1
|
Zhang Y, Sui L, Du Q, Haataja L, Yin Y, Viola R, Xu S, Nielsson CU, Leibel RL, Barbetti F, Arvan P, Egli D. Permanent neonatal diabetes-causing insulin mutations have dominant negative effects on beta cell identity. Mol Metab 2024; 80:101879. [PMID: 38237895 PMCID: PMC10839447 DOI: 10.1016/j.molmet.2024.101879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Revised: 01/08/2024] [Accepted: 01/09/2024] [Indexed: 01/25/2024] Open
Abstract
OBJECTIVE Heterozygous coding sequence mutations of the INS gene are a cause of permanent neonatal diabetes (PNDM), requiring insulin therapy similar to T1D. While the negative effects on insulin processing and secretion are known, how dominant insulin mutations result in a continued decline of beta cell function after birth is not well understood. METHODS We explored the causes of beta cell failure in two PNDM patients with two distinct INS mutations using patient-derived iPSCs and mutated hESCs. RESULTS we detected accumulation of misfolded proinsulin and impaired proinsulin processing in vitro, and a dominant-negative effect of these mutations on beta-cell mass and function after transplantation into mice. In addition to anticipated ER stress, we found evidence of beta-cell dedifferentiation, characterized by an increase of cells expressing both Nkx6.1 and ALDH1A3, but negative for insulin and glucagon. CONCLUSIONS These results highlight a novel mechanism, the loss of beta cell identity, contributing to the loss and functional failure of human beta cells with specific insulin gene mutations.
Collapse
Affiliation(s)
- Yuwei Zhang
- Naomi Berrie Diabetes Center & Department of Pediatrics, College of Physicians and Surgeons, Columbia Stem Cell Initiative, Columbia University, New York, NY, 10032, United States
| | - Lina Sui
- Naomi Berrie Diabetes Center & Department of Pediatrics, College of Physicians and Surgeons, Columbia Stem Cell Initiative, Columbia University, New York, NY, 10032, United States
| | - Qian Du
- Naomi Berrie Diabetes Center & Department of Pediatrics, College of Physicians and Surgeons, Columbia Stem Cell Initiative, Columbia University, New York, NY, 10032, United States
| | - Leena Haataja
- Metabolism Endocrinology & Diabetes, University of Michigan, Ann Arbor, MI 48105, United States
| | - Yishu Yin
- Naomi Berrie Diabetes Center & Department of Pediatrics, College of Physicians and Surgeons, Columbia Stem Cell Initiative, Columbia University, New York, NY, 10032, United States
| | - Ryan Viola
- Naomi Berrie Diabetes Center & Department of Pediatrics, College of Physicians and Surgeons, Columbia Stem Cell Initiative, Columbia University, New York, NY, 10032, United States
| | - Shuangyi Xu
- Naomi Berrie Diabetes Center & Department of Pediatrics, College of Physicians and Surgeons, Columbia Stem Cell Initiative, Columbia University, New York, NY, 10032, United States
| | - Christian Ulrik Nielsson
- Naomi Berrie Diabetes Center & Department of Pediatrics, College of Physicians and Surgeons, Columbia Stem Cell Initiative, Columbia University, New York, NY, 10032, United States
| | - Rudolph L Leibel
- Naomi Berrie Diabetes Center & Department of Pediatrics, College of Physicians and Surgeons, Columbia Stem Cell Initiative, Columbia University, New York, NY, 10032, United States
| | - Fabrizio Barbetti
- Department of Experimental Medicine, University of Rome Tor Vergata, Rome 00133, Italy; Monogenic Diabetes Clinic, Endocrinology and Diabetes Unit, Bambino Gesù Children's Hospital, Rome 00164, Italy
| | - Peter Arvan
- Metabolism Endocrinology & Diabetes, University of Michigan, Ann Arbor, MI 48105, United States
| | - Dieter Egli
- Naomi Berrie Diabetes Center & Department of Pediatrics, College of Physicians and Surgeons, Columbia Stem Cell Initiative, Columbia University, New York, NY, 10032, United States.
| |
Collapse
|
2
|
Zhang Y, Sui L, Du Q, Haataja L, Yin Y, Viola R, Xu S, Nielsson CU, Leibel RL, Barbetti F, Arvan P, Egli D. Permanent Neonatal diabetes-causing Insulin mutations have dominant negative effects on beta cell identity. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.01.555839. [PMID: 37745320 PMCID: PMC10515756 DOI: 10.1101/2023.09.01.555839] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/26/2023]
Abstract
Heterozygous coding sequence mutations of the INS gene are a cause of permanent neonatal diabetes (PNDM) that results from beta cell failure. We explored the causes of beta cell failure in two PNDM patients with two distinct INS mutations. Using b and mutated hESCs, we detected accumulation of misfolded proinsulin and impaired proinsulin processing in vitro, and a dominant-negative effect of these mutations on the in vivo performance of patient-derived SC-beta cells after transplantation into NSG mice. These insulin mutations derange endoplasmic reticulum (ER) homeostasis, and result in the loss of beta-cell mass and function. In addition to anticipated apoptosis, we found evidence of beta-cell dedifferentiation, characterized by an increase of cells expressing both Nkx6.1 and ALDH1A3, but negative for insulin and glucagon. These results highlight both known and novel mechanisms contributing to the loss and functional failure of human beta cells with specific insulin gene mutations.
