S, Ait-El-Mkadem S, Fragaki K, Burté F, Serre V, Bannwarth S, Chaussenot A, Catala M, Yu-Wai-Man P, Paquis-Flucklinger V. A novel CISD2 mutation associated with a classical Wolfram syndrome phenotype alters Ca2+ homeostasis and ER-mitochondria interactions. Hum Mol Genet 2017; 26:1599-1611. [PMID: 28335035 PMCID: PMC5411739 DOI: 10.1093/hmg/ddx060] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Accepted: 02/14/2017] [Indexed: 12/26/2022] Open
Abstract
Wolfram syndrome (WS) is a progressive neurodegenerative disease characterized by early-onset optic atrophy and diabetes mellitus, which can be associated with more extensive central nervous system and endocrine complications. The majority of patients harbour pathogenic WFS1 mutations, but recessive mutations in a second gene, CISD2, have been described in a small number of families with Wolfram syndrome type 2 (WFS2). The defining diagnostic criteria for WFS2 also consist of optic atrophy and diabetes mellitus, but unlike WFS1, this phenotypic subgroup has been associated with peptic ulcer disease and an increased bleeding tendency. Here, we report on a novel homozygous CISD2 mutation (c.215A > G; p.Asn72Ser) in a Moroccan patient with an overlapping phenotype suggesting that Wolfram syndrome type 1 and type 2 form a continuous clinical spectrum with genetic heterogeneity. The present study provides strong evidence that this particular CISD2 mutation disturbs cellular Ca2+ homeostasis with enhanced Ca2+ flux from the ER to mitochondria and cytosolic Ca2+ abnormalities in patient-derived fibroblasts. This Ca2+ dysregulation was associated with increased ER-mitochondria contact, a swollen ER lumen and a hyperfused mitochondrial network in the absence of overt ER stress. Although there was no marked alteration in mitochondrial bioenergetics under basal conditions, culture of patient-derived fibroblasts in glucose-free galactose medium revealed a respiratory chain defect in complexes I and II, and a trend towards decreased ATP levels. Our results provide important novel insight into the potential disease mechanisms underlying the neurodegenerative consequences of CISD2 mutations and the subsequent development of multisystemic disease.
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Affiliation(s)
- Cécile Rouzier
- Université Côte d'Azur, CHU, Inserm, CNRS, IRCAN, France
| | - David Moore
- Wellcome Trust Centre for Mitochondrial Research, Institute of Genetic Medicine, International Centre for Life, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK
| | - Cécile Delorme
- Fédération de Neurologie, Université Pierre et Marie Curie et Groupe Hospitalier Pitié-Salpêtrière, Paris, France
| | - Sandra Lacas-Gervais
- Joint Centre for Applied Electron Microscopy, Nice Sophia-Antipolis University, Nice, France
| | | | | | - Florence Burté
- Wellcome Trust Centre for Mitochondrial Research, Institute of Genetic Medicine, International Centre for Life, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK
| | - Valérie Serre
- UMR7592 CNRS, Jacques Monod Institute, Paris Diderot University, Paris, France
| | | | | | - Martin Catala
- UMR 7622 CNRS et UPMC et Fédération de Neurologie, Université Pierre et Marie Curie et Groupe Hospitalier Pitié-Salpêtrière, Paris, France
| | - Patrick Yu-Wai-Man
- Wellcome Trust Centre for Mitochondrial Research, Institute of Genetic Medicine, International Centre for Life, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK.,Department of Clinical Neurosciences, School of Clinical Medicine, University of Cambridge, Cambridge, UK.,NIHR Biomedical Research Centre at Moorfields Eye Hospital and UCL Institute of Ophthalmology, London, UK
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114
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Ishikawa T, Kashima M, Nagano AJ, Ishikawa-Fujiwara T, Kamei Y, Todo T, Mori K. Unfolded protein response transducer IRE1-mediated signaling independent of XBP1 mRNA splicing is not required for growth and development of medaka fish. eLife 2017; 6:26845. [PMID: 28952924 PMCID: PMC5636610 DOI: 10.7554/elife.26845] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Accepted: 09/25/2017] [Indexed: 12/14/2022] Open
Abstract
When activated by the accumulation of unfolded proteins in the endoplasmic reticulum, metazoan IRE1, the most evolutionarily conserved unfolded protein response (UPR) transducer, initiates unconventional splicing of XBP1 mRNA. Unspliced and spliced mRNA are translated to produce pXBP1(U) and pXBP1(S), respectively. pXBP1(S) functions as a potent transcription factor, whereas pXBP1(U) targets pXBP1(S) to degradation. In addition, activated IRE1 transmits two signaling outputs independent of XBP1, namely activation of the JNK pathway, which is initiated by binding of the adaptor TRAF2 to phosphorylated IRE1, and regulated IRE1-dependent decay (RIDD) of various mRNAs in a relatively nonspecific manner. Here, we conducted comprehensive and systematic genetic analyses of the IRE1-XBP1 branch of the UPR using medaka fish and found that the defects observed in XBP1-knockout or IRE1-knockout medaka were fully rescued by constitutive expression of pXBP1(S). Thus, the JNK and RIDD pathways are not required for the normal growth and development of medaka. The unfolded protein response sensor/transducer IRE1-mediated splicing of XBP1 mRNA encoding its active downstream transcription factor to maintain the homeostasis of the endoplasmic reticulum is sufficient for growth and development of medaka fish.
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Affiliation(s)
- Tokiro Ishikawa
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, Japan
| | - Makoto Kashima
- Research Institute for Food and Agriculture, Ryukoku University, Otsu, Japan
| | | | | | - Yasuhiro Kamei
- Spectrography and Bioimaging Facility, National Institute for Basic Biology, Okazaki, Japan
| | - Takeshi Todo
- Graduate School of Medicine, Osaka University, Suita, Japan
| | - Kazutoshi Mori
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, Japan
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115
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Lugea A, Waldron RT, Mareninova OA, Shalbueva N, Deng N, Su HY, Thomas DD, Jones EK, Messenger SW, Yang J, Hu C, Gukovsky I, Liu Z, Groblewski GE, Gukovskaya AS, Gorelick FS, Pandol SJ. Human Pancreatic Acinar Cells: Proteomic Characterization, Physiologic Responses, and Organellar Disorders in ex Vivo Pancreatitis. THE AMERICAN JOURNAL OF PATHOLOGY 2017; 187:2726-2743. [PMID: 28935577 DOI: 10.1016/j.ajpath.2017.08.017] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 03/04/2017] [Revised: 06/30/2017] [Accepted: 08/03/2017] [Indexed: 12/17/2022]
Abstract
Knowledge of the molecular mechanisms of acute pancreatitis is largely based on studies using rodents. To assess similar mechanisms in humans, we performed ex vivo pancreatitis studies in human acini isolated from cadaveric pancreata from organ donors. Because data on these human acinar preparations are sparse, we assessed their functional integrity and cellular and organellar morphology using light, fluorescence, and electron microscopy; and their proteome by liquid chromatography-tandem mass spectrometry. Acinar cell responses to the muscarinic agonist carbachol (CCh) and the bile acid taurolithocholic acid 3-sulfate were also analyzed. Proteomic analysis of acini from donors of diverse ethnicity showed similar profiles of digestive enzymes and proteins involved in translation, secretion, and endolysosomal function. Human acini preferentially expressed the muscarinic acetylcholine receptor M3 and maintained physiological responses to CCh for at least 20 hours. As in rodent acini, human acini exposed to toxic concentrations of CCh and taurolithocholic acid 3-sulfate responded with trypsinogen activation, decreased cell viability, organelle damage manifest by mitochondrial depolarization, disordered autophagy, and pathological endoplasmic reticulum stress. Human acini also secreted inflammatory mediators elevated in acute pancreatitis patients, including IL-6, tumor necrosis factor-α, IL-1β, chemokine (C-C motif) ligands 2 and 3, macrophage inhibitory factor, and chemokines mediating neutrophil and monocyte infiltration. In conclusion, human cadaveric pancreatic acini maintain physiological functions and have similar pathological responses and organellar disorders with pancreatitis-causing treatments as observed in rodent acini.
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Affiliation(s)
- Aurelia Lugea
- Department of Medicine and Biomedical Sciences, Samuel Oschin Comprehensive Cancer Institute, Cedars-Sinai Medical Center, Los Angeles, California; Department of Medicine, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, California; Veterans Administration Greater Los Angeles Healthcare System, Los Angeles, California.
