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Samadli S, Zhou Q, Zheng B, Gu W, Zhang A. From glucose sensing to exocytosis: takes from maturity onset diabetes of the young. Front Endocrinol (Lausanne) 2023; 14:1188301. [PMID: 37255971 PMCID: PMC10226665 DOI: 10.3389/fendo.2023.1188301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Accepted: 04/28/2023] [Indexed: 06/01/2023] Open
Abstract
Monogenic diabetes gave us simplified models of complex molecular processes occurring within β-cells, which allowed to explore the roles of numerous proteins from single protein perspective. Constellation of characteristic phenotypic features and wide application of genetic sequencing techniques to clinical practice, made the major form of monogenic diabetes - the Maturity Onset Diabetes of the Young to be distinguishable from type 1, type 2 as well as neonatal diabetes mellitus and understanding underlying molecular events for each type of MODY contributed to the advancements of antidiabetic therapy and stem cell research tremendously. The functional analysis of MODY-causing proteins in diabetes development, not only provided better care for patients suffering from diabetes, but also enriched our comprehension regarding the universal cellular processes including transcriptional and translational regulation, behavior of ion channels and transporters, cargo trafficking, exocytosis. In this review, we will overview structure and function of MODY-causing proteins, alterations in a particular protein arising from the deleterious mutations to the corresponding gene and their consequences, and translation of this knowledge into new treatment strategies.
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Affiliation(s)
- Sama Samadli
- Nanjing Key Laboratory of Pediatrics, Children’s Hospital of Nanjing Medical University, Nanjing, China
- Department of Pediatric Diseases II, Azerbaijan Medical University, Baku, Azerbaijan
| | - Qiaoli Zhou
- Department of Endocrinology, Children’s Hospital of Nanjing Medical University, Nanjing, China
| | - Bixia Zheng
- Nanjing Key Laboratory of Pediatrics, Children’s Hospital of Nanjing Medical University, Nanjing, China
| | - Wei Gu
- Department of Endocrinology, Children’s Hospital of Nanjing Medical University, Nanjing, China
| | - Aihua Zhang
- Nanjing Key Laboratory of Pediatrics, Children’s Hospital of Nanjing Medical University, Nanjing, China
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2
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Yang Y, Glidden MD, Dhayalan B, Zaykov AN, Chen YS, Wickramasinghe NP, DiMarchi RD, Weiss MA. Peptide Model of the Mutant Proinsulin Syndrome. II. Nascent Structure and Biological Implications. Front Endocrinol (Lausanne) 2022; 13:821091. [PMID: 35299958 PMCID: PMC8922542 DOI: 10.3389/fendo.2022.821091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Accepted: 01/21/2022] [Indexed: 11/13/2022] Open
Abstract
Toxic misfolding of proinsulin variants in β-cells defines a monogenic diabetes syndrome, designated mutant INS-gene induced diabetes of the young (MIDY). In our first study (previous article in this issue), we described a one-disulfide peptide model of a proinsulin folding intermediate and its use to study such variants. The mutations (LeuB15→Pro, LeuA16→Pro, and PheB24→Ser) probe residues conserved among vertebrate insulins. In this companion study, we describe 1H and 1H-13C NMR studies of the peptides; key NMR resonance assignments were verified by synthetic 13C-labeling. Parent spectra retain nativelike features in the neighborhood of the single disulfide bridge (cystine B19-A20), including secondary NMR chemical shifts and nonlocal nuclear Overhauser effects. This partial fold engages wild-type side chains LeuB15, LeuA16 and PheB24 at the nexus of nativelike α-helices α1 and α3 (as defined in native proinsulin) and flanking β-strand (residues B24-B26). The variant peptides exhibit successive structural perturbations in order: parent (most organized) > SerB24 >> ProA16 > ProB15 (least organized). The same order pertains to (a) overall α-helix content as probed by circular dichroism, (b) synthetic yields of corresponding three-disulfide insulin analogs, and (c) ER stress induced in cell culture by corresponding mutant proinsulins. These findings suggest that this and related peptide models will provide a general platform for classification of MIDY mutations based on molecular mechanisms by which nascent disulfide pairing is impaired. We propose that the syndrome's variable phenotypic spectrum-onsets ranging from the neonatal period to later in childhood or adolescence-reflects structural features of respective folding intermediates.
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Affiliation(s)
- Yanwu Yang
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Michael D. Glidden
- Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, OH, United States
- Department of Physiology & Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, United States
- Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH, United States
| | - Balamurugan Dhayalan
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, United States
| | | | - Yen-Shan Chen
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Nalinda P. Wickramasinghe
- Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, OH, United States
| | | | - Michael A. Weiss
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, United States
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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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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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Liu M, Wang Z, Feng D, Shang Y, Li X, Liu J, Li C, Yang Z. An Insulin-Inspired Supramolecular Hydrogel for Prevention of Type 1 Diabetes. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2021; 8:2003599. [PMID: 34026440 PMCID: PMC8132061 DOI: 10.1002/advs.202003599] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 01/11/2021] [Indexed: 05/10/2023]
Abstract
Supramolecular peptide hydrogel has shown promising potential in vaccine development largely because of its ability to function both as antigen depot and immune adjuvant. Nap-GdFdFdY, a tetrapeptide hydrogel that has been previously reported to exhibit adjuvant effect, is inadvertently found to contain conserved peptide sequence for insulin, proinsulin, and glutamic acid decarboxylase, 3 major autoantigens for the autoimmune type 1 diabetes (T1D). At present, despite being managed clinically with insulin replacement therapy, T1D remains a major health threat with rapidly increasing incidences, especially in children and young adults, and antigen-specific immune tolerance induction has been proposed as a feasible approach to prevent or delay T1D progression at an early stage. Here, it is reported that innoculation of Nap-GdFdFdY leads to complete protection of nonobese diabetic (NOD) mice from T1D development till the age of 36 weeks. Better maintenance of pancreatic islet morphology with minimal immune cell infiltration is also observed from mice exposed to Nap-GdFdFdY. This beneficial impact is mainly due to its facilitative role on enhancing peripheral T regulatory cell (Treg) population, shown as increased splenic Treg percentage, and function, demonstrated by maintenance of circulating TGF-β1 level. Serum cytokine microarray data further implicate a "buffering" role of Nap-GdFdFdY on systemic inflammatory tone in NOD mice. Thus, with its versatility, applicability, and excellent potency, Nap-GdFdFdY is posited as a novel therapeutic intervention for T1D.
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Affiliation(s)
- Mohan Liu
- Tianjin Key Laboratory of Biomedical MaterialsBiomedical Barriers Research CentreInstitute of Biomedical EngineeringChinese Academy of Medical Sciences & Peking Union Medical CollegeTianjin300192P. R. China
| | - Zhongyan Wang
- Key Laboratory of Bioactive MaterialsMinistry of EducationCollege of Life SciencesState Key Laboratory of Medicinal Chemical BiologyCollaborative Innovation Centre of Chemical Science and Engineeringand National Institute of Functional MaterialsNankai UniversityTianjin300071P. R. China
- Tianjin Key Laboratory of Radiation Medicine and Molecular Nuclear MedicineInstitute of Radiation MedicineChinese Academy of Medical Sciences & Peking Union Medical CollegeTianjin300192P. R. China
| | - Dandan Feng
- Tianjin Key Laboratory of Biomedical MaterialsBiomedical Barriers Research CentreInstitute of Biomedical EngineeringChinese Academy of Medical Sciences & Peking Union Medical CollegeTianjin300192P. R. China
| | - Yuna Shang
- Key Laboratory of Bioactive MaterialsMinistry of EducationCollege of Life SciencesState Key Laboratory of Medicinal Chemical BiologyCollaborative Innovation Centre of Chemical Science and Engineeringand National Institute of Functional MaterialsNankai UniversityTianjin300071P. R. China
| | - Xinxin Li
- Key Laboratory of Bioactive MaterialsMinistry of EducationCollege of Life SciencesState Key Laboratory of Medicinal Chemical BiologyCollaborative Innovation Centre of Chemical Science and Engineeringand National Institute of Functional MaterialsNankai UniversityTianjin300071P. R. China
| | - Jianfeng Liu
- Tianjin Key Laboratory of Radiation Medicine and Molecular Nuclear MedicineInstitute of Radiation MedicineChinese Academy of Medical Sciences & Peking Union Medical CollegeTianjin300192P. R. China
| | - Chen Li
- Tianjin Key Laboratory of Biomedical MaterialsBiomedical Barriers Research CentreInstitute of Biomedical EngineeringChinese Academy of Medical Sciences & Peking Union Medical CollegeTianjin300192P. R. China
| | - Zhimou Yang
- Key Laboratory of Bioactive MaterialsMinistry of EducationCollege of Life SciencesState Key Laboratory of Medicinal Chemical BiologyCollaborative Innovation Centre of Chemical Science and Engineeringand National Institute of Functional MaterialsNankai UniversityTianjin300071P. R. China
- Jiangsu Center for the Collaboration and Innovation of Cancer BiotherapyCancer InstituteXuzhou Medical UniversityXuzhouJiangsu221004P. R. China
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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: 1] [Impact Index Per Article: 0.3] [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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Vasiljević J, Torkko JM, Knoch KP, Solimena M. The making of insulin in health and disease. Diabetologia 2020; 63:1981-1989. [PMID: 32894308 PMCID: PMC7476993 DOI: 10.1007/s00125-020-05192-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Accepted: 04/28/2020] [Indexed: 12/16/2022]
Abstract
The discovery of insulin in 1921 has been one of greatest scientific achievements of the 20th century. Since then, the availability of insulin has shifted the focus of diabetes treatment from trying to keep patients alive to saving and improving the life of millions. Throughout this time, basic and clinical research has advanced our understanding of insulin synthesis and action, both in healthy and pathological conditions. Yet, multiple aspects of insulin production remain unknown. In this review, we focus on the most recent findings on insulin synthesis, highlighting their relevance in diabetes. Graphical abstract.
