101
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C-terminal modification of the insulin B:11-23 peptide creates superagonists in mouse and human type 1 diabetes. Proc Natl Acad Sci U S A 2017; 115:162-167. [PMID: 29255035 PMCID: PMC5776820 DOI: 10.1073/pnas.1716527115] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Insulin is a target of CD4 T cells in type 1 diabetes in mice and humans. Why the major epitope in the insulin B chain is presented poorly to the diabetogenic CD4 T cells by the disease-associated major histocompatibility class II (MHCII) alleles has been highly debated. Here we present high-resolution mouse and human MHCII structures and T-cell functional data to show that C-terminal modifications of this epitope are required for binding and presentation in the appropriate position in the MHCII binding groove. These results suggest that pancreas-specific posttranslational modifications of this peptide may play a role in the induction of diabetes and explain how the pathogenic T cells escape deletion in the thymus. A polymorphism at β57 in some major histocompatibility complex class II (MHCII) alleles of rodents and humans is associated with a high risk for developing type 1 diabetes (T1D). However, a highly diabetogenic insulin B chain epitope within the B:9–23 peptide is presented poorly by these alleles to a variety of mouse and human CD4 T cells isolated from either nonobese diabetic (NOD) mice or humans with T1D. We have shown for both species that mutations at the C-terminal end of this epitope dramatically improve presentation to these T cells. Here we present the crystal structures of these mutated peptides bound to mouse IAg7 and human HLA-DQ8 that show how the mutations function to improve T-cell activation. In both peptide binding grooves, the mutation of B:22R to E in the peptide changes a highly unfavorable side chain for the p9 pocket to an optimal one that is dependent on the β57 polymorphism, accounting for why these peptides bind much better to these MHCIIs. Furthermore, a second mutation of the adjacent B:21 (E to G) removes a side chain from the surface of the complex that is highly unfavorable for a subset of NOD mouse CD4 cells, thereby greatly enhancing their response to the complex. These results point out the similarities between the mouse and human responses to this B chain epitope in T1D and suggest there may be common posttranslational modifications at the C terminus of the peptide in vivo to create the pathogenic epitopes in both species.
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102
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Fan J, Wang Y, Liu L, Zhang H, Zhang F, Shi L, Yu M, Gao F, Xu Z. cTAGE5 deletion in pancreatic β cells impairs proinsulin trafficking and insulin biogenesis in mice. J Cell Biol 2017; 216:4153-4164. [PMID: 29133483 PMCID: PMC5716288 DOI: 10.1083/jcb.201705027] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2017] [Revised: 07/31/2017] [Accepted: 09/08/2017] [Indexed: 01/02/2023] Open
Abstract
In this study, Fan et al. show that cTAGE5 interacts with the v-SNARE Sec22b to regulate proinsulin processing and COPII-dependent trafficking from the ER to the Golgi, thereby influencing glucose tolerance. Proinsulin is synthesized in the endoplasmic reticulum (ER) in pancreatic β cells and transported to the Golgi apparatus for proper processing and secretion into plasma. Defects in insulin biogenesis may cause diabetes. However, the underlying mechanisms for proinsulin transport are still not fully understood. We show that β cell–specific deletion of cTAGE5, also known as Mea6, leads to increased ER stress, reduced insulin biogenesis in the pancreas, and severe glucose intolerance in mice. We reveal that cTAGE5/MEA6 interacts with vesicle membrane soluble N-ethyl-maleimide sensitive factor attachment protein receptor Sec22b. Sec22b and its interaction with cTAGE5/MEA6 are essential for proinsulin processing. cTAGE5/MEA6 may coordinate with Sec22b to control the release of COPII vesicles from the ER, and thereby the ER-to-Golgi trafficking of proinsulin. Importantly, transgenic expression of human cTAGE5/MEA6 in β cells can rescue not only the defect in islet structure, but also dysfunctional insulin biogenesis and glucose intolerance on cTAGE5/Mea6 conditional knockout background. Together our data provide more insight into the underlying mechanism of the proinsulin trafficking pathway.
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Affiliation(s)
- Junwan Fan
- State Key Laboratory of Molecular Developmental Biology, CAS Center for Excellence in Brain Science and Intelligence Technology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Yaqing Wang
- State Key Laboratory of Molecular Developmental Biology, CAS Center for Excellence in Brain Science and Intelligence Technology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Liang Liu
- State Key Laboratory of Molecular Developmental Biology, CAS Center for Excellence in Brain Science and Intelligence Technology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Hongsheng Zhang
- State Key Laboratory of Molecular Developmental Biology, CAS Center for Excellence in Brain Science and Intelligence Technology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Feng Zhang
- State Key Laboratory of Molecular Developmental Biology, CAS Center for Excellence in Brain Science and Intelligence Technology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Lei Shi
- State Key Laboratory of Molecular Developmental Biology, CAS Center for Excellence in Brain Science and Intelligence Technology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Mei Yu
- State Key Laboratory of Molecular Developmental Biology, CAS Center for Excellence in Brain Science and Intelligence Technology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Fei Gao
- State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Zhiheng Xu
- State Key Laboratory of Molecular Developmental Biology, CAS Center for Excellence in Brain Science and Intelligence Technology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China .,Parkinson's Disease Center, Beijing Institute for Brain Disorders, Beijing, China
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103
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Todd JA. Intolerable secretion and diabetes in tolerant transgenic mice, revisited. Nat Genet 2017; 48:476-7. [PMID: 27120442 DOI: 10.1038/ng.3560] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
A new mouse model linking diabetes, insulin secretion and autoimmunity with a high-fat diet supports a shared mechanism for type 1 (T1D) and type 2 (T2D) diabetes. In this model, the protein secretion system of insulin-producing pancreatic beta cells is stressed, leading to increased beta cell apoptosis and diabetes via reduced levels of the transcription factor GLIS3, a pathogenic pathway that can be mimicked by a high-fat diet.
