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Yasui T, Mashiko M, Obi A, Mori H, Ito-Murata M, Hayakawa H, Kikuchi S, Hosaka M, Kubota C, Torii S, Gomi H. Insulin granule morphology and crinosome formation in mice lacking the pancreatic β cell-specific phogrin (PTPRN2) gene. Histochem Cell Biol 2024; 161:223-238. [PMID: 38150052 DOI: 10.1007/s00418-023-02256-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/19/2023] [Indexed: 12/28/2023]
Abstract
We recently reported that phogrin, also known as IA-2β or PTPRN2, forms a complex with the insulin receptor in pancreatic β cells upon glucose stimulation and stabilizes insulin receptor substrate 2. In β cells of systemic phogrin gene knockout (IA-2β-/-) mice, impaired glucose-induced insulin secretion, decreased insulin granule density, and an increase in the number and size of lysosomes have been reported. Since phogrin is expressed not only in β cells but also in various neuroendocrine cells, the precise impact of phogrin expressed in β cells on these cells remains unclear. In this study, we performed a comprehensive analysis of morphological changes in RIP-Cre+/-Phogrinflox/flox (βKO) mice with β cell-specific phogrin gene knockout. Compared to control RIP-Cre+/- Phogrin+/+ (Ctrl) mice, aged βKO mice exhibited a decreased density of insulin granules, which can be categorized into three subtypes. While no differences were observed in the density and size of lysosomes and crinosomes, organelles involved in insulin granule reduction, significant alterations in the regions of lysosomes responding positively to carbohydrate labeling were evident in young βKO mice. These alterations differed from those in Ctrl mice and continued to change with age. These electron microscopic findings suggest that phogrin expression in pancreatic β cells plays a role in insulin granule homeostasis and crinophagy during aging, potentially through insulin autocrine signaling and other mechanisms.
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Affiliation(s)
- Tadashi Yasui
- Department of Veterinary Anatomy, College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa, Kanagawa, 252-0880, Japan
| | - Mutsumi Mashiko
- Department of Veterinary Anatomy, College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa, Kanagawa, 252-0880, Japan
| | - Akihiro Obi
- Department of Veterinary Anatomy, College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa, Kanagawa, 252-0880, Japan
| | - Hiroyuki Mori
- Department of Veterinary Anatomy, College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa, Kanagawa, 252-0880, Japan
| | - Moeko Ito-Murata
- Department of Veterinary Anatomy, College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa, Kanagawa, 252-0880, Japan
| | - Hiroki Hayakawa
- Department of Veterinary Anatomy, College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa, Kanagawa, 252-0880, Japan
| | - Shota Kikuchi
- Department of Veterinary Anatomy, College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa, Kanagawa, 252-0880, Japan
| | - Masahiro Hosaka
- Laboratory of Molecular Life Sciences, Department of Biotechnology, Akita Prefectural University, 241-438 Kaidobata-nishi, Nakano Shimoshinjo, Akita, 010-0195, Japan
| | - Chisato Kubota
- Center for Food Science and Wellness, Gunma University, 3-39-22 Showa, Maebashi, Gunma, 371-8511, Japan
- Takasaki University of Health and Welfare, 37-1 Nakaorui, Takasaki, Gunma, 370-0033, Japan
| | - Seiji Torii
- Center for Food Science and Wellness, Gunma University, 3-39-22 Showa, Maebashi, Gunma, 371-8511, Japan
| | - Hiroshi Gomi
- Department of Veterinary Anatomy, College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa, Kanagawa, 252-0880, Japan.
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2
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Mendis T, Filipova B, Wang JJ, Pietropaolo M, Jackson MW. Affinity purification of serum-derived anti-IA-2 autoantibodies in type 1 diabetes using a novel MBP-IA-2 fusion protein. Biochem Biophys Rep 2022; 33:101413. [PMID: 36578528 PMCID: PMC9791830 DOI: 10.1016/j.bbrep.2022.101413] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 12/05/2022] [Accepted: 12/14/2022] [Indexed: 12/23/2022] Open
Abstract
Autoantibodies targeting epitopes contained within the intracellular domain (IC) of the protein phosphatase-like islet antigen 2 (IA-2) are a common marker of autoimmune type 1 diabetes (T1D), however the isolation of genuine, serum derived anti-IA-2 autoantibodies has proven challenging due to a lack of suitable bioassays. In the current study, an ELISA format was developed for affinity purification of human anti-IA-2ic autoantibodies utilizing a fusion protein (FP) incorporating maltose binding protein and the full-length IA-2IC domain. Using a T1D patient cohort validated for anti-IA-2ic autoantibodies by commercial ELISA, we demonstrate the MBP-IA-2ic FP ELISA detects serum anti-IA-2IC autoantibodies from 3 of 9 IA-2 positive patients. Further to this, a multi-plate MBP-IA-2ic FP ELISA protocol specifically affinity purifies IgG enriched for anti-IA-2ic autoantibodies. Interestingly, serum derived autoantibodies immobilised on the MBP-IA-2ic FP ELISA demonstrate increased Kappa light chain usage when compared to the respective total IgG derived from donor patients, suggesting a clonally restricted repertoire of anti-IA-2ic autoantigen specific B plasma cells is responsible for autoantibodies detect by the MBP-IA-2ic FP ELISA. This study is the first to demonstrate the generation of specific, genuine human derived anti-IA-2ic autoantibodies, thereby facilitating further investigation into the origin and functional significance of IA-2 autoantibodies in T1D.
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Affiliation(s)
- Thilini Mendis
- Department of Immunology, Allergy & Arthritis, Flinders Medical Centre and Flinders University, Bedford Park, 5042, South Australia, Australia
| | - Barbora Filipova
- Department of Immunology, Allergy & Arthritis, Flinders Medical Centre and Flinders University, Bedford Park, 5042, South Australia, Australia
| | - Jing Jing Wang
- Department of Immunology, Allergy & Arthritis, Flinders Medical Centre and Flinders University, Bedford Park, 5042, South Australia, Australia
| | - Massimo Pietropaolo
- Dept of Pathology and Immunology, Baylor College of Medicine, Houston, TX, USA
| | - Michael W. Jackson
- Department of Immunology, Allergy & Arthritis, Flinders Medical Centre and Flinders University, Bedford Park, 5042, South Australia, Australia,Corresponding author. Department of Immunology, Allergy and Arthritis, Flinders University, GPO Box 2100, Adelaide, South Australia, 5001, Australia.
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3
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Finotti P, Pagetta A. A mutant α1antitrypsin in complex with heat shock proteins as the primary antigen in type 1 diabetes in silico investigation. Sci Rep 2021; 11:3002. [PMID: 33542414 PMCID: PMC7862655 DOI: 10.1038/s41598-021-82730-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Accepted: 01/25/2021] [Indexed: 11/09/2022] Open
Abstract
Based on previous results demonstrating that complexes of a mutant α1-antitrypsin with the heat shock proteins (HSP)70 and glucose-regulated protein94 (Grp94) circulate in the blood of patients with type 1 diabetes, we raised the hypothesis that these complexes could represent the primary antigen capable of triggering the autoimmune reactions leading to overt diabetes. As a first approach to this issue, we searched whether A1AT and HSPs had a sequence similarity to major islet antigen proteins so as to identify among the similar sequences those with potential relevance for the pathogenesis of diabetes. A thorough in silico analysis was performed to establish the score of similarity of the human proteins: A1AT, pro-insulin (INS), GAD65, IAPP, IA-2, ICA69, Grp94, HSP70 and HSP60. The sequences of A1AT and HSPs with the highest score of similarity to the islet peptides reported in the literature as the main autoantigens in human diabetes were recorded. At variance with other HSPs, also including HSP90 and Grp78, Grp94 contained the highest number and the longest sequences with structural similarity to A1AT and to well-known immunogenic peptides/epitopes of INS, GAD65, and IA-2. The similarity of A1AT with Grp94 and that of Grp94 with INS also suggested a functional relationship among the proteins. Specific sequences were identified in A1AT, Grp94 and HSP70, with the highest score of cross-similarity to a pattern of eight different islet protein epitopes. The similarity also involved recently discovered autoantigens in type 1 diabetes such as a hybrid peptides of insulin and the defective ribosomal insulin gene product. The significant similarity displayed by specific sequences of Grp94 and A1AT to the islet peptides considered main antigens in human diabetes, is a strong indication for testing these sequences as new peptides of immunogenic relevance in diabetes.