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Affiliation(s)
- Jovana Vasiljević
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany
- German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
- Paul Langerhans Institute Dresden (PLID), Helmholtz Center Munich, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Tatzberg 47/49, 01307, Dresden, Germany
| | - Juha M Torkko
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany
- German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
- Paul Langerhans Institute Dresden (PLID), Helmholtz Center Munich, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Tatzberg 47/49, 01307, Dresden, Germany
| | - Klaus-Peter Knoch
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany
- German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
- Paul Langerhans Institute Dresden (PLID), Helmholtz Center Munich, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Tatzberg 47/49, 01307, Dresden, Germany
| | - Michele Solimena
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany.
- German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany.
- Paul Langerhans Institute Dresden (PLID), Helmholtz Center Munich, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Tatzberg 47/49, 01307, Dresden, Germany.
- Max Planck Institute of Molecular Cell Biology and Genetics (MPI-CBG), Dresden, Germany.
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8
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Weiss MA, Lawrence MC. A thing of beauty: Structure and function of insulin's "aromatic triplet". Diabetes Obes Metab 2018; 20 Suppl 2:51-63. [PMID: 30230175 PMCID: PMC6159917 DOI: 10.1111/dom.13402] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [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: 05/25/2018] [Accepted: 05/31/2018] [Indexed: 12/30/2022]
Abstract
The classical crystal structure of insulin was determined in 1969 by D.C. Hodgkin et al. following a 35-year program of research. This structure depicted a hexamer remarkable for its self-assembly as a zinc-coordinated trimer of dimer. Prominent at the dimer interface was an "aromatic triplet" of conserved residues at consecutive positions in the B chain: PheB24 , PheB25 and TyrB26 . The elegance of this interface inspired the Oxford team to poetry: "A thing of beauty is a joy forever" (John Keats as quoted by Blundell, T.L., et al. Advances in Protein Chemistry 26:279-286 [1972]). Here, we revisit this aromatic triplet in light of recent advances in the structural biology of insulin bound as a monomer to fragments of the insulin receptor. Such co-crystal structures have defined how these side chains pack at the primary hormone-binding surface of the receptor ectodomain. On receptor binding, the B-chain β-strand (residues B24-B28) containing the aromatic triplet detaches from the α-helical core of the hormone. Whereas TyrB26 lies at the periphery of the receptor interface and may functionally be replaced by a diverse set of substitutions, PheB24 and PheB25 engage invariant elements of receptor domains L1 and αCT. These critical contacts were anticipated by the discovery of diabetes-associated mutations at these positions by Donald Steiner et al. at the University of Chicago. Conservation of PheB24 , PheB25 and TyrB26 among vertebrate insulins reflects the striking confluence of structure-based evolutionary constraints: foldability, protective self-assembly and hormonal activity.
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Affiliation(s)
- Michael A. Weiss
- Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN 46202 USA
| | - Michael C. Lawrence
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3052, AUSTRALIA
- Department of Medical Biology, University of Melbourne, Parkville, Victoria 3010, AUSTRALIA
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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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A Bystander Mechanism Explains the Specific Phenotype of a Broadly Expressed Misfolded Protein. PLoS Genet 2016; 12:e1006450. [PMID: 27926939 PMCID: PMC5142776 DOI: 10.1371/journal.pgen.1006450] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Accepted: 10/31/2016] [Indexed: 12/18/2022] Open
Abstract
Misfolded proteins in transgenic models of conformational diseases interfere with proteostasis machinery and compromise the function of many structurally and functionally unrelated metastable proteins. This collateral damage to cellular proteins has been termed 'bystander' mechanism. How a single misfolded protein overwhelms the proteostasis, and how broadly-expressed mutant proteins cause cell type-selective phenotypes in disease are open questions. We tested the gain-of-function mechanism of a R37C folding mutation in an endogenous IGF-like C.elegans protein DAF-28. DAF-28(R37C) is broadly expressed, but only causes dysfunction in one specific neuron, ASI, leading to a distinct developmental phenotype. We find that this phenotype is caused by selective disruption of normal biogenesis of an unrelated endogenous protein, DAF-7/TGF-β. The combined deficiency of DAF-28 and DAF-7 biogenesis, but not of DAF-28 alone, explains the gain-of-function phenotype—deficient pro-growth signaling by the ASI neuron. Using functional, fluorescently-tagged protein, we find that, in animals with mutant DAF-28/IGF, the wild-type DAF-7/TGF-β is mislocalized to and accumulates in the proximal axon of the ASI neuron. Activation of two different branches of the unfolded protein response can modulate both the developmental phenotype and DAF-7 mislocalization in DAF-28(R37C) animals, but appear to act through divergent mechanisms. Our finding that bystander targeting of TGF-β explains the phenotype caused by a folding mutation in an IGF-like protein suggests that, in conformational diseases, bystander misfolding may specify the distinct phenotypes caused by different folding mutations. Correct protein folding and localization ensures cellular health. Dedicated proteostasis machinery assists in protein folding and protects against misfolding. Yet, folding mutations cause many conformational diseases, including neurodegenerative diseases and certain types of diabetes and cancer. Misfolded disease-related proteins interfere with proteostasis machinery, causing global misfolding in the cell. How this global mechanism leads to the specific phenotypes in different conformational diseases is unknown. Moreover, mutant misfolded proteins that only damage specific cell-types in disease often lose this cell-selectivity when overexpressed in genetic models. Here we use an endogenous folding mutation in a C. elegans secreted IGF-like protein, DAF-28, that causes dysfunction in one neuron and a specific developmental phenotype, despite expression in many cells. We find that misfolding of mutant DAF-28 causes mislocalization and defective function of another, wild-type growth factor that is expressed in the affected neuron, the TGF-β protein DAF-7. Decrease in DAF-7 function explains the observed developmental phenotype. This targeting of the bystander protein DAF-7 by the misfolded mutant DAF-28 is specific and is not caused by the global stress. Our data suggest that rather than global effects, it is the selective targeting of specific susceptible bystander proteins that defines the specific phenotypes in conformational diseases.
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Yang Y, Chan L. Monogenic Diabetes: What It Teaches Us on the Common Forms of Type 1 and Type 2 Diabetes. Endocr Rev 2016; 37:190-222. [PMID: 27035557 PMCID: PMC4890265 DOI: 10.1210/er.2015-1116] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
To date, more than 30 genes have been linked to monogenic diabetes. Candidate gene and genome-wide association studies have identified > 50 susceptibility loci for common type 1 diabetes (T1D) and approximately 100 susceptibility loci for type 2 diabetes (T2D). About 1-5% of all cases of diabetes result from single-gene mutations and are called monogenic diabetes. Here, we review the pathophysiological basis of the role of monogenic diabetes genes that have also been found to be associated with common T1D and/or T2D. Variants of approximately one-third of monogenic diabetes genes are associated with T2D, but not T1D. Two of the T2D-associated monogenic diabetes genes-potassium inward-rectifying channel, subfamily J, member 11 (KCNJ11), which controls glucose-stimulated insulin secretion in the β-cell; and peroxisome proliferator-activated receptor γ (PPARG), which impacts multiple tissue targets in relation to inflammation and insulin sensitivity-have been developed as major antidiabetic drug targets. Another monogenic diabetes gene, the preproinsulin gene (INS), is unique in that INS mutations can cause hyperinsulinemia, hyperproinsulinemia, neonatal diabetes mellitus, one type of maturity-onset diabetes of the young (MODY10), and autoantibody-negative T1D. Dominant heterozygous INS mutations are the second most common cause of permanent neonatal diabetes. Moreover, INS gene variants are strongly associated with common T1D (type 1a), but inconsistently with T2D. Variants of the monogenic diabetes gene Gli-similar 3 (GLIS3) are associated with both T1D and T2D. GLIS3 is a key transcription factor in insulin production and β-cell differentiation during embryonic development, which perturbation forms the basis of monogenic diabetes as well as its association with T1D. GLIS3 is also required for compensatory β-cell proliferation in adults; impairment of this function predisposes to T2D. Thus, monogenic forms of diabetes are invaluable "human models" that have contributed to our understanding of the pathophysiological basis of common T1D and T2D.
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Affiliation(s)
- Yisheng Yang
- Division of Endocrinology (Y.Y.), Department of Medicine, MetroHealth Medical Center, Case Western Reserve University, Cleveland, Ohio 44109; and Diabetes and Endocrinology Research Center (L.C.), Division of Diabetes, Endocrinology and Metabolism, Departments of Medicine, Molecular and Cellular Biology, Biochemistry and Molecular Biology, and Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030
| | - Lawrence Chan
- Division of Endocrinology (Y.Y.), Department of Medicine, MetroHealth Medical Center, Case Western Reserve University, Cleveland, Ohio 44109; and Diabetes and Endocrinology Research Center (L.C.), Division of Diabetes, Endocrinology and Metabolism, Departments of Medicine, Molecular and Cellular Biology, Biochemistry and Molecular Biology, and Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030
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Kim YH, Kastner K, Abdul-Wahid B, Izaguirre JA. Evaluation of conformational changes in diabetes-associated mutation in insulin a chain: a molecular dynamics study. Proteins 2015; 83:662-9. [PMID: 25641314 PMCID: PMC4382306 DOI: 10.1002/prot.24759] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Revised: 12/15/2014] [Accepted: 12/31/2014] [Indexed: 12/24/2022]
Abstract
Insulin plays a central role in the regulation of metabolism in humans. Mutations in the insulin gene can impair the folding of its precursor protein, proinsulin, and cause permanent neonatal-onset diabetes mellitus known as Mutant INS-gene induced Diabetes of Youth (MIDY) with insulin deficiency. To gain insights into the molecular basis of this diabetes-associated mutation, we perform molecular dynamics simulations in wild-type and mutant (Cys(A7) to Tyr or C(A7)Y) insulin A chain in aqueous solutions. The C(A7)Y mutation is one of the identified mutations that impairs the protein folding by substituting the cysteine residue which is required for the disulfide bond formation. A comparative analysis reveals structural differences between the wild-type and the mutant conformations. The analyzed mutant insulin A chain forms a metastable state with major effects on its N-terminal region. This suggests that MIDY mutant involves formation of a partially folded intermediate with conformational change in N-terminal region in A chain that generates flexible N-terminal domain. This may lead to the abnormal interactions with other proinsulins in the aggregation process.
