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Kettel P, Marosits L, Spinetti E, Rechberger M, Giannini C, Radler P, Niedermoser I, Fischer I, Versteeg GA, Loose M, Covino R, Karagöz GE. Disordered regions in the IRE1α ER lumenal domain mediate its stress-induced clustering. EMBO J 2024:10.1038/s44318-024-00207-0. [PMID: 39232130 DOI: 10.1038/s44318-024-00207-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 07/02/2024] [Accepted: 07/23/2024] [Indexed: 09/06/2024] Open
Abstract
Conserved signaling cascades monitor protein-folding homeostasis to ensure proper cellular function. One of the evolutionary conserved key players is IRE1, which maintains endoplasmic reticulum (ER) homeostasis through the unfolded protein response (UPR). Upon accumulation of misfolded proteins in the ER, IRE1 forms clusters on the ER membrane to initiate UPR signaling. What regulates IRE1 cluster formation is not fully understood. Here, we show that the ER lumenal domain (LD) of human IRE1α forms biomolecular condensates in vitro. IRE1α LD condensates were stabilized both by binding to unfolded polypeptides as well as by tethering to model membranes, suggesting their role in assembling IRE1α into signaling-competent stable clusters. Molecular dynamics simulations indicated that weak multivalent interactions drive IRE1α LD clustering. Mutagenesis experiments identified disordered regions in IRE1α LD to control its clustering in vitro and in cells. Importantly, dysregulated clustering of IRE1α mutants led to defects in IRE1α signaling. Our results revealed that disordered regions in IRE1α LD control its clustering and suggest their role as a common strategy in regulating protein assembly on membranes.
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Affiliation(s)
- Paulina Kettel
- Max Perutz Laboratories Vienna, Vienna BioCenter, Vienna, Austria
- Vienna BioCenter PhD Program, Doctoral School of the University of Vienna and Medical University of Vienna, Vienna, Austria
| | - Laura Marosits
- Max Perutz Laboratories Vienna, Vienna BioCenter, Vienna, Austria
- Medical University of Vienna, Vienna, Austria
| | - Elena Spinetti
- Frankfurt Institute for Advanced Studies, Frankfurt, Germany
- Institute of Biophysics, Goethe University, Frankfurt, Germany
| | | | - Caterina Giannini
- Institute of Science and Technology Austria, Klosterneuburg, Austria
| | - Philipp Radler
- Institute of Science and Technology Austria, Klosterneuburg, Austria
| | - Isabell Niedermoser
- Max Perutz Laboratories Vienna, Vienna BioCenter, Vienna, Austria
- Medical University of Vienna, Vienna, Austria
| | - Irmgard Fischer
- Max Perutz Laboratories Vienna, Vienna BioCenter, Vienna, Austria
| | - Gijs A Versteeg
- Max Perutz Laboratories Vienna, Vienna BioCenter, Vienna, Austria
- Department of Microbiology, Immunobiology and Genetics, University of Vienna, Vienna, Austria
| | - Martin Loose
- Institute of Science and Technology Austria, Klosterneuburg, Austria
| | - Roberto Covino
- Frankfurt Institute for Advanced Studies, Frankfurt, Germany
- IMPRS on Cellular Biophysics, Frankfurt, Germany
| | - G Elif Karagöz
- Max Perutz Laboratories Vienna, Vienna BioCenter, Vienna, Austria.
- Medical University of Vienna, Vienna, Austria.
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2
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Huang P, Zhu Y, Qin J. Research advances in understanding crosstalk between organs and pancreatic β-cell dysfunction. Diabetes Obes Metab 2024. [PMID: 39044309 DOI: 10.1111/dom.15787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2024] [Revised: 06/25/2024] [Accepted: 06/26/2024] [Indexed: 07/25/2024]
Abstract
Obesity has increased dramatically worldwide. Being overweight or obese can lead to various conditions, including dyslipidaemia, hypertension, glucose intolerance and metabolic syndrome (MetS), which may further lead to type 2 diabetes mellitus (T2DM). Previous studies have identified a link between β-cell dysfunction and the severity of MetS, with multiple organs and tissues affected. Identifying the associations between pancreatic β-cell dysfunction and organs is critical. Research has focused on the interaction between the liver, gut and pancreatic β-cells. However, the mechanisms and related core targets are still not perfectly elucidated. The aims of this review were to summarize the mechanisms of β-cell dysfunction and to explore the potential pathogenic pathways and targets that connect the liver, gut, adipose tissue, muscle, and brain to pancreatic β-cell dysfunction.
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Affiliation(s)
- Peng Huang
- Department of Traditional Chinese Medicine, The Seventh Affiliated Hospital, Sun Yat-sen University, Shenzhen, China
| | - Yunling Zhu
- Department of Traditional Chinese Medicine, The Seventh Affiliated Hospital, Sun Yat-sen University, Shenzhen, China
| | - Jian Qin
- Department of Traditional Chinese Medicine, The Seventh Affiliated Hospital, Sun Yat-sen University, Shenzhen, China
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3
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Das F, Ghosh-Choudhury N, Kasinath BS, Sharma K, Choudhury GG. High glucose-induced downregulation of PTEN-Long is sufficient for proximal tubular cell injury in diabetic kidney disease. Exp Cell Res 2024; 440:114116. [PMID: 38830568 DOI: 10.1016/j.yexcr.2024.114116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Revised: 04/24/2024] [Accepted: 05/31/2024] [Indexed: 06/05/2024]
Abstract
During the progression of diabetic kidney disease, proximal tubular epithelial cells respond to high glucose to induce hypertrophy and matrix expansion leading to renal fibrosis. Recently, a non-canonical PTEN has been shown to be translated from an upstream initiation codon CUG (leucine) to produce a longer protein called PTEN-Long (PTEN-L). Interestingly, the extended sequence present in PTEN-L contains cell secretion/penetration signal. Role of this non-canonical PTEN-L in diabetic renal tubular injury is not known. We show that high glucose decreases expression of PTEN-L. As a mechanism of its function, we find that reduced PTEN-L activates Akt-2, which phosphorylates and inactivate tuberin and PRAS40, resulting in activation of mTORC1 in tubular cells. Antibacterial agent acriflavine and antiviral agent ATA regulate translation from CUG codon. Acriflavine and ATA, respectively, decreased and increased expression of PTEN-L to altering Akt-2 and mTORC1 activation in the absence of change in expression of canonical PTEN. Consequently, acriflavine and ATA modulated high glucose-induced tubular cell hypertrophy and lamininγ1 expression. Importantly, expression of PTEN-L inhibited high glucose-stimulated Akt/mTORC1 activity to abrogate these processes. Since PTEN-L contains secretion/penetration signals, addition of conditioned medium containing PTEN-L blocked Akt-2/mTORC1 activity. Notably, in renal cortex of diabetic mice, we found reduced PTEN-L concomitant with Akt-2/mTORC1 activation, leading to renal hypertrophy and lamininγ1 expression. These results present first evidence for involvement of PTEN-L in diabetic kidney disease.
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Affiliation(s)
- Falguni Das
- VA Research, South Texas Veterans Health Care System, San Antonio, TX, USA; Department of Medicine, TX, USA
| | | | | | - Kumar Sharma
- VA Research, South Texas Veterans Health Care System, San Antonio, TX, USA; Department of Medicine, TX, USA
| | - Goutam Ghosh Choudhury
- VA Research, South Texas Veterans Health Care System, San Antonio, TX, USA; Department of Medicine, TX, USA; Geriatric Research, Education and Clinical Center, South Texas Veterans Health Care System, San Antonio, TX, USA.
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4
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MacDonald T, Ryback B, da Silva Pereira JA, Wei S, Mendez B, Cai E, Ishikawa Y, Weir G, Bonner-Weir S, Kissler S, Yi P. Renalase inhibition regulates β cell metabolism to defend against acute and chronic stress. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.11.598322. [PMID: 38915698 PMCID: PMC11195134 DOI: 10.1101/2024.06.11.598322] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/26/2024]
Abstract
Renalase (Rnls), annotated as an oxidase enzyme, is a GWAS gene associated with Type 1 Diabetes (T1D) risk. We previously discovered that Rnls inhibition delays diabetes onset in mouse models of T1D in vivo , and protects pancreatic β cells against autoimmune killing, ER and oxidative stress in vitro . The molecular biochemistry and functions of Rnls are entirely uncharted. Here we find that Rnls inhibition defends against loss of β cell mass and islet dysfunction in chronically stressed Akita mice in vivo . We used RNA sequencing, untargeted and targeted metabolomics and metabolic function experiments in mouse and human β cells and discovered a robust and conserved metabolic shift towards glycolysis, amino acid abundance and GSH synthesis to counter protein misfolding stress, in vitro . Our work illustrates a function for Rnls in mammalian cells, and suggests an axis by which manipulating intrinsic properties of β cells can rewire metabolism to protect against diabetogenic stress.
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Dhayalan B, Weiss MA. Diabetes-Associated Mutations in Proinsulin Provide a "Molecular Rheostat" of Nascent Foldability. Curr Diab Rep 2022; 22:85-94. [PMID: 35119630 DOI: 10.1007/s11892-022-01447-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 01/04/2022] [Indexed: 11/28/2022]
Abstract
PURPOSE OF REVIEW Diabetes mellitus (DM) due to toxic misfolding of proinsulin variants provides a monogenic model of endoplasmic reticulum (ER) stress. The mutant proinsulin syndrome (also designated MIDY; Mutant INS-gene-induced Diabetes of Youth or Maturity-onset diabetes of the young 10 (MODY10)) ordinarily presents as permanent neonatal-onset DM, but specific amino-acid substitutions may also present later in childhood or adolescence. This review highlights structural mechanisms of proinsulin folding as inferred from phenotype-genotype relationships. RECENT FINDINGS MIDY mutations most commonly add or remove a cysteine, leading to a variant polypeptide containing an odd number of thiol groups. Such variants are associated with aberrant intermolecular disulfide pairing, ER stress, and neonatal β-cell dysfunction. Non-cysteine-related (NCR) mutations (occurring in both the B and A domains of proinsulin) define distinct determinants of foldability and vary in severity. The range of ages of onset, therefore, reflects a "molecular rheostat" connecting protein biophysics to quality-control ER checkpoints. Because in most mammalian cell lines even wild-type proinsulin exhibits limited folding efficiency, molecular barriers to folding uncovered by NCR MIDY mutations may pertain to β-cell dysfunction in non-syndromic type 2 DM due to INS-gene overexpression in the face of peripheral insulin resistance. Recent studies of MIDY mutations and related NCR variants, combining molecular and cell-based approaches, suggest that proinsulin has evolved at the edge of non-foldability. Chemical protein synthesis promises to enable comparative studies of "non-foldable" proinsulin variants to define key steps in wild-type biosynthesis. Such studies may create opportunities for novel therapeutic approaches to non-syndromic type 2 DM.
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Affiliation(s)
- Balamurugan Dhayalan
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, 46202, USA
| | - Michael A Weiss
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, 46202, USA.
- Department of Chemistry, Indiana University, Bloomington, IN, 47405, USA.
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, 47907, USA.