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Affiliation(s)
- Paola Finotti
- Department of Pharmaceutical and Pharmacological Sciences, University of Padua, Building "C", Largo E. Meneghetti, 2, 35131, Padua, Italy.
| | - Andrea Pagetta
- Department of Pharmaceutical and Pharmacological Sciences, University of Padua, Building "C", Largo E. Meneghetti, 2, 35131, Padua, Italy
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4
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Reiterer V, Pawłowski K, Desrochers G, Pause A, Sharpe HJ, Farhan H. The dead phosphatases society: a review of the emerging roles of pseudophosphatases. FEBS J 2020; 287:4198-4220. [PMID: 32484316 DOI: 10.1111/febs.15431] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 05/12/2020] [Accepted: 05/27/2020] [Indexed: 12/11/2022]
Abstract
Phosphatases are a diverse family of enzymes, comprising at least 10 distinct protein folds. Like most other enzyme families, many have sequence variations that predict an impairment or loss of catalytic activity classifying them as pseudophosphatases. Research on pseudoenzymes is an emerging area of interest, with new biological functions repurposed from catalytically active relatives. Here, we provide an overview of the pseudophosphatases identified to date in all major phosphatase families. We will highlight the degeneration of the various catalytic sequence motifs and discuss the challenges associated with the experimental determination of catalytic inactivity. We will also summarize the role of pseudophosphatases in various diseases and discuss the major challenges and future directions in this field.
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Affiliation(s)
| | | | - Guillaume Desrochers
- Department of Biochemistry, McGill University, Montréal, QC, Canada.,Goodman Cancer Research Centre, McGill University, Montréal, QC, Canada
| | - Arnim Pause
- Department of Biochemistry, McGill University, Montréal, QC, Canada.,Goodman Cancer Research Centre, McGill University, Montréal, QC, Canada
| | | | - Hesso Farhan
- Institute of Basic Medical Sciences, University of Oslo, Norway
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5
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Toledo PL, Torkko JM, Müller A, Wegbrod C, Sönmez A, Solimena M, Ermácora MR. ICA512 RESP18 homology domain is a protein-condensing factor and insulin fibrillation inhibitor. J Biol Chem 2019; 294:8564-8576. [PMID: 30979722 DOI: 10.1074/jbc.ra119.007607] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Revised: 04/09/2019] [Indexed: 12/19/2022] Open
Abstract
Type 1 diabetes islet cell autoantigen 512 (ICA512/IA-2) is a tyrosine phosphatase-like intrinsic membrane protein involved in the biogenesis and turnover of insulin secretory granules (SGs) in pancreatic islet β-cells. Whereas its membrane-proximal and cytoplasmic domains have been functionally and structurally characterized, the role of the ICA512 N-terminal segment named "regulated endocrine-specific protein 18 homology domain" (RESP18HD), which encompasses residues 35-131, remains largely unknown. Here, we show that ICA512 RESP18HD residues 91-131 encode for an intrinsically disordered region (IDR), which in vitro acts as a condensing factor for the reversible aggregation of insulin and other β-cell proteins in a pH and Zn2+-regulated fashion. At variance with what has been shown for other granule cargoes with aggregating properties, the condensing activity of ICA512 RESP18HD is displayed at a pH close to neutral, i.e. in the pH range found in the early secretory pathway, whereas it is resolved at acidic pH and Zn2+ concentrations resembling those present in mature SGs. Moreover, we show that ICA512 RESP18HD residues 35-90, preceding the IDR, inhibit insulin fibrillation in vitro Finally, we found that glucose-stimulated secretion of RESP18HD upon exocytosis of SGs from insulinoma INS-1 cells is associated with cleavage of its IDR, conceivably to prevent its aggregation upon exposure to neutral pH in the extracellular milieu. Taken together, these findings point to ICA512 RESP18HD being a condensing factor for protein sorting and granulogenesis early in the secretory pathway and for prevention of amyloidogenesis.
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Affiliation(s)
- Pamela L Toledo
- Grupo de Biología Estructural y Biotecnología, Universidad Nacional de Quilmes, 1876 Bernal, Buenos Aires, Argentina; IMBICE, CONICET-CIC-Universidad Nacional de La Plata, B1906APO La Plata, Buenos Aires, Argentina
| | - Juha M Torkko
- Grupo de Biología Estructural y Biotecnología, Universidad Nacional de Quilmes, 1876 Bernal, Buenos Aires, Argentina; IMBICE, CONICET-CIC-Universidad Nacional de La Plata, B1906APO La Plata, Buenos Aires, Argentina; Department of Molecular Diabetology, University Hospital and Faculty of Medicine, TU Dresden, 01307 Dresden, Germany; Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the University Hospital and Faculty of Medicine, TU Dresden, 01307 Dresden, Germany; German Center for Diabetes Research (DZD e.V.), 85764 Neuherberg, Germany
| | - Andreas Müller
- Department of Molecular Diabetology, University Hospital and Faculty of Medicine, TU Dresden, 01307 Dresden, Germany; Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the University Hospital and Faculty of Medicine, TU Dresden, 01307 Dresden, Germany; German Center for Diabetes Research (DZD e.V.), 85764 Neuherberg, Germany
| | - Carolin Wegbrod
- Department of Molecular Diabetology, University Hospital and Faculty of Medicine, TU Dresden, 01307 Dresden, Germany; Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the University Hospital and Faculty of Medicine, TU Dresden, 01307 Dresden, Germany; German Center for Diabetes Research (DZD e.V.), 85764 Neuherberg, Germany
| | - Anke Sönmez
- Department of Molecular Diabetology, University Hospital and Faculty of Medicine, TU Dresden, 01307 Dresden, Germany; Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the University Hospital and Faculty of Medicine, TU Dresden, 01307 Dresden, Germany; German Center for Diabetes Research (DZD e.V.), 85764 Neuherberg, Germany
| | - Michele Solimena
- Department of Molecular Diabetology, University Hospital and Faculty of Medicine, TU Dresden, 01307 Dresden, Germany; Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the University Hospital and Faculty of Medicine, TU Dresden, 01307 Dresden, Germany; German Center for Diabetes Research (DZD e.V.), 85764 Neuherberg, Germany; Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany.
| | - Mario R Ermácora
- Grupo de Biología Estructural y Biotecnología, Universidad Nacional de Quilmes, 1876 Bernal, Buenos Aires, Argentina; IMBICE, CONICET-CIC-Universidad Nacional de La Plata, B1906APO La Plata, Buenos Aires, Argentina.
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6
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Rorsman P, Ashcroft FM. Pancreatic β-Cell Electrical Activity and Insulin Secretion: Of Mice and Men. Physiol Rev 2018; 98:117-214. [PMID: 29212789 PMCID: PMC5866358 DOI: 10.1152/physrev.00008.2017] [Citation(s) in RCA: 433] [Impact Index Per Article: 72.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Revised: 05/30/2017] [Accepted: 06/18/2017] [Indexed: 12/14/2022] Open
Abstract
The pancreatic β-cell plays a key role in glucose homeostasis by secreting insulin, the only hormone capable of lowering the blood glucose concentration. Impaired insulin secretion results in the chronic hyperglycemia that characterizes type 2 diabetes (T2DM), which currently afflicts >450 million people worldwide. The healthy β-cell acts as a glucose sensor matching its output to the circulating glucose concentration. It does so via metabolically induced changes in electrical activity, which culminate in an increase in the cytoplasmic Ca2+ concentration and initiation of Ca2+-dependent exocytosis of insulin-containing secretory granules. Here, we review recent advances in our understanding of the β-cell transcriptome, electrical activity, and insulin exocytosis. We highlight salient differences between mouse and human β-cells, provide models of how the different ion channels contribute to their electrical activity and insulin secretion, and conclude by discussing how these processes become perturbed in T2DM.
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Affiliation(s)
- Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, United Kingdom; Department of Neuroscience and Physiology, Metabolic Research Unit, Göteborg, Sweden; and Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Frances M Ashcroft
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, United Kingdom; Department of Neuroscience and Physiology, Metabolic Research Unit, Göteborg, Sweden; and Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
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7
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Molecular regulation of insulin granule biogenesis and exocytosis. Biochem J 2017; 473:2737-56. [PMID: 27621482 DOI: 10.1042/bcj20160291] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Accepted: 04/19/2016] [Indexed: 12/15/2022]
Abstract
Type 2 diabetes mellitus (T2DM) is a metabolic disorder characterized by hyperglycemia, insulin resistance and hyperinsulinemia in early disease stages but a relative insulin insufficiency in later stages. Insulin, a peptide hormone, is produced in and secreted from pancreatic β-cells following elevated blood glucose levels. Upon its release, insulin induces the removal of excessive exogenous glucose from the bloodstream primarily by stimulating glucose uptake into insulin-dependent tissues as well as promoting hepatic glycogenesis. Given the increasing prevalence of T2DM worldwide, elucidating the underlying mechanisms and identifying the various players involved in the synthesis and exocytosis of insulin from β-cells is of utmost importance. This review summarizes our current understanding of the route insulin takes through the cell after its synthesis in the endoplasmic reticulum as well as our knowledge of the highly elaborate network that controls insulin release from the β-cell. This network harbors potential targets for anti-diabetic drugs and is regulated by signaling cascades from several endocrine systems.