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Affiliation(s)
- Yong Hwan Kim
- Bioengineering Graduate Program, University of Notre Dame, Notre Dame, IN
| | - Kevin Kastner
- Department of Computer Science and Engineering, University of Notre Dame, Notre Dame, IN
| | - Badi Abdul-Wahid
- Department of Computer Science and Engineering, University of Notre Dame, Notre Dame, IN
| | - Jesús A. Izaguirre
- Bioengineering Graduate Program, University of Notre Dame, Notre Dame, IN
- Department of Computer Science and Engineering, University of Notre Dame, Notre Dame, IN
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13
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Liu M, Sun J, Cui J, Chen W, Guo H, Barbetti F, Arvan P. INS-gene mutations: from genetics and beta cell biology to clinical disease. Mol Aspects Med 2014; 42:3-18. [PMID: 25542748 DOI: 10.1016/j.mam.2014.12.001] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Revised: 12/02/2014] [Accepted: 12/04/2014] [Indexed: 02/06/2023]
Abstract
A growing list of insulin gene mutations causing a new form of monogenic diabetes has drawn increasing attention over the past seven years. The mutations have been identified in the untranslated regions of the insulin gene as well as the coding sequence of preproinsulin including within the signal peptide, insulin B-chain, C-peptide, insulin A-chain, and the proteolytic cleavage sites both for signal peptidase and the prohormone convertases. These mutations affect a variety of different steps of insulin biosynthesis in pancreatic beta cells. Importantly, although many of these mutations cause proinsulin misfolding with early onset autosomal dominant diabetes, some of the mutant alleles appear to engage different cellular and molecular mechanisms that underlie beta cell failure and diabetes. In this article, we review the most recent advances in the field and discuss challenges as well as potential strategies to prevent/delay the development and progression of autosomal dominant diabetes caused by INS-gene mutations. It is worth noting that although diabetes caused by INS gene mutations is rare, increasing evidence suggests that defects in the pathway of insulin biosynthesis may also be involved in the progression of more common types of diabetes. Collectively, the (pre)proinsulin mutants provide insightful molecular models to better understand the pathogenesis of all forms of diabetes in which preproinsulin processing defects, proinsulin misfolding, and ER stress are involved.
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Affiliation(s)
- Ming Liu
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, 300052, China; Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI, 48105, USA.
| | - Jinhong Sun
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI, 48105, USA
| | - Jinqiu Cui
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, 300052, China
| | - Wei Chen
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI, 48105, USA
| | - Huan Guo
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI, 48105, USA
| | - Fabrizio Barbetti
- Department of Experimental Medicine, University of Tor Vergata, Rome and Bambino Gesù Children's Hospital, Rome, Italy
| | - Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI, 48105, USA.
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Teo AKK, Wagers AJ, Kulkarni RN. New opportunities: harnessing induced pluripotency for discovery in diabetes and metabolism. Cell Metab 2013; 18:775-91. [PMID: 24035588 PMCID: PMC3858409 DOI: 10.1016/j.cmet.2013.08.010] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The landmark discovery of induced pluripotent stem cells (iPSCs) by Shinya Yamanaka has transformed regenerative biology. Previously, insights into the pathogenesis of chronic human diseases have been hindered by the inaccessibility of patient samples. However, scientists are now able to convert patient fibroblasts into iPSCs and differentiate them into disease-relevant cell types. This ability opens new avenues for investigating disease pathogenesis and designing novel treatments. In this review, we highlight the uses of human iPSCs to uncover the underlying causes and pathological consequences of diabetes and metabolic syndromes, multifactorial diseases whose etiologies have been difficult to unravel using traditional methodologies.
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Affiliation(s)
- Adrian Kee Keong Teo
- Section of Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA 02215, USA
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15
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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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16
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MALIK AJAMALUDDIN, AL-SENAIDY ABDULRAHMAN, SKRZYPCZAK-JANKUN EWA, JANKUN JERZY. A study of the anti-diabetic agents of camel milk. Int J Mol Med 2012; 30:585-92. [DOI: 10.3892/ijmm.2012.1051] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2012] [Accepted: 05/29/2012] [Indexed: 11/05/2022] Open
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17
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Tenore A, Driul D. Genomics in pediatric endocrinology-genetic disorders and new techniques. Pediatr Clin North Am 2011; 58:1061-81, ix. [PMID: 21981949 DOI: 10.1016/j.pcl.2011.07.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
In the last few years, there have been remarkable advances in the development of new and more sophisticated genetic techniques. These have allowed a better understanding of the molecular mechanisms of genetically determined pediatric endocrine disorders and are paving the way for a radical change in diagnosis and treatment. This article introduces some of these concepts and some of the genetic techniques being used.
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Affiliation(s)
- Alfred Tenore
- Division of Pediatric Endocrinology, Department of Pediatrics DPMSC, University of Udine School of Medicine, Padiglione Petracco, Piazzale S.M. della Misericordia, 33100 Udine, Italy.
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18
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Abstract
Insulin is a hormone that is essential for regulating energy storage and glucose metabolism in the body. Insulin in liver, muscle, and fat tissues stimulates the cell to take up glucose from blood and store it as glycogen in liver and muscle. Failure of insulin control causes diabetes mellitus (DM). Insulin is the unique medicine to treat some forms of DM. The population of diabetics has dramatically increased over the past two decades, due to high absorption of carbohydrates (or fats and proteins), lack of physical exercise, and development of new diagnostic techniques. At present, the two largest developing countries (India and China) and the largest developed country (United States) represent the top three countries in terms of diabetic population. Insulin is a small protein, but contains almost all structural features typical of proteins: α-helix, β-sheet, β-turn, high order assembly, allosteric T®R-transition, and conformational changes in amyloidal fibrillation. More than ten years' efforts on studying insulin disulfide intermediates by NMR have enabled us to decipher the whole picture of insulin folding coupled to disulfide pairing, especially at the initial stage that forms the nascent peptide. Two structural switches are also known to regulate insulin binding to receptors and progress has been made to identify the residues involved in binding. However, resolving the complex structure of insulin and its receptor remains a challenge in insulin research. Nevertheless, the accumulated knowledge of insulin structure has allowed us to specifically design a new ultra-stable and active single-chain insulin analog (SCI-57), and provides a novel way to design super-stable, fast-acting and cheaper insulin formulations for DM patients. Continuing this long journey of insulin study will benefit basic research in proteins and in pharmaceutical therapy.
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Affiliation(s)
- Qingxin Hua
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106-4935, USA.
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19
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Abstract
Some mutations of the insulin gene cause hyperinsulinemia or hyperproinsulinemia. Replacement of biologically important amino acid leads to defective receptor binding, longer half-life and hyperinsulinemia. Three mutant insulins have been identified: (i) insulin Chicago (F49L or PheB25Leu); (ii) insulin Los Angeles (F48S or PheB24Ser); (iii) and insulin Wakayama (V92L or ValA3Leu). Replacement of amino acid is necessary for proinsulin processing results in hyperproinsulinemia. Four types have been identified: (i) proinsulin Providence (H34D); (ii) proinsulin Tokyo (R89H); (iii) proinsulin Kyoto (R89L); and (iv) proinsulin Oxford (R89P). Three of these are processing site mutations. The mutation of proinsulin Providence, in contrast, is thought to cause sorting abnormality. Compared with normal proinsulin, a significant amount of proinsulin Providence enters the constitutive pathway where processing does not occur. These insulin gene mutations with hyper(pro)insulinemia were very rare, showed only mild diabetes or glucose intolerance, and hyper(pro)insulinemia was the key for their diagnosis. However, this situation changed dramatically after the identification of insulin gene mutations as a cause of neonatal diabetes. This class of insulin gene mutations does not show hyper(pro)insulinemia. Mutations at the cysteine residue or creating a new cysteine will disturb the correct disulfide bonding and proper conformation, and finally will lead to misfolded proinsulin accumulation, endoplasmic reticulum stress and apoptosis of pancreatic β-cells. Maturity-onset diabetes of the young (MODY) or an autoantibody-negative type 1-like phenotype has also been reported. Very recently, recessive mutations with reduced insulin biosynthesis have been reported. The importance of insulin gene mutation in the pathogenesis of diabetes will increase a great deal and give us a new understanding of β-cell biology and diabetes. (J Diabetes Invest, doi: 10.1111/j.2040-1124.2011.00100.x, 2011).
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Affiliation(s)
- Masahiro Nishi
- Department of Metabolism and Clinical Nutrition, Wakayama Medical University
| | - Kishio Nanjo
- Research Center of Rural Medicine, Nachi‐Katsuura Spa Hospital, Wakayama, Japan
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20
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Liu M, Hodish I, Haataja L, Lara-Lemus R, Rajpal G, Wright J, Arvan P. Proinsulin misfolding and diabetes: mutant INS gene-induced diabetes of youth. Trends Endocrinol Metab 2010; 21:652-9. [PMID: 20724178 PMCID: PMC2967602 DOI: 10.1016/j.tem.2010.07.001] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2010] [Revised: 07/07/2010] [Accepted: 07/08/2010] [Indexed: 12/23/2022]
Abstract
Type 1B diabetes (typically with early onset and without islet autoantibodies) has been described in patients bearing small coding sequence mutations in the INS gene. Not all mutations in the INS gene cause the autosomal dominant Mutant INS-gene Induced Diabetes of Youth (MIDY) syndrome, but most missense mutations affecting proinsulin folding produce MIDY. MIDY patients are heterozygotes, with the expressed mutant proinsulins exerting dominant-negative (toxic gain of function) behavior in pancreatic beta cells. Here we focus primarily on proinsulin folding in the endoplasmic reticulum, providing insight into perturbations of this folding pathway in MIDY. Accumulated evidence indicates that, in the molecular pathogenesis of the disease, misfolded proinsulin exerts dominant effects that initially inhibit insulin production, progressing to beta cell demise with diabetes.