| | - Richard T Waldron
- Department of Medicine and Biomedical Sciences, Samuel Oschin Comprehensive Cancer Institute, Cedars-Sinai Medical Center, Los Angeles, California; Department of Medicine, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, California; Veterans Administration Greater Los Angeles Healthcare System, Los Angeles, California
| | - Olga A Mareninova
- Department of Medicine, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, California; Veterans Administration Greater Los Angeles Healthcare System, Los Angeles, California
| | - Natalia Shalbueva
- Department of Medicine, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, California; Veterans Administration Greater Los Angeles Healthcare System, Los Angeles, California
| | - Nan Deng
- Department of Biostatistics and Bioinformatics, Samuel Oschin Comprehensive Cancer Institute, Cedars-Sinai Medical Center, Los Angeles, California
| | - Hsin-Yuan Su
- Department of Medicine and Biomedical Sciences, Samuel Oschin Comprehensive Cancer Institute, Cedars-Sinai Medical Center, Los Angeles, California
| | - Diane D Thomas
- Department of Nutritional Sciences, University of Wisconsin, Madison, Wisconsin
| | - Elaina K Jones
- Department of Nutritional Sciences, University of Wisconsin, Madison, Wisconsin
| | - Scott W Messenger
- Department of Nutritional Sciences, University of Wisconsin, Madison, Wisconsin
| | - Jiayue Yang
- Department of Medicine and Biomedical Sciences, Samuel Oschin Comprehensive Cancer Institute, Cedars-Sinai Medical Center, Los Angeles, California
| | - Cheng Hu
- Department of Medicine and Biomedical Sciences, Samuel Oschin Comprehensive Cancer Institute, Cedars-Sinai Medical Center, Los Angeles, California
| | - Ilya Gukovsky
- Department of Medicine, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, California; Veterans Administration Greater Los Angeles Healthcare System, Los Angeles, California
| | - Zhenqiu Liu
- Department of Biostatistics and Bioinformatics, Samuel Oschin Comprehensive Cancer Institute, Cedars-Sinai Medical Center, Los Angeles, California
| | - Guy E Groblewski
- Department of Nutritional Sciences, University of Wisconsin, Madison, Wisconsin
| | - Anna S Gukovskaya
- Department of Medicine, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, California; Veterans Administration Greater Los Angeles Healthcare System, Los Angeles, California
| | - Fred S Gorelick
- Departments of Internal Medicine and Cell Biology, Yale University School of Medicine, New Haven, Connecticut; Veterans Administration Connecticut Healthcare, West Haven, Connecticut
| | - Stephen J Pandol
- Department of Medicine and Biomedical Sciences, Samuel Oschin Comprehensive Cancer Institute, Cedars-Sinai Medical Center, Los Angeles, California; Department of Medicine, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, California; Veterans Administration Greater Los Angeles Healthcare System, Los Angeles, California
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116
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Mahameed M, Tirosh B. Engineering CHO cells with an oncogenic KIT improves cells growth, resilience to stress, and productivity. Biotechnol Bioeng 2017. [DOI: 10.1002/bit.26356] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Mohamed Mahameed
- Institute for Drug Research; The School of Pharmacy; The Hebrew University of Jerusalem; POB 12065 Jerusalem, 9112002 Israel
| | - Boaz Tirosh
- Institute for Drug Research; The School of Pharmacy; The Hebrew University of Jerusalem; POB 12065 Jerusalem, 9112002 Israel
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117
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118
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Huang HW, Zeng X, Rhim T, Ron D, Ryoo HD. The requirement of IRE1 and XBP1 in resolving physiological stress during Drosophila development. J Cell Sci 2017; 130:3040-3049. [PMID: 28775151 PMCID: PMC5612175 DOI: 10.1242/jcs.203612] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2017] [Accepted: 07/31/2017] [Indexed: 01/11/2023] Open
Abstract
IRE1 mediates the unfolded protein response (UPR) in part by regulating XBP1 mRNA splicing in response to endoplasmic reticulum (ER) stress. In cultured metazoan cells, IRE1 also exhibits XBP1-independent biochemical activities. IRE1 and XBP1 are developmentally essential genes in Drosophila and mammals, but the source of the physiological ER stress and the relative contributions of XBP1 activation versus other IRE1 functions to development remain unknown. Here, we employed Drosophila to address this question. Explicitly, we find that specific regions of the developing alimentary canal, fat body and the male reproductive organ are the sources of physiological stress that require Ire1 and Xbp1 for resolution. In particular, the developmental lethality associated with an Xbp1 null mutation was rescued by transgenic expression of Xbp1 in the alimentary canal. The domains of IRE1 that are involved in detecting unfolded proteins, cleaving RNAs and activating XBP1 splicing were all essential for development. The earlier onset of developmental defects in Ire1 mutant larvae compared to in Xbp1-null flies supports a developmental role for XBP1-independent IRE1 RNase activity, while challenging the importance of RNase-independent effector mechanisms of Drosophila IRE1 function.
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Affiliation(s)
- Huai-Wei Huang
- Department of Cell Biology, New York University School of Medicine, New York 10016, USA
| | - Xiaomei Zeng
- Key Laboratory of Molecular Biophysics of Ministry of Education, Center for Human Genome Research, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430000, China
| | - Taiyoun Rhim
- Department of Bioengineering, Hanyang University, Seoul 04763, Korea
| | - David Ron
- Department of Clinical Biochemistry, Cambridge Institute for Medical Research, Cambridge CB2 0XY, UK
| | - Hyung Don Ryoo
- Department of Cell Biology, New York University School of Medicine, New York 10016, USA
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119
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Liu AP, Botelho RJ, Antonescu CN. The big and intricate dreams of little organelles: Embracing complexity in the study of membrane traffic. Traffic 2017; 18:567-579. [DOI: 10.1111/tra.12497] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2017] [Revised: 05/30/2017] [Accepted: 05/30/2017] [Indexed: 12/16/2022]
Affiliation(s)
- Allen P. Liu
- Department of Mechanical Engineering University of Michigan Ann Arbor Michigan
- Department of Biomedical Engineering University of Michigan Ann Arbor Michigan
- Cellular and Molecular Biology Program University of Michigan Ann Arbor Michigan
- Biophysics Program University of Michigan Ann Arbor Michigan
| | - Roberto J. Botelho
- The Graduate Program in Molecular Science and Department of Chemistry and Biology Ryerson University Toronto Canada
| | - Costin N. Antonescu
- The Graduate Program in Molecular Science and Department of Chemistry and Biology Ryerson University Toronto Canada
- Keenan Research Centre for Biomedical Science St. Michael's Hospital Toronto Canada
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121
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Sala AJ, Bott LC, Morimoto RI. Shaping proteostasis at the cellular, tissue, and organismal level. J Cell Biol 2017; 216:1231-1241. [PMID: 28400444 PMCID: PMC5412572 DOI: 10.1083/jcb.201612111] [Citation(s) in RCA: 157] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Revised: 03/20/2017] [Accepted: 03/20/2017] [Indexed: 01/22/2023] Open
Abstract
The proteostasis network (PN) regulates protein synthesis, folding, transport, and degradation to maintain proteome integrity and limit the accumulation of protein aggregates, a hallmark of aging and degenerative diseases. In multicellular organisms, the PN is regulated at the cellular, tissue, and systemic level to ensure organismal health and longevity. Here we review these three layers of PN regulation and examine how they collectively maintain cellular homeostasis, achieve cell type-specific proteomes, and coordinate proteostasis across tissues. A precise understanding of these layers of control has important implications for organismal health and could offer new therapeutic approaches for neurodegenerative diseases and other chronic disorders related to PN dysfunction.
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Affiliation(s)
- Ambre J Sala
- Department of Molecular Biosciences, Rice Institute for Biomedical Research, Northwestern University, Evanston, IL 60208
| | - Laura C Bott
- Department of Molecular Biosciences, Rice Institute for Biomedical Research, Northwestern University, Evanston, IL 60208
| | - Richard I Morimoto
- Department of Molecular Biosciences, Rice Institute for Biomedical Research, Northwestern University, Evanston, IL 60208
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122
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Regulated IRE1-dependent mRNA decay sets the threshold for dendritic cell survival. Nat Cell Biol 2017; 19:698-710. [PMID: 28459443 DOI: 10.1038/ncb3518] [Citation(s) in RCA: 81] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Accepted: 03/21/2017] [Indexed: 12/23/2022]
Abstract
The IRE1-XBP1 signalling pathway is part of a cellular programme that protects against endoplasmic reticulum (ER) stress, but also controls development and survival of immune cells. Loss of XBP1 in splenic type 1 conventional dendritic cells (cDC1s) results in functional alterations without affecting cell survival. However, in mucosal cDC1s, loss of XBP1 impaired survival in a tissue-specific manner-while lung cDC1s die, intestinal cDC1s survive. This was not caused by differential activation of ER stress cell-death regulators CHOP or JNK. Rather, survival of intestinal cDC1s was associated with their ability to shut down protein synthesis through a protective integrated stress response and their marked increase in regulated IRE1-dependent messenger RNA decay. Furthermore, loss of IRE1 endonuclease on top of XBP1 led to cDC1 loss in the intestine. Thus, mucosal DCs differentially mount ATF4- and IRE1-dependent adaptive mechanisms to survive in the face of ER stress.
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Wang X, Mi Y, Zhong B, Mao H, Wan Y, Zhang T, Wang H, Hu C. Identification of grass carp (Ctenopharyngodon idella) XBP1S as a primary member in ER stress. FISH & SHELLFISH IMMUNOLOGY 2017; 64:84-92. [PMID: 28215742 DOI: 10.1016/j.fsi.2017.02.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Revised: 01/21/2017] [Accepted: 02/11/2017] [Indexed: 06/06/2023]
Abstract
X-box binding protein 1 (XBP1), a vital basic leucine zipper transcription factor for the related gene transcription in endoplasmic reticulum (ER) stress, belongs to the CREB/ATF family. In mammals, XBP1S is the activated one of XBP1 isoform. In order to study the role of fish XBP1S, we cloned and identified the XBP1S (KU509247) from grass carp (Ctenopharyngodon idella) (named CiXBP1S) by homologous cloning and RACE technique. The full length of CiXBP1S is 1694 bp along with 124 bp of 5' UTR, 418 bp of 3' UTR and the longest open reading frame (1152 bp) encoding a polypeptide of 383 amino acids with a well conserved DNA binding domain (BRLZ domain). CiXBP1S shares significant homology to zebrafish XBP1S (∼90%) at amino acid level. RT-PCR showed that the expression of CiXBP1S was ubiquitous in all tested grass carp tissues and was significantly up-regulated under the stimulation with tunicamycin (Tm) in CIK (C. idellus kidney) cells. To study the molecular mechanism of transcriptional regulation for XBP1 signaling pathway in fish, we cloned grass carp XBP1 promoter sequence. Its promoter is 1036 bp in length and divided into two distinct regions in which an ER stress response element (ERSE) exists in the proximal region. Meanwhile, grass carp ATF6 (CiATF6N) and CiXBP1S were expressed in Escherichia coli BL21 and purified by affinity chromatography with the Ni-NTA His-Bind resin. Gel mobility shift assay showed that CiATF6N and CiXBP1S had the high affinity with CiXBP1 promoter sequence in vitro. Co-transfection of pcDNA3.1-CiATF6 (or pcDNA3.1-CiXBP1S respectively) with pGL3-CiXBP1P2 (or pGL3-CiXBP1P1 respectively) into epithelioma papulosum cyprini (EPC) cells showed that CiATF6 and CiXBP1S played a positive role in CiXBP1S transcription. CiXBP1S also had high affinity with CiGRP78 and CiGRP94 promoter sequences. In addition, recombinant plasmids of pGL3-CiGRP78P and pGL3-CiGRP94P were constructed and transiently co-transfected with pcDNA3.1-CiXBP1S (pcDN3.1-CiXBP1S-nBRLZ, respectively) into EPC cells. The result showed that CiXBP1S can activate CiGRP78 and CiGRP94 promoters.