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8
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Müller A, Neukam M, Ivanova A, Sönmez A, Münster C, Kretschmar S, Kalaidzidis Y, Kurth T, Verbavatz JM, Solimena M. A Global Approach for Quantitative Super Resolution and Electron Microscopy on Cryo and Epoxy Sections Using Self-labeling Protein Tags. Sci Rep 2017; 7:23. [PMID: 28154417 PMCID: PMC5428382 DOI: 10.1038/s41598-017-00033-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Accepted: 12/20/2016] [Indexed: 01/19/2023] Open
Abstract
Correlative light and electron microscopy (CLEM) is a powerful approach to investigate the molecular ultrastructure of labeled cell compartments. However, quantitative CLEM studies are rare, mainly due to small sample sizes and the sensitivity of fluorescent proteins to strong fixatives and contrasting reagents for EM. Here, we show that fusion of a self-labeling protein to insulin allows for the quantification of age-distinct insulin granule pools in pancreatic beta cells by a combination of super resolution and transmission electron microscopy on Tokuyasu cryosections. In contrast to fluorescent proteins like GFP organic dyes covalently bound to self-labeling proteins retain their fluorescence also in epoxy resin following high pressure freezing and freeze substitution, or remarkably even after strong chemical fixation. This enables for the assessment of age-defined granule morphology and degradation. Finally, we demonstrate that this CLEM protocol is highly versatile, being suitable for single and dual fluorescent labeling and detection of different proteins with optimal ultrastructure preservation and contrast.
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Affiliation(s)
- Andreas Müller
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany.,Paul Langerhans Institute Dresden (PLID) of the Helmholtz Center Munich at the University Hospital Carl Gustav Carus and Faculty of Medicine of the TU Dresden, Dresden, Germany
| | - Martin Neukam
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany.,Paul Langerhans Institute Dresden (PLID) of the Helmholtz Center Munich at the University Hospital Carl Gustav Carus and Faculty of Medicine of the TU Dresden, Dresden, Germany
| | - Anna Ivanova
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany.,Paul Langerhans Institute Dresden (PLID) of the Helmholtz Center Munich at the University Hospital Carl Gustav Carus and Faculty of Medicine of the TU Dresden, Dresden, Germany
| | - Anke Sönmez
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany.,Paul Langerhans Institute Dresden (PLID) of the Helmholtz Center Munich at the University Hospital Carl Gustav Carus and Faculty of Medicine of the TU Dresden, Dresden, Germany
| | - Carla Münster
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany.,Paul Langerhans Institute Dresden (PLID) of the Helmholtz Center Munich at the University Hospital Carl Gustav Carus and Faculty of Medicine of the TU Dresden, Dresden, Germany
| | - Susanne Kretschmar
- Center for Regenerative Therapies Dresden (CRTD), TU Dresden, Dresden, Germany.,Biotechnology Center of the TU Dresden (BIOTEC), Dresden, Germany
| | - Yannis Kalaidzidis
- Max Planck Institute of Molecular Cell Biology and Genetics (MPI-CBG), Dresden, Germany.,Faculty of Bioengineering and Bioinformatics, Moscow State University, Moscow, Russia
| | - Thomas Kurth
- Center for Regenerative Therapies Dresden (CRTD), TU Dresden, Dresden, Germany.,Biotechnology Center of the TU Dresden (BIOTEC), Dresden, Germany
| | - Jean-Marc Verbavatz
- Max Planck Institute of Molecular Cell Biology and Genetics (MPI-CBG), Dresden, Germany.,Institut Jacques Monod, Université Paris Diderot, Paris, France
| | - Michele Solimena
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany. .,Paul Langerhans Institute Dresden (PLID) of the Helmholtz Center Munich at the University Hospital Carl Gustav Carus and Faculty of Medicine of the TU Dresden, Dresden, Germany. .,Max Planck Institute of Molecular Cell Biology and Genetics (MPI-CBG), Dresden, Germany.
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9
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Guerra LL, Faccinetti NI, Trabucchi A, Rovitto BD, Sabljic AV, Poskus E, Iacono RF, Valdez SN. Novel prokaryotic expression of thioredoxin-fused insulinoma associated protein tyrosine phosphatase 2 (IA-2), its characterization and immunodiagnostic application. BMC Biotechnol 2016; 16:84. [PMID: 27881117 PMCID: PMC5122161 DOI: 10.1186/s12896-016-0309-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Accepted: 10/21/2016] [Indexed: 11/11/2022] Open
Abstract
Background The insulinoma associated protein tyrosine phosphatase 2 (IA-2) is one of the immunodominant autoantigens involved in the autoimmune attack to the beta-cell in Type 1 Diabetes Mellitus. In this work we have developed a complete and original process for the production and recovery of the properly folded intracellular domain of IA-2 fused to thioredoxin (TrxIA-2ic) in Escherichia coli GI698 and GI724 strains. We have also carried out the biochemical and immunochemical characterization of TrxIA-2icand design variants of non-radiometric immunoassays for the efficient detection of IA-2 autoantibodies (IA-2A). Results The main findings can be summarized in the following statements: i) TrxIA-2ic expression after 3 h of induction on GI724 strain yielded ≈ 10 mg of highly pure TrxIA-2ic/L of culture medium by a single step purification by affinity chromatography, ii) the molecular weight of TrxIA-2ic (55,358 Da) could be estimated by SDS-PAGE, size exclusion chromatography and mass spectrometry, iii) TrxIA-2ic was properly identified by western blot and mass spectrometric analysis of proteolytic digestions (63.25 % total coverage), iv) excellent immunochemical behavior of properly folded full TrxIA-2ic was legitimized by inhibition or displacement of [35S]IA-2 binding from IA-2A present in Argentinian Type 1 Diabetic patients, v) great stability over time was found under proper storage conditions and vi) low cost and environmentally harmless ELISA methods for IA-2A assessment were developed, with colorimetric or chemiluminescent detection. Conclusions E. coli GI724 strain emerged as a handy source of recombinant IA-2ic, achieving high levels of expression as a thioredoxin fusion protein, adequately validated and applicable to the development of innovative and cost-effective immunoassays for IA-2A detection in most laboratories. Electronic supplementary material The online version of this article (doi:10.1186/s12896-016-0309-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Luciano Lucas Guerra
- Universidad de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Estudios de la Inmunidad Humoral "Prof. Ricardo A. Margni" (IDEHU), Facultad de Farmacia y Bioquímica, Buenos Aires, Argentina
| | - Natalia Inés Faccinetti
- Universidad de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Estudios de la Inmunidad Humoral "Prof. Ricardo A. Margni" (IDEHU), Facultad de Farmacia y Bioquímica, Buenos Aires, Argentina
| | - Aldana Trabucchi
- Universidad de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Estudios de la Inmunidad Humoral "Prof. Ricardo A. Margni" (IDEHU), Facultad de Farmacia y Bioquímica, Buenos Aires, Argentina
| | - Bruno David Rovitto
- Universidad de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Estudios de la Inmunidad Humoral "Prof. Ricardo A. Margni" (IDEHU), Facultad de Farmacia y Bioquímica, Buenos Aires, Argentina
| | - Adriana Victoria Sabljic
- Universidad de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Estudios de la Inmunidad Humoral "Prof. Ricardo A. Margni" (IDEHU), Facultad de Farmacia y Bioquímica, Buenos Aires, Argentina
| | - Edgardo Poskus
- Universidad de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Estudios de la Inmunidad Humoral "Prof. Ricardo A. Margni" (IDEHU), Facultad de Farmacia y Bioquímica, Buenos Aires, Argentina
| | - Ruben Francisco Iacono
- Universidad de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Estudios de la Inmunidad Humoral "Prof. Ricardo A. Margni" (IDEHU), Facultad de Farmacia y Bioquímica, Buenos Aires, Argentina
| | - Silvina Noemí Valdez
- Universidad de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Estudios de la Inmunidad Humoral "Prof. Ricardo A. Margni" (IDEHU), Facultad de Farmacia y Bioquímica, Buenos Aires, Argentina.