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Amirruddin NS, Tan WX, Tan YS, Gardner DSL, Bee YM, Verma CS, Hoon S, Lee KO, Teo AKK. Progressive endoplasmic reticulum stress over time due to human insulin gene mutation contributes to pancreatic beta cell dysfunction. Diabetologia 2021; 64:2534-2549. [PMID: 34448879 DOI: 10.1007/s00125-021-05530-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Accepted: 05/14/2021] [Indexed: 10/20/2022]
Abstract
AIMS/HYPOTHESIS We studied the effects of heterozygous human INS gene mutations on insulin secretion, endoplasmic reticulum (ER) stress and other mechanisms in both MIN6 and human induced pluripotent stem cells (hiPSC)-derived beta-like cells, as well as the effects of prolonged overexpression of mutant human INS in MIN6 cells. METHODS We modelled the structure of mutant C109Y and G32V proinsulin computationally to examine the in silico effects. We then overexpressed either wild-type (WT), mutant (C109Y or G32V), or both WT and mutant human preproinsulin in MIN6 cells, both transiently and stably over several weeks. We measured the levels of human and rodent insulin secreted, and examined the transcript and protein levels of several ER stress and apoptotic markers. We also reprogrammed human donor fibroblasts heterozygous for the C109Y mutation into hiPSCs and differentiated these into pancreatic beta-like cells, which were subjected to single-cell RNA-sequencing and transcript and protein analyses for ER stress and apoptotic markers. RESULTS The computational modelling studies, and short-term and long-term expression studies in beta cells, revealed the presence of ER stress, organelle changes and insulin processing defects, resulting in a decreased amount of insulin secreted but not the ability to secrete insulin. By 9 weeks of expression of mutant human INS, dominant-negative effects of mutant INS were evident and beta cell insulin secretory capacity declined. INS+/C109Y patient-derived beta-like cells and single-cell RNA-sequencing analyses then revealed compensatory upregulation in genes involved in insulin secretion, processing and inflammatory response. CONCLUSIONS/INTERPRETATION The results provide deeper insights into the mechanisms of beta cell failure during INS mutation-mediated diabetes disease progression. Decreasing spliced X-box binding protein 1 (sXBP1) or inflammatory response could be avenues to restore the function of the remaining WT INS allele.
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Affiliation(s)
- Nur Shabrina Amirruddin
- Stem Cells and Diabetes Laboratory, Institute of Molecular and Cell Biology (IMCB), Agency for Science, Technology and Research (A*STAR), Singapore, Republic of Singapore
- Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Republic of Singapore
| | - Wei Xuan Tan
- Stem Cells and Diabetes Laboratory, Institute of Molecular and Cell Biology (IMCB), Agency for Science, Technology and Research (A*STAR), Singapore, Republic of Singapore
- Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Republic of Singapore
| | - Yaw Sing Tan
- Bioinformatics Institute, A*STAR, Singapore, Republic of Singapore
| | - Daphne Su-Lyn Gardner
- Department of Endocrinology, Singapore General Hospital, Singapore, Republic of Singapore
| | - Yong Mong Bee
- Department of Endocrinology, Singapore General Hospital, Singapore, Republic of Singapore
| | - Chandra Shekhar Verma
- Bioinformatics Institute, A*STAR, Singapore, Republic of Singapore
- Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
- School of Biological Sciences, Nanyang Technological University, Singapore, Republic of Singapore
| | - Shawn Hoon
- Molecular Engineering Laboratory, IMCB, A*STAR, Singapore, Republic of Singapore
| | - Kok Onn Lee
- Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Republic of Singapore
| | - Adrian Kee Keong Teo
- Stem Cells and Diabetes Laboratory, Institute of Molecular and Cell Biology (IMCB), Agency for Science, Technology and Research (A*STAR), Singapore, Republic of Singapore.
- Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Republic of Singapore.
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Republic of Singapore.
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7
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Dhayalan B, Chatterjee D, Chen YS, Weiss MA. Structural Lessons From the Mutant Proinsulin Syndrome. Front Endocrinol (Lausanne) 2021; 12:754693. [PMID: 34659132 PMCID: PMC8514764 DOI: 10.3389/fendo.2021.754693] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 09/13/2021] [Indexed: 12/30/2022] Open
Abstract
Insight into folding mechanisms of proinsulin has been provided by analysis of dominant diabetes-associated mutations in the human insulin gene (INS). Such mutations cause pancreatic β-cell dysfunction due to toxic misfolding of a mutant proinsulin and impairment in trans of wild-type insulin secretion. Anticipated by the "Akita" mouse (a classical model of monogenic diabetes mellitus; DM), this syndrome illustrates the paradigm endoreticulum (ER) stress leading to intracellular proteotoxicity. Diverse clinical mutations directly or indirectly perturb native disulfide pairing leading to protein misfolding and aberrant aggregation. Although most introduce or remove a cysteine (Cys; leading in either case to an unpaired thiol group), non-Cys-related mutations identify key determinants of folding efficiency. Studies of such mutations suggest that the hormone's evolution has been constrained not only by structure-function relationships, but also by the susceptibility of its single-chain precursor to impaired foldability. An intriguing hypothesis posits that INS overexpression in response to peripheral insulin resistance likewise leads to chronic ER stress and β-cell dysfunction in the natural history of non-syndromic Type 2 DM. Cryptic contributions of conserved residues to folding efficiency, as uncovered by rare genetic variants, define molecular links between biophysical principles and the emerging paradigm of Darwinian medicine: Biosynthesis of proinsulin at the edge of non-foldability provides a key determinant of "diabesity" as a pandemic disease of civilization.
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Affiliation(s)
| | | | | | - Michael A. Weiss
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, United States
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8
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O'Sullivan JDB, Cruickshank SM, Withers PJ, Else KJ. Morphological variability in the mucosal attachment site of Trichuris muris revealed by X-ray microcomputed tomography. Int J Parasitol 2021; 51:797-807. [PMID: 34216623 DOI: 10.1016/j.ijpara.2021.04.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Revised: 04/06/2021] [Accepted: 04/09/2021] [Indexed: 11/27/2022]
Abstract
Parasitic infections can be challenging to study because two dimensional light and electron microscopy are often limited in visualising complex and inaccessible attachment sites. Exemplifying this, Trichuris spp. inhabit a tunnel of epithelial cells within the host caecum and colon. A significant global burden of this infection persists, partly because available anthelminthics lack efficacy, although the mechanisms underlying this remain unknown. Consequently, there is a need to pioneer new approaches to better characterize the parasite niche within the host and investigate how variation in its morphology and integrity may contribute to resistance to therapeutic intervention. To address these aims, we exploited three-dimensional X-ray micro-computed tomography (microCT) to image the mouse whipworm, Trichuris muris, in caeca of wild-type C57BL/6 and SCID mice ex vivo. Using osmium tetroxide staining to effectively enhance the contrast of worms, we found that a subset exhibited preferential positioning towards the bases of the intestinal crypts. Moreover, in one rare event, we demonstrated whipworm traversal of the lamina propria. This morphological variability contradicts widely accepted conclusions from conventional microscopy of the parasite niche, showing Trichuris in close contact with the host proliferative and immune compartments that may facilitate immunomodulation. Furthermore, by using a skeletonization-based approach we demonstrate considerable variation in tunnel length and integrity. The qualitative and quantitative observations provide a new morphological point of reference for future in vitro study of host-Trichuris interactions, and highlight the potential of microCT to characterise enigmatic host-parasite interactions more accurately.
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Affiliation(s)
- James D B O'Sullivan
- Henry Royce Institute, Department of Materials, The University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom; Lydia Becker Institute for Immunology and Inflammation, The University of Manchester, Oxford Road, M13 9PT, United Kingdom
| | - Sheena M Cruickshank
- Lydia Becker Institute for Immunology and Inflammation, The University of Manchester, Oxford Road, M13 9PT, United Kingdom
| | - Philip J Withers
- Henry Royce Institute, Department of Materials, The University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Kathryn J Else
- Lydia Becker Institute for Immunology and Inflammation, The University of Manchester, Oxford Road, M13 9PT, United Kingdom.
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9
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Dhayalan B, Chatterjee D, Chen YS, Weiss MA. Diabetes mellitus due to toxic misfolding of proinsulin variants. Mol Metab 2021:101229. [PMID: 33823319 DOI: 10.1016/j.molmet.2021.101229] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 03/10/2021] [Accepted: 03/29/2021] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Dominant mutations in the human insulin gene (INS) lead to pancreatic β-cell dysfunction and diabetes mellitus (DM) due to toxic misfolding of a mutant proinsulin. Analogous to a classical mouse model of monogenic DM ("Akita"), this syndrome highlights the susceptibility of β-cells to endoreticulum (ER) stress due to protein misfolding and aberrant aggregation. SCOPE OF REVIEW Diverse clinical mutations directly or indirectly perturb native disulfide pairing. Whereas most introduce or remove a cysteine (Cys; leading in either case to an unpaired thiol group), non-Cys-related mutations identify key determinants of folding efficiency. Studies of such mutations suggest that the hormone's evolution has been constrained not only by structure-function relationships but also by the susceptibility of its single-chain precursor to impaired foldability. An intriguing hypothesis posits that INS overexpression in response to peripheral insulin resistance likewise leads to chronic ER stress and β-cell dysfunction in the natural history of nonsyndromic Type 2 DM. MAJOR CONCLUSIONS Cryptic contributions of conserved residues to folding efficiency, as uncovered by rare genetic variants, define molecular links between biophysical principles and the emerging paradigm of Darwinian medicine: Biosynthesis of proinsulin at the edge of nonfoldability provides a key determinant of "diabesity" as a pandemic disease of civilization.
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Affiliation(s)
- Balamurugan Dhayalan
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Deepak Chatterjee
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Yen-Shan Chen
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Michael A Weiss
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
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10
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Austin ALF, Daniels Gatward LF, Cnop M, Santos G, Andersson D, Sharp S, Gentry C, Bevan S, Jones PM, King AJF. The KINGS Ins2 +/G32S Mouse: A Novel Model of β-Cell Endoplasmic Reticulum Stress and Human Diabetes. Diabetes 2020; 69:2667-2677. [PMID: 32994272 PMCID: PMC7679781 DOI: 10.2337/db20-0570] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 09/21/2020] [Indexed: 02/06/2023]
Abstract
Animal models are important tools in diabetes research because ethical and logistical constraints limit access to human tissue. β-Cell dysfunction is a common contributor to the pathogenesis of most types of diabetes. Spontaneous hyperglycemia was developed in a colony of C57BL/6J mice at King's College London (KCL). Sequencing identified a mutation in the Ins2 gene, causing a glycine-to-serine substitution at position 32 on the B chain of the preproinsulin 2 molecule. Mice with the Ins2 +/G32S mutation were named KCL Ins2 G32S (KINGS) mice. The same mutation in humans (rs80356664) causes dominantly inherited neonatal diabetes. Mice were characterized, and β-cell function was investigated. Male mice became overtly diabetic at ∼5 weeks of age, whereas female mice had only slightly elevated nonfasting glycemia. Islets showed decreased insulin content and impaired glucose-induced insulin secretion, which was more severe in males. Transmission electron microscopy and studies of gene and protein expression showed β-cell endoplasmic reticulum (ER) stress in both sexes. Despite this, β-cell numbers were only slightly reduced in older animals. In conclusion, the KINGS mouse is a novel model of a human form of diabetes that may be useful to study β-cell responses to ER stress.