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Affiliation(s)
| | | | | | | | | | | | - Peter Arvan
- To whom correspondence may be addressed: Division of Metabolism, Endocrinology & Diabetes University of Michigan, 5560 MSRB2 1150 W. Medical Center Drive Ann Arbor, MI 48109-0678 Telephone: 734-936-5006 FAX: 734-936-6684
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21
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Liu M, Haataja L, Wright J, Wickramasinghe NP, Hua QX, Phillips NF, Barbetti F, Weiss MA, Arvan P. Mutant INS-gene induced diabetes of youth: proinsulin cysteine residues impose dominant-negative inhibition on wild-type proinsulin transport. PLoS One 2010; 5:e13333. [PMID: 20948967 PMCID: PMC2952628 DOI: 10.1371/journal.pone.0013333] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2010] [Accepted: 09/13/2010] [Indexed: 02/06/2023] Open
Abstract
Recently, a syndrome of Mutant INS-gene-induced Diabetes of Youth (MIDY, derived from one of 26 distinct mutations) has been identified as a cause of insulin-deficient diabetes, resulting from expression of a misfolded mutant proinsulin protein in the endoplasmic reticulum (ER) of insulin-producing pancreatic beta cells. Genetic deletion of one, two, or even three alleles encoding insulin in mice does not necessarily lead to diabetes. Yet MIDY patients are INS-gene heterozygotes; inheritance of even one MIDY allele, causes diabetes. Although a favored explanation for the onset of diabetes is that insurmountable ER stress and ER stress response from the mutant proinsulin causes a net loss of beta cells, in this report we present three surprising and interlinked discoveries. First, in the presence of MIDY mutants, an increased fraction of wild-type proinsulin becomes recruited into nonnative disulfide-linked protein complexes. Second, regardless of whether MIDY mutations result in the loss, or creation, of an extra unpaired cysteine within proinsulin, Cys residues in the mutant protein are nevertheless essential in causing intracellular entrapment of co-expressed wild-type proinsulin, blocking insulin production. Third, while each of the MIDY mutants induces ER stress and ER stress response; ER stress and ER stress response alone appear insufficient to account for blockade of wild-type proinsulin. While there is general agreement that ultimately, as diabetes progresses, a significant loss of beta cell mass occurs, the early events described herein precede cell death and loss of beta cell mass. We conclude that the molecular pathogenesis of MIDY is initiated by perturbation of the disulfide-coupled folding pathway of wild-type proinsulin.
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Affiliation(s)
- Ming Liu
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical Center, Ann Arbor, Michigan, United States of America
| | - Leena Haataja
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical Center, Ann Arbor, Michigan, United States of America
| | - Jordan Wright
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical Center, Ann Arbor, Michigan, United States of America
| | - Nalinda P. Wickramasinghe
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Qing-Xin Hua
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Nelson F. Phillips
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Fabrizio Barbetti
- Laboratory of Molecular Endocrinology and Metabolism, Bambino Gesù Children's Hospital, Scientific Institute (IRCCS), Rome, Italy
- Department of Internal Medicine, University of Tor Vergata, Rome, Italy
| | - Michael A. Weiss
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio, United States of America
- * E-mail: (PA); (MAW)
| | - Peter Arvan
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical Center, Ann Arbor, Michigan, United States of America
- * E-mail: (PA); (MAW)
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22
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Montes-Cortes DH, Hicks JJ, Ceballos-Reyes GM, Garcia-Sanchez JR, Medina-Navarro R, Olivares-Corichi IM. Chemical and functional changes of human insulin by in vitro incubation with blood from diabetic patients in oxidative stress. Metabolism 2010; 59:935-42. [PMID: 20022071 DOI: 10.1016/j.metabol.2009.10.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2009] [Revised: 08/12/2009] [Accepted: 10/15/2009] [Indexed: 01/27/2023]
Abstract
Oxidative stress damage to biomolecules has been implicated in several diseases including diabetes mellitus. In the present study, we investigated the effect of oxidative stress in whole blood (WB) from diabetic patients (n = 60) on recombinant human insulin. Insulin was incubated with WB obtained from diabetic patients (DP) who had hyperglycemia (>300 mg/dL) or from 41 healthy volunteers (HV). Whole blood of DP, unlike WB of HV, induced higher values of formazan (142%), dityrosines (279%), and carbonyls (58%) in the insulin residues. Interestingly, the insulin modified by WB of DP showed less hypoglycemic activity in rat (30%) in comparison with insulin incubated with WB of HV. The incubation of insulin in WB from DP induces chemical changes in insulin and a decrease in its biological activity, events that might be associated with the high levels of oxidative stress markers found in the plasma of these patients.
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Affiliation(s)
- Daniel H Montes-Cortes
- General Hospital, Nacional Medical Center La Raza, Mexican Institute for Social Security, Mexico City, Mexico
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23
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Park SY, Ye H, Steiner DF, Bell GI. Mutant proinsulin proteins associated with neonatal diabetes are retained in the endoplasmic reticulum and not efficiently secreted. Biochem Biophys Res Commun 2009; 391:1449-54. [PMID: 20034470 DOI: 10.1016/j.bbrc.2009.12.090] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2009] [Accepted: 12/16/2009] [Indexed: 11/17/2022]
Abstract
Mutations in the preproinsulin protein that affect processing of preproinsulin to proinsulin or lead to misfolding of proinsulin are associated with diabetes. We examined the subcellular localization and secretion of 13 neonatal diabetes-associated human proinsulin proteins (A24D, G32R, G32S, L35P, C43G, G47V, F48C, G84R, R89C, G90C, C96Y, S101C and Y108C) in rat INS-1 insulinoma cells. These mutant proinsulin proteins accumulate in the endoplasmic reticulum (ER) and are poorly secreted except for G84R and in contrast to wild-type and hyperproinsulinemia-associated mutant proteins (H34D and R89H) which were sorted to secretory granules and efficiently secreted. We also examined the effect of C96Y mutant proinsulin on the synthesis and secretion of wild-type insulin and observed a dominant-negative effect of the mutant proinsulin on the synthesis and secretion of wild-type insulin due to induction of the unfolded protein response and resulting attenuation of overall translation.
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Affiliation(s)
- Soo-Young Park
- Department of Medicine, The University of Chicago, 5841 S. Maryland Avenue, MC 1027, Chicago, IL 60637, USA.
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24
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Tenore A, Driul D. Genomics in pediatric endocrinology--genetic disorders and new techniques. Endocrinol Metab Clin North Am 2009; 38:471-90. [PMID: 19717000 DOI: 10.1016/j.ecl.2009.06.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
In the last few years, there have been remarkable advances in the development of new and more sophisticated genetic techniques. These have allowed a better understanding of the molecular mechanisms of genetically determined pediatric endocrine disorders and are paving the way for a radical change in diagnosis and treatment. This article introduces some of these concepts and some of the genetic techniques being used.
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Affiliation(s)
- Alfred Tenore
- Division of Pediatric Endocrinology, Department of Pediatrics DPMSC, University of Udine School of Medicine, Padiglione Petracco, Piazzale S.M. della Misericordia, 33100, Udine, Italy.
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25
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Xu B, Huang K, Chu YC, Hu SQ, Nakagawa S, Wang S, Wang RY, Whittaker J, Katsoyannis PG, Weiss MA. Decoding the cryptic active conformation of a protein by synthetic photoscanning: insulin inserts a detachable arm between receptor domains. J Biol Chem 2009; 284:14597-608. [PMID: 19321435 PMCID: PMC2682907 DOI: 10.1074/jbc.m900087200] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2009] [Revised: 03/20/2009] [Indexed: 12/15/2022] Open
Abstract
Proteins evolve in a fitness landscape encompassing a complex network of biological constraints. Because of the interrelation of folding, function, and regulation, the ground-state structure of a protein may be inactive. A model is provided by insulin, a vertebrate hormone central to the control of metabolism. Whereas native assembly mediates storage within pancreatic beta-cells, the active conformation of insulin and its mode of receptor binding remain elusive. Here, functional surfaces of insulin were probed by photocross-linking of an extensive set of azido derivatives constructed by chemical synthesis. Contacts are circumferential, suggesting that insulin is encaged within its receptor. Mapping of photoproducts to the hormone-binding domains of the insulin receptor demonstrated alternating contacts by the B-chain beta-strand (residues B24-B28). Whereas even-numbered probes (at positions B24 and B26) contact the N-terminal L1 domain of the alpha-subunit, odd-numbered probes (at positions B25 and B27) contact its C-terminal insert domain. This alternation corresponds to the canonical structure of abeta-strand (wherein successive residues project in opposite directions) and so suggests that the B-chain inserts between receptor domains. Detachment of a receptor-binding arm enables photo engagement of surfaces otherwise hidden in the free hormone. The arm and associated surfaces contain sites also required for nascent folding and self-assembly of storage hexamers. The marked compression of structural information within a short polypeptide sequence rationalizes the diversity of diabetes-associated mutations in the insulin gene. Our studies demonstrate that photoscanning mutagenesis can decode the active conformation of a protein and so illuminate cryptic constraints underlying its evolution.