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10
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Ahn M, Yoder SM, Wang Z, Oh E, Ramalingam L, Tunduguru R, Thurmond DC. The p21-activated kinase (PAK1) is involved in diet-induced beta cell mass expansion and survival in mice and human islets. Diabetologia 2016; 59:2145-55. [PMID: 27394663 PMCID: PMC5266538 DOI: 10.1007/s00125-016-4042-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Accepted: 06/10/2016] [Indexed: 01/09/2023]
Abstract
AIMS/HYPOTHESIS Human islets from type 2 diabetic donors are reportedly 80% deficient in the p21 (Cdc42/Rac)-activated kinase, PAK1. PAK1 is implicated in beta cell function and maintenance of beta cell mass. We questioned the mechanism(s) by which PAK1 deficiency potentially contributes to increased susceptibility to type 2 diabetes. METHODS Non-diabetic human islets and INS 832/13 beta cells cultured under diabetogenic conditions (i.e. with specific cytokines or under glucolipotoxic [GLT] conditions) were evaluated for changes to PAK1 signalling. Combined effects of PAK1 deficiency with GLT stress were assessed using classic knockout (Pak1 (-/-) ) mice fed a 45% energy from fat/palmitate-based, 'western' diet (WD). INS 832/13 cells overexpressing or depleted of PAK1 were also assessed for apoptosis and signalling changes. RESULTS Exposure of non-diabetic human islets to diabetic stressors attenuated PAK1 protein levels, concurrent with increased caspase 3 cleavage. WD-fed Pak1 knockout mice exhibited fasting hyperglycaemia and severe glucose intolerance. These mice also failed to mount an insulin secretory response following acute glucose challenge, coinciding with a 43% loss of beta cell mass when compared with WD-fed wild-type mice. Pak1 knockout mice had fewer total beta cells per islet, coincident with decreased beta cell proliferation. In INS 832/13 beta cells, PAK1 deficiency combined with GLT exposure heightened beta cell death relative to either condition alone; PAK1 deficiency resulted in decreased extracellular signal-related kinase (ERK) and B cell lymphoma 2 (Bcl2) phosphorylation levels. Conversely, PAK1 overexpression prevented GLT-induced cell death. CONCLUSIONS/INTERPRETATION These findings suggest that PAK1 deficiency may underlie an increased diabetic susceptibility. Discovery of ways to remediate glycaemic dysregulation via altering PAK1 or its downstream effectors offers promising opportunities for disease intervention.
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Affiliation(s)
- Miwon Ahn
- Department of Molecular & Cellular Endocrinology, Beckman Research Institute of City of Hope, 1500 E. Duarte Rd., Duarte, CA, 91010, USA
| | - Stephanie M Yoder
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Zhanxiang Wang
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Eunjin Oh
- Department of Molecular & Cellular Endocrinology, Beckman Research Institute of City of Hope, 1500 E. Duarte Rd., Duarte, CA, 91010, USA
| | - Latha Ramalingam
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Ragadeepthi Tunduguru
- Department of Molecular & Cellular Endocrinology, Beckman Research Institute of City of Hope, 1500 E. Duarte Rd., Duarte, CA, 91010, USA
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Debbie C Thurmond
- Department of Molecular & Cellular Endocrinology, Beckman Research Institute of City of Hope, 1500 E. Duarte Rd., Duarte, CA, 91010, USA.
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN, USA.
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, USA.
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11
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Mziaut H, Mulligan B, Hoboth P, Otto O, Ivanova A, Herbig M, Schumann D, Hildebrandt T, Dehghany J, Sönmez A, Münster C, Meyer-Hermann M, Guck J, Kalaidzidis Y, Solimena M. The F-actin modifier villin regulates insulin granule dynamics and exocytosis downstream of islet cell autoantigen 512. Mol Metab 2016; 5:656-668. [PMID: 27656403 PMCID: PMC5021679 DOI: 10.1016/j.molmet.2016.05.015] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Revised: 05/20/2016] [Accepted: 05/24/2016] [Indexed: 01/02/2023] Open
Abstract
Objective Insulin release from pancreatic islet β cells should be tightly controlled to avoid hypoglycemia and insulin resistance. The cortical actin cytoskeleton is a gate for regulated exocytosis of insulin secretory granules (SGs) by restricting their mobility and access to the plasma membrane. Prior studies suggest that SGs interact with F-actin through their transmembrane cargo islet cell autoantigen 512 (Ica512) (also known as islet antigen 2/Ptprn). Here we investigated how Ica512 modulates SG trafficking and exocytosis. Methods Transcriptomic changes in Ica512−/− mouse islets were analyzed. Imaging as well as biophysical and biochemical methods were used to validate if and how the Ica512-regulated gene villin modulates insulin secretion in mouse islets and insulinoma cells. Results The F-actin modifier villin was consistently downregulated in Ica512−/− mouse islets and in Ica512-depleted insulinoma cells. Villin was enriched at the cell cortex of β cells and dispersed villin−/− islet cells were less round and less deformable. Basal mobility of SGs in villin-depleted cells was enhanced. Moreover, in cells depleted either of villin or Ica512 F-actin cages restraining cortical SGs were enlarged, basal secretion was increased while glucose-stimulated insulin release was blunted. The latter changes were reverted by overexpressing villin in Ica512-depleted cells, but not vice versa. Conclusion Our findings show that villin controls the size of the F-actin cages restricting SGs and, thus, regulates their dynamics and availability for exocytosis. Evidence that villin acts downstream of Ica512 also indicates that SGs directly influence the remodeling properties of the cortical actin cytoskeleton for tight control of insulin secretion. Ica512-depletion reduces the genetic expression of the F-actin modifier villin. Villin-depletion enhances basal insulin granule mobility and exocytosis. Villin regulates the size of actin cages restraining insulin granules. Villin acts downstream of insulin granule cargo Ica512. The Ica512-villin genetic link enables granules to control cytoskeleton plasticity.
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Key Words
- D, diffusion coefficient
- EGFP, enhanced green fluorescent protein
- F-actin
- Granules
- IPGTT, intraperitoneal glucose tolerance test
- IVGTT, intravenous glucose tolerance test
- Ica512
- Ica512, islet cell autoantigen
- Insulin
- OGTT, oral glucose tolerance test
- RT-DC, real-time deformability cytometry
- SE, standard error
- SG, secretory granules
- Secretion
- TIRFM, total internal reflection fluorescence microscopy
- Villin
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Affiliation(s)
- Hassan Mziaut
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the Univ. Hospital, Faculty of Medicine Carl Gustav Carus, Technische Univ. Dresden, 01307 Dresden, Germany; German Center for Diabetes Research (DZD e.V.), 85674 Neuherberg, Germany
| | - Bernard Mulligan
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the Univ. Hospital, Faculty of Medicine Carl Gustav Carus, Technische Univ. Dresden, 01307 Dresden, Germany; German Center for Diabetes Research (DZD e.V.), 85674 Neuherberg, Germany
| | - Peter Hoboth
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the Univ. Hospital, Faculty of Medicine Carl Gustav Carus, Technische Univ. Dresden, 01307 Dresden, Germany; German Center for Diabetes Research (DZD e.V.), 85674 Neuherberg, Germany
| | - Oliver Otto
- Biotechnology Center Dresden, 01307 Dresden, Germany
| | - Anna Ivanova
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the Univ. Hospital, Faculty of Medicine Carl Gustav Carus, Technische Univ. Dresden, 01307 Dresden, Germany; German Center for Diabetes Research (DZD e.V.), 85674 Neuherberg, Germany
| | - Maik Herbig
- Biotechnology Center Dresden, 01307 Dresden, Germany
| | - Desiree Schumann
- Boehringer Ingelheim Pharma GmbH & Co. KG. Cardiometabolic Research, 88397 Biberach, Germany
| | - Tobias Hildebrandt
- Boehringer Ingelheim Pharma GmbH & Co. KG. Cardiometabolic Research, 88397 Biberach, Germany
| | - Jaber Dehghany
- Helmholtz Centre for Infection Research (HZI), Braunschweig Integrated Centre for Systems Biology (BRICS), 38124 Braunschweig, Germany
| | - Anke Sönmez
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the Univ. Hospital, Faculty of Medicine Carl Gustav Carus, Technische Univ. Dresden, 01307 Dresden, Germany; German Center for Diabetes Research (DZD e.V.), 85674 Neuherberg, Germany
| | - Carla Münster
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the Univ. Hospital, Faculty of Medicine Carl Gustav Carus, Technische Univ. Dresden, 01307 Dresden, Germany; German Center for Diabetes Research (DZD e.V.), 85674 Neuherberg, Germany
| | - Michael Meyer-Hermann
- Helmholtz Centre for Infection Research (HZI), Braunschweig Integrated Centre for Systems Biology (BRICS), 38124 Braunschweig, Germany
| | - Jochen Guck
- Biotechnology Center Dresden, 01307 Dresden, Germany
| | - Yannis Kalaidzidis
- Max Planck Institute for Molecular Cell Biology and Genetics, 01307 Dresden, Germany
| | - Michele Solimena
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the Univ. Hospital, Faculty of Medicine Carl Gustav Carus, Technische Univ. Dresden, 01307 Dresden, Germany; German Center for Diabetes Research (DZD e.V.), 85674 Neuherberg, Germany; Max Planck Institute for Molecular Cell Biology and Genetics, 01307 Dresden, Germany.