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Affiliation(s)
- Amazon L F Austin
- Department of Diabetes, School of Life Course Sciences, King's College London, London, U.K
| | | | - Miriam Cnop
- ULB Center for Diabetes Research, Université Libre de Bruxelles, Brussels, Belgium
- Division of Endocrinology, ULB Erasmus Hospital, Université Libre de Bruxelles, Brussels, Belgium
| | - Gabriel Santos
- Department of Diabetes, School of Life Course Sciences, King's College London, London, U.K
| | - David Andersson
- Wolfson Centre for Age-Related Diseases, Institute of Psychiatry, Psychology, and Neuroscience, King's College London, London, U.K
| | - Sally Sharp
- Wolfson Centre for Age-Related Diseases, Institute of Psychiatry, Psychology, and Neuroscience, King's College London, London, U.K
| | - Clive Gentry
- Wolfson Centre for Age-Related Diseases, Institute of Psychiatry, Psychology, and Neuroscience, King's College London, London, U.K
| | - Stuart Bevan
- Wolfson Centre for Age-Related Diseases, Institute of Psychiatry, Psychology, and Neuroscience, King's College London, London, U.K
| | - Peter M Jones
- Department of Diabetes, School of Life Course Sciences, King's College London, London, U.K
| | - Aileen J F King
- Department of Diabetes, School of Life Course Sciences, King's College London, London, U.K.
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11
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Balboa D, Saarimäki-Vire J, Borshagovski D, Survila M, Lindholm P, Galli E, Eurola S, Ustinov J, Grym H, Huopio H, Partanen J, Wartiovaara K, Otonkoski T. Insulin mutations impair beta-cell development in a patient-derived iPSC model of neonatal diabetes. eLife 2018; 7:38519. [PMID: 30412052 PMCID: PMC6294552 DOI: 10.7554/elife.38519] [Citation(s) in RCA: 97] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2018] [Accepted: 11/06/2018] [Indexed: 02/06/2023] Open
Abstract
Insulin gene mutations are a leading cause of neonatal diabetes. They can lead to proinsulin misfolding and its retention in endoplasmic reticulum (ER). This results in increased ER-stress suggested to trigger beta-cell apoptosis. In humans, the mechanisms underlying beta-cell failure remain unclear. Here we show that misfolded proinsulin impairs developing beta-cell proliferation without increasing apoptosis. We generated induced pluripotent stem cells (iPSCs) from people carrying insulin (INS) mutations, engineered isogenic CRISPR-Cas9 mutation-corrected lines and differentiated them to beta-like cells. Single-cell RNA-sequencing analysis showed increased ER-stress and reduced proliferation in INS-mutant beta-like cells compared with corrected controls. Upon transplantation into mice, INS-mutant grafts presented reduced insulin secretion and aggravated ER-stress. Cell size, mTORC1 signaling, and respiratory chain subunits expression were all reduced in INS-mutant beta-like cells, yet apoptosis was not increased at any stage. Our results demonstrate that neonatal diabetes-associated INS-mutations lead to defective beta-cell mass expansion, contributing to diabetes development.
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Affiliation(s)
- Diego Balboa
- Research Programs Unit, Molecular Neurology and Biomedicum Stem Cell Centre, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Jonna Saarimäki-Vire
- Research Programs Unit, Molecular Neurology and Biomedicum Stem Cell Centre, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | | | - Mantas Survila
- Department of Biosciences, University of Helsinki, Helsinki, Finland
| | - Päivi Lindholm
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
| | - Emilia Galli
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
| | - Solja Eurola
- Research Programs Unit, Molecular Neurology and Biomedicum Stem Cell Centre, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Jarkko Ustinov
- Research Programs Unit, Molecular Neurology and Biomedicum Stem Cell Centre, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Heli Grym
- Research Programs Unit, Molecular Neurology and Biomedicum Stem Cell Centre, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Hanna Huopio
- University of Eastern Finland and Kuopio University Hospital, Kuopio, Finland
| | - Juha Partanen
- Department of Biosciences, University of Helsinki, Helsinki, Finland
| | - Kirmo Wartiovaara
- Research Programs Unit, Molecular Neurology and Biomedicum Stem Cell Centre, Faculty of Medicine, University of Helsinki, Helsinki, Finland.,Clinical Genetics, HUSLAB, Helsinki University Central Hospital, Helsinki, Finland
| | - Timo Otonkoski
- Research Programs Unit, Molecular Neurology and Biomedicum Stem Cell Centre, Faculty of Medicine, University of Helsinki, Helsinki, Finland.,Children's Hospital, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
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12
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Riahi Y, Israeli T, Cerasi E, Leibowitz G. Effects of proinsulin misfolding on β-cell dynamics, differentiation and function in diabetes. Diabetes Obes Metab 2018; 20 Suppl 2:95-103. [PMID: 30230182 DOI: 10.1111/dom.13379] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Revised: 05/17/2018] [Accepted: 05/23/2018] [Indexed: 12/12/2022]
Abstract
ER stress due to proinsulin misfolding has an important role in the pathophysiology of rare forms of permanent neonatal diabetes (PNDM) and probably also of common type 1 (T1D) and type 2 diabetes (T2D). Accumulation of misfolded proinsulin in the ER stimulates the unfolded protein response (UPR) that may eventually lead to apoptosis through a process called the terminal UPR. However, the β-cell ER has an incredible ability to cope with accumulation of misfolded proteins; therefore, it is not clear whether in common forms of diabetes the accumulation of misfolded proinsulin exceeds the point of no return in which terminal UPR is activated. Many studies showed that the UPR is altered in both T1D and T2D; however, the observed changes in the expression of different UPR markers are inconsistent and it is not clear whether they reflect an adaptive response to stress or indeed mediate the β-cell dysfunction of diabetes. Herein, we critically review the literature on the effects of proinsulin misfolding and ER stress on β-cell dysfunction and loss in diabetes with emphasis on β-cell dynamics, and discuss the gaps in understanding the role of proinsulin misfolding in the pathophysiology of diabetes.
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Affiliation(s)
- Yael Riahi
- The Diabetes Unit and the Endocrine Service, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Tal Israeli
- The Diabetes Unit and the Endocrine Service, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Erol Cerasi
- The Diabetes Unit and the Endocrine Service, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Gil Leibowitz
- The Diabetes Unit and the Endocrine Service, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
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Saraste J, Marie M. Intermediate compartment (IC): from pre-Golgi vacuoles to a semi-autonomous membrane system. Histochem Cell Biol 2018; 150:407-430. [PMID: 30173361 PMCID: PMC6182704 DOI: 10.1007/s00418-018-1717-2] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/27/2018] [Indexed: 12/19/2022]
Abstract
Despite its discovery more than three decades ago and well-established role in protein sorting and trafficking in the early secretory pathway, the intermediate compartment (IC) has remained enigmatic. The prevailing view is that the IC evolved as a specialized organelle to mediate long-distance endoplasmic reticulum (ER)–Golgi communication in metazoan cells, but is lacking in other eukaryotes, such as plants and fungi. However, this distinction is difficult to reconcile with the high conservation of the core machineries that regulate early secretory trafficking from yeast to man. Also, it has remained unclear whether the pleiomorphic IC components—vacuoles, tubules and vesicles—represent transient transport carriers or building blocks of a permanent pre-Golgi organelle. Interestingly, recent studies have revealed that the IC maintains its compositional, structural and spatial properties throughout the cell cycle, supporting a model that combines the dynamic and stable aspects of the organelle. Moreover, the IC has been assigned novel functions, such as cell signaling, Golgi-independent trafficking and autophagy. The emerging permanent nature of the IC and its connections with the centrosome and the endocytic recycling system encourage reconsideration of its relationship with the Golgi ribbon, role in Golgi biogenesis and ubiquitous presence in eukaryotic cells.
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Affiliation(s)
- Jaakko Saraste
- Department of Biomedicine and Molecular Imaging Center (MIC), University of Bergen, Jonas Lies vei 91, 5009, Bergen, Norway.
| | - Michaël Marie
- Department of Biomedicine and Molecular Imaging Center (MIC), University of Bergen, Jonas Lies vei 91, 5009, Bergen, Norway
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Barbetti F, D'Annunzio G. Genetic causes and treatment of neonatal diabetes and early childhood diabetes. Best Pract Res Clin Endocrinol Metab 2018; 32:575-591. [PMID: 30086875 DOI: 10.1016/j.beem.2018.06.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Diabetes mellitus and impaired fasting glucose associated with single gene mutations are less rare than previously thought and may account for more than 6% of patients attending a pediatric diabetes clinic. The number of loci involved in monogenic diabetes exceed 25, and appropriate genetic diagnosis is crucial to direct therapy, for genetic counseling and for prognosis of short- and long-term complications. Among patients with neonatal diabetes (i.e. with onset within first 6 months of life) and patients with Maturity Onset Diabetes of the Young (MODY; an autosomal dominant form of diabetes), those carrying mutations in KCNJ11, ABCC8, HNF1A and HNF4A genes usually respond to oral therapy with sulphonylurea, while those bearing GCK mutations do not necessitate any treatment. Sensor-augmented continuous subcutaneous insulin infusion has been successfully employed in neonatal diabetes, and long-lasting effectiveness of sulfonylurea in KCNJ11 mutation carriers with neonatal diabetes well documented.
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Affiliation(s)
- Fabrizio Barbetti
- Department of Experimental Medicine and Surgery, University of Rome Tor Vergata, Via Montpellier, 100133 Rome, Italy; S. Pietro Fatebenefratelli Hospital, 00189 Rome, Italy.
| | - Giuseppe D'Annunzio
- Pediatric Clinic, Regional Center for Pediatric Diabetes, IRCCS Istituto Giannina Gaslini, Via Gaslini 5, 16147, Genoa, Italy.
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15
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Ooi CP, Smith TK, Gluenz E, Wand NV, Vaughan S, Rudenko G. Blocking variant surface glycoprotein synthesis alters endoplasmic reticulum exit sites/Golgi homeostasis in Trypanosoma brucei. Traffic 2018; 19:391-405. [PMID: 29533496 PMCID: PMC6001540 DOI: 10.1111/tra.12561] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Revised: 03/08/2018] [Accepted: 03/08/2018] [Indexed: 12/31/2022]
Abstract
The predominant secretory cargo of bloodstream form Trypanosoma brucei is variant surface glycoprotein (VSG), comprising ~10% total protein and forming a dense protective layer. Blocking VSG translation using Morpholino oligonucleotides triggered a precise pre‐cytokinesis arrest. We investigated the effect of blocking VSG synthesis on the secretory pathway. The number of Golgi decreased, particularly in post‐mitotic cells, from 3.5 ± 0.6 to 2.0 ± 0.04 per cell. Similarly, the number of endoplasmic reticulum exit sites (ERES) in post‐mitotic cells dropped from 3.9 ± 0.6 to 2.7 ± 0.1 eight hours after blocking VSG synthesis. The secretory pathway was still functional in these stalled cells, as monitored using Cathepsin L. Rates of phospholipid and glycosylphosphatidylinositol‐anchor biosynthesis remained relatively unaffected, except for the level of sphingomyelin which increased. However, both endoplasmic reticulum and Golgi morphology became distorted, with the Golgi cisternae becoming significantly dilated, particularly at the trans‐face. Membrane accumulation in these structures is possibly caused by reduced budding of nascent vesicles due to the drastic reduction in the total amount of secretory cargo, that is, VSG. These data argue that the total flux of secretory cargo impacts upon the biogenesis and maintenance of secretory structures and organelles in T. brucei, including the ERES and Golgi.