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Affiliation(s)
- Bin Xu
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106, USA
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26
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Hua QX, Xu B, Huang K, Hu SQ, Nakagawa S, Jia W, Wang S, Whittaker J, Katsoyannis PG, Weiss MA. Enhancing the activity of a protein by stereospecific unfolding: conformational life cycle of insulin and its evolutionary origins. J Biol Chem 2009; 284:14586-96. [PMID: 19321436 DOI: 10.1074/jbc.m900085200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A central tenet of molecular biology holds that the function of a protein is mediated by its structure. An inactive ground-state conformation may nonetheless be enjoined by the interplay of competing biological constraints. A model is provided by insulin, well characterized at atomic resolution by x-ray crystallography. Here, we demonstrate that the activity of the hormone is enhanced by stereospecific unfolding of a conserved structural element. A bifunctional beta-strand mediates both self-assembly (within beta-cell storage vesicles) and receptor binding (in the bloodstream). This strand is anchored by an invariant side chain (Phe(B24)); its substitution by Ala leads to an unstable but native-like analog of low activity. Substitution by d-Ala is equally destabilizing, and yet the protein diastereomer exhibits enhanced activity with segmental unfolding of the beta-strand. Corresponding photoactivable derivatives (containing l- or d-para-azido-Phe) cross-link to the insulin receptor with higher d-specific efficiency. Aberrant exposure of hydrophobic surfaces in the analogs is associated with accelerated fibrillation, a form of aggregation-coupled misfolding associated with cellular toxicity. Conservation of Phe(B24), enforced by its dual role in native self-assembly and induced fit, thus highlights the implicit role of misfolding as an evolutionary constraint. Whereas classical crystal structures of insulin depict its storage form, signaling requires engagement of a detachable arm at an extended receptor interface. Because this active conformation resembles an amyloidogenic intermediate, we envisage that induced fit and self-assembly represent complementary molecular adaptations to potential proteotoxicity. The cryptic threat of misfolding poses a universal constraint in the evolution of polypeptide sequences.
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Affiliation(s)
- Qing-xin Hua
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106, USA
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27
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Aigner B, Rathkolb B, Herbach N, Hrabé de Angelis M, Wanke R, Wolf E. Diabetes models by screen for hyperglycemia in phenotype-driven ENU mouse mutagenesis projects. Am J Physiol Endocrinol Metab 2008; 294:E232-40. [PMID: 18056790 DOI: 10.1152/ajpendo.00592.2007] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
More than 150 million people suffer from diabetes mellitus worldwide, and this number is expected to rise substantially within the next decades. Despite its high prevalence, the pathogenesis of diabetes mellitus is not completely understood. Therefore, appropriate experimental models are essential tools to gain more insight into the genetics and pathogenesis of the disease. Here, we describe the current efforts to establish novel diabetes models derived from unbiased, phenotype-driven, large-scale N-ethyl-N-nitrosourea (ENU) mouse mutagenesis projects started a decade ago using hyperglycemia as a high-throughput screen parameter. Mouse lines were established according to their hyperglycemia phenotype over several generations, thereby revealing a mutation as cause for the aberrant phenotype. Chromosomal assignment of the causative mutation and subsequent candidate gene analysis led to the detection of the mutations that resulted in novel alleles of genes already known to be involved in glucose homeostasis, like glucokinase, insulin 2, and insulin receptor. Additional ENU-induced hyperglycemia lines are under genetic analysis. Improvements in screen for diabetic animals are implemented to detect more subtle phenotypes. Moreover, diet challenge assays are being employed to uncover interactions between genetic and environmental factors in the pathogenesis of diabetes mellitus. The new mouse mutants recovered in phenotype-driven ENU mouse mutagenesis projects complement the available models generated by targeted mutagenesis of candidate genes, all together providing the large resource of models required for a systematic dissection of the pathogenesis of diabetes mellitus.
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Affiliation(s)
- Bernhard Aigner
- Institute of Molecular Animal Breeding and Biotechnology, Hackerstrasse 27, Oberschleissheim, Germany.
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28
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Nakagawa SH, Hua QX, Hu SQ, Jia W, Wang S, Katsoyannis PG, Weiss MA. Chiral mutagenesis of insulin. Contribution of the B20-B23 beta-turn to activity and stability. J Biol Chem 2006; 281:22386-22396. [PMID: 16751187 DOI: 10.1074/jbc.m603547200] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Insulin contains a beta-turn (residues B20-B23) interposed between two receptor-binding elements, the central alpha-helix of the B chain (B9-B19) and its C-terminal beta-strand (B24-B28). The turn contains conserved glycines at B20 and B23. Although insulin exhibits marked conformational variability among crystal forms, these glycines consistently maintain positive phi dihedral angles within a classic type-I beta-turn. Because the Ramachandran conformations of GlyB20 and GlyB23 are ordinarily forbidden to L-amino acids, turn architecture may contribute to structure or function. Here, we employ "chiral mutagenesis," comparison of corresponding D- and L-Ala substitutions, to investigate this turn. Control substitutions are introduced at GluB21, a neighboring residue exhibiting a conventional (negative) phi angle. The D- and L-Ala substitutions at B23 are associated with a marked stereospecific difference in activity. Whereas the D-AlaB23 analog retains native activity, the L analog exhibits a 20-fold decrease in receptor binding. By contrast, D- and L-AlaB20 analogs each exhibit high activity. Stereospecific differences between the thermodynamic stabilities of the analogs are nonetheless more pronounced at B20 (delta deltaG(u) 2.0 kcal/mole) than at B23 (delta deltaG(u) 0.7 kcal/mole). Control substitutions at B21 are well tolerated without significant stereospecificity. Chiral mutagenesis thus defines the complementary contributions of these conserved glycines to protein stability (GlyB20) or receptor recognition (GlyB23).
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Affiliation(s)
- Satoe H Nakagawa
- Department of Biochemistry & Molecular Biology, University of Chicago, Chicago, Illinois 60637
| | - Qing-Xin Hua
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio, 44106
| | - Shi-Quan Hu
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio, 44106
| | - Wenhua Jia
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio, 44106
| | - Shuhua Wang
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio, 44106
| | - Panayotis G Katsoyannis
- Department of Pharmacology & Biological Chemistry, Mt. Sinai School of Medicine, New York, New York 10029
| | - Michael A Weiss
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio, 44106.
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Nakagawa SH, Zhao M, Hua QX, Hu SQ, Wan ZL, Jia W, Weiss MA. Chiral mutagenesis of insulin. Foldability and function are inversely regulated by a stereospecific switch in the B chain. Biochemistry 2005; 44:4984-99. [PMID: 15794637 PMCID: PMC3845378 DOI: 10.1021/bi048025o] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
How insulin binds to its receptor is unknown despite decades of investigation. Here, we employ chiral mutagenesis-comparison of corresponding d and l amino acid substitutions in the hormone-to define a structural switch between folding-competent and active conformations. Our strategy is motivated by the T --> R transition, an allosteric feature of zinc-hexamer assembly in which an invariant glycine in the B chain changes conformations. In the classical T state, Gly(B8) lies within a beta-turn and exhibits a positive phi angle (like a d amino acid); in the alternative R state, Gly(B8) is part of an alpha-helix and exhibits a negative phi angle (like an l amino acid). Respective B chain libraries containing mixtures of d or l substitutions at B8 exhibit a stereospecific perturbation of insulin chain combination: l amino acids impede native disulfide pairing, whereas diverse d substitutions are well-tolerated. Strikingly, d substitutions at B8 enhance both synthetic yield and thermodynamic stability but markedly impair biological activity. The NMR structure of such an inactive analogue (as an engineered T-like monomer) is essentially identical to that of native insulin. By contrast, l analogues exhibit impaired folding and stability. Although synthetic yields are very low, such analogues can be highly active. Despite the profound differences between the foldabilities of d and l analogues, crystallization trials suggest that on protein assembly substitutions of either class can be accommodated within classical T or R states. Comparison between such diastereomeric analogues thus implies that the T state represents an inactive but folding-competent conformation. We propose that within folding intermediates the sign of the B8 phi angle exerts kinetic control in a rugged landscape to distinguish between trajectories associated with productive disulfide pairing (positive T-like values) or off-pathway events (negative R-like values). We further propose that the crystallographic T -->R transition in part recapitulates how the conformation of an insulin monomer changes on receptor binding. At the very least the ostensibly unrelated processes of disulfide pairing, allosteric assembly, and receptor binding appear to utilize the same residue as a structural switch; an "ambidextrous" glycine unhindered by the chiral restrictions of the Ramachandran plane. We speculate that this switch operates to protect insulin-and the beta-cell-from protein misfolding.
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Affiliation(s)
- Satoe H. Nakagawa
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637
| | - Ming Zhao
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637
| | - Qing-xin Hua
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106-4935
| | - Shi-Quan Hu
- Department of Pharmacology and Biological Chemistry, Mt. Sinai School of Medicine of New York University, New York, New York 10029
| | - Zhu-li Wan
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106-4935
| | - Wenhua Jia
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106-4935
| | - Michael A. Weiss
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106-4935
- To whom correspondence should be addressed. ; telephone: (216) 368-5991; fax: (216) 368-3419
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Xu B, Hu SQ, Chu YC, Wang S, Wang RY, Nakagawa SH, Katsoyannis PG, Weiss MA. Diabetes-associated mutations in insulin identify invariant receptor contacts. Diabetes 2004; 53:1599-602. [PMID: 15161767 DOI: 10.2337/diabetes.53.6.1599] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Mutations in human insulin cause an autosomal-dominant syndrome of diabetes and fasting hyperinsulinemia. We demonstrate by residue-specific photo cross-linking that diabetes-associated mutations occur at receptor-binding sites. The studies use para-azido-phenylalanine, introduced at five sites by total protein synthesis. Because two such sites (Val(A3) and Phe(B24)) are largely buried in crystal structures of the free hormone, their participation in receptor binding is likely to require a conformational change to expose a hidden functional surface. Our results demonstrate that this surface spans both chains of the insulin molecule and includes sites of rare human mutations that cause diabetes.