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Affiliation(s)
- John A Todd
- JDRF/Wellcome Trust Diabetes and Inflammation Laboratory, Department of Medical Genetics, NIHR Cambridge Biomedical Research Centre, Cambridge Institute for Medical Research, University of Cambridge, Addenbrookes Hospital, Cambridge, UK
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104
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Qian WJ, Cheng QH. Endoplasmic reticulum stress-mediated apoptosis signal pathway is involved in sepsis-induced liver injury. INTERNATIONAL JOURNAL OF CLINICAL AND EXPERIMENTAL PATHOLOGY 2017; 10:9990-9997. [PMID: 31966888 PMCID: PMC6965985] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Accepted: 08/29/2017] [Indexed: 06/10/2023]
Abstract
Endoplasmic reticulum (ER) stress has been increasingly recognized to have an important role in various liver diseases. Sepsis-induced multi-organ failure remains to have a high mortality rate, and the liver plays a central pathophysiological role. This study aims to explore whether ER stress is involved in liver injury in septic rats. Sepsis was induced via cecal ligation and puncture (CLP). Rats were randomly divided into five groups as follows: sham, CLP 2 h, CLP 6 h, CLP 12 h, and CLP 24 h. They were monitored to record body weight (BW) and liver weight changes for every time point after surgery. The levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were detected via colorimetric activity assays. In addition, the morphological changes of the liver tissue were evaluated by staining the sections with hematoxylin and eosin and observing under light microscopy. The levels of glucose-regulated protein 78 (GRP78), CCAAT/enhancer-binding protein homologous protein (CHOP), and cleaved caspase-12 were detected via Western blot analysis. Apoptosis was detected via terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) method. The results showed that septic rat serums ALT and AST were increased, with the increase being more obvious in the CLP 24 h group. In addition, septic rats appeared to have histopathological abnormalities in the liver. The liver weight and index increased after CLP. No differences were noted in the BW between septic groups. The level of GRP78, CHOP, and cleaved caspase-12 were upregulated after CLP. However, CHOP and caspase-12 were induced later than GRP78. The density of TUNEL-positive apoptotic hepatocytes was significantly increased after 12 h and 24 h CLP. It indicates that the unfolded protein response occurred in the early stage of sepsis-induced liver damage. The ER stress-mediated apoptosis signal pathway is among the mechanisms of septic liver injury and may be a target in clinical prevention and therapy of sepsis-induced liver injury.
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Affiliation(s)
- Wen-Juan Qian
- Medical College of Shihezi UniversityShihezi, Xinjiang, China
| | - Qing-Hong Cheng
- Department of Critical Care Medicine, First Affiliated Hospital of The Medical College of Shihezi UniversityShihezi, Xinjiang, China
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105
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Boland BB, Rhodes CJ, Grimsby JS. The dynamic plasticity of insulin production in β-cells. Mol Metab 2017; 6:958-973. [PMID: 28951821 PMCID: PMC5605729 DOI: 10.1016/j.molmet.2017.04.010] [Citation(s) in RCA: 117] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Revised: 04/27/2017] [Accepted: 04/28/2017] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND Although the insulin-producing pancreatic β-cells are quite capable of adapting to both acute and chronic changes in metabolic demand, persistently high demand for insulin will ultimately lead to their progressive dysfunction and eventual loss. Recent and historical studies highlight the importance of 'resting' the β-cell as a means of preserving functional β-cell mass. SCOPE OF REVIEW We provide experimental evidence to highlight the remarkable plasticity for insulin production and secretion by the pancreatic β-cell alongside some clinical evidence that supports leveraging this unique ability to preserve β-cell function. MAJOR CONCLUSIONS Treatment strategies for type 2 diabetes mellitus (T2DM) targeted towards reducing the systemic metabolic burden, rather than demanding greater insulin production from an already beleaguered β-cell, should be emphasized to maintain endogenous insulin secretory function and delay the progression of T2DM.
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Key Words
- ATF6, Activating Transcription Factor 6
- CHOP, CCAAT/Enhancer-Binding Homologous Protein
- EPAC, Exchange Factor Directly Activated by cAMP
- EROβ1, ER-resident oxidoreductase β1
- GIP, Gastric Inhibitory Polypeptide
- GLP-1, Glucagon-like Peptide 1
- GLUT2, Glucose Transporter 2
- GSIS, Glucose Stimulated Insulin Secretion
- IREα, Inositol Requiring Enzyme α
- Insulin production
- NEFA, Non-esterified Fatty Acid
- PERK, Protein Kinase RNA-like Endoplasmic Reticulum Kinase
- PKA, Protein Kinase A
- PKC, Protein Kinase C
- PLC, Phospholipase C
- ROS, Reactive Oxygen Species
- SNAP-25, Soluble NSF Attachment Protein 25
- SNARE, Soluble NSF Attachment Protein Receptor
- STZ, Streptozotocin
- T2DM
- T2DM, Type 2 Diabetes Mellitus
- TRP, Transient Receptor Potential
- VAMP-2, Vehicle Associated Membrane Protein 2
- VDCC, Voltage Dependent Calcium Channel
- mTORC1, Mammalian Target of Rapamycin 1
- nH, Hill coefficient
- β-cell rest
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Affiliation(s)
- Brandon B. Boland
- MedImmune, Cardiovascular and Metabolic Disease Research, 1 MedImmune Way, Gaithersburg, MD 20878, USA
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106
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Meng XH, Chen B, Zhang JP. Intracellular Insulin and Impaired Autophagy in a Zebrafish model and a Cell Model of Type 2 diabetes. Int J Biol Sci 2017; 13:985-995. [PMID: 28924380 PMCID: PMC5599904 DOI: 10.7150/ijbs.19249] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Accepted: 05/13/2017] [Indexed: 12/16/2022] Open
Abstract
Type 2 diabetes mellitus is characterized by insulin resistance. However, the complete molecular mechanism remains unclear. In this study, zebrafish were fed a long-term high-fat diet to induce type 2 diabetes, which resulted in a higher body weight, body mass index, more lipid vacuoles in liver, increased insulin transcription level in liver, brain and muscle, and high fasting blood glucose in the high-fat diet zebrafish. Oppositely, the transcription levels of insulin substrate-2 and glucose transporter 2 were significantly decreased, indicating insulin signaling pathway and glucose transport impaired in the insulin-targeting tissues. Transcription of the autophagy-related genes, ATG3, ATG4B, ATG5, ATG7, ATG12, and FOXO3, were decreased but autophagy inhibitor gene m-TOR increased, and autophagy-flux was inhibited in liver of the high-fat diet zebrafish. Main of these changes were confirmed in palmitic acid-treated HepG2 cells. Further, in co-immunoprecipitation and subcellular co-localization experiments, the conjunction of preproinsulin with cargo-recognition protein p62 increased, but conjuncts of autophagosome with p62-cargo, lysosomes with p62-cargo, and autolysosomes decreased apparently. Interestingly, lysosomes, autolysosomes and conjuncts of p62-insulin localized at the periphery of palmitic acid-treated cells, the margination of lysosomes may mediate deactivation of proteases activity. These findings suggest that intracellular high-lipid may trigger defective autophagy, defective downstream signaling of insulin and accumulated intracellular preproinsulin, leading to dysregulation of cell homeostasis mechanism, which may be one of reasons involved in insulin-resistance in type 2 diabetes.