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Affiliation(s)
- Cher-Pheng Ooi
- Department of Life Sciences, Imperial College London, London, UK
| | - Terry K Smith
- BSRC, School of Biology, University of St. Andrews, St. Andrews, UK
| | - Eva Gluenz
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | | | - Sue Vaughan
- Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, UK
| | - Gloria Rudenko
- Department of Life Sciences, Imperial College London, London, UK
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16
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Arunagiri A, Haataja L, Cunningham CN, Shrestha N, Tsai B, Qi L, Liu M, Arvan P. Misfolded proinsulin in the endoplasmic reticulum during development of beta cell failure in diabetes. Ann N Y Acad Sci 2018; 1418:5-19. [PMID: 29377149 DOI: 10.1111/nyas.13531] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Revised: 09/14/2017] [Accepted: 09/25/2017] [Indexed: 02/06/2023]
Abstract
The endoplasmic reticulum (ER) is broadly distributed throughout the cytoplasm of pancreatic beta cells, and this is where all proinsulin is initially made. Healthy beta cells can synthesize 6000 proinsulin molecules per second. Ordinarily, nascent proinsulin entering the ER rapidly folds via the formation of three evolutionarily conserved disulfide bonds (B7-A7, B19-A20, and A6-A11). A modest amount of proinsulin misfolding, including both intramolecular disulfide mispairing and intermolecular disulfide-linked protein complexes, is a natural by-product of proinsulin biosynthesis, as is the case for many proteins. The steady-state level of misfolded proinsulin-a potential ER stressor-is linked to (1) production rate, (2) ER environment, (3) presence or absence of naturally occurring (mutational) defects in proinsulin, and (4) clearance of misfolded proinsulin molecules. Accumulation of misfolded proinsulin beyond a certain threshold begins to interfere with the normal intracellular transport of bystander proinsulin, leading to diminished insulin production and hyperglycemia, as well as exacerbating ER stress. This is most obvious in mutant INS gene-induced Diabetes of Youth (MIDY; an autosomal dominant disease) but also likely to occur in type 2 diabetes owing to dysregulation in proinsulin synthesis, ER folding environment, or clearance.
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Affiliation(s)
- Anoop Arunagiri
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, Michigan
| | - Leena Haataja
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, Michigan
| | - Corey N Cunningham
- Cellular and Molecular Biology Program, University of Michigan, Ann Arbor, Michigan
| | - Neha Shrestha
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - Billy Tsai
- Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, Michigan
| | - Ling Qi
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - Ming Liu
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, Michigan.,Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
| | - Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, Michigan
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Riahi Y, Wikstrom JD, Bachar-Wikstrom E, Polin N, Zucker H, Lee MS, Quan W, Haataja L, Liu M, Arvan P, Cerasi E, Leibowitz G. Autophagy is a major regulator of beta cell insulin homeostasis. Diabetologia 2016; 59:1480-1491. [PMID: 26831301 PMCID: PMC5912938 DOI: 10.1007/s00125-016-3868-9] [Citation(s) in RCA: 106] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Accepted: 12/23/2015] [Indexed: 02/04/2023]
Abstract
AIMS/HYPOTHESIS We studied the role of protein degradation pathways in the regulation of insulin production and secretion and hypothesised that autophagy regulates proinsulin degradation, thereby modulating beta cell function. METHODS Proinsulin localisation in autophagosomes was demonstrated by confocal and electron microscopy. Autophagy was inhibited by knockdown of autophagy-related (ATG) proteins and using the H(+)-ATPase inhibitor bafilomycin-A1. Proinsulin and insulin content and secretion were assessed in static incubations by ELISA and RIA. RESULTS Confocal and electron microscopy showed proinsulin localised in autophagosomes and lysosomes. Beta-Atg7 (-/-) mice had proinsulin-containing sequestosome 1 (p62 [also known as SQSTM1])(+) aggregates in beta cells, indicating proinsulin is regulated by autophagy in vivo. Short-term bafilomycin-A1 treatment and ATG5/7 knockdown increased steady-state proinsulin and hormone precursor chromogranin A content. ATG5/7 knockdown also increased glucose- and non-fuel-stimulated insulin secretion. Finally, mutated forms of proinsulin that are irreparably misfolded and trapped in the endoplasmic reticulum are more resistant to degradation by autophagy. CONCLUSIONS/INTERPRETATION In the beta cell, transport-competent secretory peptide precursors, including proinsulin, are regulated by autophagy, whereas efficient clearance of transport-incompetent mutated forms of proinsulin by alternative degradative pathways may be necessary to avoid beta cell proteotoxicity. Reduction of autophagic degradation of proinsulin increases its residency in the secretory pathway, followed by enhanced secretion in response to stimuli.
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Affiliation(s)
- Yael Riahi
- Endocrinology and Metabolism Service, Department of Medicine, Hadassah-Hebrew University Medical Center, PO Box 12000, Jerusalem, 91120, Israel
| | - Jakob D Wikstrom
- Endocrinology and Metabolism Service, Department of Medicine, Hadassah-Hebrew University Medical Center, PO Box 12000, Jerusalem, 91120, Israel
- Molecular Dermatology Research Group, Unit of Dermatology and Venereology, Department of Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Etty Bachar-Wikstrom
- Endocrinology and Metabolism Service, Department of Medicine, Hadassah-Hebrew University Medical Center, PO Box 12000, Jerusalem, 91120, Israel
| | - Nava Polin
- Endocrinology and Metabolism Service, Department of Medicine, Hadassah-Hebrew University Medical Center, PO Box 12000, Jerusalem, 91120, Israel
| | - Hava Zucker
- Endocrinology and Metabolism Service, Department of Medicine, Hadassah-Hebrew University Medical Center, PO Box 12000, Jerusalem, 91120, Israel
| | - Myung-Shik Lee
- Severance Biomedical Research Institute and Department of Internal Medicine, Yonsei University College of Medicine, Seoul, South Korea
| | - Wenying Quan
- Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea
| | - Leena Haataja
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan, Ann Arbor, MI, USA
| | - Ming Liu
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan, Ann Arbor, MI, USA
| | - Peter Arvan
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan, Ann Arbor, MI, USA
| | - Erol Cerasi
- Endocrinology and Metabolism Service, Department of Medicine, Hadassah-Hebrew University Medical Center, PO Box 12000, Jerusalem, 91120, Israel
| | - Gil Leibowitz
- Endocrinology and Metabolism Service, Department of Medicine, Hadassah-Hebrew University Medical Center, PO Box 12000, Jerusalem, 91120, Israel.
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Barbetti F, Colombo C, Haataja L, Cras-Méneur C, Bernardini S, Arvan P. Hyperglucagonemia in an animal model of insulin- deficient diabetes: what therapy can improve it? Clin Diabetes Endocrinol 2016; 2:11. [PMID: 28702245 PMCID: PMC5471666 DOI: 10.1186/s40842-016-0029-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Accepted: 04/11/2016] [Indexed: 02/06/2023] Open
Abstract
Background Intra-islet insulin contributes to alpha-cell suppression. Akita mice carry a toxic-gain-of- function Ins2 gene mutation encoding proinsulin-C(A7)Y, similar to that described in human Mutant Ins-gene induced Diabetes of Youth, which decreases intra-islet insulin. Herein, we examined Akita mice for examination of circulating insulin and circulating glucagon levels. The possibility that loss of intra-islet suppression of alpha-cells, with increased circulating glucagon, contributes to diabetes under conditions of intra-islet insulin deficiency, raises questions about effective treatments that may be available. Methods Blood glucose, plasma insulin, C-peptide I, C-peptide II, and glucagon were measured at various times during development of diabetes in Akita mice. We also used Akita- like hProC(A7)Y-CpepGFP transgenic mice in Ins2+/+, Ins2+/− and Ins2−/− genetic backgrounds (providing animals with greater or lesser defects in islet insulin production, respectively) in order to examine the relative abundance of immunostainable intra-islet glucagon-positive and insulin-positive cells. Similar measurements were made in Akita mice. Finally, the effects of treatment with insulin, exendin-4, and leptin on blood glucose were then compared in Akita mice. Results Interestingly, total insulin levels in the circulation were not frankly low in Akita mice, although they did not rise appropriately with the onset of hyperglycemia. By contrast, in severely diabetic Akita mice at 6 weeks of age, circulating glucagon levels were significantly elevated. Additionally, in Ins2+/− and Ins2−/− mice bearing the Akita-like hProC(A7)Y-CpepGFP transgene, development of diabetes correlated with an increase in the relative intra-islet abundance of immunostainable glucagon-positive cells, and a similar observation was made in Akita islets. In Akita mice, whereas a brief treatment with exendin-4 resulted in no apparent improvement in hyperglycemia, leptin treatment resulted in restoration of normoglycemia. Curiously, leptin treatment also suppressed circulating glucagon levels. Conclusions Loss of insulin-mediated intra-islet suppression of glucagon production may be a contributor to hyperglycemia in Akita mice, and leptin treatment appears beneficial in such a circumstance. This treatment might also be considered in some human diabetes patients with diminished insulin reserve.
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Affiliation(s)
- Fabrizio Barbetti
- Department of Experimental Medicine and Surgery, University of Tor Vergata, Rome, Italy.,Bambino Gesù Children's Hospital, IRCCS, Rome, Italy.,Department of Experimental Medicine and Surgery, University of Tor Vergata. Tor Vergata University Hospital, first floor, section D, room 118, Viale Oxford 81, 00133 Rome, Italy
| | - Carlo Colombo
- Department of Experimental Medicine and Surgery, University of Tor Vergata, Rome, Italy
| | - Leena Haataja
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical Center, Ann Arbor, MI USA
| | - Corentin Cras-Méneur
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical Center, Ann Arbor, MI USA
| | - Sergio Bernardini
- Department of Experimental Medicine and Surgery, University of Tor Vergata, Rome, Italy
| | - Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical Center, Ann Arbor, MI USA.,University of Michigan Medical Center, Brehm Tower room 5112, 1000 Wall St., Ann Arbor, MI 48105 USA
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19
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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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20
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Xu Z, Chikka MR, Xia H, Ready DF. Ire1 supports normal ER differentiation in developing Drosophila photoreceptors. J Cell Sci 2016; 129:921-9. [PMID: 26787744 PMCID: PMC4813318 DOI: 10.1242/jcs.180406] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Accepted: 01/12/2016] [Indexed: 01/09/2023] Open
Abstract
The endoplasmic reticulum (ER) serves virtually all aspects of cell physiology and, by pathways that are incompletely understood, is dynamically remodeled to meet changing cell needs. Inositol-requiring enzyme 1 (Ire1), a conserved core protein of the unfolded protein response (UPR), participates in ER remodeling and is particularly required during the differentiation of cells devoted to intense secretory activity, so-called 'professional' secretory cells. Here, we characterize the role of Ire1 in ER differentiation in the developing Drosophila compound eye photoreceptors (R cells). As part of normal development, R cells take a turn as professional secretory cells with a massive secretory effort that builds the photosensitive membrane organelle, the rhabdomere. We find rough ER sheets proliferate as rhabdomere biogenesis culminates, and Ire1 is required for normal ER differentiation. Ire1 is active early in R cell development and is required in anticipation of peak biosynthesis. Without Ire1, the amount of rough ER sheets is strongly reduced and the extensive cortical ER network at the rhabdomere base, the subrhabdomere cisterna (SRC), fails. Instead, ER proliferates in persistent and ribosome-poor tubular tangles. A phase of Ire1 activity early in R cell development thus shapes dynamic ER.