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Affiliation(s)
- Bin Xu
- Case Western Reserve University, Department of Biochemistry, 10900 Euclid Ave., SOM Room W427, Cleveland, OH 44106-4935, USA
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Dong J, Wan Z, Popov M, Carey PR, Weiss MA. Insulin assembly damps conformational fluctuations: Raman analysis of amide I linewidths in native states and fibrils. J Mol Biol 2003; 330:431-42. [PMID: 12823980 DOI: 10.1016/s0022-2836(03)00536-9] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The crystal structure of insulin has been investigated in a variety of dimeric and hexameric assemblies. Interest in dynamics has been stimulated by conformational variability among crystal forms and evidence suggesting that the functional monomer undergoes a conformational change on receptor binding. Here, we employ Raman spectroscopy and Raman microscopy to investigate well-defined oligomeric species: monomeric and dimeric analogs in solution, native T(6) and R(6) hexamers in solution and corresponding polycrystalline samples. Remarkably, linewidths of Raman bands associated with the polypeptide backbone (amide I) exhibit progressive narrowing with successive self-assembly. Whereas dimerization damps fluctuations at an intermolecular beta-sheet, deconvolution of the amide I band indicates that formation of hexamers stabilizes both helical and non-helical elements. Although the structure of a monomer in solution resembles a crystallographic protomer, its encagement in a native assembly damps main-chain fluctuations. Further narrowing of a beta-sheet-specific amide I band is observed on reorganization of insulin in a cross-beta fibril. Enhanced flexibility of the native insulin monomer is in accord with molecular dynamics simulations. Such conformational fluctuations may initiate formation of an amyloidogenic nucleus and enable induced fit on receptor binding.
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Affiliation(s)
- Jian Dong
- Department of Biochemistry, Case Western Reserve University School of Medicine, 10900 Euclid Avenue SOM-W427, Cleveland, OH 44106-4935, USA
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Ratnakant S, Ochs ME, Solomon SS. Sounding board: diabetes mellitus in the elderly: a truly heterogeneous entity? Diabetes Obes Metab 2003; 5:81-92. [PMID: 12630932 DOI: 10.1046/j.1463-1326.2003.00242.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Sanjay Ratnakant
- Medical Services, Department of Veterans Affairs Medical Center, Memphis, TN, USA
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Izumi T, Yokota-Hashimoto H, Zhao S, Wang J, Halban PA, Takeuchi T. Dominant negative pathogenesis by mutant proinsulin in the Akita diabetic mouse. Diabetes 2003; 52:409-16. [PMID: 12540615 DOI: 10.2337/diabetes.52.2.409] [Citation(s) in RCA: 168] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Autosomal dominant diabetes in the Akita mouse is caused by mutation of the insulin 2 gene, whose product replaces a cysteine residue that is engaged in the formation of an intramolecular disulfide bond. These heterozygous mice exhibit severe insulin deficiency despite coexpression of normal insulin molecules derived from three other wild-type alleles of the insulin 1 and 2 genes. Although the results of our previous study suggested that the mutant proinsulin 2 is misfolded and blocked in the transport from the endoplasmic reticulum to the Golgi apparatus, its dominant negative nature has not been fully characterized. In the present study, we investigated the possible pathogenic mechanisms induced by the mutant proinsulin 2. There is no evidence that the mutant proinsulin 2 attenuates the overall protein synthesis rate or promotes the formation of aberrant disulfide bonds. The trafficking of constitutively secreted alkaline phosphatase, however, is significantly decreased in the islets of Akita mice, indicating that the function of early secretory pathways is nonspecifically impaired. Morphological analysis has revealed that secretory pathway organelle architecture is progressively devastated in the beta-cells of Akita mice. These findings suggest that the organelle dysfunction resulting from the intracellular accumulation of misfolded proinsulin 2 is primarily responsible for the defect of coexisting wild-type insulin secretion in Akita beta-cells.
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Affiliation(s)
- Tetsuro Izumi
- Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan.
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Abstract
Twin and family studies have demonstrated a strong genetic component to type 2 diabetes mellitus (T2DM), but mapping the susceptibility genes that account for this risk has proved difficult. At least seven single gene defects are known to cause T2DM, often with early onset and insulin deficiency, but these causes account for 5% or less of all T2DM. A large number of candidate genes have been evaluated for typical T2DM, but few have been confirmed in multiple studies, and among these, the effect on individual risk is modest. A large number of genome-wide scans have been published in the last few years, and at least four regions show evidence in multiple studies. However, only NIDDM1 has been mapped to a single gene, and that gene (calpain 10) appears to have a major role only in selected populations. Work is ongoing in many laboratories and multiple populations to map additional regions, but T2DM and other complex diseases have proved recalcitrant to current methodology. In addition to the ongoing progress in completing the genome sequence and in developing a comprehensive map of single nucleotide polymorphisms, new statistical models will be needed to incorporate the multiple loci with modest effect and the known environmental interactions that characterize the susceptibility to T2DM.
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Affiliation(s)
- Steven C Elbein
- Central Arkansas Veterans Healthcare System, Little Rock, Arkansas 72205, USA.
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Pang CY, Lee HC, Wei YH. Enhanced oxidative damage in human cells harboring A3243G mutation of mitochondrial DNA: implication of oxidative stress in the pathogenesis of mitochondrial diabetes. Diabetes Res Clin Pract 2001; 54 Suppl 2:S45-56. [PMID: 11733109 DOI: 10.1016/s0168-8227(01)00335-7] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Mitochondrial oxidative phosphorylation and the ATP production in pancreatic beta cells play significant roles in insulin secretion in response to glucose and other nutrients. An A to G mutation in the tRNA(Leu(UUR)) gene at nucleotide position (np) 3243 of mitochondrial DNA (mtDNA) has been observed in patients with MELAS syndrome and mitochondrial diabetes. Recently, some patients with mitochondrial diabetes associated with the A3243G mtDNA mutation were found to respond to coenzyme Q10 therapy. Thus, we investigated oxidative stress and peroxidative damage in a series of cybrids carrying either the wild-type adenine or the mutant-type guanine at np 3243 but having otherwise identical mtDNA sequence. The cybrids harboring >90% of the A3243G mutant mtDNA were found to have significantly lower oxygen consumption rate and electron transfer activities, and thereby had lower ATP/ADP ratios and declined energy charge. Importantly, the defective respiratory function elicited by the A3243G mtDNA mutation caused an increased oxidative stress as indicated by the decreased GSH/GSSG ratio and enhanced oxidative damage to lipids. Moreover, the cybrids harboring high proportions of the A3243G mtDNA mutation were found to be much more vulnerable to an exogenous oxidant, tert-butylhydroperoxide. We thus suggest that enhanced oxidative damage and elevated oxidative stress contribute to the decline of mitochondrial function and may be involved in the initiation and progression of the MELAS syndrome and mitochondrial diabetes.
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Affiliation(s)
- C Y Pang
- Department of Biochemistry and Center for Cellular and Molecular Biology, National Yang-Ming University, 112, Republic of China, Taipei, Taiwan
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36
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Sano R, Miki T, Suzuki Y, Shimada F, Taira M, Kanatsuka A, Makino H, Hashimoto N, Saito Y. Analysis of the insulin-sensitive phosphodiesterase 3B gene in type 2 diabetes. Diabetes Res Clin Pract 2001; 54:79-88. [PMID: 11640991 DOI: 10.1016/s0168-8227(01)00287-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We screened for mutations in the gene of insulin-sensitive phosphodiesterase 3B (PDE3B), which regulates antilipolytic actions of insulin via reduction of intracellular cyclic AMP levels, in Japanese patients with type 2 diabetes mellitus and lipoatrophic diabetes mellitus using single-stranded conformation polymorphism analysis and Southern analysis and investigated frequencies of variable number of tandem repeats. A silent polymorphism at the Arg463 codon (AGG-->AGA) in exon 4 was identified after examining all 16 exons and exon-intron splicing junctions of the gene. This polymorphism was found in 53 of 100 subjects with type 2 diabetes mellitus, 2 of 5 lipoatrophic diabetic patients and 24 of 50 control subjects, without any significant difference in allele frequency between groups. An EcoRI restriction fragment length polymorphism was identified in patients with type 2 diabetes mellitus and control subjects, again with no differences in occurrence. The allelic distribution of two polymorphic tandem repeats sequences in introns 5 and 12 of the gene did not differ significantly between patients with type 2 diabetes mellitus and control subjects. In conclusion, alterations in the PDE3B gene are unlikely to contribute importantly to the pathogenesis of type 2 diabetes mellitus or lipoatrophic diabetes mellitus in Japan.
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Affiliation(s)
- R Sano
- Department of Clinical Cell Biology, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, 260-8670, Chiba, Japan
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Shih DQ, Screenan S, Munoz KN, Philipson L, Pontoglio M, Yaniv M, Polonsky KS, Stoffel M. Loss of HNF-1alpha function in mice leads to abnormal expression of genes involved in pancreatic islet development and metabolism. Diabetes 2001; 50:2472-80. [PMID: 11679424 DOI: 10.2337/diabetes.50.11.2472] [Citation(s) in RCA: 179] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Mutations in hepatocyte nuclear factor 1alpha (HNF-1alpha) lead to maturity-onset diabetes of the young type 3 as a result of impaired insulin secretory response in pancreatic beta-cells. The expression of 50 genes essential for normal beta-cell function was studied to better define the molecular mechanism underlying the insulin secretion defect in Hnf-1alpha(-/-) mice. We found decreased steady-state mRNA levels of genes encoding glucose transporter 2 (Glut2), neutral and basic amino acid transporter, liver pyruvate kinase (L-Pk), and insulin in Hnf-1alpha(-/-) mice. In addition, we determined that the expression of several islet-enriched transcription factors, including Pdx-1, Hnf-4alpha, and Neuro-D1/Beta-2, was reduced in Hnf-1alpha(-/-) mice. These changes in pancreatic islet mRNA levels were already apparent in newborn animals, suggesting that loss of Hnf-1alpha function rather than chronic hyperglycemia is the primary cause of the altered gene expression. This expression profile was pancreatic islet-specific and distinct from hepatocytes, where we found normal expression of Glut2, L-Pk, and Hnf-4alpha in the liver of Hnf-1alpha(-/-) mice. The expression of small heterodimer partner (Shp-1), an orphan receptor that can heterodimerize with Hnf-4alpha and inhibit its transcriptional activity, was also reduced in Hnf-1alpha(-/-) islets. We characterized a 0.58-kb Shp-1 promoter and determined that the decreased expression of Shp-1 may be indirectly mediated by a downregulation of Hnf-4alpha. We further showed that Shp-1 can repress its own transcriptional activation by inhibiting Hnf-4alpha function, thereby establishing a feedback autoregulatory loop. Our results indicate that loss of Hnf-1alpha function leads to altered expression of genes involved in glucose-stimulated insulin secretion, insulin synthesis, and beta-cell differentiation.