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Affiliation(s)
- Xiangqin Wang
- College of Life Science, Key Lab of Aquatic Resources and Utilization of Jiangxi Province, Nanchang University, Nanchang, 330031, China
| | - Yichuan Mi
- College of Life Science, Key Lab of Aquatic Resources and Utilization of Jiangxi Province, Nanchang University, Nanchang, 330031, China
| | - Bin Zhong
- College of Life Science, Key Lab of Aquatic Resources and Utilization of Jiangxi Province, Nanchang University, Nanchang, 330031, China
| | - Huiling Mao
- College of Life Science, Key Lab of Aquatic Resources and Utilization of Jiangxi Province, Nanchang University, Nanchang, 330031, China
| | - Yiqi Wan
- College of Life Science, Key Lab of Aquatic Resources and Utilization of Jiangxi Province, Nanchang University, Nanchang, 330031, China
| | - Tao Zhang
- College of Life Science, Key Lab of Aquatic Resources and Utilization of Jiangxi Province, Nanchang University, Nanchang, 330031, China
| | - Haizhou Wang
- College of Life Science, Key Lab of Aquatic Resources and Utilization of Jiangxi Province, Nanchang University, Nanchang, 330031, China
| | - Chengyu Hu
- College of Life Science, Key Lab of Aquatic Resources and Utilization of Jiangxi Province, Nanchang University, Nanchang, 330031, China.
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Tsuchiya M, Koizumi Y, Hayashi S, Hanaoka M, Tokutake Y, Yonekura S. The role of unfolded protein response in differentiation of mammary epithelial cells. Biochem Biophys Res Commun 2017; 484:903-908. [DOI: 10.1016/j.bbrc.2017.02.042] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Accepted: 02/07/2017] [Indexed: 12/15/2022]
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Miller C, Cai Y, Patton T, Graves SH, Li H, Sabbatini ME. RCAD/BiP pathway is necessary for the proper synthesis of digestive enzymes and secretory function of the exocrine pancreas. Am J Physiol Gastrointest Liver Physiol 2017; 312:G314-G326. [PMID: 28104585 DOI: 10.1152/ajpgi.00176.2016] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Revised: 01/11/2017] [Accepted: 01/16/2017] [Indexed: 02/07/2023]
Abstract
Alcoholism causes an imbalance of endoplasmic reticulum (ER) homeostasis in pancreatic acini. In those cells, the ER is involved in the synthesis and folding of pancreatic enzymes. Ubiquitin-fold modifier 1 (Ufm1) is part of a novel ubiquitin-like modification system involved in maintaining ER homeostasis. Among the components of the Ufm1 system, Regulator of C53 and DDRGK1 (RCAD) has recently been identified as a Ufm1-specific E3 ligase that promotes ufmylation of DDRGK1, an RCAD-interacting protein. We determined the importance of RCAD in the proper synthesis and secretion of pancreatic enzymes using mice with genetically deleted RCAD. The pancreas of RCAD-deficient mice was of normal size and histology. Using quantitative PCR and Western blotting, we found that amylase was upregulated in pancreas organs from RCAD-knockout (KO) mice. Constitutive amylase secretion was much higher in isolated pancreatic acini from RCAD KO mice, whereas CCK-stimulated amylase secretion was disturbed. RCAD deficiency caused a downregulation in expression of ER chaperone BiP, which affected ER homeostasis and activated both apoptosis and trypsin. We also found that both RCAD and DDRGK1 transcript levels were upregulated in pancreatic acini from alcohol-preferring rats. Elevated expression of RCAD and DDRGK1 was associated with increased ER stress and UPR activation. Because of the lack of BiP expression, caspase 3 and trypsin activation we enhanced in RCAD-deficient pancreatic acini upon treatment with ethanol and CCK. In conclusion, the RCAD/BiP pathway is required for proper synthesis and secretion of pancreatic enzymes. In alcoholism, increased levels of components of the Ufm1 system could prevent the deleterious effects of alcohol in the pancreas by regulating BiP levels.NEW & NOTEWORTHY RCAD/BiP pathway is required for the proper synthesis and secretion of amylase from pancreatic acini, as well as for the maintenance of the ER homeostasis. In alcoholism, the exocrine pancreas could increase the levels of components of the Ufm1 system to protect itself from alcohol's deleterious effects by regulating the expression of ER chaperone BiP.
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Affiliation(s)
- Camille Miller
- Department of Biological Sciences, Augusta University, Augusta, Georgia
| | - Yafei Cai
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Cancer Center, Augusta University, Augusta, Georgia; and
| | - Tadd Patton
- Department of Psychological Sciences, Augusta University, Augusta, Georgia
| | | | - Honglin Li
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Cancer Center, Augusta University, Augusta, Georgia; and
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Impairment of both IRE1 expression and XBP1 activation is a hallmark of GCB DLBCL and contributes to tumor growth. Blood 2017; 129:2420-2428. [PMID: 28167662 DOI: 10.1182/blood-2016-09-741348] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Accepted: 01/31/2017] [Indexed: 12/12/2022] Open
Abstract
The endoplasmic reticulum kinase inositol-requiring enzyme 1 (IRE1) and its downstream target X-box-binding protein 1 (XBP1) drive B-cell differentiation toward plasma cells and have been shown to contribute to multiple myeloma development; yet, little is known of the role of this pathway in diffuse large B-cell lymphoma (DLBCL). Here, we show that in the germinal center B-cell-like (GCB) DLBCL subtype, IRE1 expression is reduced to a level that prevents XBP1 activation. Gene expression profiles indicated that, in GCB DLBCL cancer samples, expression of IRE1 messenger RNA was inversely correlated with the levels and activity of the epigenetic repressor, histone methyltransferase enhancer of zeste homolog 2 (EZH2). Correspondingly, in GCB-derived cell lines, the IRE1 promoter carried increased levels of the repressive epigenetic mark histone 3 lysine 27 trimethylation. Pharmacological inhibition of EZH2 erased those marks and restored IRE1 expression and function in vitro and in vivo. Moreover, reconstitution of the IRE1-signaling pathway, by expression of the XBP1-active form, compromised GCB DLBCL tumor growth in a mouse xenograft cancer model. These findings indicate that IRE1-XBP1 downregulation distinguishes GCB DLBCL from other DLBCL subtypes and contributes to tumor growth.
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A novel approach to analyze lysosomal dysfunctions through subcellular proteomics and lipidomics: the case of NPC1 deficiency. Sci Rep 2017; 7:41408. [PMID: 28134274 PMCID: PMC5278418 DOI: 10.1038/srep41408] [Citation(s) in RCA: 85] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 12/19/2016] [Indexed: 01/21/2023] Open
Abstract
Superparamagnetic iron oxide nanoparticles (SPIONs) have mainly been used as cellular carriers for genes and therapeutic products, while their use in subcellular organelle isolation remains underexploited. We engineered SPIONs targeting distinct subcellular compartments. Dimercaptosuccinic acid-coated SPIONs are internalized and accumulate in late endosomes/lysosomes, while aminolipid-SPIONs reside at the plasma membrane. These features allowed us to establish standardized magnetic isolation procedures for these membrane compartments with a yield and purity permitting proteomic and lipidomic profiling. We validated our approach by comparing the biomolecular compositions of lysosomes and plasma membranes isolated from wild-type and Niemann-Pick disease type C1 (NPC1) deficient cells. While the accumulation of cholesterol and glycosphingolipids is seen as a primary hallmark of NPC1 deficiency, our lipidomics analysis revealed the buildup of several species of glycerophospholipids and other storage lipids in selectively late endosomes/lysosomes of NPC1-KO cells. While the plasma membrane proteome remained largely invariable, we observed pronounced alterations in several proteins linked to autophagy and lysosomal catabolism reflecting vesicular transport obstruction and defective lysosomal turnover resulting from NPC1 deficiency. Thus the use of SPIONs provides a major advancement in fingerprinting subcellular compartments, with an increased potential to identify disease-related alterations in their biomolecular compositions.