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Affiliation(s)
- Zuyuan Xu
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
| | | | - Hongai Xia
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
| | - Donald F Ready
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
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21
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Saraste J, Marie M. Intermediate Compartment: A Sorting Station between the Endoplasmic Reticulum and the Golgi Apparatus. ENCYCLOPEDIA OF CELL BIOLOGY 2016. [PMCID: PMC7150006 DOI: 10.1016/b978-0-12-394447-4.20013-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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22
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Sharma G, Rani I, Bhatnagar A, Agnihotri N. Documentation of Ultrastructural Changes in Nucleus and Microvilli by Fish Oil in Experimental Colon Carcinogenesis. Ultrastruct Pathol 2015. [PMID: 26213844 DOI: 10.3109/01913123.2015.1048914] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Fish oil (FO) exerts a chemopreventive effect by regulating apoptosis in colon carcinogenesis. The present study reports the ultrastructural changes in various organelles on supplementation of FO in experimental colon carcinogenesis. The carcinogen treatment led to abnormal nuclear shape and alteration in microvilli number indicating cancer establishment. On the other hand, different ratios of FO and corn oil increased chromatin condensation along with an extensive loss of microvilli in a dose- and time-dependent manner which depicts an increase in apoptosis. The associated ultrastuctural alterations support the facilitation of apoptosis by FO as a mechanism for its beneficial effect in colon carcinogenesis.
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Affiliation(s)
- Gayatri Sharma
- a Department of Biochemistry , Panjab University , Chandigarh , Punjab , India
| | - Isha Rani
- a Department of Biochemistry , Panjab University , Chandigarh , Punjab , India
| | - Archana Bhatnagar
- a Department of Biochemistry , Panjab University , Chandigarh , Punjab , India
| | - Navneet Agnihotri
- a Department of Biochemistry , Panjab University , Chandigarh , Punjab , India
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GUAN CUIPING, XU WEN, HONG WEISONG, ZHOU MIAONI, LIN FUQUAN, FU LIFANG, LIU DONGYIN, XU AIE. Quercetin attenuates the effects of H2O2 on endoplasmic reticulum morphology and tyrosinase export from the endoplasmic reticulum in melanocytes. Mol Med Rep 2015; 11:4285-90. [DOI: 10.3892/mmr.2015.3242] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Accepted: 10/24/2014] [Indexed: 11/06/2022] Open
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Sugawara T, Kano F, Murata M. Rab2A is a pivotal switch protein that promotes either secretion or ER-associated degradation of (pro)insulin in insulin-secreting cells. Sci Rep 2014; 4:6952. [PMID: 25377857 PMCID: PMC5381769 DOI: 10.1038/srep06952] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Accepted: 10/14/2014] [Indexed: 12/15/2022] Open
Abstract
Rab2A, a small GTPase localizing to the endoplasmic reticulum (ER)-Golgi intermediate compartment (ERGIC), regulates COPI-dependent vesicular transport from the ERGIC. Rab2A knockdown inhibited glucose-stimulated insulin secretion and concomitantly enlarged the ERGIC in insulin-secreting cells. Large aggregates of polyubiquitinated proinsulin accumulated in the cytoplasmic vicinity of a unique large spheroidal ERGIC, designated the LUb-ERGIC. Well-known components of ER-associated degradation (ERAD) also accumulated at the LUb-ERGIC, creating a suitable site for ERAD-mediated protein quality control. Moreover, chronically high glucose levels, which induced the enlargement of the LUb-ERGIC and ubiquitinated protein aggregates, impaired Rab2A activity by promoting dissociation from its effector, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), in response to poly (ADP-ribosyl)ation of GAPDH. The inactivation of Rab2A relieved glucose-induced ER stress and inhibited ER stress-induced apoptosis. Collectively, these results suggest that Rab2A is a pivotal switch that controls whether insulin should be secreted or degraded at the LUb-ERGIC and Rab2A inactivation ensures alleviation of ER stress and cell survival under chronic glucotoxicity.
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Affiliation(s)
- Taichi Sugawara
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo 153-8902, Japan
| | - Fumi Kano
- 1] Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo 153-8902, Japan [2] PRESTO, Japan Science and Technology Agency, Saitama 332-0012, Japan
| | - Masayuki Murata
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo 153-8902, Japan
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25
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Jonatan D, Spence JR, Method AM, Kofron M, Sinagoga K, Haataja L, Arvan P, Deutsch GH, Wells JM. Sox17 regulates insulin secretion in the normal and pathologic mouse β cell. PLoS One 2014; 9:e104675. [PMID: 25144761 PMCID: PMC4140688 DOI: 10.1371/journal.pone.0104675] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2014] [Accepted: 07/16/2014] [Indexed: 02/06/2023] Open
Abstract
SOX17 is a key transcriptional regulator that can act by regulating other transcription factors including HNF1β and FOXA2, which are known to regulate postnatal β cell function. Given this, we investigated the role of SOX17 in the developing and postnatal pancreas and found a novel role for SOX17 in regulating insulin secretion. Deletion of the Sox17 gene in the pancreas (Sox17-paLOF) had no observable impact on pancreas development. However, Sox17-paLOF mice had higher islet proinsulin protein content, abnormal trafficking of proinsulin, and dilated secretory organelles suggesting that Sox17-paLOF adult mice are prediabetic. Consistant with this, Sox17-paLOF mice were more susceptible to aged-related and high fat diet-induced hyperglycemia and diabetes. Overexpression of Sox17 in mature β cells using Ins2-rtTA driver mice resulted in precocious secretion of proinsulin. Transcriptionally, SOX17 appears to broadly regulate secretory networks since a 24-hour pulse of SOX17 expression resulted in global transcriptional changes in factors that regulate hormone transport and secretion. Lastly, transient SOX17 overexpression was able to reverse the insulin secretory defects observed in MODY4 animals and restored euglycemia. Together, these data demonstrate a critical new role for SOX17 in regulating insulin trafficking and secretion and that modulation of Sox17-regulated pathways might be used therapeutically to improve cell function in the context of diabetes.
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Affiliation(s)
- Diva Jonatan
- Division of Developmental Biology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, United States of America
| | - Jason R. Spence
- Department of Internal Medicine, Division of Gastroenterology, University of Michigan Medical School, Ann Arbor, MI, United States of America
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, United States of America
- Center for Organogenesis, University of Michigan Medical School, Ann Arbor, MI, United States of America
| | - Anna M. Method
- Division of Developmental Biology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, United States of America
| | - Matthew Kofron
- Division of Developmental Biology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, United States of America
| | - Katie Sinagoga
- Division of Developmental Biology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, United States of America
| | - Leena Haataja
- Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, MI, United States of America
| | - Peter Arvan
- Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, MI, United States of America
| | - Gail H. Deutsch
- Seattle Children’s Hospital, Seattle, WA, United States of America
| | - James M. Wells
- Division of Developmental Biology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, United States of America
- Division of Endocrinology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, United States of America
- * E-mail:
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Taatjes DJ. Cell biology of protein glycosylation: a celebration of the career of Jürgen Roth on the occasion of his 70th birthday. Cell Biol Int 2014; 38:547-52. [PMID: 24375674 DOI: 10.1002/cbin.10239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Accepted: 12/24/2013] [Indexed: 11/08/2022]
Affiliation(s)
- Douglas J Taatjes
- Department of Pathology and Microscopy Imaging Center, College of Medicine, University of Vermont, Burlington, Vermont, USA
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Martínez-Alonso E, Tomás M, Martínez-Menárguez JA. Golgi tubules: their structure, formation and role in intra-Golgi transport. Histochem Cell Biol 2013; 140:327-39. [PMID: 23812035 DOI: 10.1007/s00418-013-1114-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/16/2013] [Indexed: 11/28/2022]
Abstract
Tubules are common Golgi elements that can form extensive networks associated with the cis-, lateral and trans-Golgi sides, but despite this, they have almost been forgotten for decades. The molecular mechanisms involved in their formation, elongation and fission are only just beginning to be understood. However, the role of these membranes is not well understood. In the present review, we analyze the mechanisms that induce Golgi tubulation or, conversely, disrupt tubules in order to throw some lights on the nature of these elements. The putative role of these elements in the framework of current models for intra-Golgi transport is also discussed.
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Affiliation(s)
- Emma Martínez-Alonso
- Department of Cell Biology and Histology, Medical School, University of Murcia, 30100 Murcia, Spain
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Diabetes mellitus due to the toxic misfolding of proinsulin variants. FEBS Lett 2013; 587:1942-50. [PMID: 23669362 DOI: 10.1016/j.febslet.2013.04.044] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Revised: 04/29/2013] [Accepted: 04/30/2013] [Indexed: 02/06/2023]
Abstract
Dominant mutations in the human insulin gene can lead to pancreatic β-cell dysfunction and diabetes mellitus due to toxic folding of a mutant proinsulin. Analogous to a classical mouse model (the Akita mouse), this monogenic syndrome highlights the susceptibility of human β-cells to endoreticular stress due to protein misfolding and aberrant aggregation. The clinical mutations directly or indirectly perturb native disulfide pairing. Whereas the majority of mutations introduce or remove a cysteine (leading in either case to an unpaired residue), non-cysteine-related mutations identify key determinants of folding efficiency. Studies of such mutations suggest that the evolution of insulin has been constrained not only by its structure and function, but also by the susceptibility of its single-chain precursor to impaired foldability.
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Schönthal AH. Endoplasmic reticulum stress: its role in disease and novel prospects for therapy. SCIENTIFICA 2012; 2012:857516. [PMID: 24278747 PMCID: PMC3820435 DOI: 10.6064/2012/857516] [Citation(s) in RCA: 214] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Accepted: 11/12/2012] [Indexed: 05/19/2023]
Abstract
The endoplasmic reticulum (ER) is a multifunctional organelle required for lipid biosynthesis, calcium storage, and protein folding and processing. A number of physiological and pathological conditions, as well as a variety of pharmacological agents, are able to disturb proper ER function and thereby cause ER stress, which severely impairs protein folding and therefore poses the risk of proteotoxicity. Specific triggers for ER stress include, for example, particular intracellular alterations (e.g., calcium or redox imbalances), certain microenvironmental conditions (e.g., hypoglycemia, hypoxia, and acidosis), high-fat and high-sugar diet, a variety of natural compounds (e.g., thapsigargin, tunicamycin, and geldanamycin), and several prescription drugs (e.g., bortezomib/Velcade, celecoxib/Celebrex, and nelfinavir/Viracept). The cell reacts to ER stress by initiating a defensive process, called the unfolded protein response (UPR), which is comprised of cellular mechanisms aimed at adaptation and safeguarding cellular survival or, in cases of excessively severe stress, at initiation of apoptosis and elimination of the faulty cell. In recent years, this dichotomic stress response system has been linked to several human diseases, and efforts are underway to develop approaches to exploit ER stress mechanisms for therapy. For example, obesity and type 2 diabetes have been linked to ER stress-induced failure of insulin-producing pancreatic beta cells, and current research efforts are aimed at developing drugs that ameliorate cellular stress and thereby protect beta cell function. Other studies seek to pharmacologically aggravate chronic ER stress in cancer cells in order to enhance apoptosis and achieve tumor cell death. In the following, these principles will be presented and discussed.