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Abstract
Islet autoantibodies are the main markers of pancreatic autoimmunity in type 1 diabetes (T1D). Islet autoantibodies recognize insulin (IAA), glutamic acid decarboxylase (GADA), protein phosphatase-like IA-2 (IA-2A), and ZnT8 (ZnT8A), all antigens that are found on secretory granules within pancreatic beta cells. Islet antibodies, measured by sensitive and specific liquid phase assays, are the key parameters of the autoimmune response monitored for diagnostics or prognostics in patients with T1D or for disease prediction in at-risk individuals before T1D onset. Islet autoantibodies have been the main tool used to explore the natural history of T1D; this review summarizes the current knowledge about the autoantigens and the phenotype of islets autoantibodies acquired in large prospective studies from birth in children at risk of developing T1D.
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Affiliation(s)
- Vito Lampasona
- Division of Genetics and Cell Biology, IRCCS San Raffaele Scientific Institute, via Olgettina 60, 20132, Milano, Italy.
- Diabetes Research Institute, IRCCS San Raffaele Scientific Institute, via Olgettina 60, 20132, Milano, Italy.
| | - Daniela Liberati
- Division of Genetics and Cell Biology, IRCCS San Raffaele Scientific Institute, via Olgettina 60, 20132, Milano, Italy
- Diabetes Research Institute, IRCCS San Raffaele Scientific Institute, via Olgettina 60, 20132, Milano, Italy
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13
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Biochemical, biophysical, and functional properties of ICA512/IA-2 RESP18 homology domain. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2016; 1864:511-22. [DOI: 10.1016/j.bbapap.2016.01.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Revised: 01/04/2016] [Accepted: 01/29/2016] [Indexed: 02/04/2023]
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Stability of proICA512/IA-2 and its targeting to insulin secretory granules require β4-sheet-mediated dimerization of its ectodomain in the endoplasmic reticulum. Mol Cell Biol 2015; 35:914-27. [PMID: 25561468 DOI: 10.1128/mcb.00994-14] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The type 1 diabetes autoantigen ICA512/IA-2/RPTPN is a receptor protein tyrosine phosphatase of the insulin secretory granules (SGs) which regulates the size of granule stores, possibly via cleavage/signaling of its cytosolic tail. The role of its extracellular region remains unknown. Structural studies indicated that β2- or β4-strands in the mature ectodomain (ME ICA512) form dimers in vitro. Here we show that ME ICA512 prompts proICA512 dimerization in the endoplasmic reticulum. Perturbation of ME ICA512 β2-strand N-glycosylation upon S508A replacement allows for proICA512 dimerization, O-glycosylation, targeting to granules, and conversion, which are instead precluded upon G553D replacement in the ME ICA512 β4-strand. S508A/G553D and N506A/G553D double mutants dimerize but remain in the endoplasmic reticulum. Removal of the N-terminal fragment (ICA512-NTF) preceding ME ICA512 allows an ICA512-ΔNTF G553D mutant to exit the endoplasmic reticulum, and ICA512-ΔNTF is constitutively delivered to the cell surface. The signal for SG sorting is located within the NTF RESP18 homology domain (RESP18-HD), whereas soluble NTF is retained in the endoplasmic reticulum. Hence, we propose that the ME ICA512 β2-strand fosters proICA512 dimerization until NTF prevents N506 glycosylation. Removal of this constraint allows for proICA512 β4-strand-induced dimerization, exit from the endoplasmic reticulum, O-glycosylation, and RESP18-HD-mediated targeting to granules.
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15
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X-ray structure of the mature ectodomain of phogrin. ACTA ACUST UNITED AC 2014; 16:1-9. [PMID: 25421040 DOI: 10.1007/s10969-014-9191-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Accepted: 11/19/2014] [Indexed: 10/24/2022]
Abstract
Phogrin/IA-2β and ICA512/IA-2 are two paralogs receptor-type protein-tyrosine phosphatases (RPTP) that localize in secretory granules of various neuroendocrine cells. In pancreatic islet β-cells, they participate in the regulation of insulin secretion, ensuring proper granulogenesis, and β-cell proliferation. The role of their cytoplasmic tail has been partially unveiled, while that of their luminal region remains unclear. To advance the understanding of its structure-function relationship, the X-ray structure of the mature ectodomain of phogrin (ME phogrin) at pH 7.4 and 4.6 has been solved at 1.95- and 2.01-Å resolution, respectively. Similarly to the ME of ICA512, ME phogrin adopts a ferredoxin-like fold: a sheet of four antiparallel β-strands packed against two α-helices. Sequence conservation among vertebrates, plants and insects suggests that the structural similarity extends to all the receptor family. Crystallized ME phogrin is monomeric, in agreement with solution studies but in striking contrast with the behavior of homodimeric ME ICA512. The structural details that may cause the quaternary structure differences are analyzed. The results provide a basis for building models of the overall orientation and oligomerization state of the receptor in biological membranes.
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16
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Fernando R, Vonberg A, Atkins SJ, Pietropaolo S, Pietropaolo M, Smith TJ. Human fibrocytes express multiple antigens associated with autoimmune endocrine diseases. J Clin Endocrinol Metab 2014; 99:E796-803. [PMID: 24517144 PMCID: PMC4010713 DOI: 10.1210/jc.2013-3072] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT Factors common to multiple autoimmune diseases have been sought vigorously. Graves' disease (GD) and type 1 diabetes mellitus (T1DM) involve end-organ remodeling. Fibrocytes participate in inflammatory diseases and were recently shown to express thyroid-specific proteins such as the thyrotropin receptor and thyroglobulin. OBJECTIVE The objective of the study was to determine whether a broader repertoire of autoantigen expression, such as proteins associated with T1DM, can be ascribed to fibrocytes. DESIGN, SETTING, AND PARTICIPANTS Fibrocytes and fibroblasts were collected and analyzed from healthy individuals and those with autoimmune diseases in an academic clinical practice. MAIN OUTCOME MEASURES Real-time PCR, Western blot analysis, gene promoter analysis, cell transfections, and flow cytometric cell sorting were performed. RESULTS Islet cell antigen ICA512 (IA-2) and islet cell autoantigen of 69 kDa (ICA69), two islet-specific proteins implicated in T1DM, are expressed by fibrocytes from healthy donors and those with T1DM, GD, and multiple sclerosis. Both transcripts are detected by PCR, the proteins are resolved on Western blots, and both gene promoters are active in fibrocytes. Levels of ICA69 are substantially higher than those of IA-2 in fibrocytes. ICA69 localizes to CD34(+) GD orbital fibroblasts putatively derived from fibrocytes, whereas higher levels of IA-2 are found in CD34(-) fibroblasts. CONCLUSIONS In addition to autoantigens implicated in thyroid autoimmunity, fibrocytes and derivative fibroblasts express multiple autoantigens associated with T1DM. This expression results from active gene promoters and abundant steady-state mRNA encoding ICA69 and IA-2. These latest findings demonstrate that fibrocytes express antigens relevant to multiple forms of endocrine autoimmunity. They suggest the potential for these cells playing a direct role in immune reactivity directed at the thyroid and pancreatic islets.
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Affiliation(s)
- Roshini Fernando
- Department of Ophthalmology and Visual Sciences (R.F., S.J.A., T.J.S.), Kellogg Eye Center and Division of Metabolism, Endocrinology, and Diabetes (A.V., S.P., M.P., T.J.S.), Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan 48105
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17
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Bhat HF, Adams ME, Khanday FA. Syntrophin proteins as Santa Claus: role(s) in cell signal transduction. Cell Mol Life Sci 2013; 70:2533-54. [PMID: 23263165 PMCID: PMC11113789 DOI: 10.1007/s00018-012-1233-9] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2012] [Revised: 11/21/2012] [Accepted: 12/03/2012] [Indexed: 11/30/2022]
Abstract
Syntrophins are a family of cytoplasmic membrane-associated adaptor proteins, characterized by the presence of a unique domain organization comprised of a C-terminal syntrophin unique (SU) domain and an N-terminal pleckstrin homology (PH) domain that is split by insertion of a PDZ domain. Syntrophins have been recognized as an important component of many signaling events, and they seem to function more like the cell's own personal 'Santa Claus' that serves to 'gift' various signaling complexes with precise proteins that they 'wish for', and at the same time care enough for the spatial, temporal control of these signaling events, maintaining overall smooth functioning and general happiness of the cell. Syntrophins not only associate various ion channels and signaling proteins to the dystrophin-associated protein complex (DAPC), via a direct interaction with dystrophin protein but also serve as a link between the extracellular matrix and the intracellular downstream targets and cell cytoskeleton by interacting with F-actin. They play an important role in regulating the postsynaptic signal transduction, sarcolemmal localization of nNOS, EphA4 signaling at the neuromuscular junction, and G-protein mediated signaling. In our previous work, we reported a differential expression pattern of alpha-1-syntrophin (SNTA1) protein in esophageal and breast carcinomas. Implicated in several other pathologies, like cardiac dys-functioning, muscular dystrophies, diabetes, etc., these proteins provide a lot of scope for further studies. The present review focuses on the role of syntrophins in membrane targeting and regulation of cellular proteins, while highlighting their relevance in possible development and/or progression of pathologies including cancer which we have recently demonstrated.