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Salzberg Y, Coleman AJ, Celestrin K, Cohen-Berkman M, Biederer T, Henis-Korenblit S, Bülow HE. Reduced Insulin/Insulin-Like Growth Factor Receptor Signaling Mitigates Defective Dendrite Morphogenesis in Mutants of the ER Stress Sensor IRE-1. PLoS Genet 2017; 13:e1006579. [PMID: 28114319 PMCID: PMC5293268 DOI: 10.1371/journal.pgen.1006579] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Revised: 02/06/2017] [Accepted: 01/11/2017] [Indexed: 11/18/2022] Open
Abstract
Neurons receive excitatory or sensory inputs through their dendrites, which often branch extensively to form unique neuron-specific structures. How neurons regulate the formation of their particular arbor is only partially understood. In genetic screens using the multidendritic arbor of PVD somatosensory neurons in the nematode Caenorhabditis elegans, we identified a mutation in the ER stress sensor IRE-1/Ire1 (inositol requiring enzyme 1) as crucial for proper PVD dendrite arborization in vivo. We further found that regulation of dendrite growth in cultured rat hippocampal neurons depends on Ire1 function, showing an evolutionarily conserved role for IRE-1/Ire1 in dendrite patterning. PVD neurons of nematodes lacking ire-1 display reduced arbor complexity, whereas mutations in genes encoding other ER stress sensors displayed normal PVD dendrites, specifying IRE-1 as a selective ER stress sensor that is essential for PVD dendrite morphogenesis. Although structure function analyses indicated that IRE-1's nuclease activity is necessary for its role in dendrite morphogenesis, mutations in xbp-1, the best-known target of non-canonical splicing by IRE-1/Ire1, do not exhibit PVD phenotypes. We further determined that secretion and distal localization to dendrites of the DMA-1/leucine rich transmembrane receptor (DMA-1/LRR-TM) is defective in ire-1 but not xbp-1 mutants, suggesting a block in the secretory pathway. Interestingly, reducing Insulin/IGF1 signaling can bypass the secretory block and restore normal targeting of DMA-1, and consequently normal PVD arborization even in the complete absence of functional IRE-1. This bypass of ire-1 requires the DAF-16/FOXO transcription factor. In sum, our work identifies a conserved role for ire-1 in neuronal branching, which is independent of xbp-1, and suggests that arborization defects associated with neuronal pathologies may be overcome by reducing Insulin/IGF signaling and improving ER homeostasis and function.
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Affiliation(s)
- Yehuda Salzberg
- Department of Genetics, Albert Einstein College of Medicine, Bronx, New York, United States of America
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
| | - Andrew J. Coleman
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, United States of America
| | - Kevin Celestrin
- Department of Genetics, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Moran Cohen-Berkman
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
| | - Thomas Biederer
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, United States of America
| | - Sivan Henis-Korenblit
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
| | - Hannes E. Bülow
- Department of Genetics, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York, United States of America
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Gomez JA, Rutkowski DT. Experimental reconstitution of chronic ER stress in the liver reveals feedback suppression of BiP mRNA expression. eLife 2016; 5. [PMID: 27938665 PMCID: PMC5179193 DOI: 10.7554/elife.20390] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Accepted: 12/09/2016] [Indexed: 12/13/2022] Open
Abstract
Endoplasmic reticulum (ER) stress is implicated in many chronic diseases, but very little is known about how the unfolded protein response (UPR) responds to persistent ER stress in vivo. Here, we experimentally reconstituted chronic ER stress in the mouse liver, using repeated injection of a low dose of the ER stressor tunicamycin. Paradoxically, this treatment led to feedback-mediated suppression of a select group of mRNAs, including those encoding the ER chaperones BiP and GRP94. This suppression was due to both silencing of the ATF6α pathway of UPR-dependent transcription and enhancement of mRNA degradation, possibly via regulated IRE1-dependent decay (RIDD). The suppression of mRNA encoding BiP was phenocopied by ectopic overexpression of BiP protein, and was also observed in obese mice. Our findings suggest that persistent cycles of UPR activation and deactivation create an altered, quasi-stable setpoint for UPR-dependent transcriptional regulation—an outcome that could be relevant to conditions such as metabolic syndrome. DOI:http://dx.doi.org/10.7554/eLife.20390.001 Toxic chemicals, extreme temperatures and other abnormal environmental conditions can cause the cells in our bodies to become stressed. Several kinds of stresses overwhelm a compartment in the cell called the endoplasmic reticulum, which is critical for processing new proteins so that they can work correctly. Endoplasmic reticulum stress has been linked to long-term diseases such as diabetes, cancer and neurodegenerative diseases. Most of what is known about how cells sense and respond to endoplasmic reticulum stress comes from studies on isolated cells that were subjected to harsh conditions that cells cannot tolerate for longer than a day or two. By contrast, little is known about how cells within whole organisms respond to milder but longer-lasting endoplasmic reticulum stress, which is closer to what occurs during disease. To investigate this issue, Gomez and Rutkowski treated mice repeatedly with a chemical that causes mild endoplasmic reticulum stress in the liver. The cells exposed to this persistent stress responded differently to those exposed to severe short-term stress. Whereas short-term stress causes liver cells to turn on genes that help the endoplasmic reticulum to process proteins more efficiently, long-term stress causes cells to turn off some of those genes. Further investigation revealed that cells in the livers of obese mice show similar patterns of gene activity as cells exposed to long-term endoplasmic reticulum stress. The findings presented by Gomez and Rutkowski could therefore also help us to understand more about the liver problems that often occur during obesity and diabetes. Further studies are now needed to examine exactly how long-lasting stress can shut off the cells’ protective mechanisms. Future experiments could also investigate whether other types of cells and organs respond to long-term endoplasmic reticulum stress in the same way as cells in the liver. DOI:http://dx.doi.org/10.7554/eLife.20390.002
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Affiliation(s)
- Javier A Gomez
- Graduate Program in Molecular and Cellular Biology, University of Iowa Carver College of Medicine, Iowa City, United States
| | - D Thomas Rutkowski
- Departments of Anatomy and Cell Biology and Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, United States
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130
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Navid F, Colbert RA. Causes and consequences of endoplasmic reticulum stress in rheumatic disease. Nat Rev Rheumatol 2016; 13:25-40. [PMID: 27904144 DOI: 10.1038/nrrheum.2016.192] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Rheumatic diseases represent a heterogeneous group of inflammatory conditions, many of which involve chronic activation of both innate and adaptive immune responses by multiple genetic and environmental factors. These immune responses involve the secretion of excessive amounts of cytokines and other signalling mediators by activated immune cells. The endoplasmic reticulum (ER) is the cellular organelle that directs the folding, processing and trafficking of membrane-bound and secreted proteins, including many key components of the immune response. Maintaining homeostasis in the ER is critical to cell function and survival. Consequently, elaborate mechanisms have evolved to sense and respond to ER stress through three main signalling pathways that together comprise the unfolded protein response (UPR). Activation of the UPR can rapidly resolve the accumulation of misfolded proteins, direct permanent changes in the size and function of cells during differentiation, and critically influence the immune response and inflammation. Recognition of the importance of ER stress and UPR signalling pathways in normal and dysregulated immune responses has greatly increased in the past few years. This Review discusses several settings in which ER stress contributes to the pathogenesis of rheumatic diseases and considers some of the therapeutic opportunities that these discoveries provide.
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Affiliation(s)
- Fatemeh Navid
- Pediatric Translational Research Branch, National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), National Institutes of Health, Building 10, Room 12N248B,10 Center Drive, Bethesda, Maryland 20892, USA
| | - Robert A Colbert
- Pediatric Translational Research Branch, National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), National Institutes of Health, Building 10, Room 12N248B,10 Center Drive, Bethesda, Maryland 20892, USA
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131
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MIST1 and PTF1 Collaborate in Feed-Forward Regulatory Loops That Maintain the Pancreatic Acinar Phenotype in Adult Mice. Mol Cell Biol 2016; 36:2945-2955. [PMID: 27644326 DOI: 10.1128/mcb.00370-16] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Revised: 07/22/2016] [Accepted: 09/10/2016] [Indexed: 12/26/2022] Open
Abstract
Much remains unknown regarding the regulatory networks formed by transcription factors in mature, differentiated mammalian cells in vivo, despite many studies of individual DNA-binding transcription factors. We report a constellation of feed-forward loops formed by the pancreatic transcription factors MIST1 and PTF1 that govern the differentiated phenotype of the adult pancreatic acinar cell. PTF1 is an atypical basic helix-loop-helix transcription factor complex of pancreatic acinar cells and is critical to acinar cell fate specification and differentiation. MIST1, also a basic helix-loop-helix transcription factor, enhances the formation and maintenance of the specialized phenotype of professional secretory cells. The MIST1 and PTF1 collaboration controls a wide range of specialized cellular processes, including secretory protein synthesis and processing, exocytosis, and homeostasis of the endoplasmic reticulum. PTF1 drives Mist1 transcription, and MIST1 and PTF1 bind and drive the transcription of over 100 downstream acinar genes. PTF1 binds two canonical bipartite sites within a 0.7-kb transcriptional enhancer upstream of Mist1 that are essential for the activity of the enhancer in vivo MIST1 and PTF1 coregulate target genes synergistically or additively, depending on the target transcriptional enhancer. The frequent close binding proximity of PTF1 and MIST1 in pancreatic acinar cell chromatin implies extensive collaboration although the collaboration is not dependent on a stable physical interaction.