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Affiliation(s)
- Axel H. Schönthal
- Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, 2011 Zonal Avenue, HMR-405, Los Angeles, CA 90033, USA
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Yuan Q, Tang W, Zhang X, Hinson JA, Liu C, Osei K, Wang J. Proinsulin atypical maturation and disposal induces extensive defects in mouse Ins2+/Akita β-cells. PLoS One 2012; 7:e35098. [PMID: 22509386 PMCID: PMC3318013 DOI: 10.1371/journal.pone.0035098] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Accepted: 03/08/2012] [Indexed: 02/06/2023] Open
Abstract
Because of its low relative folding rate and plentiful manufacture in β-cells, proinsulin maintains a homeostatic balance of natively and plentiful non-natively folded states (i.e., proinsulin homeostasis, PIHO) through the integration of maturation and disposal processes. PIHO is susceptible to genetic and environmental influences, and its disorder has been critically linked to defects in β-cells in diabetes. To explore this hypothesis, we performed polymerase chain reaction (PCR), metabolic-labeling, immunoblotting, and histological studies to clarify what defects result from primary disorder of PIHO in model Ins2+/Akita β-cells. We used T antigen-transformed Ins2+/Akita and control Ins2+/+ β-cells established from Akita and wild-type littermate mice. In Ins2+/Akita β-cells, we found no apparent defect at the transcriptional and translational levels to contribute to reduced cellular content of insulin and its precursor and secreted insulin. Glucose response remained normal in proinsulin biosynthesis but was impaired for insulin secretion. The size and number of mature insulin granules were reduced, but the size/number of endoplasmic reticulum, Golgi, mitochondrion, and lysosome organelles and vacuoles were expanded/increased. Moreover, cell death increased, and severe oxidative stress, which manifested as increased reactive oxygen species, thioredoxin-interacting protein, and protein tyrosine nitration, occurred in Ins2+/Akita β-cells and/or islets. These data show the first clear evidence that primary PIHO imbalance induces severe oxidative stress and impairs glucose-stimulated insulin release and β-cell survival as well as producing other toxic consequences. The defects disclosed/clarified in model Ins2+/Akita β-cells further support a role of the genetic and stress-susceptible PIHO disorder in β-cell failure and diabetes.
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Affiliation(s)
- Qingxin Yuan
- Division of Endocrinology, Diabetes, and Metabolism, Department of Internal Medicine, The Ohio State University, Columbus, Ohio, United States of America
| | - Wei Tang
- Division of Endocrinology, Diabetes, and Metabolism, Department of Internal Medicine, The Ohio State University, Columbus, Ohio, United States of America
| | - Xiaoping Zhang
- Division of Endocrinology, Diabetes, and Metabolism, Department of Internal Medicine, The Ohio State University, Columbus, Ohio, United States of America
| | - Jack A. Hinson
- Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States of America
| | - Chao Liu
- Division of Endocrinology, Jiangsu Province Hospital on Integration of Chinese and Western Medicine, Nanjing University of Chinese and Western Medicine, Nanjing, Jiangsu, China
| | - Kwame Osei
- Division of Endocrinology, Diabetes, and Metabolism, Department of Internal Medicine, The Ohio State University, Columbus, Ohio, United States of America
| | - Jie Wang
- Division of Endocrinology, Diabetes, and Metabolism, Department of Internal Medicine, The Ohio State University, Columbus, Ohio, United States of America
- Division of Endocrinology, Jiangsu Province Hospital on Integration of Chinese and Western Medicine, Nanjing University of Chinese and Western Medicine, Nanjing, Jiangsu, China
- * E-mail:
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Fullwood MJ, Zhou W, Shenolikar S. Targeting Phosphorylation of Eukaryotic Initiation Factor-2α to Treat Human Disease. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2012; 106:75-106. [DOI: 10.1016/b978-0-12-396456-4.00005-5] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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Abstract
Neonatal diabetes mellitus (NDM) is the term commonly used to describe diabetes with onset before 6 months-of-age. It occurs in approximately one out of every 100,000-300,000 live births. Although this term encompasses diabetes of any etiology, it is recognized that NDM diagnosed before 6 months-of-age is most often monogenic in nature. Clinically, NDM subgroups include transient (TNDM) and permanent NDM (PNDM), as well as syndromic cases of NDM. TNDM often develops within the first few weeks of life and remits by a few months of age. However, relapse occurs in 50% of cases, typically in adolescence or adulthood. TNDM is most frequently caused by abnormalities in the imprinted region of chromosome 6q24, leading to overexpression of paternally derived genes. Mutations in KCNJ11 and ABCC8, encoding the two subunits of the adenosine triphosphate-sensitive potassium channel on the β-cell membrane, can cause TNDM, but more often result in PNDM. NDM as a result of mutations in KCNJ11 and ABCC8 often responds to sulfonylureas, allowing transition from insulin therapy. Mutations in other genes important to β-cell function and regulation, and in the insulin gene itself, also cause NDM. In 40% of NDM cases, the genetic cause remains unknown. Correctly identifying monogenic NDM has important implications for appropriate treatment, expected disease course and associated conditions, and genetic testing for at-risk family members. Early recognition of monogenic NDM allows for the implementation of appropriate therapy, leading to improved outcomes and potential societal cost savings. (J Diabetes Invest, doi:10.1111/j.2040-1124.2011.00106.x, 2011).
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Affiliation(s)
| | | | - Graeme I Bell
- Medicine, Section of Adult and Pediatric Endocrinology, Diabetes and Metabolism, The University of Chicago, Chicago, Illinois, USA
| | - Louis H Philipson
- Departments of Pediatrics
- Medicine, Section of Adult and Pediatric Endocrinology, Diabetes and Metabolism, The University of Chicago, Chicago, Illinois, USA
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Fujitani Y, Uchida T, Komiya K, Abe H, Kawamori R, Watada H. Roles of autophagy in pancreatic β-cell function and type 2 diabetes. Diabetol Int 2011. [DOI: 10.1007/s13340-011-0020-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Ionescu-Tirgoviste C, Despa F. Biophysical alteration of the secretory track in β-cells due to molecular overcrowding: the relevance for diabetes. Integr Biol (Camb) 2010; 3:173-9. [PMID: 21180710 DOI: 10.1039/c0ib00029a] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Recent data demonstrate that accumulation of misfolded proteins within the early part of the secretory track of β-cells causes impaired insulin synthesis and development of diabetes. The molecular mechanism of this cellular dysfunction remains largely unknown. Using basic molecular principles and computer simulations, we suggested recently that hyperglycemic conditions can generate substantial molecular crowding effects in the secretory track of β-cells leading to significant alterations of the insulin biosynthesis capabilities. Here, we review the major molecular mechanisms that may be implicated in the alteration of insulin synthesis in susceptible β-cells. Steric repulsions and volume exclusion in the endoplasmic reticulum (ER) increase the propensity of misfolding of proinsulin (the precursor molecule of insulin). In addition, similar forces might act in the next secretory compartments (Golgi and vesicles) leading to (i) altered packaging of proinsulin in vesicles (ii) entrapment of proinsulin convertases and/or restricted accessibility for these convertases to the cleavage sites on the surface of the proinsulin and (iii) depressed kinetic rate of the transformation of the native proinsulin in active insulin and C-peptide. These concepts are expressed in simple mathematical terms relating the kinetic coefficient of proinsulin to insulin conversion to the levels of proinsulin misfolding and hyperglycemic stress. The present approach is useful for understanding molecular phenomena associated with the pathogenesis of diabetes. It also offers practical means for predicting the state of pancreatic β-cells from measurements of the insulin to proinsulin ratio in the blood. This is of immediate clinical relevance and may improve the diagnosis of diabetes.
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Roth J, Zuber C, Park S, Jang I, Lee Y, Kysela KG, Le Fourn V, Santimaria R, Guhl B, Cho JW. Protein N-glycosylation, protein folding, and protein quality control. Mol Cells 2010; 30:497-506. [PMID: 21340671 DOI: 10.1007/s10059-010-0159-z] [Citation(s) in RCA: 119] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Accepted: 11/11/2010] [Indexed: 11/27/2022] Open
Abstract
Quality control of protein folding represents a fundamental cellular activity. Early steps of protein N-glycosylation involving the removal of three glucose and some specific mannose residues in the endoplasmic reticulum have been recognized as being of importance for protein quality control. Specific oligosaccharide structures resulting from the oligosaccharide processing may represent a glycocode promoting productive protein folding, whereas others may represent glyco-codes for routing not correctly folded proteins for dislocation from the endoplasmic reticulum to the cytosol and subsequent degradation. Although quality control of protein folding is essential for the proper functioning of cells, it is also the basis for protein folding disorders since the recognition and elimination of non-native conformers can result either in loss-of-function or pathological-gain-of-function. The machinery for protein folding control represents a prime example of an intricate interactome present in a single organelle, the endoplasmic reticulum. Here, current views of mechanisms for the recognition and retention leading to productive protein folding or the eventual elimination of misfolded glycoproteins in yeast and mammalian cells are reviewed.
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Affiliation(s)
- Jürgen Roth
- Department of Integrated OMICs for Biomedical Sciences, WCU Program of Graduate School, Yonsei University, Seoul 120-749, Korea.
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Abstract
BACKGROUND Pancreatic β cells respond to chronic hyperglycemia by increasing the synthesis of proinsulin (the precursor molecule of insulin). Prolonged stimulations lead to accumulation of misfolded proinsulin in the secretory track, delayed insulin secretion, and release of unprocessed proinsulin in the blood. The molecular mechanisms connecting the state of endoplasmic reticulum overloading with the efficiency of proinsulin to insulin conversion remain largely unknown. METHODS Computer simulations can help us to understand mechanistic features of the β-cell secretory defect and to design experiments that may reveal the molecular basis of this dysfunction. We used molecular crowding concepts and statistical thermodynamics to dissect possible biophysical mechanisms underlying the alteration of the secretory track of β cells and to elucidate the chemistry aspects of the secretory dysfunction. We then used numerical algorithms to relate the degree of biophysical alteration of these secretory compartments with the change of proinsulin to insulin conversion rate. RESULTS Our computer simulations suggest that overloading the endoplasmic reticulum initiates downstream molecular crowding effects that affect protein translational mechanisms, including proinsulin misfolding, delayed packing of proinsulin in secretory vesicles, and low kinetic coefficient of proinsulin to insulin conversion. CONCLUSIONS Together with previous experimental data, the present study can help us to better understand chemistry aspects related to the secondary translational mechanisms in β cells and how hyperglycemic stress can alter secretory function. This can give a further impetus to the development of novel software to be used in a clinical setup for prediction and assessment of diabetic states in susceptible patients.
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Affiliation(s)
- Florin Despa
- Department of Pharmacology, University of California Davis, Davis, California 95616, USA.
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Despa F. Endoplasmic reticulum overcrowding as a mechanism of beta-cell dysfunction in diabetes. Biophys J 2010; 98:1641-8. [PMID: 20409485 DOI: 10.1016/j.bpj.2009.12.4295] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2009] [Revised: 09/24/2009] [Accepted: 12/14/2009] [Indexed: 01/25/2023] Open
Abstract
This study suggests a molecular mechanism that explains the accumulation of denaturated proinsulin in the endoplasmic reticulum (ER) of beta-cells. Such states were frequently observed in beta-cells experiencing increased demand for insulin production and were shown to lead to secretory dysfunction and diabetes. Here, a self-consistent kinetic model is used to investigate changes in protein translation due to ER overloading. The model is based on a molecular theory that relates the molecular composition and level of molecular crowding in the ER to the kinetic rates of protein folding/misfolding and transit to the Golgi apparatus (GA). This study suggests that molecular crowding forces can increase protein misfolding and impair the transport to the GA, thus overwhelming the quality control mechanism in the ER. A continual accumulation of toxic residues in the ER enhances even further the molecular crowding, accelerating protein denaturation. This article shows that molecular crowding affects differently the transit of various proteins through the ER. Apparently, the molecular crowding level that can inhibit the transport of native proinsulin to the GA influences to a lesser extent the transit of proamylin, a much smaller peptide cosynthesized with proinsulin in the ER. Smaller-volume misfolded proinsulin species may also win the passage competition through the ER and move on the secretory track. However, misfolded proinsulin fails the conversion to active insulin. This study can help us to decipher circumstances leading to the alteration of the secretory function in susceptible beta-cells and the onset of diabetes.
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Affiliation(s)
- F Despa
- Department of Pharmacology, University of California, Davis, California, USA.