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Affiliation(s)
- Xiang-Hui Meng
- Laboratory of pharmacology, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Bo Chen
- Laboratory of pharmacology, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Jing-Pu Zhang
- Laboratory of pharmacology, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
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107
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Rodriguez-Calvo T, Zapardiel-Gonzalo J, Amirian N, Castillo E, Lajevardi Y, Krogvold L, Dahl-Jørgensen K, von Herrath MG. Increase in Pancreatic Proinsulin and Preservation of β-Cell Mass in Autoantibody-Positive Donors Prior to Type 1 Diabetes Onset. Diabetes 2017; 66:1334-1345. [PMID: 28137793 PMCID: PMC5399615 DOI: 10.2337/db16-1343] [Citation(s) in RCA: 78] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Accepted: 01/26/2017] [Indexed: 12/14/2022]
Abstract
Type 1 diabetes is characterized by the loss of insulin production caused by β-cell dysfunction and/or destruction. The hypothesis that β-cell loss occurs early during the prediabetic phase has recently been challenged. Here we show, for the first time in situ, that in pancreas sections from autoantibody-positive (Ab+) donors, insulin area and β-cell mass are maintained before disease onset and that production of proinsulin increases. This suggests that β-cell destruction occurs more precipitously than previously assumed. Indeed, the pancreatic proinsulin-to-insulin area ratio was also increased in these donors with prediabetes. Using high-resolution confocal microscopy, we found a high accumulation of vesicles containing proinsulin in β-cells from Ab+ donors, suggesting a defect in proinsulin conversion or an accumulation of immature vesicles caused by an increase in insulin demand and/or a dysfunction in vesicular trafficking. In addition, islets from Ab+ donors were larger and contained a higher number of β-cells per islet. Our data indicate that β-cell mass (and function) is maintained until shortly before diagnosis and declines rapidly at the time of clinical onset of disease. This suggests that secondary prevention before onset, when β-cell mass is still intact, could be a successful therapeutic strategy.
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Affiliation(s)
| | | | - Natalie Amirian
- Type 1 Diabetes Center, La Jolla Institute for Allergy and Immunology, La Jolla, CA
| | - Ericka Castillo
- Type 1 Diabetes Center, La Jolla Institute for Allergy and Immunology, La Jolla, CA
| | - Yasaman Lajevardi
- Type 1 Diabetes Center, La Jolla Institute for Allergy and Immunology, La Jolla, CA
| | - Lars Krogvold
- Division of Paediatric and Adolescent Medicine, Oslo University Hospital, and Faculty of Medicine, University of Oslo, Oslo, Norway
| | - Knut Dahl-Jørgensen
- Division of Paediatric and Adolescent Medicine, Oslo University Hospital, and Faculty of Medicine, University of Oslo, Oslo, Norway
| | - Matthias G von Herrath
- Type 1 Diabetes Center, La Jolla Institute for Allergy and Immunology, La Jolla, CA
- Novo Nordisk Diabetes Research & Development Center, Seattle, WA
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108
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Aivazidis S, Coughlan CM, Rauniyar AK, Jiang H, Liggett LA, Maclean KN, Roede JR. The burden of trisomy 21 disrupts the proteostasis network in Down syndrome. PLoS One 2017; 12:e0176307. [PMID: 28430800 PMCID: PMC5400264 DOI: 10.1371/journal.pone.0176307] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2017] [Accepted: 04/07/2017] [Indexed: 12/27/2022] Open
Abstract
Down syndrome (DS) is a genetic disorder caused by trisomy of chromosome 21. Abnormalities in chromosome number have the potential to lead to disruption of the proteostasis network (PN) and accumulation of misfolded proteins. DS individuals suffer from several comorbidities, and we hypothesized that disruption of proteostasis could contribute to the observed pathology and decreased cell viability in DS. Our results confirm the presence of a disrupted PN in DS, as several of its elements, including the unfolded protein response, chaperone system, and proteasomal degradation exhibited significant alterations compared to euploid controls in both cell and mouse models. Additionally, when cell models were treated with compounds that promote disrupted proteostasis, we observed diminished levels of cell viability in DS compared to controls. Collectively our findings provide a cellular-level characterization of PN dysfunction in DS and an improved understanding of the potential pathogenic mechanisms contributing to disrupted cellular physiology in DS. Lastly, this study highlights the future potential of designing therapeutic strategies that mitigate protein quality control dysfunction.