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MIST1 Links Secretion and Stress as both Target and Regulator of the Unfolded Protein Response. Mol Cell Biol 2016; 36:2931-2944. [PMID: 27644325 DOI: 10.1128/mcb.00366-16] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Revised: 07/22/2016] [Accepted: 09/10/2016] [Indexed: 12/28/2022] Open
Abstract
Transcriptional networks that govern secretory cell specialization, including instructing cells to develop a unique cytoarchitecture, amass extensive protein synthesis machinery, and be embodied to respond to endoplasmic reticulum (ER) stress, remain largely uncharacterized. In this study, we discovered that the secretory cell transcription factor MIST1 (Bhlha15), previously shown to be essential for cytoskeletal organization and secretory activity, also functions as a potent ER stress-inducible transcriptional regulator. Genome-wide DNA binding studies, coupled with genetic mouse models, revealed MIST1 gene targets that function along the entire breadth of the protein synthesis, processing, transport, and exocytosis networks. Additionally, key MIST1 targets are essential for alleviating ER stress in these highly specialized cells. Indeed, MIST1 functions as a coregulator of the unfolded protein response (UPR) master transcription factor XBP1 for a portion of target genes that contain adjacent MIST1 and XBP1 binding sites. Interestingly, Mist1 gene expression is induced during ER stress by XBP1, but as ER stress subsides, MIST1 serves as a feedback inhibitor, directly binding the Xbp1 promoter and repressing Xbp1 transcript production. Together, our findings provide a new paradigm for XBP1-dependent UPR regulation and position MIST1 as a potential biotherapeutic for numerous human diseases.
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The MET Receptor Tyrosine Kinase Confers Repair of Murine Pancreatic Acinar Cells following Acute and Chronic Injury. PLoS One 2016; 11:e0165485. [PMID: 27798657 PMCID: PMC5087859 DOI: 10.1371/journal.pone.0165485] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Accepted: 10/12/2016] [Indexed: 01/07/2023] Open
Abstract
Acinar cells represent the primary target in necroinflammatory diseases of the pancreas, including pancreatitis. The signaling pathways guiding acinar cell repair and regeneration following injury remain poorly understood. The purpose of this study was to determine the importance of Hepatocyte Growth Factor Receptor/MET signaling as an intrinsic repair mechanism for acinar cells following acute damage and chronic alcohol-associated injury. Here, we generated mice with targeted deletion of MET in adult acinar cells (MET-/-). Acute and repetitive pancreatic injury was induced in MET-/- and control mice with cerulein, and chronic injury by feeding mice Lieber-DeCarli diets containing alcohol with or without enhancement of repetitive pancreatic injury. We examined the exocrine pancreas of these mice histologically for acinar death, edema, inflammation and collagen deposition and changes in the transcriptional program. We show that MET expression is relatively low in normal adult pancreas. However, MET levels were elevated in ductal and acinar cells in human pancreatitis specimens, consistent with a role for MET in an adaptive repair mechanism. We report that genetic deletion of MET in adult murine acinar cells was linked to increased acinar cell death, chronic inflammation and delayed recovery (regeneration) of pancreatic exocrine tissue. Notably, increased pancreatic collagen deposition was detected in MET knockout mice following repetitive injury as well alcohol-associated injury. Finally, we identified specific alterations of the pancreatic transcriptome associated with MET signaling during injury, involved in tissue repair, inflammation and endoplasmic reticulum stress. Together, these data demonstrate the importance of MET signaling for acinar repair and regeneration, a novel finding that could attenuate the symptomology of pancreatic injury.
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Wu FL, Liu WY, Van Poucke S, Braddock M, Jin WM, Xiao J, Li XK, Zheng MH. Targeting endoplasmic reticulum stress in liver disease. Expert Rev Gastroenterol Hepatol 2016; 10:1041-52. [PMID: 27093595 DOI: 10.1080/17474124.2016.1179575] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
INTRODUCTION The accumulation of unfolded protein in the endoplasmic reticulum (ER) initiates an unfolded protein response (UPR) via three signal transduction cascades, which involve protein kinase RNA-like ER kinase (PERK), inositol requiring enzyme-1α (IRE1α) and activating transcription factor-6α (ATF6α). An ER stress response is observed in nearly all physiologies related to acute and chronic liver disease and therapeutic targeting of the mechanisms implicated in UPR signaling have attracted considerable attention. AREAS COVERED This review focuses on the correlation between ER stress and liver disease and the possible targets which may drive the potential for novel therapeutic intervention. Expert Commentary: We describe pathways which are involved in UPR signaling and their potential correlation with various liver diseases and underlying mechanisms which may present opportunities for novel therapeutic strategies are discussed.
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Affiliation(s)
- Fa-Ling Wu
- a Department of Hepatology, Liver Research Center , the First Affiliated Hospital of Wenzhou Medical University , Wenzhou , China.,b Institute of Hepatology , Wenzhou Medical University , Wenzhou , China
| | - Wen-Yue Liu
- c Department of Endocrinology , the First Affiliated Hospital of Wenzhou Medical University , Wenzhou , China
| | - Sven Van Poucke
- d Department of Anesthesiology, Intensive Care, Emergency Medicine and Pain Therapy , Ziekenhuis Oost-Limburg , Genk , Belgium
| | - Martin Braddock
- e Global Medicines Development , AstraZeneca R&D , Alderley Park , UK
| | - Wei-Min Jin
- f Department of Infection Diseases , People Hospital of Wencheng County , Wenzhou , China
| | - Jian Xiao
- g Institute of Biology Science , Wenzhou University , Wenzhou , China.,h School of Pharmacy , Wenzhou Medical University , Wenzhou , China
| | - Xiao-Kun Li
- g Institute of Biology Science , Wenzhou University , Wenzhou , China.,h School of Pharmacy , Wenzhou Medical University , Wenzhou , China
| | - Ming-Hua Zheng
- a Department of Hepatology, Liver Research Center , the First Affiliated Hospital of Wenzhou Medical University , Wenzhou , China.,b Institute of Hepatology , Wenzhou Medical University , Wenzhou , China
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Storm M, Sheng X, Arnoldussen YJ, Saatcioglu F. Prostate cancer and the unfolded protein response. Oncotarget 2016; 7:54051-54066. [PMID: 27303918 PMCID: PMC5288241 DOI: 10.18632/oncotarget.9912] [Citation(s) in RCA: 51] [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: 02/04/2016] [Accepted: 05/23/2016] [Indexed: 01/01/2023] Open
Abstract
The endoplasmic reticulum (ER) is an essential organelle that contributes to several key cellular functions, including lipogenesis, gluconeogenesis, calcium storage, and organelle biogenesis. The ER also serves as the major site for protein folding and trafficking, especially in specialized secretory cells. Accumulation of misfolded proteins and failure of ER adaptive capacity activates the unfolded protein response (UPR) which has been implicated in several chronic diseases, including cancer. A number of recent studies have implicated UPR in prostate cancer (PCa) and greatly expanded our understanding of this key stress signaling pathway and its regulation in PCa. Here we summarize these developments and discuss their potential therapeutic implications.
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Affiliation(s)
| | - Xia Sheng
- Department of Biosciences, University of Oslo, Oslo, Norway
| | - Yke Jildouw Arnoldussen
- Department of Biological and Chemical Work Environment, National Institute of Occupational Health, Oslo, Norway
| | - Fahri Saatcioglu
- Department of Biosciences, University of Oslo, Oslo, Norway
- Institute for Cancer Genetics and Informatics, Oslo University Hospital, Oslo, Norway
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136
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Phosphatidylcholine as a metabolic cue for determining B cell fate and function. Cell Immunol 2016; 310:78-88. [PMID: 27502364 DOI: 10.1016/j.cellimm.2016.08.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2016] [Revised: 07/27/2016] [Accepted: 08/02/2016] [Indexed: 01/14/2023]
Abstract
In activated B cells, increased production of phosphatidylcholine (PtdCho), the most abundant cellular phospholipid, is handled primarily by the CDP-choline pathway. B cell-specific deletion of CTP:phosphocholine cytidylyltransferase α (CCTα), the rate-limiting enzyme in the CDP-choline pathway, led to augmented IgM secretion and reduced IgG production, suggesting that PtdCho synthesis is required for germinal center reactions. To specifically assess whether PtdCho influences B cell fate during germinal center responses, we examined immune responses in mice whereby PtdCho synthesis is disrupted in B cells that have undergone class switch recombination to IgG1 (referred to as either Cγ1wt/wt, Cγ1Cre/wt or Cγ1Cre/Cre based on Cre copy number). Serum IgG1 was markedly reduced in naïve Cγ1Cre/wt and Cγ1Cre/Cre mice, while levels of IgM and other IgG subclasses were similar between Cγ1Cre/wt and Cγ1wt/wt control mice. Serum IgG2b titers were notably reduced and IgG3 titers were increased in Cγ1Cre/Cre mice compared with controls. Following immunization with T cell-dependent antigen NP-KLH, control mice generated high titer IgG anti-NP while IgG anti-NP titers were markedly reduced in both immunized Cγ1Cre/wt and Cγ1Cre/Cre mice. Correspondingly, the frequency of NP-specific IgG antibody-secreting cells was also reduced in spleens and bone marrow of Cγ1Cre/wt and Cγ. 1Cre/Cre mice compared to control mice. Interestingly, though antigen-specific IgM B cells were comparable between Cγ1Cre/wt, Cγ1Cre/Cre and control mice, the frequency and number of IgG1 NP-specific B cells was reduced only in Cγ1Cre/Cre mice. These data indicate that PtdCho is required for the generation of both germinal center-derived B cells and antibody-secreting cells. Further, the reduction in class-switched ASC but not B cells in Cγ1Cre/wt mice suggests that ASC have a greater demand for PtdCho compared to germinal center B cells.