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Affiliation(s)
- D Q Shih
- Laboratory of Metabolic Diseases, the Rockefeller University, New York, New York 10021, USA
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Osawa H, Onuma H, Murakami A, Ochi M, Nishimiya T, Kato K, Shimizu I, Fujii Y, Ohashi J, Makino H. Systematic search for single nucleotide polymorphisms in the insulin gene: evidence for a high frequency of -23T-->A in Japanese subjects. Biochem Biophys Res Commun 2001; 286:451-5. [PMID: 11511079 DOI: 10.1006/bbrc.2001.5414] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It has recently been shown that the A/A genotype at g.-23 of the insulin gene correlates with impaired insulin secretion in response to body weight gain in subjects of European descent. To examine whether there are single nucleotide polymorphisms (SNPs) in the insulin gene associated with type 2 diabetes, all exons with their flanking sequences for 113 Japanese type 2 diabetic patients and 99 nondiabetic control subjects were analyzed using PCR direct sequencing. We have only found g.-23T --> A, 806G --> C, 1128T --> C, and 1141A --> C, which have previously been reported in alpha (A-C-C-C) and beta (T-G-T-A) alleles. The allele frequency of -23T --> A in control Japanese subjects was 97.4%, whereas that in Europeans is about 30%. The A/A genotype was found in 94 of 99 Japanese subjects (94.9%) and the allele frequencies of 806G --> C, 1128T --> C, and 1141A --> C were all 96.5%. The estimated haplotype frequencies were (A-C-C-C) (96.0%), (T-G-T-A) (2.0%), (A-G-T-A) (1.5%), and (T-C-C-C) (0.5%). No association of these SNPs or haplotypes with type 2 diabetes was evident. Thus, the A/A genotype at the g.-23 of insulin gene was generally high in Japanese subjects, which could account for the fact that they typically secrete lower levels of insulin.
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Affiliation(s)
- H Osawa
- Department of Laboratory Medicine, Ehime University School of Medicine, Shigenobu, Ehime, 791-0295, Japan.
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Yamada Y, Kuroe A, Li Q, Someya Y, Kubota A, Ihara Y, Tsuura Y, Seino Y. Genomic variation in pancreatic ion channel genes in Japanese type 2 diabetic patients. Diabetes Metab Res Rev 2001; 17:213-6. [PMID: 11424233 DOI: 10.1002/dmrr.193] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
BACKGROUND Many genetic diseases are caused by mutations in ion channel genes. Because type 2 diabetes is characterized by pancreatic beta-cell insensitivity to glucose, the genes responsible for glucose metabolism and calcium signaling in pancreatic beta-cells are candidate type 2 diabetes susceptibility genes. METHODS We have examined genomic variations in two ion channel genes relevant to the molecular pathology of diabetes mellitus, the Kir6.2 subunit of the ATP-sensitive potassium channel gene and alpha(1D) subunit of the voltage-dependent calcium channel (VDCC) gene among Japanese type 2 diabetic patients. RESULTS There are two alleles in the Kir6.2 gene: EI, glutamic acid at codon 23 and isoleucine at codon 337 and KV, lysine at codon 23 and valine at codon 337. The allelic frequencies of these polymorphisms are similar in type 2 diabetic patients and normal subjects. We also detected trinucleotide repeat polymorphisms in the amino terminus and the carboxyl terminal region of the alpha(1D) gene. Expansion of the ATG trinucleotide repeat from seven to eight was detected only in type 2 diabetic patients, but the frequency was low and was similar in type 2 diabetic patients and normal subjects. CONCLUSIONS Although variations of the Kir6.2 and alpha(1D) genes are not associated with the development of common type 2 diabetes, further studies may determine the role of these genomic variations, especially those in the alpha(1D) VDCC gene, in the pathogenesis of certain subsets of type 2 diabetes, or as a co-factor in the polygenic disorder generally.
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Affiliation(s)
- Y Yamada
- Department of Metabolism and Clinical Nutrition, Kyoto University Graduate School of Medicine, Kyoto, Japan.
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Affiliation(s)
- S I Taylor
- Diabetes Branch, National Institutes of Diabetes and Digestive and Kidney Disease, National Institutes of Health, Bethesda, Maryland 20892, USA.
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Abstract
Success in controlling hyperglycemia in type I diabetics will require a restoration of basal insulin. To this end, three plasmid DNAs (pDNA) encoding preproinsulin were compared for constitutive expression and processing to insulin in nonendocrine cells in vitro. The pDNAs were designed to express rat proinsulin I (VR-3501), rat proinsulin I with the B10 aspartic acid point mutation (VR-3502), and a derivative of VR-3502 with a furin cleavage site added at the B-chain and C-peptide junction (VR-3503). Cells transfected with VR-3501 or VR-3502 were able to secrete only proinsulin, whereas transfection with VR-3503 yielded 30-70% mature insulin, which could be increased to >99% by cotransfection with a furin expression plasmid (VR-3505). The insulin produced was biologically active. The bilateral injection of 100 microg of VR-3502 plasmid into the tibialis anterior muscles of mice on two consecutive days yielded, on average, several hundred picograms of heterologous proinsulin per milliliter of serum. In BALB/c mice, serum proinsulin peaked 7-14 days postinjection and declined to preinjection levels by days 21-28. In athymic nude mice, serum proinsulin was sustained for at least 6 weeks. The therapeutic efficacy of delivering insulin via muscle injection of pDNA was evaluated in athymic nude mice made diabetic with the beta cell toxin streptozotocin (STZ). All animals given control DNA died within 1 week of receiving STZ while 40% of the mice coinjected with plasmids VR-3503 and VR-3505 lived through the duration of the 4-week experiment. Muscles of the surviving animals contained 17-100 ng of immune-reactive insulin (IRI), 86-94% of which was mature insulin. The results suggest that heterologous insulin made in muscle increased the survival rate. We propose that insulin plasmid expression in skeletal muscle may be a valid approach to basal insulin delivery. The feasibility of plasmid DNA-based delivery of basal insulin was investigated. An expression system consisting of pDNAs encoding a selectively mutated rat preproinsulin and mouse furin was developed and characterized in vitro and in vivo. When injected with preproinsulin pDNA, the mouse tibialis anterior muscle expressed and released proinsulin into serum at levels comparable to normal basal insulin in rodents. These heterologous proinsulin levels were sustained for several weeks in immune-compromised nondiabetic mice. Mouse muscle coinjected with a pDNA encoding the endopeptidase furin and a pDNA encoding a pre-proinsulin modified to contain two furin cleavage sites produced fully processed insulin. This muscle-made insulin appears to have contributed to the survival of mice treated with a highly diabetogenic dose of streptozotocin, a beta cell toxin. The results demonstrate that skeletal muscle is able to express and deliver therapeutic insulin from plasmid DNA.
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Affiliation(s)
- A M Abai
- Department of Molecular Biology, Vical, Inc., San Diego, CA 92121, USA.
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Heikkinen S, Pietilä M, Halmekytö M, Suppola S, Pirinen E, Deeb SS, Jänne J, Laakso M. Hexokinase II-deficient mice. Prenatal death of homozygotes without disturbances in glucose tolerance in heterozygotes. J Biol Chem 1999; 274:22517-23. [PMID: 10428828 DOI: 10.1074/jbc.274.32.22517] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Type 2 diabetes is characterized by decreased rates of insulin-stimulated glucose uptake and utilization, reduced hexokinase II mRNA and enzyme production, and low basal levels of glucose 6-phosphate in insulin-sensitive skeletal muscle and adipose tissues. Hexokinase II is primarily expressed in muscle and adipose tissues where it catalyzes the phosphorylation of glucose to glucose 6-phosphate, a possible rate-limiting step for glucose disposal. To investigate the role of hexokinase II in insulin action and in glucose homeostasis as well as in mouse development, we generated a hexokinase II knock-out mouse. Mice homozygous for hexokinase II deficiency (HKII(-/-)) died at approximately 7.5 days post-fertilization, indicating that hexokinase II is vital for mouse embryogenesis after implantation and before organogenesis. HKII(+/-) mice were viable, fertile, and grew normally. Surprisingly, even though HKII(+/-) mice had significantly reduced (by 50%) hexokinase II mRNA and activity levels in skeletal muscle, heart, and adipose tissue, they did not exhibit impaired insulin action or glucose tolerance even when challenged with a high-fat diet.