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38
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Roy L, Laboissière S, Abdou E, Thibault G, Hamel N, Taheri M, Boismenu D, Lanoix J, Kearney RE, Paiement J. Proteomic analysis of the transitional endoplasmic reticulum in hepatocellular carcinoma: an organelle perspective on cancer. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2010; 1804:1869-81. [PMID: 20576523 DOI: 10.1016/j.bbapap.2010.05.008] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2010] [Revised: 05/05/2010] [Accepted: 05/18/2010] [Indexed: 02/06/2023]
Abstract
The transitional endoplasmic reticulum (tER) is composed of both rough and smooth ER membranes and thus participates in functions attributed to both these two subcellular compartments. In this paper we have compared the protein composition of tER isolated from dissected liver tumor nodules of aflatoxin B1-treated rats with that of tER from control liver. Tandem mass spectrometry (MS), peptide counts and immunoblot validation were used to identify and determine the relative expression level of proteins. Inhibitors of apoptosis (i.e. PGRMC1, tripeptidyl peptidase II), proteins involved in ribosome biogenesis (i.e. nucleophosmin, nucleolin), proteins involved in translation (i.e. eEF-2, and subunits of eIF-3), proteins involved in ubiquitin metabolism (i.e. proteasome subunits, USP10) and proteins involved in membrane traffic (i.e. SEC13-like 1, SEC23B, dynactin 1) were found overexpressed in tumor tER. Transcription factors (i.e. Pur-beta, BTF3) and molecular targets for C-Myc and NF-kappa B were observed overexpressed in tER from tumor nodules. Down-regulated proteins included cytochrome P450 proteins and enzymes involved in fatty acid metabolism and in steroid metabolism. Unexpectedly expression of the protein folding machinery (i.e. calreticulin) and proteins of the MHC class I peptide-loading complex did not change. Proteins of unknown function were detected in association with the tER and the novel proteins showing differential expression are potential new tumor markers. In many cases differential expression of proteins in tumor tER was comparable to that of corresponding genes reported in the Oncomine human database. Thus the molecular profile of tumor tER is different and this may confer survival advantage to tumor cells in cancer.
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Affiliation(s)
- Line Roy
- McGill University and Genome Quebec Innovation Centre, Proteomics Services, Genome Quebec, Montreal, Quebec, Canada
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39
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Shaker A, Swietlicki EA, Wang L, Jiang S, Onal B, Bala S, DeSchryver K, Newberry R, Levin MS, Rubin DC. Epimorphin deletion protects mice from inflammation-induced colon carcinogenesis and alters stem cell niche myofibroblast secretion. J Clin Invest 2010; 120:2081-93. [PMID: 20458144 DOI: 10.1172/jci40676] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2009] [Accepted: 03/03/2010] [Indexed: 01/07/2023] Open
Abstract
Epithelial-mesenchymal interactions regulate normal gut epithelial homeostasis and have a putative role in inflammatory bowel disease and colon cancer pathogenesis. Epimorphin is a mesenchymal and myofibroblast protein with antiproliferative, promorphogenic effects in intestinal epithelium. We previously showed that deletion of epimorphin partially protects mice from acute colitis, associated with an increase in crypt cell proliferation. Here we explored the potential therapeutic utility of modulating epimorphin expression by examining the effects of epimorphin deletion on chronic inflammation-associated colon carcinogenesis using the azoxymethane/dextran sodium sulfate (AOM/DSS) model. We found that mice in which epimorphin expression was absent had a marked reduction in incidence and extent of colonic dysplasia. Furthermore, epimorphin deletion in myofibroblasts altered the morphology and growth of cocultured epithelial cells. Loss of epimorphin affected secretion of soluble mesenchymal regulators of the stem cell niche such as Chordin. Importantly, IL-6 secretion from LPS-treated epimorphin-deficient myofibroblasts was completely inhibited, and stromal IL-6 expression was reduced in vivo. Taken together, these data show that epimorphin deletion inhibits chronic inflammation-associated colon carcinogenesis in mice, likely as a result of increased epithelial repair, decreased myofibroblast IL-6 secretion, and diminished IL-6-induced inflammation. Furthermore, we believe that modulation of epimorphin expression may have therapeutic benefits in appropriate clinical settings.
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Affiliation(s)
- Anisa Shaker
- Department of Internal Medicine, Washington University School of Medicine, Saint Louis, Missouri, USA
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40
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Schröder M, Sutcliffe L. Consequences of stress in the secretory pathway: The ER stress response and its role in the metabolic syndrome. Methods Mol Biol 2010; 648:43-62. [PMID: 20700704 DOI: 10.1007/978-1-60761-756-3_3] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The unfolded protein response (UPR) was originally identified as a signaling network coordinating adaptive and apoptotic responses to accumulation of unfolded proteins in the endoplasmic reticulum (ER). More recent work has shown that UPR signaling can be triggered by a multitude of cellular events and that the UPR plays a critical role in the prevention, and also the progression, of a wide variety of diseases. Much attention has been paid to the role of the UPR in neurodegenerative diseases in the past. More recently, important roles for the UPR in diseases associated with the metabolic syndrome have been discovered. Here we review the role of the UPR in these diseases, including type 2 diabetes, atherosclerosis, fatty liver disease, and ischemia.
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Abstract
The preeminent role of the beta cell is to manufacture, store and release insulin. The mature insulin molecule is composed of two polypeptide chains designated as A and B that are joined by two pairs of disulfide bonds with an additional intramolecular disulfide bond in the A chain. However, the two chains of the insulin molecule are not synthesized as separate polypeptide chains but rather are generated by specific proteolytic processing of a larger precursor, proinsulin. This discovery in 1967 and the concept of prohormones changed our view of the biosynthesis of hormones and neuropeptides. It allowed studies of the regulation of insulin biosynthesis that highlighted the key role of glucose. In addition, the C-peptide, the polypeptide that joins the A and B chains in proinsulin and is stored with insulin in the secretory granules and secreted in equimolar amounts, allowed studies of pancreatic beta cell function in vivo including in patients with diabetes. Subsequent studies have identified the specific proteases, prohormone convertases 1/3 and 2 and carboxypeptidase E, that are involved in the conversion of proinsulin to proinsulin intermediates and then to insulin. Disorders of (pro)insulin biosynthesis continue to illuminate important aspects of this pathway, revealing important connections to diabetes pathogenesis. Recent studies of patients with insulin gene mutations that cause permanent neonatal diabetes have identified key residues affecting the folding and structural organization of the preproinsulin molecule and its subsequent processing. These findings have renewed interest in the key role of endoplasmic reticulum function in insulin biosynthesis and the maintainance of normal beta cell health.
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Affiliation(s)
- D F Steiner
- Department of Biochemistry, The University of Chicago, IL 60637, USA.
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42
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Liu M, Wan ZL, Chu YC, Aladdin H, Klaproth B, Choquette M, Hua QX, Mackin RB, Rao JS, De Meyts P, Katsoyannis PG, Arvan P, Weiss MA. Crystal structure of a "nonfoldable" insulin: impaired folding efficiency despite native activity. J Biol Chem 2009; 284:35259-72. [PMID: 19850922 DOI: 10.1074/jbc.m109.046888] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Protein evolution is constrained by folding efficiency ("foldability") and the implicit threat of toxic misfolding. A model is provided by proinsulin, whose misfolding is associated with beta-cell dysfunction and diabetes mellitus. An insulin analogue containing a subtle core substitution (Leu(A16) --> Val) is biologically active, and its crystal structure recapitulates that of the wild-type protein. As a seeming paradox, however, Val(A16) blocks both insulin chain combination and the in vitro refolding of proinsulin. Disulfide pairing in mammalian cell culture is likewise inefficient, leading to misfolding, endoplasmic reticular stress, and proteosome-mediated degradation. Val(A16) destabilizes the native state and so presumably perturbs a partial fold that directs initial disulfide pairing. Substitutions elsewhere in the core similarly destabilize the native state but, unlike Val(A16), preserve folding efficiency. We propose that Leu(A16) stabilizes nonlocal interactions between nascent alpha-helices in the A- and B-domains to facilitate initial pairing of Cys(A20) and Cys(B19), thus surmounting their wide separation in sequence. Although Val(A16) is likely to destabilize this proto-core, its structural effects are mitigated once folding is achieved. Classical studies of insulin chain combination in vitro have illuminated the impact of off-pathway reactions on the efficiency of native disulfide pairing. The capability of a polypeptide sequence to fold within the endoplasmic reticulum may likewise be influenced by kinetic or thermodynamic partitioning among on- and off-pathway disulfide intermediates. The properties of [Val(A16)]insulin and [Val(A16)]proinsulin demonstrate that essential contributions of conserved residues to folding may be inapparent once the native state is achieved.
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Affiliation(s)
- Ming Liu
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical Center, Ann Arbor, Michigan 48109, USA
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43
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Despa F. Dilation of the endoplasmic reticulum in beta cells due to molecular overcrowding? Kinetic simulations of extension limits and consequences on proinsulin synthesis. Biophys Chem 2008; 140:115-21. [PMID: 19121888 DOI: 10.1016/j.bpc.2008.12.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2008] [Revised: 12/10/2008] [Accepted: 12/11/2008] [Indexed: 01/05/2023]
Abstract
Insulin regulates the energy homeostasis of the human body. This is synthesized in the endoplasmic reticulum (ER) of pancreatic beta cells from proinsulin. Chronic hyperglycemia increases considerably the proinsulin secretion, overcrowding the ER. Recent experimental evidence demonstrates that such states favor the proinsulin denaturation. The biophysical mechanism of this cellular dysfunction remains largely unknown. We use basic molecular principles and numerical simulations of time-dependent crowding conditions in the ER to show that crowding effects enhance the propensity of proinsulin molecules to (mis)fold in compressed, nonnative structures. Present results suggest: i) misfolding events and toxic accumulations increase dramatically if the proinsulin load exceeds 50% of the available space and ii) insufficient lag time for the relaxation of the ER between consecutive proinsulin uploads can cause irreversible alterations of folding capabilities. Present study may prove useful in generating new testable statements on circumstances leading to the development of diabetes.
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Affiliation(s)
- F Despa
- Department of Pharmacology, University of California Davis, Davis, CA 95616, USA.
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44
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Colombo C, Porzio O, Liu M, Massa O, Vasta M, Salardi S, Beccaria L, Monciotti C, Toni S, Pedersen O, Hansen T, Federici L, Pesavento R, Cadario F, Federici G, Ghirri P, Arvan P, Iafusco D, Barbetti F. Seven mutations in the human insulin gene linked to permanent neonatal/infancy-onset diabetes mellitus. J Clin Invest 2008; 118:2148-56. [PMID: 18451997 DOI: 10.1172/jci33777] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2007] [Accepted: 03/19/2008] [Indexed: 11/17/2022] Open
Abstract
Permanent neonatal diabetes mellitus (PNDM) is a rare disorder usually presenting within 6 months of birth. Although several genes have been linked to this disorder, in almost half the cases documented in Italy, the genetic cause remains unknown. Because the Akita mouse bearing a mutation in the Ins2 gene exhibits PNDM associated with pancreatic beta cell apoptosis, we sequenced the human insulin gene in PNDM subjects with unidentified mutations. We discovered 7 heterozygous mutations in 10 unrelated probands. In 8 of these patients, insulin secretion was detectable at diabetes onset, but rapidly declined over time. When these mutant proinsulins were expressed in HEK293 cells, we observed defects in insulin protein folding and secretion. In these experiments, expression of the mutant proinsulins was also associated with increased Grp78 protein expression and XBP1 mRNA splicing, 2 markers of endoplasmic reticulum stress, and with increased apoptosis. Similarly transfected INS-1E insulinoma cells had diminished viability compared with those expressing WT proinsulin. In conclusion, we find that mutations in the insulin gene that promote proinsulin misfolding may cause PNDM.