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Horiuchi K, Tohmonda T, Morioka H. The unfolded protein response in skeletal development and homeostasis. Cell Mol Life Sci 2016; 73:2851-69. [PMID: 27002737 PMCID: PMC11108572 DOI: 10.1007/s00018-016-2178-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Revised: 03/06/2016] [Accepted: 03/10/2016] [Indexed: 12/20/2022]
Abstract
Osteoblasts and chondrocytes produce a large number of extracellular matrix proteins to generate and maintain the skeletal system. To cope with their functions as secretory cells, these cells must acquire a considerable capacity for protein synthesis and also the machinery for the quality-control and transport of newly synthesized secreted proteins. The unfolded protein response (UPR) plays a crucial role during the differentiation of these cells to achieve this goal. Unexpectedly, however, studies in the past several years have revealed that the UPR has more extensive functions in skeletal development than was initially assumed, and the UPR critically orchestrates many facets of skeletal development and homeostasis. This review focuses on recent findings on the functions of the UPR in the differentiation of osteoblasts, chondrocytes, and osteoclasts. These findings may have a substantial impact on our understanding of bone metabolism and also on establishing treatments for congenital and acquired skeletal disorders.
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Affiliation(s)
- Keisuke Horiuchi
- Department of Orthopedic Surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
- Department of Anti-aging Orthopedic Research, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
| | - Takahide Tohmonda
- Department of Orthopedic Surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan
- Department of Anti-aging Orthopedic Research, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan
| | - Hideo Morioka
- Department of Orthopedic Surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan
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Barrera MJ, Aguilera S, Castro I, Cortés J, Bahamondes V, Quest AFG, Molina C, González S, Hermoso M, Urzúa U, Leyton C, González MJ. Pro-inflammatory cytokines enhance ERAD and ATF6α pathway activity in salivary glands of Sjögren's syndrome patients. J Autoimmun 2016; 75:68-81. [PMID: 27461470 DOI: 10.1016/j.jaut.2016.07.006] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Revised: 06/21/2016] [Accepted: 07/15/2016] [Indexed: 12/12/2022]
Abstract
Salivary gland (SG) acinar-cells are susceptible to endoplasmic reticulum (ER) stress related to their secretory activity and the complexity of synthesized secretory products. SGs of Sjögren's syndrome patients (SS)-patients show signs of inflammation and altered proteostasis, associated with low IRE1α/XBP-1 pathway activity without avert increases in apoptosis. Acinar-cells may avoid apoptosis by activation of the ATF6α pathway and ER-associated protein degradation (ERAD). The aim of this study was to evaluate the role of pro-inflammatory cytokines in ATF6α pathway/ERAD activation and cell viability in labial salivary glands (LSG) of SS-patients. In biopsies from SS-patients increased ATF6α signaling pathway activity, as evidenced by generation of the ATF6f cleavage fragment, and increased expression of ERAD machinery components, such as EDEM1, p97, SEL1L, gp78, UBE2J1, UBE2G2, HERP and DERLIN1, were observed compared to controls. Alternatively, for pro- (active-caspase-3) and anti-apoptotic (cIAP2) markers no significant difference between the two experimental groups was detected. Increased presence of ATF6f and ERAD molecules correlated significantly with increased expression of pro-inflammatory cytokines. These observations were corroborated in vitro in 3D-acini treated with TNF-α and/or IFN-γ, where an increase in the expression and activation of the ATF6α sensor and ERAD machinery components was detected under ER stress conditions, while changes in cell viability and caspase-3 activation were not observed. Cytokine stimulation protected cells from death when co-incubated with an ERAD machinery inhibitor. Alternatively, when cytokines were eliminated from the medium prior to ERAD inhibition, cell death increased, suggesting that the presence of pro-inflammatory cytokines in the medium is essential to maintain cell viability. In conclusion, the ATF6α pathway and the ERAD machinery are active in LSG of SS-patients. Both were also activated by TNF-α and IFN-γ in vitro in 3D-acini and aided in preventing apoptosis. IFN-γ levels were elevated in SS-patients and UPR responses triggered in vitro by this cytokine closely matched those observed in LSG from SS-patients, suggesting that cytokines may induce ER stress.
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Affiliation(s)
- María-José Barrera
- Programa de Biología Celular y Molecular, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Sergio Aguilera
- Departamento de Reumatología, Clínica INDISA, Santiago, Chile
| | - Isabel Castro
- Programa de Biología Celular y Molecular, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Juan Cortés
- Programa de Biología Celular y Molecular, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Verónica Bahamondes
- Programa de Biología Celular y Molecular, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Andrew F G Quest
- Programa de Biología Celular y Molecular, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina, Universidad de Chile, Santiago, Chile; Center for Molecular Studies of the Cell (CEMC), Advanced Center for Chronic Diseases (ACCDiS), Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Claudio Molina
- Escuela Dental, Facultad de Ciencias, Universidad Mayor, Santiago, Chile
| | - Sergio González
- Escuela Dental, Facultad de Ciencias, Universidad Mayor, Santiago, Chile
| | - Marcela Hermoso
- Programa de Inmunología, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Ulises Urzúa
- Programa de Biología Celular y Molecular, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Cecilia Leyton
- Programa de Biología Celular y Molecular, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - María-Julieta González
- Programa de Biología Celular y Molecular, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina, Universidad de Chile, Santiago, Chile.
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139
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Heindryckx F, Binet F, Ponticos M, Rombouts K, Lau J, Kreuger J, Gerwins P. Endoplasmic reticulum stress enhances fibrosis through IRE1α-mediated degradation of miR-150 and XBP-1 splicing. EMBO Mol Med 2016; 8:729-44. [PMID: 27226027 PMCID: PMC4931288 DOI: 10.15252/emmm.201505925] [Citation(s) in RCA: 116] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Revised: 04/16/2016] [Accepted: 04/20/2016] [Indexed: 01/08/2023] Open
Abstract
ER stress results in activation of the unfolded protein response and has been implicated in the development of fibrotic diseases. In this study, we show that inhibition of the ER stress-induced IRE1α signaling pathway, using the inhibitor 4μ8C, blocks TGFβ-induced activation of myofibroblasts in vitro, reduces liver and skin fibrosis in vivo, and reverts the fibrotic phenotype of activated myofibroblasts isolated from patients with systemic sclerosis. By using IRE1α(-/-) fibroblasts and expression of IRE1α-mutant proteins lacking endoribonuclease activity, we confirmed that IRE1α plays an important role during myofibroblast activation. IRE1α was shown to cleave miR-150 and thereby to release the suppressive effect that miR-150 exerted on αSMA expression through c-Myb. Inhibition of IRE1α was also demonstrated to block ER expansion through an XBP-1-dependent pathway. Taken together, our results suggest that ER stress could be an important and conserved mechanism in the pathogenesis of fibrosis and that components of the ER stress pathway may be therapeutically relevant for treating patients with fibrotic diseases.
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Affiliation(s)
- Femke Heindryckx
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - François Binet
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Markella Ponticos
- Centre for Rheumatology and Connective Tissue Diseases, University College London, London, UK
| | - Krista Rombouts
- Institute for Liver and Digestive Health, University College London, London, UK
| | - Joey Lau
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Johan Kreuger
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Pär Gerwins
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden Department of Radiology, Uppsala University Hospital, Uppsala, Sweden
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140
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Taniguchi M, Sasaki-Osugi K, Oku M, Sawaguchi S, Tanakura S, Kawai Y, Wakabayashi S, Yoshida H. MLX Is a Transcriptional Repressor of the Mammalian Golgi Stress Response. Cell Struct Funct 2016; 41:93-104. [PMID: 27251850 DOI: 10.1247/csf.16005] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The Golgi stress response is a homeostatic mechanism that controls the capacity of the Golgi apparatus in accordance with cellular demands. When the capacity of the Golgi apparatus becomes insufficient (Golgi stress), transcription levels of Golgi-related genes encoding glycosylation enzymes, a Golgi structural protein, and components of vesicular transport are upregulated through a common cis-acting enhancer-the Golgi apparatus stress response element (GASE). Here, we identified the transcription factor MLX as a GASE-binding protein. MLX resides in the cytoplasm and does not bind to GASE in normal growth conditions, whereas MLX translocates into the nucleus and specifically binds to GASE in response to Golgi stress. Suppression of MLX expression increased transcriptional induction of target genes of the Golgi stress response, whereas overexpression of MLX reduced GASE-binding of TFE3 as well as transcriptional induction from GASE, suggesting that MLX is a transcriptional repressor of the mammalian Golgi stress response.
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Affiliation(s)
- Mai Taniguchi
- Department of Molecular Biochemistry, Graduate School of Life Science, University of Hyogo
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141
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Wu JS, Li WM, Chen YN, Zhao Q, Chen QF. Endoplasmic reticulum stress is activated in acute pancreatitis. J Dig Dis 2016; 17:295-303. [PMID: 27059531 DOI: 10.1111/1751-2980.12347] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/29/2015] [Revised: 03/21/2016] [Accepted: 03/31/2016] [Indexed: 12/11/2022]
Abstract
Endoplasmic reticulum (ER) is one of the most important cell organelles in the body, regulating protein synthesis, folding and aggregation. Endoplasmic reticulum stress (ERS) is a particular subcellular pathological process involving an imbalance of homeostasis and ER disorder. In the early stage of ERS, cells show a protective unfolded protein response that changes the cellular transcriptional and translational programs to alleviate the process. Therefore, a certain degree of ERS can activate the protective adaptation of cells, whereas sustained severe ERS triggers an apoptotic signal and leads to apoptosis. Acute pancreatitis is a disease caused by trypsin digestion of the pancreas, although the pathogenesis is not completely understood. However, a close association has been suggested between pancreatitis and ERS. This article reviewed relevant research advances and discussed the effect of ERS on the development and progression of acute pancreatitis.