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Affiliation(s)
- Stefanos Aivazidis
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado, Aurora, CO, United States of America
| | - Christina M. Coughlan
- Department of Neurology, University of Colorado School of Medicine, Aurora, CO, United States of America
- The Linda Crnic Institute for Down Syndrome, University of Colorado, Aurora, CO, United States of America
| | - Abhishek K. Rauniyar
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado, Aurora, CO, United States of America
| | - Hua Jiang
- The Linda Crnic Institute for Down Syndrome, University of Colorado, Aurora, CO, United States of America
- Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO, United States of America
| | - L. Alexander Liggett
- The Linda Crnic Institute for Down Syndrome, University of Colorado, Aurora, CO, United States of America
- Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO, United States of America
| | - Kenneth N. Maclean
- The Linda Crnic Institute for Down Syndrome, University of Colorado, Aurora, CO, United States of America
- Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO, United States of America
| | - James R. Roede
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado, Aurora, CO, United States of America
- * E-mail:
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109
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Dickerson MT, Vierra NC, Milian SC, Dadi PK, Jacobson DA. Osteopontin activates the diabetes-associated potassium channel TALK-1 in pancreatic β-cells. PLoS One 2017; 12:e0175069. [PMID: 28403169 PMCID: PMC5389796 DOI: 10.1371/journal.pone.0175069] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Accepted: 03/20/2017] [Indexed: 12/17/2022] Open
Abstract
Glucose-stimulated insulin secretion (GSIS) relies on β-cell Ca2+ influx, which is modulated by the two-pore-domain K+ (K2P) channel, TALK-1. A gain-of-function polymorphism in KCNK16, the gene encoding TALK-1, increases risk for developing type-2 diabetes. While TALK-1 serves an important role in modulating GSIS, the regulatory mechanism(s) that control β-cell TALK-1 channels are unknown. Therefore, we employed a membrane-specific yeast two-hybrid (MYTH) assay to identify TALK-1-interacting proteins in human islets, which will assist in determining signaling modalities that modulate TALK-1 function. Twenty-one proteins from a human islet cDNA library interacted with TALK-1. Some of these interactions increased TALK-1 activity, including intracellular osteopontin (iOPN). Intracellular OPN is highly expressed in β-cells and is upregulated under pre-diabetic conditions to help maintain normal β-cell function; however, the functional role of iOPN in β-cells is poorly understood. We found that iOPN colocalized with TALK-1 in pancreatic sections and coimmunoprecipitated with human islet TALK-1 channels. As human β-cells express two K+ channel-forming variants of TALK-1, regulation of these TALK-1 variants by iOPN was assessed. At physiological voltages iOPN activated TALK-1 transcript variant 3 channels but not TALK-1 transcript variant 2 channels. Activation of TALK-1 channels by iOPN also hyperpolarized resting membrane potential (Vm) in HEK293 cells and in primary mouse β-cells. Intracellular OPN was also knocked down in β-cells to test its effect on β-cell TALK-1 channel activity. Reducing β-cell iOPN significantly decreased TALK-1 K+ currents and increased glucose-stimulated Ca2+ influx. Importantly, iOPN did not affect the function of other K2P channels or alter Ca2+ influx into TALK-1 deficient β-cells. These results reveal the first protein interactions with the TALK-1 channel and found that an interaction with iOPN increased β-cell TALK-1 K+ currents. The TALK-1/iOPN complex caused Vm hyperpolarization and reduced β-cell glucose-stimulated Ca2+ influx, which is predicted to inhibit GSIS.
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Affiliation(s)
- Matthew T. Dickerson
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Nicholas C. Vierra
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Sarah C. Milian
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Prasanna K. Dadi
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States of America
| | - David A. Jacobson
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States of America
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110
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Sato H, Shiba Y, Tsuchiya Y, Saito M, Kohno K. 4μ8C Inhibits Insulin Secretion Independent of IRE1α RNase Activity. Cell Struct Funct 2017; 42:61-70. [PMID: 28321016 DOI: 10.1247/csf.17002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
IRE1α plays an important role in the unfolded protein response (UPR), which is activated by the accumulation of unfolded proteins in the endoplasmic reticulum. 4μ8C, a well-known inhibitor of IRE1α RNase activity, is commonly used to analyze IRE1α function during ER stress in cultured mammalian cells. However, the off-target effects of 4μ8C remain elusive. Pancreatic β-cells synthesize a large amount of insulin in response to high glucose stimulation, and IRE1α plays an important role in insulin secretion from pancreatic β-cells. Here, to analyze the role of IRE1α in pancreatic β-cells, we examined insulin secretion after 4μ8C treatment. Although 4μ8C inhibited insulin secretion within 2 hr, neither insulin synthesis nor maturation was inhibited by 4μ8C under the same conditions. This result prompted us to examine the precise effects of 4μ8C on insulin secretion in pancreatic β-cells. Unexpectedly, with just 5 min of treatment, 4μ8C blocked insulin secretion in cultured pancreatic β-cells as well as in pancreatic islets. Furthermore, insulin secretion was prevented by 4μ8C, even in pancreatic β-cells lacking the IRE1α RNase domain, suggesting that 4μ8C blocked the late stage of the insulin secretory process, independent of the IRE1α-XBP1 pathway. Our results indicate that 4μ8C has an off-target effect on insulin secretion in pancreatic β-cells. These findings inform the researchers in the field that the use of 4μ8C requires the special consideration for the future studies.Key words: 4μ8C, XBP1, insulin, IRE1α, pancreatic β-cells.