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Affiliation(s)
- Carlo Colombo
- Laboratory of Molecular Endocrinology and Metabolism, Bambino Gesù Children's Hospital, Scientific Institute and Department of Internal Medicine, University of Tor Vergata, Rome, Italy
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45
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Anelli T, Sitia R. Protein quality control in the early secretory pathway. EMBO J 2008; 27:315-27. [PMID: 18216874 DOI: 10.1038/sj.emboj.7601974] [Citation(s) in RCA: 474] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2007] [Accepted: 12/05/2007] [Indexed: 12/16/2022] Open
Abstract
Eukaryotic cells are able to discriminate between native and non-native polypeptides, selectively transporting the former to their final destinations. Secretory proteins are scrutinized at the endoplasmic reticulum (ER)-Golgi interface. Recent findings reveal novel features of the underlying molecular mechanisms, with several chaperone networks cooperating in assisting the maturation of complex proteins and being selectively induced to match changing synthetic demands. 'Public' and 'private' chaperones, some of which enriched in specializes subregions, operate for most or selected substrates, respectively. Moreover, sequential checkpoints are distributed along the early secretory pathway, allowing efficiency and fidelity in protein secretion.
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Affiliation(s)
- Tiziana Anelli
- Department of Functional Genomics and Molecular Biology, Università Vita-Salute San Raffaele Scientific Institute, DiBiT-HSR, Milano, Italy
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46
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Granell S, Baldini G, Mohammad S, Nicolin V, Narducci P, Storrie B, Baldini G. Sequestration of mutated alpha1-antitrypsin into inclusion bodies is a cell-protective mechanism to maintain endoplasmic reticulum function. Mol Biol Cell 2008; 19:572-86. [PMID: 18045994 PMCID: PMC2230602 DOI: 10.1091/mbc.e07-06-0587] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2007] [Revised: 10/18/2007] [Accepted: 11/16/2007] [Indexed: 12/21/2022] Open
Abstract
A variant alpha1-antitrypsin with E342K mutation has a high tendency to form intracellular polymers, and it is associated with liver disease. In the hepatocytes of individuals carrying the mutation, alpha1-antitrypsin localizes both to the endoplasmic reticulum (ER) and to membrane-surrounded inclusion bodies (IBs). It is unclear whether the IBs contribute to cell toxicity or whether they are protective to the cell. We found that in hepatoma cells, mutated alpha1-antitrypsin exited the ER and accumulated in IBs that were negative for autophagosomal and lysosomal markers, and contained several ER components, but not calnexin. Mutated alpha1-antitrypsin induced IBs also in neuroendocrine cells, showing that formation of these organelles is not cell type specific. In the presence of IBs, ER function was largely maintained. Increased levels of calnexin, but not of protein disulfide isomerase, inhibited formation of IBs and lead to retention of mutated alpha1-antitrypsin in the ER. In hepatoma cells, shift of mutated alpha1-antitrypsin localization to the ER by calnexin overexpression lead to cell shrinkage, ER stress, and impairment of the secretory pathway at the ER level. We conclude that segregation of mutated alpha1-antitrypsin from the ER to the IBs is a protective cell response to maintain a functional secretory pathway.
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Affiliation(s)
| | - Giovanna Baldini
- Dipartimento Universitario Clinico di Biomedicina, Universita' degli Studi di Trieste, Trieste I-34138, Italy
| | | | - Vanessa Nicolin
- Dipartimento Universitario Clinico di Biomedicina, Universita' degli Studi di Trieste, Trieste I-34138, Italy
| | - Paola Narducci
- Dipartimento Universitario Clinico di Biomedicina, Universita' degli Studi di Trieste, Trieste I-34138, Italy
| | - Brian Storrie
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR 72205; and
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Roth J, Yam GHF, Fan J, Hirano K, Gaplovska-Kysela K, Le Fourn V, Guhl B, Santimaria R, Torossi T, Ziak M, Zuber C. Protein quality control: the who's who, the where's and therapeutic escapes. Histochem Cell Biol 2008; 129:163-77. [PMID: 18075753 PMCID: PMC2228381 DOI: 10.1007/s00418-007-0366-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/28/2007] [Indexed: 01/01/2023]
Abstract
In cells the quality of newly synthesized proteins is monitored in regard to proper folding and correct assembly in the early secretory pathway, the cytosol and the nucleoplasm. Proteins recognized as non-native in the ER will be removed and degraded by a process termed ERAD. ERAD of aberrant proteins is accompanied by various changes of cellular organelles and results in protein folding diseases. This review focuses on how the immunocytochemical labeling and electron microscopic analyses have helped to disclose the in situ subcellular distribution pattern of some of the key machinery proteins of the cellular protein quality control, the organelle changes due to the presence of misfolded proteins, and the efficiency of synthetic chaperones to rescue disease-causing trafficking defects of aberrant proteins.
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Affiliation(s)
- Jürgen Roth
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
| | - Gary Hin-Fai Yam
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
- Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, University Eye Centre, Mongkok, Kowloon Hong Kong
| | - Jingyu Fan
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
- Department of Biophysics, Peking University Health Science Center, 100083 Beijing, P. R. China
| | - Kiyoko Hirano
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
- The Noguchi Institute, 1-8-1 Kaga, Itabashi, Tokyo 173-0003 Japan
| | - Katarina Gaplovska-Kysela
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
| | - Valerie Le Fourn
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
| | - Bruno Guhl
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
| | - Roger Santimaria
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
| | - Tania Torossi
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
| | - Martin Ziak
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
| | - Christian Zuber
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
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48
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Lavoie C, Paiement J. Topology of molecular machines of the endoplasmic reticulum: a compilation of proteomics and cytological data. Histochem Cell Biol 2008; 129:117-28. [PMID: 18172663 PMCID: PMC2228376 DOI: 10.1007/s00418-007-0370-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/06/2007] [Indexed: 11/20/2022]
Abstract
The endoplasmic reticulum (ER) is a key organelle of the secretion pathway involved in the synthesis of both proteins and lipids destined for multiple sites within and without the cell. The ER functions to both co- and post-translationally modify newly synthesized proteins and lipids and sort them for housekeeping within the ER and for transport to their sites of function away from the ER. In addition, the ER is involved in the metabolism and degradation of specific xenobiotics and endogenous biosynthetic products. A variety of proteomics studies have been reported on different subcompartments of the ER providing an ER protein dictionary with new data being made available on many protein complexes of relevance to the biology of the ER including the ribosome, the translocon, coatomer proteins, cytoskeletal proteins, folding proteins, the antigen-processing machinery, signaling proteins and proteins involved in membrane traffic. This review examines proteomics and cytological data in support of the presence of specific molecular machines at specific sites or subcompartments of the ER.
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Affiliation(s)
- Christine Lavoie
- Département de pharmacologie, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, QC, Canada, J1H 5N4
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49
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Marchetti P, Bugliani M, Lupi R, Marselli L, Masini M, Boggi U, Filipponi F, Weir GC, Eizirik DL, Cnop M. The endoplasmic reticulum in pancreatic beta cells of type 2 diabetes patients. Diabetologia 2007; 50:2486-94. [PMID: 17906960 DOI: 10.1007/s00125-007-0816-8] [Citation(s) in RCA: 305] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2007] [Accepted: 07/19/2007] [Indexed: 12/23/2022]
Abstract
AIMS/HYPOTHESIS Pancreatic beta cells have highly developed endoplasmic reticulum (ER) due to their role in insulin secretion. Since ER stress has been associated with beta cell dysfunction, we studied several features of beta cell ER in human type 2 diabetes. METHODS Pancreatic samples and/or isolated islets from non-diabetic controls (ND) and type 2 diabetes patients were evaluated for insulin secretion, apoptosis (electron microscopy and ELISA), morphometric ER assessment (electron microscopy), and expression of ER stress markers in beta cell prepared by laser capture microdissection and in isolated islets. RESULTS Insulin release was lower and beta cell apoptosis higher in type 2 diabetes than ND islets. ER density volume was significantly increased in type 2 diabetes beta cells. Expression of alpha-mannosidase (also known as mannosidase, alpha, class 1A, member 1) and UDP-glucose glycoprotein glucosyl transferase like 2 (UGCGL2), assessed by microarray and/or real-time reverse transcriptase polymerase chain reaction (RT-PCR), differed between ND and type 2 diabetes beta cells. Expression of immunoglobulin heavy chain binding protein (BiP, also known as heat shock 70 kDa protein 5 [glucose-regulated protein, 78 kDa] [HSPA5]), X-box binding protein 1 (XBP-1, also known as XBP1) and C/EBP homologous protein (CHOP, also known as damage-inducible transcript 3 [DDIT3]) was not higher in type 2 diabetes beta cell or isolated islets cultured at 5.5 mmol/l glucose (microarray and real-time RT-PCR) than in ND samples. When islets were cultured for 24 h at 11.1 mmol/l glucose, there was induction of BiP and XBP-1 in type 2 diabetes islets but not in ND islets. CONCLUSIONS/INTERPRETATION Beta cell in type 2 diabetes showed modest signs of ER stress when studied in pancreatic samples or isolated islets maintained at physiological glucose concentration. However, exposure to increased glucose levels induced ER stress markers in type 2 diabetes islet cells, which therefore may be more susceptible to ER stress induced by metabolic perturbations.
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Affiliation(s)
- P Marchetti
- Department of Endocrinology and Metabolism, Metabolic Unit, Ospedale Cisanello, University of Pisa, Via Paradisa 2, 56100, Pisa, Italy.
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50
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Liu M, Hodish I, Rhodes CJ, Arvan P. Proinsulin maturation, misfolding, and proteotoxicity. Proc Natl Acad Sci U S A 2007; 104:15841-6. [PMID: 17898179 PMCID: PMC2000385 DOI: 10.1073/pnas.0702697104] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
As a tool to explore proinsulin (PI) trafficking, a human PI cDNA has been constructed with GFP fused within the C peptide. In regulated secretory cells containing appropriate prohormone convertases, the hProCpepGFP construct undergoes endoproteolytic processing to CpepGFP and native human insulin, which are specifically detected and cosecreted in parallel with endogenous insulin. Expression of C(A7)Y mutant PI results in autosomal dominant diabetes in Akita mice. We directly identify the misfolded PI in Akita islets and also show that C(A7)Y mutant PI, either in the context of the hProCpepGFP chimera or not, engages directly in protein complexes with nonmutant PI, impairing the trafficking and recovery of nonmutant PI. This trapping mechanism decreases insulin production in beta cells. Thereafter we observe a loss of beta cell viability. The data imply that PI misfolding leading to impaired endoplasmic reticulum exit of nonmutant PI may be a key early step in a chain reaction of beta cell dysfunction and demise leading to onset and progression of diabetes.
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Affiliation(s)
- Ming Liu
- *Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical Center, Ann Arbor, MI 48109; and
| | - Israel Hodish
- *Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical Center, Ann Arbor, MI 48109; and
| | - Christopher J. Rhodes
- Section of Endocrinology, Diabetes, and Metabolism, University of Chicago, Chicago, IL 60637
| | - Peter Arvan
- *Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical Center, Ann Arbor, MI 48109; and
- To whom correspondence should be addressed at:
Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, 5560 Medical Science Research Building II, 1150 West Medical Center Drive, Ann Arbor, MI 48109-0678. E-mail:
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