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Affiliation(s)
- Jian Sheng Wu
- Department of Gastroenterology, First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, China
| | - Wei Min Li
- Department of Gastroenterology, First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, China
| | - Yi Na Chen
- Department of Gastroenterology, First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, China
| | - Qian Zhao
- Department of Gastroenterology, First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, China
| | - Qin Fen Chen
- Department of Gastroenterology, First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, China
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142
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Godin JD, Creppe C, Laguesse S, Nguyen L. Emerging Roles for the Unfolded Protein Response in the Developing Nervous System. Trends Neurosci 2016; 39:394-404. [PMID: 27130659 DOI: 10.1016/j.tins.2016.04.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Revised: 03/23/2016] [Accepted: 04/04/2016] [Indexed: 01/04/2023]
Abstract
The unfolded protein response (UPR) is a homeostatic signaling pathway triggered by protein misfolding in the endoplasmic reticulum (ER). Beyond its protective role, it plays important functions during normal development in response to elevated demand for protein folding. Several UPR effectors show dynamic temporal and spatial expression patterns that correlate with milestones of the central nervous system (CNS) development. Here, we discuss recent studies suggesting that a dynamic regulation of UPR supports generation, maturation, and maintenance of differentiated neurons in the CNS. We further highlight studies supporting a developmental vulnerability of CNS to UPR dysregulation, which underlies neurodevelopmental disorders. We believe that a better understanding of UPR functions may provide novel opportunities for therapeutic strategies to fight ER/UPR-associated human neurological disorders.
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Affiliation(s)
- Juliette D Godin
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM U964, CNRS UMR7104, University of Strasbourg, Illkirch, France.
| | - Catherine Creppe
- GIGA-Neurosciences, University of Liège, C.H.U. Sart Tilman, Liège 4000, Belgium; Interdisciplinary Cluster for Applied Genoproteomics (GIGA-R), University of Liège, C.H.U. Sart Tilman, Liège 4000, Belgium
| | - Sophie Laguesse
- GIGA-Neurosciences, University of Liège, C.H.U. Sart Tilman, Liège 4000, Belgium; Interdisciplinary Cluster for Applied Genoproteomics (GIGA-R), University of Liège, C.H.U. Sart Tilman, Liège 4000, Belgium
| | - Laurent Nguyen
- GIGA-Neurosciences, University of Liège, C.H.U. Sart Tilman, Liège 4000, Belgium; Interdisciplinary Cluster for Applied Genoproteomics (GIGA-R), University of Liège, C.H.U. Sart Tilman, Liège 4000, Belgium; Walloon Excellence in Lifesciences and Biotechnology (WELBIO), University of Liège, C.H.U. Sart Tilman, Liège 4000, Belgium.
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143
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miR-148a is a downstream effector of X-box-binding protein 1 that silences Wnt10b during adipogenesis of 3T3-L1 cells. Exp Mol Med 2016; 48:e226. [PMID: 27055562 PMCID: PMC4855278 DOI: 10.1038/emm.2016.3] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Revised: 12/17/2015] [Accepted: 12/22/2015] [Indexed: 01/21/2023] Open
Abstract
Wnt10b, an endogenous inhibitor of adipogenesis, maintains preadipocytes in an undifferentiated state by suppressing adipogenic transcription factors. We have previously demonstrated that Wnt10b transcription during adipogenesis is negatively regulated by X-box-binding protein 1 (XBP1), an important transcription factor of the unfolded protein response. In this report, we demonstrate that XBP1s can directly induce the transcription of microRNA-148a, which in turn mediates the silencing of Wnt10b mRNA during adipogenic differentiation of 3T3-L1 cells. Stability of Wnt10b mRNA was found to be significantly increased by knockdown of XBP1s. Using computational algorithms, a set of microRNAs was predicted to bind Wnt10b mRNA, of which microRNA-148a was selected as a potential target for XBP1s. Our results revealed that microRNA-148a could bind to the 3′UTR of Wnt10b mRNA. Its ectopic expression significantly suppressed both Wnt10b expression and β-catenin activity. When we altered the expression of XBP1 in 3T3-L1 cells, microRNA-148a levels changed accordingly. A potential XBP1 response element was found in the promoter region of microRNA-148a, and XBP1s directly bound to this response element as shown by point mutation analysis and chromatin immunoprecipitation assay. In addition, a microRNA-148a mimic significantly restored adipogenic potential in XBP1-deficient 3T3-L1 cells. These findings provide the first evidence that XBP1s can regulate Wnt10b by a post-transcriptional mechanism through directly inducing microRNA-148a.
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144
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Cubillos-Ruiz JR, Bettigole SE, Glimcher LH. Molecular Pathways: Immunosuppressive Roles of IRE1α-XBP1 Signaling in Dendritic Cells of the Tumor Microenvironment. Clin Cancer Res 2016; 22:2121-6. [PMID: 26979393 DOI: 10.1158/1078-0432.ccr-15-1570] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Accepted: 03/04/2016] [Indexed: 12/11/2022]
Abstract
The endoplasmic reticulum (ER) is a massive cytoplasmic membrane network that functions primarily to ensure proper folding and posttranslational modification of newly synthesized secreted and transmembrane proteins. Abnormal accumulation of unfolded proteins in this organelle causes a state of "ER stress," which is a hallmark feature of various diseases, including cancer, neurodegeneration, and metabolic dysfunction. Cancer cells exploit the IRE1α-XBP1 arm of the ER stress response to efficiently adjust their protein-folding capacity and ensure survival under hostile tumor microenvironmental conditions. However, we recently found that dendritic cells (DC) residing in the ovarian cancer microenvironment also experience sustained ER stress and demonstrate persistent activation of the IRE1α-XBP1 pathway. This previously unrecognized process disrupts metabolic homeostasis and antigen-presenting capacity in DCs, thereby crippling their natural ability to support the protective functions of infiltrating antitumor T cells. In this review, we briefly discuss some of the mechanisms that fuel ER stress in tumor-associated DCs, the biologic processes altered by aberrant IRE1α-XBP1 signaling in these innate immune cells, and the unique immunotherapeutic potential of targeting this pathway in cancer hosts. Clin Cancer Res; 22(9); 2121-6. ©2016 AACR.
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Affiliation(s)
- Juan R Cubillos-Ruiz
- Department of Obstetrics and Gynecology, Weill Cornell Medical College, New York, New York. Sandra and Edward Meyer Cancer Center, Weill Cornell Medical College, New York, New York.
| | - Sarah E Bettigole
- Sandra and Edward Meyer Cancer Center, Weill Cornell Medical College, New York, New York. Department of Medicine, Weill Cornell Medical College, New York, New York
| | - Laurie H Glimcher
- Sandra and Edward Meyer Cancer Center, Weill Cornell Medical College, New York, New York. Department of Medicine, Weill Cornell Medical College, New York, New York.
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145
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Activation of the unfolded protein response promotes axonal regeneration after peripheral nerve injury. Sci Rep 2016; 6:21709. [PMID: 26906090 PMCID: PMC4764858 DOI: 10.1038/srep21709] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2015] [Accepted: 01/12/2016] [Indexed: 12/13/2022] Open
Abstract
Although protein-folding stress at the endoplasmic reticulum (ER) is emerging as a driver of neuronal dysfunction in models of spinal cord injury and neurodegeneration, the contribution of this pathway to peripheral nerve damage remains poorly explored. Here we targeted the unfolded protein response (UPR), an adaptive reaction against ER stress, in mouse models of sciatic nerve injury and found that ablation of the transcription factor XBP1, but not ATF4, significantly delay locomotor recovery. XBP1 deficiency led to decreased macrophage recruitment, a reduction in myelin removal and axonal regeneration. Conversely, overexpression of XBP1s in the nervous system in transgenic mice enhanced locomotor recovery after sciatic nerve crush, associated to an improvement in key pro-regenerative events. To assess the therapeutic potential of UPR manipulation to axonal regeneration, we locally delivered XBP1s or an shRNA targeting this transcription factor to sensory neurons of the dorsal root ganglia using a gene therapy approach and found an enhancement or reduction of axonal regeneration in vivo, respectively. Our results demonstrate a functional role of specific components of the ER proteostasis network in the cellular changes associated to regeneration and functional recovery after peripheral nerve injury.
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146
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Aronov M, Tirosh B. Metabolic Control of Plasma Cell Differentiation- What We Know and What We Don't Know. J Clin Immunol 2016; 36 Suppl 1:12-7. [PMID: 26910101 DOI: 10.1007/s10875-016-0246-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2016] [Accepted: 02/16/2016] [Indexed: 12/21/2022]
Abstract
Antibody secretion is executed by plasma cells that are generated in the periphery and migrate to the bone marrow to establish a long lived pool. The terminal differentiation of B lymphocytes into plasma cells is executed by a network of transcription factors that cross-regulate each other in order to irreversibly promote this transition. While major progress has been made in the understanding the transcriptional activity of the underlying master regulators, much less is known on the metabolic regulation of plasma cell differentiation that is required to support antibody synthesis, folding and secretion at high levels and allow their long-lasting survival. In this review we will address the known cross talks between the transcription and metabolic control of plasma cells and elaborate on the gaps of knowledge in the field.
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Affiliation(s)
- Michael Aronov
- Institute for Drug Research, The School of Pharmacy, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Boaz Tirosh
- Institute for Drug Research, The School of Pharmacy, The Hebrew University of Jerusalem, Jerusalem, Israel.