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Affiliation(s)
- Hitomi Sato
- Laboratory of Molecular and Cell Genetics, Graduate School of Biological Sciences, Nara Institute of Science and Technology
| | - Yoko Shiba
- Laboratory of Molecular and Cell Genetics, Graduate School of Biological Sciences, Nara Institute of Science and Technology.,Faculty of Science and Engineering, Iwate University
| | - Yuichi Tsuchiya
- Laboratory of Molecular and Cell Genetics, Graduate School of Biological Sciences, Nara Institute of Science and Technology
| | - Michiko Saito
- Laboratory of Molecular and Cell Genetics, Graduate School of Biological Sciences, Nara Institute of Science and Technology
| | - Kenji Kohno
- Laboratory of Molecular and Cell Genetics, Graduate School of Biological Sciences, Nara Institute of Science and Technology
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111
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Lombardi A, Tomer Y. Interferon alpha impairs insulin production in human beta cells via endoplasmic reticulum stress. J Autoimmun 2017; 80:48-55. [PMID: 28238527 DOI: 10.1016/j.jaut.2017.02.002] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2016] [Revised: 02/02/2017] [Accepted: 02/07/2017] [Indexed: 02/06/2023]
Abstract
Despite substantial advances in the research exploring the pathogenesis of Type 1 Diabetes (T1D), the pathophysiological mechanisms involved remain unknown. We hypothesized in this study that interferon alpha (IFNα) participates in the early stages of T1D development by triggering endoplasmic reticulum (ER) stress. To verify our hypothesis, human islets and human EndoC-βH1 cells were exposed to IFNα and tested for ER stress markers, glucose stimulated insulin secretion (GSIS) and insulin content. IFNα treatment induced upregulation of ER stress markers including Binding immunoglobulin Protein, phospho-eukaryotic translation initiation factor 2α, spliced- X-box binding protein-1, C/EBP homologous protein and activating transcription factor 4. Intriguingly, IFNα treatment did not impair GSIS but significantly decreased insulin production in both human islets and EndoC-βH1 cells. Furthermore, IFNα decreased the expression of both proinsulin convertase 1 and proinsulin convertase 2, suggesting an altered functional state of the beta cells characterized by a slower proinsulin-insulin conversion. Pretreatment of both human islets and EndoC-βH1 cells with chemical chaperones 4-phenylbutyric acid and tauroursodeoxycholic acid completely prevented IFNα effects, indicating an ER stress-mediated impairment of insulin production. We demonstrated for the first time that IFNα elicits ER stress in human beta cells providing a novel mechanistic role for this virus-induced cytokine in the development of T1D. Compounds targeting molecular processes altered in ER-stressed beta cells could represent a potential therapeutic strategy to prevent IFNα-induced beta cell dysfunction in the early onset of T1D.
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Affiliation(s)
- Angela Lombardi
- Department of Medicine, Albert Einstein College of Medicine, Bronx, NY, USA.
| | - Yaron Tomer
- Department of Medicine, Albert Einstein College of Medicine, Bronx, NY, USA.
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112
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Ariyasu D, Yoshida H, Hasegawa Y. Endoplasmic Reticulum (ER) Stress and Endocrine Disorders. Int J Mol Sci 2017; 18:ijms18020382. [PMID: 28208663 PMCID: PMC5343917 DOI: 10.3390/ijms18020382] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Revised: 01/24/2017] [Accepted: 02/03/2017] [Indexed: 12/15/2022] Open
Abstract
The endoplasmic reticulum (ER) is the organelle where secretory and membrane proteins are synthesized and folded. Unfolded proteins that are retained within the ER can cause ER stress. Eukaryotic cells have a defense system called the “unfolded protein response” (UPR), which protects cells from ER stress. Cells undergo apoptosis when ER stress exceeds the capacity of the UPR, which has been revealed to cause human diseases. Although neurodegenerative diseases are well-known ER stress-related diseases, it has been discovered that endocrine diseases are also related to ER stress. In this review, we focus on ER stress-related human endocrine disorders. In addition to diabetes mellitus, which is well characterized, several relatively rare genetic disorders such as familial neurohypophyseal diabetes insipidus (FNDI), Wolfram syndrome, and isolated growth hormone deficiency type II (IGHD2) are discussed in this article.
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Affiliation(s)
- Daisuke Ariyasu
- Division of Developmental Genetics, Institute of Resource Development and Analysis, Kumamoto University, Kumamoto 860-0811, Japan.
| | - Hiderou Yoshida
- Department of Biochemistry and Molecular Biology, Graduate School of Life Science, University of Hyogo, Hyogo 678-1297, Japan.
| | - Yukihiro Hasegawa
- Division of Endocrinology and Metabolism, Tokyo Metropolitan Children's Medical Center, Tokyo 183-8561, Japan.
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113
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Abstract
Prediabetes, defined by blood glucose levels between normal and diabetic levels, is increasing rapidly worldwide. This abnormal physiologic state reflects the rapidly changing access to high-calorie food and decreasing levels of physical activity occurring worldwide, with resultant obesity and metabolic consequences. This is particularly marked in developing countries. Prediabetes poses several threats; there is increased risk of developing type 2 diabetes mellitus (T2DM), and there are risks inherent to the prediabetes state, including microvascular and macrovascular disease. Studies have helped to elucidate the underlying pathophysiology of prediabetes and to establish the potential for treating prediabetes and preventing T2DM.