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Affiliation(s)
- Hina F Bhat
- Department of Biotechnology, University of Kashmir, Srinagar, Jammu and Kashmir, India.
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18
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Gomi H, Kubota-Murata C, Yasui T, Tsukise A, Torii S. Immunohistochemical analysis of IA-2 family of protein tyrosine phosphatases in rat gastrointestinal endocrine cells. J Histochem Cytochem 2012; 61:156-68. [PMID: 23087044 DOI: 10.1369/0022155412466872] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Islet-associated protein-2 (IA-2) and IA-2β (also known as phogrin) are unique neuroendocrine-specific protein tyrosine phosphatases (PTPs). The IA-2 family of PTPs was originally identified from insulinoma cells and discovered to be major autoantigens in type 1 diabetes. Despite its expression in the neural and canonical endocrine tissues, data on expression of the IA-2 family of PTPs in gastrointestinal endocrine cells (GECs) are limited. Therefore, we immunohistochemically investigated the expression of the IA-2 family of PTPs in the rat gastrointestinal tract. In the stomach, IA-2 and IA-2β were expressed in GECs that secrete serotonin, somatostatin, and cholecystokinin/gastrin-1. In addition to these hormones, secretin, gastric inhibitory polypeptide (also known as the glucose-dependent insulinotropic peptide), glucagon-like peptide-1, and glucagon, but not ghrelin were coexpressed with IA-2 or IA-2β in duodenal GECs. Pancreatic islet cells that secrete gut hormones expressed the IA-2 family of PTPs. The expression patterns of IA-2 and IA-2β were comparable. These results reveal that the IA-2 family of PTPs is expressed in a cell type-specific manner in rat GECs. The extensive expression of the IA-2 family of PTPs in pancreo-gastrointestinal endocrine cells and in the enteric plexus suggests their systemic contribution to nutritional control through a neuroendocrine signaling network.
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Affiliation(s)
- Hiroshi Gomi
- Department of Veterinary Anatomy, College of Bioresource Sciences, Nihon University, Kanagawa, Japan.
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19
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Brambillasca S, Altkrueger A, Colombo SF, Friederich A, Eickelmann P, Mark M, Borgese N, Solimena M. CDK5 regulatory subunit-associated protein 1-like 1 (CDKAL1) is a tail-anchored protein in the endoplasmic reticulum (ER) of insulinoma cells. J Biol Chem 2012; 287:41808-19. [PMID: 23048041 DOI: 10.1074/jbc.m112.376558] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Genome-wide association studies have led to the identification of numerous susceptibility genes for type 2 diabetes. Among them is Cdkal1, which is associated with reduced β-cell function and insulin release. Recently, CDKAL1 has been shown to be a methylthiotransferase that modifies tRNA(Lys) to enhance translational fidelity of transcripts, including the one encoding proinsulin. Here, we report that out of several CDKAL1 isoforms deposited in public databases, only isoform 1, which migrates as a 61-kDa protein by SDS-PAGE, is expressed in human islets and pancreatic insulinoma INS-1 and MIN6 cells. We show that CDKAL1 is a novel member of the tail-anchored protein family and exploits the TCR40/Get3-assisted pathway for insertion of its C-terminal transmembrane domain into the endoplasmic reticulum. Using endo-β-N-acetylglucosaminidase H and peptide:N-glycosidase F sensitivity assays on CDKAL1 constructs carrying an N-glycosylation site within the luminal domain, we further established that CDKAL1 is an endoplasmic reticulum-resident protein. Moreover, we observed that silencing CDKAL1 in INS-1 cells reduces the expression of secretory granule proteins prochromogranin A and proICA512/ICA512-TMF, in addition to proinsulin and insulin. This correlated with reduced glucose-stimulated insulin secretion. Taken together, our findings provide new insight into the role of CDKAL1 in insulin-producing cells and help to understand its involvement in the pathogenesis of diabetes.
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Affiliation(s)
- Silvia Brambillasca
- Molecular Diabetology, Paul Langerhans Institute Dresden, Uniklinikum Carl Gustav Carus, Dresden University of Technology, Fetscherstrasse 74, 01307 Dresden, Germany
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20
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Arvan P, Pietropaolo M, Ostrov D, Rhodes CJ. Islet autoantigens: structure, function, localization, and regulation. Cold Spring Harb Perspect Med 2012; 2:cshperspect.a007658. [PMID: 22908193 DOI: 10.1101/cshperspect.a007658] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Islet autoantigens associated with autoimmune type 1 diabetes (T1D) are expressed in pancreatic β cells, although many show wider patterns of expression in the neuroendocrine system. Within pancreatic β cells, every T1D autoantigen is in one way or another linked to the secretory pathway. Together, these autoantigens play diverse roles in glucose regulation, metabolism of biogenic amines, as well as the regulation, formation, and packaging of secretory granules. The mechanism(s) by which immune tolerance to islet-cell antigens is lost during the development of T1D, remains unclear. Antigenic peptide creation for immune presentation may potentially link to the secretory biology of β cells in a number of ways, including proteasomal digestion of misfolded products, exocytosis and endocytosis of cell-surface products, or antigen release from dying β cells during normal or pathological turnover. In this context, we evaluate the biochemical nature and immunogenicity of the major autoantigens in T1D including (pro)insulin, GAD65, ZnT8, IA2, and ICA69.
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Affiliation(s)
- Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI 48105, USA.
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21
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Torchio GM, Ermácora MR, Sica MP. Equilibrium unfolding of the PDZ domain of β2-syntrophin. Biophys J 2012; 102:2835-44. [PMID: 22735534 DOI: 10.1016/j.bpj.2012.05.021] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Revised: 04/23/2012] [Accepted: 05/04/2012] [Indexed: 10/28/2022] Open
Abstract
β2-syntrophin, a dystrophin-associated protein, plays a pivotal role in insulin secretion by pancreatic β-cells. It contains a PDZ domain (β2S-PDZ) that, in complex with protein-tyrosine phosphatase ICA512, anchors the dense insulin granules to actin filaments. The phosphorylation state of β2-syntrophin allosterically regulates the affinity of β2S-PDZ for ICA512, and the disruption of the complex triggers the mobilization of the insulin granule stores. Here, we investigate the thermal unfolding of β2S-PDZ at different pH and urea concentrations. Our results indicate that, unlike other PDZ domains, β2S-PDZ is marginally stable. Thermal denaturation experiments show broad transitions and cold denaturation, and a two-state model fit reveals a significant unfolded fraction under physiological conditions. Furthermore, T(m) and T(max) denaturant-dependent shifts and noncoincidence of melting curves monitored at different wavelengths suggest that two-state and three-state models fail to explain the equilibrium data properly and are in better agreement with a downhill scenario. Its higher stability at pH >9 and the results of molecular dynamics simulations indicate that this behavior of β2S-PDZ might be related to its charge distribution. All together, our results suggest a link between the conformational plasticity of the native ensemble of this PDZ domain and the regulation of insulin secretion.
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Affiliation(s)
- Gabriela María Torchio
- Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Bernal, Buenos Aires, Argentina
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Rajagopal C, Mains RE, Eipper BA. Signaling from the secretory granule to the nucleus. Crit Rev Biochem Mol Biol 2012; 47:391-406. [PMID: 22681236 DOI: 10.3109/10409238.2012.694845] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Neurons and endocrine cells use a complex array of signaling molecules to communicate with each other and with various targets. The majority of these signaling molecules are stored in specialized organelles awaiting release on demand: 40-60 nm vesicles carry conventional or small molecule neurotransmitters, and 200-400 nm granules contain bioactive peptides. The supply of small molecule neurotransmitters is tightly regulated by local feedback of synthetic rates and transport processes at sites of release. The larger granules that contain bioactive peptides present the secretory cell with special challenges, as the peptide precursors are inserted into the lumen of the secretory pathway in the cell soma and undergo biosynthetic processing while being transported to distant sites for eventual secretion. One solution to this dilemma in information handling has been to employ proteolytic cleavage of secretory granule membrane proteins to produce cytosolic fragments that can signal to the nucleus, affecting gene expression. The use of regulated intramembrane proteolysis to signal from secretory granules to the nucleus is compared to its much better understood role in relaying information from the endoplasmic reticulum by SREBP and ATF6 and from the plasma membrane by cadherins, Notch and ErbB4.