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Affiliation(s)
- S Heikkinen
- Department of Medicine, University of Kuopio, FIN-70211 Kuopio, Finland
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Affiliation(s)
- S I Taylor
- Diabetes Branch, Division of Intramural Research, National Institute of Diabetes and Digestive and Kidney Disease, National Institutes of Health, Bethesda, Maryland 20892, USA
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Pathogenesis of non-insulin-dependent (type II) diabetes mellitus (NIDDM) - genetic predisposition and metabolic abnormalities. Adv Drug Deliv Rev 1999; 35:157-177. [PMID: 10837696 DOI: 10.1016/s0169-409x(98)00071-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Non-insulin-dependent diabetes mellitus (NIDDM), also known as type II diabetes, is characterized by abnormal glucose homeostasis, resulting in hyperglycemia, and is associated with microvascular, macrovascular, and neuropathic complications. NIDDM is a complex disease with many causes. Both genetic and environmental factors play important roles in the pathogenesis of NIDDM. Cumulative evidence on the high prevalence of NIDDM in certain ethnic groups, the high concordance rate for the disease in monozygotic twins, familial aggregation, and familial transmission patterns suggests that the genetic component plays an important etiological role in the development of NIDDM. In genetically predisposed individuals, there is a slow progression from a normal state to hyperglycemia, largely due to a combination of insulin resistance and defects in insulin secretion. Although numerous candidate genes responsible for insulin resistance and for the defects in insulin secretion have been reported, no specific gene(s) accounting for the majority of cases of the common type of NIDDM has been identified. Considerable evidence indicates that environmental and other factors, including diet, stress, physical activity, obesity and aging, also play an important role in the development of the disease. In conclusion, the pathogenic process of NIDDM depends on a complex interaction between genetic and environmental factors.
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Wang J, Takeuchi T, Tanaka S, Kubo SK, Kayo T, Lu D, Takata K, Koizumi A, Izumi T. A mutation in the insulin 2 gene induces diabetes with severe pancreatic beta-cell dysfunction in the Mody mouse. J Clin Invest 1999; 103:27-37. [PMID: 9884331 PMCID: PMC407861 DOI: 10.1172/jci4431] [Citation(s) in RCA: 454] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The mouse autosomal dominant mutation Mody develops hyperglycemia with notable pancreatic beta-cell dysfunction. This study demonstrates that one of the alleles of the gene for insulin 2 in Mody mice encodes a protein product that substitutes tyrosine for cysteine at the seventh amino acid of the A chain in its mature form. This mutation disrupts a disulfide bond between the A and B chains and can induce a drastic conformational change of this molecule. Although there was no gross defect in the transcription from the wild-type insulin 2 allele or two alleles of insulin 1, levels of proinsulin and insulin were profoundly diminished in the beta cells of Mody mice, suggesting that the number of wild-type (pro)insulin molecules was also decreased. Electron microscopy revealed a dramatic reduction of secretory granules and a remarkably enlarged lumen of the endoplasmic reticulum. Little proinsulin was processed to insulin, but high molecular weight forms of proinsulin existed with concomitant overexpression of BiP, a molecular chaperone in the endoplasmic reticulum. Furthermore, mutant proinsulin expressed in Chinese hamster ovary cells was inefficiently secreted, and its intracellular fraction formed complexes with BiP and was eventually degraded. These findings indicate that mutant proinsulin was trapped and accumulated in the endoplasmic reticulum, which could induce beta-cell dysfunction and account for the dominant phenotype of this mutation.
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Affiliation(s)
- J Wang
- Department of Molecular Medicine, Gunma University, Maebashi, Japan
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Condorelli G, Vigliotta G, Iavarone C, Caruso M, Tocchetti CG, Andreozzi F, Cafieri A, Tecce MF, Formisano P, Beguinot L, Beguinot F. PED/PEA-15 gene controls glucose transport and is overexpressed in type 2 diabetes mellitus. EMBO J 1998; 17:3858-66. [PMID: 9670003 PMCID: PMC1170721 DOI: 10.1093/emboj/17.14.3858] [Citation(s) in RCA: 132] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We have used differential display to identify genes whose expression is altered in type 2 diabetes thus contributing to its pathogenesis. One mRNA is overexpressed in fibroblasts from type 2 diabetics compared with non-diabetic individuals, as well as in skeletal muscle and adipose tissues, two major sites of insulin resistance in type 2 diabetes. The levels of the protein encoded by this mRNA are also elevated in type 2 diabetic tissues; thus, we named it PED for phosphoprotein enriched in diabetes. PED cloning shows that it encodes a 15 kDa phosphoprotein identical to the protein kinase C (PKC) substrate PEA-15. The PED gene maps on human chromosome 1q21-22. Transfection of PED/PEA-15 in differentiating L6 skeletal muscle cells increases the content of Glut1 transporters on the plasma membrane and inhibits insulin-stimulated glucose transport and cell-surface recruitment of Glut4, the major insulin-sensitive glucose transporter. These effects of PED overexpression are reversed by blocking PKC activity. Overexpression of the PED/PEA-15 gene may contribute to insulin resistance in glucose uptake in type 2 diabetes.
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Affiliation(s)
- G Condorelli
- Dipartimento di Biologia e Patologia Cellulare e Molecolare and Centro di Endocrinologia ed Oncologia Sperimentale del C.N.R., Federico II University of Naples, Naples, Italy
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Ikehata F, Satoh J, Nata K, Tohgo A, Nakazawa T, Kato I, Kobayashi S, Akiyama T, Takasawa S, Toyota T, Okamoto H. Autoantibodies against CD38 (ADP-ribosyl cyclase/cyclic ADP-ribose hydrolase) that impair glucose-induced insulin secretion in noninsulin- dependent diabetes patients. J Clin Invest 1998; 102:395-401. [PMID: 9664081 PMCID: PMC508898 DOI: 10.1172/jci1656] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Cyclic ADP-ribose (cADPR) has been shown to be a mediator for intracellular Ca2+ mobilization for insulin secretion by glucose in pancreatic beta cells, and CD38 shows both ADP-ribosyl cyclase to synthesize cADPR from NAD+ and cADPR hydrolase to hydrolyze cADPR to ADP-ribose. We show here that 13.8% of Japanese non-insulin-dependent diabetes (NIDDM) patients examined have autoantibodies against CD38 and that the sera containing anti-CD38 autoantibodies inhibit the ADP-ribosyl cyclase activity of CD38 (P </= 0.05). Insulin secretion from pancreatic islets by glucose is significantly inhibited by the addition of the NIDDM sera with anti-CD38 antibodies (P </= 0.04-0.0001), and the inhibition of insulin secretion is abolished by the addition of recombinant CD38 (P </= 0.02). The increase of cADPR levels in pancreatic islets by glucose was also inhibited by the addition of the sera (P </= 0.05). These results strongly suggest that the presence of anti-CD38 autoantibodies in NIDDM patients can be one of the major causes of impaired glucose-induced insulin secretion in NIDDM.
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Affiliation(s)
- F Ikehata
- Department of Biochemistry, Tohoku University School of Medicine, Sendai 980-8575, Japan
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Ranheim T, Dumke C, Schueler KL, Cartee GD, Attie AD. Interaction between BTBR and C57BL/6J genomes produces an insulin resistance syndrome in (BTBR x C57BL/6J) F1 mice. Arterioscler Thromb Vasc Biol 1997; 17:3286-93. [PMID: 9409324 DOI: 10.1161/01.atv.17.11.3286] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Insulin resistance is a common syndrome that often precedes the development of noninsulin-dependent diabetes mellitus (NIDDM). Both diet and genetic factors are associated with insulin resistance. BTBR and C57BL/6J (B6) mice have normal insulin responsiveness and normal fasting plasma insulin levels. However, a cross between these two strains yielded male offspring with severe insulin resistance. Surprisingly, on a basal diet (6.5% fat), the insulin resistance was not associated with fasting hyperinsulinemia. However, a 15% fat diet produced significant hyperinsulinemia in the male mice (twofold at 10 weeks; P < .05). At 10 weeks of age, visceral fat contributed approximately 4.3% of the total body weight in the males versus 1.8% in females. In the males, levels of plasma triacylglycerol and total cholesterol increased 40% and 30%, respectively, compared to females. Plasma free fatty acid concentrations were unchanged. Oral glucose tolerance tests revealed significant levels of hyperglycemia and hyperinsulinemia 15 to 90 minutes after oral glucose administration in the male mice. This was particularly dramatic in males on a 15% fat diet. Glucose transport was examined in skeletal muscles in (BTBR x B6)F1 mice. In the nonhyperinsulinemic animals (females), insulin stimulated 2-deoxyglucose transport 3.5-fold in the soleus and 2.8-fold in the extensor digitorum longus muscles. By contrast, glucose transport was not stimulated in the hyperinsulinemic male mice. Hypoxia stimulates glucose transport through an insulin-independent mechanism. This is known to involve the translocation of GLUT4 from an intracellular pool to the plasma membrane. In the insulin-resistant male mice, hypoxia induced glucose transport as effectively as it did in the insulin-responsive mice. Thus, defective glucose transport in the (BTBR x B6)F1 mice is specific for insulin-stimulated glucose transport. This is similar to what has been observed in muscles taken from obese NIDDM patients. These animals represent an excellent genetic model for studying insulin resistance and investigating the transition from insulin resistance in the absence of hyperinsulinemia to insulin resistance with hyperinsulinemia.
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Affiliation(s)
- T Ranheim
- Department of Biochemistry and Comparative Biosciences, University of Wisconsin-Madison 53706, USA
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Abstract
Familial aggregation and concordance in monozygotic and dizygotic twins argue strongly for a genetic etiology to noninsulin-dependent diabetes (NIDDM). Nonetheless, studies of pathways implicated by the known physiology have failed to identify gene defects that can explain the genetic susceptibility. In contrast, studies of early onset dominant diabetes have revealed three major loci resulting in diminished insulin secretion. Recently, studies have taken a new approach to map the genes causing typical NIDDM using large numbers of families or sibling pairs. The first reports of these studies have suggested possible loci on chromosomes 1, 2 and 12, but no report has been confirmed. Other studies have examined the quantitative defects that may be precursors of clinical NIDDM such as hyperinsulinemia, hyperglycemia, insulin response to glucose and obesity. These studies have suggested additional loci that may contribute to NIDDM susceptibility, but the genes responsible for most of these loci remain unknown. Studies of NIDDM susceptibility and the role of obesity genes in that susceptibility have entered an exciting new phase, but the challenges of complex disease genetics in humans will have to be conquered to translate this research into preventive or therapeutic benefits.
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Affiliation(s)
- S C Elbein
- Division of Endocrinology and Metabolism, Veterans Affairs Medical Center and University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
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