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Affiliation(s)
- Catherine M Edwards
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Florida College of Medicine, 1600 Southwest Archer Road, Gainesville, FL 32610, USA.
| | - Kenneth Cusi
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Florida College of Medicine, 1600 Southwest Archer Road, Gainesville, FL 32610, USA; Division of Endocrinology, Diabetes and Metabolism, Malcom Randall Veterans Affairs Medical Center, 1601 South West Archer Road, Gainesville, FL 32608, USA
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114
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Harris JE. Cellular stress and innate inflammation in organ-specific autoimmunity: lessons learned from vitiligo. Immunol Rev 2016; 269:11-25. [PMID: 26683142 DOI: 10.1111/imr.12369] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
For decades, research in autoimmunity has focused primarily on immune contributions to disease. Yet recent studies report elevated levels of reactive oxygen species and abnormal activation of the unfolded protein response in cells targeted by autoimmunity, implicating cellular stress originating from the target tissue as a contributing factor. A better understanding of this contribution may help to answer important lingering questions in organ-specific autoimmunity, as to what factors initiate disease and what directs its tissue specificity. Vitiligo, an autoimmune disease of the skin, has been the focus of translational research for over 30 years, and both melanocyte stress and immune mechanisms have been thought to be mutually exclusive explanations for pathogenesis. Chemical-induced vitiligo is a unique clinical presentation that reflects the importance of environmental influences on autoimmunity, provides insight into a new paradigm linking cell stress to the immune response, and serves as a template for other autoimmune diseases. In this review, I will discuss the evidence for cell stress contributions to a number of autoimmune diseases, the questions that remain, and how vitiligo, an underappreciated example of organ-specific autoimmunity, helps to answer them.
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Affiliation(s)
- John E Harris
- Department of Medicine, Division of Dermatology, University of Massachusetts Medical School, Worcester, MA, USA
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115
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Meyerovich K, Ortis F, Allagnat F, Cardozo AK. Endoplasmic reticulum stress and the unfolded protein response in pancreatic islet inflammation. J Mol Endocrinol 2016; 57:R1-R17. [PMID: 27067637 DOI: 10.1530/jme-15-0306] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2016] [Accepted: 04/11/2016] [Indexed: 12/13/2022]
Abstract
Insulin-secreting pancreatic β-cells are extremely dependent on their endoplasmic reticulum (ER) to cope with the oscillatory requirement of secreted insulin to maintain normoglycemia. Insulin translation and folding rely greatly on the unfolded protein response (UPR), an array of three main signaling pathways designed to maintain ER homeostasis and limit ER stress. However, prolonged or excessive UPR activation triggers alternative molecular pathways that can lead to β-cell dysfunction and apoptosis. An increasing number of studies suggest a role of these pro-apoptotic UPR pathways in the downfall of β-cells observed in diabetic patients. Particularly, the past few years highlighted a cross talk between the UPR and inflammation in the context of both type 1 (T1D) and type 2 diabetes (T2D). In this article, we describe the recent advances in research regarding the interplay between ER stress, the UPR, and inflammation in the context of β-cell apoptosis leading to diabetes.
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Affiliation(s)
- Kira Meyerovich
- ULB Center for Diabetes ResearchUniversité Libre de Bruxelles (ULB), Brussels, Belgium
| | - Fernanda Ortis
- Department of Cell and Developmental BiologyUniversidade de São Paulo, São Paulo, Brazil
| | - Florent Allagnat
- Department of Vascular SurgeryCentre Hospitalier Universitaire Vaudois (CHUV), Lausanne, Switzerland
| | - Alessandra K Cardozo
- ULB Center for Diabetes ResearchUniversité Libre de Bruxelles (ULB), Brussels, Belgium
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116
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Haataja L, Manickam N, Soliman A, Tsai B, Liu M, Arvan P. Disulfide Mispairing During Proinsulin Folding in the Endoplasmic Reticulum. Diabetes 2016; 65:1050-60. [PMID: 26822090 PMCID: PMC4806660 DOI: 10.2337/db15-1345] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2015] [Accepted: 01/14/2016] [Indexed: 02/06/2023]
Abstract
Proinsulin folding within the endoplasmic reticulum (ER) remains incompletely understood, but it is clear that in mutant INS gene-induced diabetes of youth (MIDY), progression of the (three) native disulfide bonds of proinsulin becomes derailed, causing insulin deficiency, β-cell ER stress, and onset of diabetes. Herein, we have undertaken a molecular dissection of proinsulin disulfide bond formation, using bioengineered proinsulins that can form only two (or even only one) of the native proinsulin disulfide bonds. In the absence of preexisting proinsulin disulfide pairing, Cys(B19)-Cys(A20) (a major determinant of ER stress response activation and proinsulin stability) preferentially initiates B-A chain disulfide bond formation, whereas Cys(B7)-Cys(A7) can initiate only under oxidizing conditions beyond that existing within the ER of β-cells. Interestingly, formation of these two "interchain" disulfide bonds demonstrates cooperativity, and together, they are sufficient to confer intracellular transport competence to proinsulin. The three most common proinsulin disulfide mispairings in the ER appear to involve Cys(A11)-Cys(A20), Cys(A7)-Cys(A20), and Cys(B19)-Cys(A11), each disrupting the critical Cys(B19)-Cys(A20) pairing. MIDY mutations inhibit Cys(B19)-Cys(A20) formation, but treatment to force oxidation of this disulfide bond improves folding and results in a small but detectable increase of proinsulin export. These data suggest possible therapeutic avenues to ameliorate ER stress and diabetes.
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Affiliation(s)
- Leena Haataja
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical Center, Ann Arbor, MI
| | - Nandini Manickam
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical Center, Ann Arbor, MI
| | - Ann Soliman
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical Center, Ann Arbor, MI
| | - Billy Tsai
- Department of Cell & Developmental Biology, University of Michigan Medical Center, Ann Arbor, MI
| | - Ming Liu
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical Center, Ann Arbor, MI Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
| | - Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical Center, Ann Arbor, MI
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117
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Hasnain SZ, Prins JB, McGuckin MA. Oxidative and endoplasmic reticulum stress in β-cell dysfunction in diabetes. J Mol Endocrinol 2016; 56:R33-54. [PMID: 26576641 DOI: 10.1530/jme-15-0232] [Citation(s) in RCA: 179] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 11/17/2015] [Indexed: 12/12/2022]
Abstract
The inability of pancreatic β-cells to make sufficient insulin to control blood sugar is a central feature of the aetiology of most forms of diabetes. In this review we focus on the deleterious effects of oxidative stress and endoplasmic reticulum (ER) stress on β-cell insulin biosynthesis and secretion and on inflammatory signalling and apoptosis with a particular emphasis on type 2 diabetes (T2D). We argue that oxidative stress and ER stress are closely entwined phenomena fundamentally involved in β-cell dysfunction by direct effects on insulin biosynthesis and due to consequences of the ER stress-induced unfolded protein response. We summarise evidence that, although these phenomenon can be driven by intrinsic β-cell defects in rare forms of diabetes, in T2D β-cell stress is driven by a range of local environmental factors including increased drivers of insulin biosynthesis, glucolipotoxicity and inflammatory cytokines. We describe our recent findings that a range of inflammatory cytokines contribute to β-cell stress in diabetes and our discovery that interleukin 22 protects β-cells from oxidative stress regardless of the environmental triggers and can correct much of diabetes pathophysiology in animal models. Finally we summarise evidence that β-cell dysfunction is reversible in T2D and discuss therapeutic opportunities for relieving oxidative and ER stress and restoring glycaemic control.