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Affiliation(s)
- Chitra Rajagopal
- Department of Molecular, Microbial and Structural Biology, University of Connecticut Health Center, Farmington, CT, USA
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Coupling of metabolic, second messenger pathways and insulin granule dynamics in pancreatic beta-cells: a computational analysis. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2011; 107:293-303. [PMID: 21920379 DOI: 10.1016/j.pbiomolbio.2011.09.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2011] [Revised: 08/26/2011] [Accepted: 09/01/2011] [Indexed: 12/26/2022]
Abstract
Insulin secretory responses to nutrient stimuli and hormonal modulators in pancreatic beta-cells are controlled by a variety of secondary messengers. We have analyzed numerous mechanisms responsible for regulated exocytosis in these cells and present an integrated mathematical model of cytosolic Ca²⁺, cAMP and granule dynamics. The insulin-containing granules in the beta-cell were divided into four classes: a large "reserve" granule pool, a smaller pool of the morphologically docked granules that is chemically 'primed' for release or the "readily releasable pool", and a pool of "restless newcomer granules" that undergoes preferential exocytosis. The model incorporates glucose and other aspects of metabolism, the cAMP amplifying pathway, insulin granule dynamics and the exocyst concept for granule binding. The values of most of the model parameters were inferred from available experimental data. The model can generate both the fast first phase and slow biphasic insulin secretion found experimentally in response to a step increase of membrane potential or of glucose. The numerical simulations have also reproduced a variety of experimental conditions, such as periodic stimulation by high K⁺ and the potentiation induced in islets by pre-incubation with cAMP pathway activators. The explicit incorporation of Ca²⁺ channels, Ca²⁺ and cAMP dynamics allows the model to be further connected to current models for calcium and metabolic dynamics and provides an interpretation of the roles of the triggering and amplifying pathways of glucose-stimulated insulin secretion. The model may be important in the identification of pharmacological targets for improving insulin secretion in type 2 diabetes.
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Hodish I, Absood A, Liu L, Liu M, Haataja L, Larkin D, Al-Khafaji A, Zaki A, Arvan P. In vivo misfolding of proinsulin below the threshold of frank diabetes. Diabetes 2011; 60:2092-101. [PMID: 21677281 PMCID: PMC3142084 DOI: 10.2337/db10-1671] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
OBJECTIVE Endoplasmic reticulum (ER) stress has been described in pancreatic β-cells after onset of diabetes-a situation in which failing β-cells have exhausted available compensatory mechanisms. Herein we have compared two mouse models expressing equally small amounts of transgenic proinsulin in pancreatic β-cells. RESEARCH DESIGN AND METHODS In hProCpepGFP mice, human proinsulin (tagged with green fluorescent protein [GFP] within the connecting [C]-peptide) is folded in the ER, exported, converted to human insulin, and secreted. In hProC(A7)Y-CpepGFP mice, misfolding of transgenic mutant proinsulin causes its retention in the ER. Analysis of neonatal pancreas in both transgenic animals shows each β-cell stained positively for endogenous insulin and transgenic protein. RESULTS At this transgene expression level, most male hProC(A7)Y-CpepGFP mice do not develop frank diabetes, yet the misfolded proinsulin perturbs insulin production from endogenous proinsulin and activates ER stress response. In nondiabetic adult hProC(A7)Y-CpepGFP males, all β-cells continue to abundantly express transgene mRNA. Remarkably, however, a subset of β-cells in each islet becomes largely devoid of endogenous insulin, with some of these cells accumulating large quantities of misfolded mutant proinsulin, whereas another subset of β-cells has much less accumulated misfolded mutant proinsulin, with some of these cells containing abundant endogenous insulin. CONCLUSIONS The results indicate a source of pancreatic compensation before the development of diabetes caused by proinsulin misfolding with ER stress, i.e., the existence of an important subset of β-cells with relatively limited accumulation of misfolded proinsulin protein and maintenance of endogenous insulin production. Generation and maintenance of such a subset of β-cells may have implications in the avoidance of type 2 diabetes.
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Affiliation(s)
- Israel Hodish
- Corresponding authors: Israel Hodish, ; Peter Arvan,
| | | | | | | | | | | | | | | | - Peter Arvan
- Corresponding authors: Israel Hodish, ; Peter Arvan,
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Liu Y, Suckale J, Masjkur J, Magro MG, Steffen A, Anastassiadis K, Solimena M. Tamoxifen-independent recombination in the RIP-CreER mouse. PLoS One 2010; 5:e13533. [PMID: 21063464 PMCID: PMC2965077 DOI: 10.1371/journal.pone.0013533] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2010] [Accepted: 09/27/2010] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND The inducible Cre-lox system is a valuable tool to study gene function in a spatial and time restricted fashion in mouse models. This strategy relies on the limited background activity of the modified Cre recombinase (CreER) in the absence of its inducer, the competitive estrogen receptor ligand, tamoxifen. The RIP-CreER mouse (Tg (Ins2-cre/Esr1) 1Dam) is among the few available β-cell specific CreER mouse lines and thus it has been often used to manipulate gene expression in the insulin-producing cells of the endocrine pancreas. PRINCIPAL FINDINGS Here, we report the detection of tamoxifen-independent Cre activity as early as 2 months of age in RIP-CreER mice crossed with three distinct reporter strains. SIGNIFICANCE Evidence of Cre-mediated recombination of floxed alleles even in the absence of tamoxifen administration should warrant cautious use of this mouse for the study of pancreatic β-cells.
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Affiliation(s)
- Yanmei Liu
- Molecular Diabetology, Paul Langerhans Institute Dresden, School of Medicine and University Clinic ‘Carl Gustav Carus’, Dresden University of Technology, Dresden, Germany
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Jakob Suckale
- Molecular Diabetology, Paul Langerhans Institute Dresden, School of Medicine and University Clinic ‘Carl Gustav Carus’, Dresden University of Technology, Dresden, Germany
| | - Jimmy Masjkur
- Molecular Diabetology, Paul Langerhans Institute Dresden, School of Medicine and University Clinic ‘Carl Gustav Carus’, Dresden University of Technology, Dresden, Germany
| | - Maria Grazia Magro
- Molecular Diabetology, Paul Langerhans Institute Dresden, School of Medicine and University Clinic ‘Carl Gustav Carus’, Dresden University of Technology, Dresden, Germany
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Anja Steffen
- Molecular Diabetology, Paul Langerhans Institute Dresden, School of Medicine and University Clinic ‘Carl Gustav Carus’, Dresden University of Technology, Dresden, Germany
- Medical Clinic III, University Clinic ‘Carl Gustav Carus’, Dresden University of Technology, Dresden, Germany
| | - Konstantinos Anastassiadis
- Genetic Engineering of Stem Cells, BioInnovations Zentrum, Dresden University of Technology, Dresden, Germany
- Center for Regenerative Therapies Dresden, Dresden University of Technology, Dresden, Germany
| | - Michele Solimena
- Molecular Diabetology, Paul Langerhans Institute Dresden, School of Medicine and University Clinic ‘Carl Gustav Carus’, Dresden University of Technology, Dresden, Germany
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
- Center for Regenerative Therapies Dresden, Dresden University of Technology, Dresden, Germany
- * E-mail:
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26
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Suckale J, Solimena M. The insulin secretory granule as a signaling hub. Trends Endocrinol Metab 2010; 21:599-609. [PMID: 20609596 DOI: 10.1016/j.tem.2010.06.003] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2010] [Revised: 06/01/2010] [Accepted: 06/03/2010] [Indexed: 02/06/2023]
Abstract
The insulin granule was previously thought of as merely a container, but accumulating evidence suggests that it also acts as a signaling node. Regulatory pathways intersect at but also originate from the insulin granule membrane. Examples include the small G-proteins Rab3a and Rab27a, which influence granule movement, and the transmembrane proteins (tyrosine phosphatase receptors type N) PTPRN and PTPRN2, which upregulate β-cell transcription and proliferation. In addition, many cosecreted compounds possess regulatory functions, often related to energy metabolism. For instance, ATP and γ-amino butyric acid (GABA) modulate insulin and glucagon secretion, respectively; C-peptide protects β-cells and kidney cells; and amylin reduces gastric emptying and food intake via the brain. In this paper, we review the current knowledge of the insulin granule proteome and discuss its regulatory functions.