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147
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The role of the endoplasmic reticulum stress in stemness, pluripotency and development. Eur J Cell Biol 2016; 95:115-23. [PMID: 26905505 DOI: 10.1016/j.ejcb.2016.02.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Revised: 02/01/2016] [Accepted: 02/05/2016] [Indexed: 01/15/2023] Open
Abstract
The molecular machinery of endoplasmic reticulum (ER) integrates various intracellular and extracellular cues to maintain homeostasis in diverse physiological or pathological scenarios. ER stress and the unfolded protein response (UPR) have been found to mediate molecular and biochemical mechanisms that affect cell proliferation, differentiation, and apoptosis. Although a number of reviews on the ER stress response have been published, comprehensive reviews that broadly summarize ER physiology in the context of pluripotency, embryonic development, and tissue homeostasis are lacking. This review complements the current ER literature and provides a summary of the important findings on the role of the ER stress and UPR in embryonic development and pluripotent stem cells.
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148
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Moore BD, Jin RU, Lo H, Jung M, Wang H, Battle MA, Wollheim CB, Urano F, Mills JC. Transcriptional Regulation of X-Box-binding Protein One (XBP1) by Hepatocyte Nuclear Factor 4α (HNF4Α) Is Vital to Beta-cell Function. J Biol Chem 2016; 291:6146-57. [PMID: 26792861 DOI: 10.1074/jbc.m115.685750] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Indexed: 12/20/2022] Open
Abstract
The transcription factor, X-box-binding protein-1 (XBP1), controls the development and maintenance of the endoplasmic reticulum (ER) in multiple secretory cell lineages. We show here that Hepatocyte Nuclear Factor 4α (HNF4α) directly induces XBP1 expression. Mutations in HNF4α cause Mature-Onset Diabetes of the Young I (MODYI), a subset of diabetes characterized by diminished GSIS. In mouse models, cell lines, and ex vivo islets, using dominant negative and human- disease-allele point mutants or knock-out and knockdown models, we show that disruption of HNF4α caused decreased expression of XBP1 and reduced cellular ER networks. GSIS depends on ER Ca(2+) signaling; we show that diminished XBP1 and/or HNF4α in β-cells led to impaired ER Ca(2+) homeostasis. Restoring XBP1 expression was sufficient to completely rescue GSIS in HNF4α-deficient β-cells. Our findings uncover a transcriptional relationship between HNF4α and Xbp1 with potentially broader implications about MODYI and the importance of transcription factor signaling in the regulation of secretion.
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Affiliation(s)
- Benjamin D Moore
- From the Division of Gastroenterology, Departments of Medicine, Pathology & Immunology, and Developmental Biology, Washington University, St. Louis, Missouri 63110
| | - Ramon U Jin
- From the Division of Gastroenterology, Departments of Medicine, Pathology & Immunology, and Developmental Biology, Washington University, St. Louis, Missouri 63110
| | - Heiyong Lo
- From the Division of Gastroenterology, Departments of Medicine, Pathology & Immunology, and Developmental Biology, Washington University, St. Louis, Missouri 63110
| | - Min Jung
- From the Division of Gastroenterology, Departments of Medicine, Pathology & Immunology, and Developmental Biology, Washington University, St. Louis, Missouri 63110
| | - Haiyan Wang
- Roche Pharma Research and Early Development, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Grenzacherstrasse 124, CH-4070 Basel, Switzerland
| | - Michele A Battle
- Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Claes B Wollheim
- Lund University Diabetes Center, Department of Clinical Sciences, Diabetes & Endocrinology, Skåne University Hospital, Lund University, Malmö 20502, Sweden, Department of Cell Physiology and Metabolism, Université de Genève, University Medical Centre, 1 rue Michel-Servet, Geneva 4 1211, Switzerland, and
| | - Fumihiko Urano
- Division of Endocrinology, Departments of Medicine, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Jason C Mills
- From the Division of Gastroenterology, Departments of Medicine, Pathology & Immunology, and Developmental Biology, Washington University, St. Louis, Missouri 63110,
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149
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Davis KR, Giesy SL, Long Q, Krumm CS, Harvatine KJ, Boisclair YR. XBP1 Regulates the Biosynthetic Capacity of the Mammary Gland During Lactation by Controlling Epithelial Expansion and Endoplasmic Reticulum Formation. Endocrinology 2016; 157:417-28. [PMID: 26562262 DOI: 10.1210/en.2015-1676] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Cells composing the mammary secretory compartment have evolved a high capacity to secrete not only proteins but also triglycerides and carbohydrates. This feature is illustrated by the mouse, which can secrete nearly twice its own weight in milk proteins, triglycerides and lactose over a short 20-day lactation. The coordination of synthesis and export of products in other secretory cells is orchestrated in part by the transcription factor X-box binding protein 1 (XBP1). To assess the role of XBP1 in mammary epithelial cells (MEC), we studied floxed XBP1 female mice lacking (wild type; WT) or expressing the Cre recombinase under the control of the ovine β-lactoglobulin promoter (ΔXBP1(MEC)). Pregnant ΔXBP1(MEC) females had morphologically normal mammary development and gave birth to the same number of pups as WT mice. Their litters, however, suffered a weight gain deficit by lactation day 3 (L3)3 that grew to 80% by L14. ΔXBP1(MEC) dams had only modest changes in milk composition (-21% protein, +24% triglyceride) and in the expression of associated genes in isolated MEC. By L5, WT glands were fully occupied by dilated alveoli, whereas ΔXBP1(MEC) glands contained fewer, mostly unfilled alveoli and retained a prominent adipocyte population. The smaller epithelial compartment in ΔXBP1(MEC) glands was explained by lower MEC proliferation and increased apoptosis. Finally, endoplasmic reticulum ribbons were less abundant in ΔXBP1(MEC) at pregnancy day 18 and failed to increase in abundance by L5. Collectively, these results show that XBP1 is required for MEC population expansion during lactation and its ability to develop an elaborate endoplasmic reticulum compartment.
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Affiliation(s)
- Kristen R Davis
- Department of Animal Science (K.R.D., S.L.G., C.S.K., Y.R.B.), Cornell University, Ithaca, New York 14853; Cam-Su Genome Resources and Laboratory Animal Research Center (Q.L.), Suzhou University, Suzhou 215123, Peoples Republic of China; and Department of Animal Science (K.J.H.), Penn State University, University Park, Pennsylvania 16802
| | - Sarah L Giesy
- Department of Animal Science (K.R.D., S.L.G., C.S.K., Y.R.B.), Cornell University, Ithaca, New York 14853; Cam-Su Genome Resources and Laboratory Animal Research Center (Q.L.), Suzhou University, Suzhou 215123, Peoples Republic of China; and Department of Animal Science (K.J.H.), Penn State University, University Park, Pennsylvania 16802
| | - Qiaoming Long
- Department of Animal Science (K.R.D., S.L.G., C.S.K., Y.R.B.), Cornell University, Ithaca, New York 14853; Cam-Su Genome Resources and Laboratory Animal Research Center (Q.L.), Suzhou University, Suzhou 215123, Peoples Republic of China; and Department of Animal Science (K.J.H.), Penn State University, University Park, Pennsylvania 16802
| | - Christopher S Krumm
- Department of Animal Science (K.R.D., S.L.G., C.S.K., Y.R.B.), Cornell University, Ithaca, New York 14853; Cam-Su Genome Resources and Laboratory Animal Research Center (Q.L.), Suzhou University, Suzhou 215123, Peoples Republic of China; and Department of Animal Science (K.J.H.), Penn State University, University Park, Pennsylvania 16802
| | - Kevin J Harvatine
- Department of Animal Science (K.R.D., S.L.G., C.S.K., Y.R.B.), Cornell University, Ithaca, New York 14853; Cam-Su Genome Resources and Laboratory Animal Research Center (Q.L.), Suzhou University, Suzhou 215123, Peoples Republic of China; and Department of Animal Science (K.J.H.), Penn State University, University Park, Pennsylvania 16802
| | - Yves R Boisclair
- Department of Animal Science (K.R.D., S.L.G., C.S.K., Y.R.B.), Cornell University, Ithaca, New York 14853; Cam-Su Genome Resources and Laboratory Animal Research Center (Q.L.), Suzhou University, Suzhou 215123, Peoples Republic of China; and Department of Animal Science (K.J.H.), Penn State University, University Park, Pennsylvania 16802
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An inhibitor of HIV-1 protease modulates constitutive eIF2α dephosphorylation to trigger a specific integrated stress response. Proc Natl Acad Sci U S A 2015; 113:E117-26. [PMID: 26715744 DOI: 10.1073/pnas.1514076113] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Inhibitors of the HIV aspartyl protease [HIV protease inhibitors (HIV-PIs)] are the cornerstone of treatment for HIV. Beyond their well-defined antiretroviral activity, these drugs have additional effects that modulate cell viability and homeostasis. However, little is known about the virus-independent pathways engaged by these molecules. Here we show that the HIV-PI Nelfinavir decreases translation rates and promotes a transcriptional program characteristic of the integrated stress response (ISR). Mice treated with Nelfinavir display hallmarks of this stress response in the liver, including α subunit of translation initiation factor 2 (eIF2α) phosphorylation, activating transcription factor-4 (ATF4) induction, and increased expression of known downstream targets. Mechanistically, Nelfinavir-mediated ISR bypassed direct activation of the eIF2α stress kinases and instead relied on the inhibition of the constitutive eIF2α dephosphorylation and down-regulation of the phophatase cofactor CReP (Constitutive Repressor of eIF2α Phosphorylation; also known as PPP1R15B). These findings demonstrate that the modulation of eIF2α-specific phosphatase cofactor activity can be a rheostat of cellular homeostasis that initiates a functional ISR and suggest that the HIV-PIs could be repositioned as therapeutics in human diseases to modulate translation rates and stress responses.
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