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Affiliation(s)
- Sumaira Z Hasnain
- ImmunityInfection and Inflammation Program, Mater Research Institute, Translational Research Institute, University of Queensland, 37 Kent Street, Woolloongabba, Brisbane, Queensland 4102, AustraliaMetabolic Diseases ProgramMater Research Institute, The University of Queensland, Translational Research Institute, 37 Kent Street, Woolloongabba, Brisbane, Queensland 4102, Australia
| | - Johannes B Prins
- ImmunityInfection and Inflammation Program, Mater Research Institute, Translational Research Institute, University of Queensland, 37 Kent Street, Woolloongabba, Brisbane, Queensland 4102, AustraliaMetabolic Diseases ProgramMater Research Institute, The University of Queensland, Translational Research Institute, 37 Kent Street, Woolloongabba, Brisbane, Queensland 4102, Australia
| | - Michael A McGuckin
- ImmunityInfection and Inflammation Program, Mater Research Institute, Translational Research Institute, University of Queensland, 37 Kent Street, Woolloongabba, Brisbane, Queensland 4102, AustraliaMetabolic Diseases ProgramMater Research Institute, The University of Queensland, Translational Research Institute, 37 Kent Street, Woolloongabba, Brisbane, Queensland 4102, Australia
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118
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Vannuvel K, Van Steenbrugge M, Demazy C, Ninane N, Fattaccioli A, Fransolet M, Renard P, Raes M, Arnould T. Effects of a Sublethal and Transient Stress of the Endoplasmic Reticulum on the Mitochondrial Population. J Cell Physiol 2016; 231:1913-31. [PMID: 26680008 DOI: 10.1002/jcp.25292] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Accepted: 12/15/2015] [Indexed: 12/12/2022]
Abstract
Endoplasmic reticulum (ER) and mitochondria are not discrete intracellular organelles but establish close physical and functional interactions involved in several biological processes including mitochondrial bioenergetics, calcium homeostasis, lipid synthesis, and the regulation of apoptotic cell death pathways. As many cell types might face a transient and sublethal ER stress during their lifetime, it is thus likely that the adaptive UPR response might affect the mitochondrial population. The aim of this work was to study the putative effects of a non-lethal and transient endoplasmic reticulum stress on the mitochondrial population in HepG2 cells. The results show that thapsigargin and brefeldin A, used to induce a transient and sublethal ER stress, rapidly lead to the fragmentation of the mitochondrial network associated with a decrease in mitochondrial membrane potential, O2 (•-) production and less efficient respiration. These changes in mitochondrial function are transient and preceded by the phosphorylation of JNK. Inhibition of JNK activation by SP600125 prevents the decrease in O2 (•-) production and the mitochondrial network fragmentation observed in cells exposed to the ER stress but has no impact on the reduction of the mitochondrial membrane potential. In conclusion, our data show that a non-lethal and transient ER stress triggers a rapid activation of JNK without inducing apoptosis, leading to the fragmentation of the mitochondrial network and a reduction of O2 (•-) production. J. Cell. Physiol. 231: 1913-1931, 2016. © 2015 Wiley Periodicals, Inc.
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Affiliation(s)
- Kayleen Vannuvel
- Laboratory of Biochemistry and Cell Biology (URBC), Namur Research Institute for Life Sciences (NARILIS), University of Namur (UNamur), Namur, Belgium
| | - Martine Van Steenbrugge
- Laboratory of Biochemistry and Cell Biology (URBC), Namur Research Institute for Life Sciences (NARILIS), University of Namur (UNamur), Namur, Belgium
| | - Catherine Demazy
- Laboratory of Biochemistry and Cell Biology (URBC), Namur Research Institute for Life Sciences (NARILIS), University of Namur (UNamur), Namur, Belgium
| | - Noëlle Ninane
- Laboratory of Biochemistry and Cell Biology (URBC), Namur Research Institute for Life Sciences (NARILIS), University of Namur (UNamur), Namur, Belgium
| | - Antoine Fattaccioli
- Laboratory of Biochemistry and Cell Biology (URBC), Namur Research Institute for Life Sciences (NARILIS), University of Namur (UNamur), Namur, Belgium
| | - Maude Fransolet
- Laboratory of Biochemistry and Cell Biology (URBC), Namur Research Institute for Life Sciences (NARILIS), University of Namur (UNamur), Namur, Belgium
| | - Patricia Renard
- Laboratory of Biochemistry and Cell Biology (URBC), Namur Research Institute for Life Sciences (NARILIS), University of Namur (UNamur), Namur, Belgium
| | - Martine Raes
- Laboratory of Biochemistry and Cell Biology (URBC), Namur Research Institute for Life Sciences (NARILIS), University of Namur (UNamur), Namur, Belgium
| | - Thierry Arnould
- Laboratory of Biochemistry and Cell Biology (URBC), Namur Research Institute for Life Sciences (NARILIS), University of Namur (UNamur), Namur, Belgium
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119
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120
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Sala G, Badalamenti S, Ponticelli C. The Renal Connexome and Possible Roles of Connexins in Kidney Diseases. Am J Kidney Dis 2015; 67:677-87. [PMID: 26613807 DOI: 10.1053/j.ajkd.2015.09.030] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Accepted: 09/30/2015] [Indexed: 12/21/2022]
Abstract
Connexins are membrane-spanning proteins that allow for the formation of cell-to-cell channels and cell-to-extracellular space hemichannels. Many connexin subtypes are expressed in kidney cells. Some mutations in connexin genes have been linked to various human pathologies, including cardiovascular, neurodegenerative, lung, and skin diseases, but the exact role of connexins in kidney disease remains unclear. Some hypotheses about a connection between genetic mutations, endoplasmic reticulum (ER) stress, and the unfolded protein response (UPR) in kidney pathology have been explored. The potential relationship of kidney disease to abnormal production of connexin proteins, mutations in their genes together with ER stress, or the UPR is still a matter of debate. In this scenario, it is tantalizing to speculate about a possible role of connexins in the setting of kidney pathologies that are thought to be caused by a deregulated podocyte protein expression, the so-called podocytopathies. In this article, we give examples of the roles of connexins in kidney (patho)physiology and propose avenues for further research concerning connexins, ER stress, and UPR in podocytopathies that may ultimately help refine drug treatment.