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Affiliation(s)
- Jakob Suckale
- Molecular Diabetology, Paul Langerhans Institute Dresden, School of Medicine and University Clinic Carl Gustav Carus, Dresden University of Technology, Dresden 01307, Germany
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Schubert S, Knoch KP, Ouwendijk J, Mohammed S, Bodrov Y, Jäger M, Altkrüger A, Wegbrod C, Adams ME, Kim Y, Froehner SC, Jensen ON, Kalaidzidis Y, Solimena M. β2-Syntrophin is a Cdk5 substrate that restrains the motility of insulin secretory granules. PLoS One 2010; 5:e12929. [PMID: 20886068 PMCID: PMC2944849 DOI: 10.1371/journal.pone.0012929] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2009] [Accepted: 08/23/2010] [Indexed: 11/18/2022] Open
Abstract
The molecular basis for the interaction of insulin granules with the cortical cytoskeleton of pancreatic β-cells remains unknown. We have proposed that binding of the granule protein ICA512 to the PDZ domain of β2-syntrophin anchors granules to actin filaments and that the phosphorylation/dephosphorylation of β2-syntrophin regulates this association. Here we tested this hypothesis by analyzing INS-1 cells expressing GFP-β2-syntrophin through the combined use of biochemical approaches, imaging studies by confocal and total internal reflection fluorescence microscopy as well as electron microscopy. Our results support the notion that β2-syntrophin restrains the mobility of cortical granules in insulinoma INS-1 cells, thereby reducing insulin secretion and increasing insulin stores in resting cells, while increasing insulin release upon stimulation. Using mass spectrometry, in vitro phosphorylation assays and β2-syntrophin phosphomutants we found that phosphorylation of β2-syntrophin on S75 near the PDZ domain decreases its binding to ICA512 and correlates with increased granule motility, while phosphorylation of S90 has opposite effects. We further show that Cdk5, which regulates insulin secretion, phosphorylates S75. These findings provide mechanistic insight into how stimulation displaces insulin granules from cortical actin, thus promoting their motility and exocytosis.
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Affiliation(s)
- Sandra Schubert
- Molecular Diabetology, Paul Langerhans Institute Dresden, Uniklinikum Carl Gustav Carus at Dresden University of Technology, Dresden, Germany
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Klaus-Peter Knoch
- Molecular Diabetology, Paul Langerhans Institute Dresden, Uniklinikum Carl Gustav Carus at Dresden University of Technology, Dresden, Germany
| | - Joke Ouwendijk
- Molecular Diabetology, Paul Langerhans Institute Dresden, Uniklinikum Carl Gustav Carus at Dresden University of Technology, Dresden, Germany
| | - Shabaz Mohammed
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
| | - Yury Bodrov
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Melanie Jäger
- Molecular Diabetology, Paul Langerhans Institute Dresden, Uniklinikum Carl Gustav Carus at Dresden University of Technology, Dresden, Germany
| | - Anke Altkrüger
- Molecular Diabetology, Paul Langerhans Institute Dresden, Uniklinikum Carl Gustav Carus at Dresden University of Technology, Dresden, Germany
| | - Carolin Wegbrod
- Molecular Diabetology, Paul Langerhans Institute Dresden, Uniklinikum Carl Gustav Carus at Dresden University of Technology, Dresden, Germany
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Marvin E. Adams
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington, United States of America
| | - Yong Kim
- Laboratory of Molecular and Cellular Neuroscience, The Rockefeller University, New York, New York, United States of America
| | - Stanley C. Froehner
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington, United States of America
| | - Ole N. Jensen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
| | - Yannis Kalaidzidis
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
- A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow, Russia
| | - Michele Solimena
- Molecular Diabetology, Paul Langerhans Institute Dresden, Uniklinikum Carl Gustav Carus at Dresden University of Technology, Dresden, Germany
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
- * E-mail:
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Morran MP, Casu A, Arena VC, Pietropaolo S, Zhang YJ, Satin LS, Nelson P, Omenn GS, Trucco M, Becker DJ, Pietropaolo M. Humoral autoimmunity against the extracellular domain of the neuroendocrine autoantigen IA-2 heightens the risk of type 1 diabetes. Endocrinology 2010; 151:2528-37. [PMID: 20382696 PMCID: PMC2875834 DOI: 10.1210/en.2009-1257] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The objective of this study was to determine whether antigenic determinants localized within the extracellular domain of the neuroendocrine autoantigen tyrosine phosphatase-like protein IA-2 are targets of humoral responses in type 1 diabetes (T1DM). Previous studies indicated that the immunodominant region of IA-2 is localized within its intracellular domain (IA-2ic; amino acids 601-979). We analyzed 333 subjects from the Children's Hospital of Pittsburgh study, 102 of whom progressed to insulin-requiring diabetes (prediabetics). Autoantibodies from these individuals were initially assayed for ICA512bdc (Barbara Davis Center amino acids 257-556; 630-979), IA-2ic (amino acids 601-979), and IA-2 full-length (amino acids 1-979) in addition to islet cell antibody (ICA), glutamic acid decarboxylase, 65-kDa isoform, and insulin autoantibodies. We identified an autoantibody response reactive with the extracellular domain of IA-2 that is associated with very high risk of T1DM progression. Relatives with no detectable autoantibodies against ICA512bdc (or IA-2ic) exhibited antibody responses against the IA-2 full-length peptide (log rank, P = 0.008). This effect was also observed in first-degree relatives who were positive for glutamic acid decarboxylase, 65-kDa isoform (log rank, P = 0.026) or at least two islet autoantibodies but were negative for ICA512bdc (log rank, P = 0.022). Competitive binding experiments and immunoprecipitation of the IA-2 extracellular domain (amino acid residues 26-577) further lend support for the presence of autoantibodies reactive with new antigenic determinants within the extracellular domain of IA-2. In summary, the addition of measurements of autoantibodies reactive with the IA-2 extracellular domain to assays geared to assess the progression of autoimmunity to clinical T1DM may more accurately characterize this risk. This has considerable implications not only for stratifying high diabetes risk but also facilitating the search for pathogenic epitopes to enable the design of peptide-based immunotherapies that may prevent the progression to overt T1DM at its preclinical stages.
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Affiliation(s)
- Michael P Morran
- Laboratory of Immunogenetics, The Brehm Center for Diabetes Research, 1000 Wall Street, Ann Arbor, Michigan 48105.
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29
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Nishimura T, Harashima SI, Yafang H, Notkins AL. IA-2 modulates dopamine secretion in PC12 cells. Mol Cell Endocrinol 2010; 315:81-6. [PMID: 19799965 PMCID: PMC3495171 DOI: 10.1016/j.mce.2009.09.023] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2009] [Revised: 09/16/2009] [Accepted: 09/22/2009] [Indexed: 11/28/2022]
Abstract
The secretion of the hormone insulin from beta cells is modulated by the expression of the dense core vesicle transmembrane protein IA-2. Since IA-2 is found in neuroendocrine cells throughout the body, the present experiments were initiated to determine whether the expression of IA-2 also modulates the secretion of neurotransmitters. Using the dopamine-secreting pheochromocytoma cell line PC12, we found that the overexpressions of IA-2 increased the cellular content and secretion of dopamine, whereas the knockdown of IA-2 by siRNA decreased the cellular content and secretion of dopamine. Neither the overexpression nor knockdown of IA-2 influenced the uptake of [H(3)]dopamine by PC12 cells, but did influence the amount of [H(3)]dopamine secreted. Overexpression of IA-2 also increased the level of the dense core vesicle-associated proteins Rab3A, IA-2beta and secretogranin II, whereas the knockdown of IA-2 decreased the level of these proteins. We conclude that the expression of IA-2 profoundly influences the function of dense core vesicles and has a broad modulating effect on the cellular content and secretion of both hormones and neurotransmitters.
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Affiliation(s)
- Takuya Nishimura
- Experimental Medicine Section, Oral Infection and Immunity Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
| | - Shin-ichi Harashima
- Experimental Medicine Section, Oral Infection and Immunity Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Hu Yafang
- Experimental Medicine Section, Oral Infection and Immunity Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
- Center for Cancer and Immunology Research, Children’s National Medical Center, Washington, DC, USA
| | - Abner Louis Notkins
- Experimental Medicine Section, Oral Infection and Immunity Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
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Liu Y, Mziaut H, Ivanova A, Solimena M. beta-Cells at the crossroads: choosing between insulin granule production and proliferation. Diabetes Obes Metab 2009; 11 Suppl 4:54-64. [PMID: 19817789 DOI: 10.1111/j.1463-1326.2009.01107.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Pancreatic beta-cells are the sole source of insulin, the major hormonal regulator of glycaemia. In physiological and pathological conditions with increased insulin demand, beta-cells adjust their insulin output either through increased insulin secretory granule (ISG) biogenesis and secretion, or hyperplasia. Failure of these compensatory mechanisms eventually results in hyperglycaemia and diabetes mellitus. Both of these major adaptive behaviours are positively regulated by several extrinsic factors, such as glucose, GLP-1, insulin and growth hormones (GH). Still unclear, however, it is how beta-cells in response to these stimuli opt for one or the other strategy at a given time. Here we review recent advances concerning the factors and pathways that enhance ISG biogenesis and beta-cell replication, and propose the existence of 'switch factors' that play a key role in regulating the shift between these two adaptive responses.
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Affiliation(s)
- Yanmei Liu
- Paul Langerhans Institute Dresden, Dresden University of Technology, Germany
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