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Affiliation(s)
- Gabriele Sala
- Nephrology and Dialysis Unit, Humanitas Clinical Research Center, Rozzano (Milano), Italy.
| | - Salvatore Badalamenti
- Nephrology and Dialysis Unit, Humanitas Clinical Research Center, Rozzano (Milano), Italy
| | - Claudio Ponticelli
- Nephrology and Dialysis Unit, Humanitas Clinical Research Center, Rozzano (Milano), Italy
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121
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Cui J, Chen W, Sun J, Guo H, Madley R, Xiong Y, Pan X, Wang H, Tai AW, Weiss MA, Arvan P, Liu M. Competitive Inhibition of the Endoplasmic Reticulum Signal Peptidase by Non-cleavable Mutant Preprotein Cargos. J Biol Chem 2015; 290:28131-28140. [PMID: 26446786 DOI: 10.1074/jbc.m115.692350] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Indexed: 12/30/2022] Open
Abstract
Upon translocation across the endoplasmic reticulum (ER) membrane, secretory proteins are proteolytically processed to remove their signal peptide by signal peptidase (SPase). This process is critical for subsequent folding, intracellular trafficking, and maturation of secretory proteins. Prokaryotic SPase has been shown to be a promising antibiotic target. In contrast, to date, no eukaryotic SPase inhibitors have been reported. Here we report that introducing a proline immediately following the natural signal peptide cleavage site not only blocks preprotein cleavage but also, in trans, impairs the processing and maturation of co-expressed preproteins in the ER. Specifically, we find that a variant preproinsulin, pPI-F25P, is translocated across the ER membrane, where it binds to the catalytic SPase subunit SEC11A, inhibiting SPase activity in a dose-dependent manner. Similar findings were obtained with an analogous variant of preproparathyroid hormone, demonstrating that inhibition of the SPase does not depend strictly on the sequence or structure of the downstream mature protein. We further show that inhibiting SPase in the ER impairs intracellular processing of viral polypeptides and their subsequent maturation. These observations suggest that eukaryotic SPases (including the human ortholog) are, in principle, suitable therapeutic targets for antiviral drug design.
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Affiliation(s)
- Jingqiu Cui
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin 300052, China,; Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105
| | - Wei Chen
- Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105,; Beijing Institute of Pharmacology and Toxicology, Beijing 100850, China
| | - Jinhong Sun
- Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105
| | - Huan Guo
- Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105
| | - Rachel Madley
- Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105
| | - Yi Xiong
- Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105
| | - Xingyi Pan
- Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105
| | - Hongliang Wang
- Division of Gastroenterology, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan 48109
| | - Andrew W Tai
- Division of Gastroenterology, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan 48109
| | - Michael A Weiss
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106.
| | - Peter Arvan
- Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105
| | - Ming Liu
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin 300052, China,; Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105
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122
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Khadra A, Schnell S. Development, growth and maintenance of β-cell mass: models are also part of the story. Mol Aspects Med 2015; 42:78-90. [PMID: 25720614 DOI: 10.1016/j.mam.2015.01.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Revised: 01/26/2015] [Accepted: 01/26/2015] [Indexed: 01/09/2023]
Abstract
Pancreatic β-cells in the islets of Langerhans play a crucial role in regulating glucose homeostasis in the circulation. Loss of β-cell mass or function due to environmental, genetic and immunological factors leads to the manifestation of diabetes mellitus. The mechanisms regulating the dynamics of pancreatic β-cell mass during normal development and diabetes progression are complex. To fully unravel such complexity, experimental and clinical approaches need to be combined with mathematical and computational models. In the natural sciences, mathematical and computational models have aided the identification of key mechanisms underlying the behavior of systems comprising multiple interacting components. A number of mathematical and computational models have been proposed to explain the development, growth and death of pancreatic β-cells. In this review, we discuss some of these models and how their predictions provide novel insight into the mechanisms controlling β-cell mass during normal development and diabetes progression. Lastly, we discuss a handful of the major open questions in the field.
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Affiliation(s)
- Anmar Khadra
- Department of Physiology, McGill University, McIntyre Medical Building, 3655 Promenade Sir William Osler, Montreal, Quebec H3G 1Y6, Canada
| | - Santiago Schnell
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan 48105, USA; Department of Computational Medicine & Bioinformatics, University of Michigan Medical School, Ann Arbor, Michigan 48105, USA; Brehm Center for Diabetes Research, University of Michigan Medical School, Ann Arbor, Michigan 48105, USA.
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