Collapse
Affiliation(s)
- Yuwei Zhang
- Naomi Berrie Diabetes Center & Department of Pediatrics, College of Physicians and Surgeons, Columbia University, New York, New York, 10032, United States
- These authors contributed equally
| | - Lina Sui
- Naomi Berrie Diabetes Center & Department of Pediatrics, College of Physicians and Surgeons, Columbia University, New York, New York, 10032, United States
- These authors contributed equally
| | - Qian Du
- Naomi Berrie Diabetes Center & Department of Pediatrics, College of Physicians and Surgeons, Columbia University, New York, New York, 10032, United States
| | - Leena Haataja
- Metabolism Endocrinology & Diabetes, University of Michigan, Ann Arbor, MI 48105, United States
| | - Yishu Yin
- Naomi Berrie Diabetes Center & Department of Pediatrics, College of Physicians and Surgeons, Columbia University, New York, New York, 10032, United States
| | - Ryan Viola
- Naomi Berrie Diabetes Center & Department of Pediatrics, College of Physicians and Surgeons, Columbia University, New York, New York, 10032, United States
| | - Shuangyi Xu
- Naomi Berrie Diabetes Center & Department of Pediatrics, College of Physicians and Surgeons, Columbia University, New York, New York, 10032, United States
| | - Christian Ulrik Nielsson
- Naomi Berrie Diabetes Center & Department of Pediatrics, College of Physicians and Surgeons, Columbia University, New York, New York, 10032, United States
| | - Rudolph L. Leibel
- Naomi Berrie Diabetes Center & Department of Pediatrics, College of Physicians and Surgeons, Columbia University, New York, New York, 10032, United States
| | - Fabrizio Barbetti
- Department of Experimental Medicine, University of Rome Tor Vergata, Rome 00133, Italy
- Monogenic Diabetes Clinic, Endocrinology and Diabetes Unit, Bambino Gesù Children’s Hospital, Rome 00164, Italy
| | - Peter Arvan
- Metabolism Endocrinology & Diabetes, University of Michigan, Ann Arbor, MI 48105, United States
| | - Dieter Egli
- Naomi Berrie Diabetes Center & Department of Pediatrics, College of Physicians and Surgeons, Columbia University, New York, New York, 10032, United States
- Lead Contact
| |
Collapse
|
3
|
Klyosova E, Azarova I, Polonikov A. A Polymorphism in the Gene Encoding Heat Shock Factor 1 ( HSF1) Increases the Risk of Type 2 Diabetes: A Pilot Study Supports a Role for Impaired Protein Folding in Disease Pathogenesis. Life (Basel) 2022; 12:life12111936. [PMID: 36431071 PMCID: PMC9694443 DOI: 10.3390/life12111936] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 11/09/2022] [Accepted: 11/17/2022] [Indexed: 11/22/2022] Open
Abstract
The aim of this pilot study was to investigate whether polymorphisms in the gene encoding heat shock factor 1 (HSF1), a transcriptional activator of molecular chaperones, play a role in the development of type 2 diabetes (T2D). A total of 3229 unrelated individuals of Slavic origin, including 1569 T2D patients and 1660 age- and sex-matched healthy controls, were enrolled for the study. Five common single nucleotide polymorphisms (SNPs) of the HSF1 gene were genotyped using the MassArray-4 system. SNPs rs7838717 (p = 0.002) and rs3757971 (p = 0.005) showed an association with an increased risk of T2D in females with a body mass index ≥ 25 kg/m2. The rs7838717T-rs4279640T-rs3757971C and rs7838717T-rs4279640T-rs3757971T haplotypes were associated with increased and decreased disease risk in overweight or obese females, respectively. The associations were replicated as disease susceptibility genes in large cohorts from the UK Biobank (p = 0.008), DIAMANTE (p = 2.7 × 10-13), and DIAGRAM (p = 0.0004) consortiums. The functional annotation of the SNPs revealed that the rs7838717-T and rs3757971C alleles correlated with increased expression of the genes involved in unfolded protein response. The present study showed, for the first time, that genetic variation of HSF1 is associated with the risk of type 2 diabetes, supporting a role for impaired protein folding in disease pathogenesis.
Collapse
Affiliation(s)
- Elena Klyosova
- Laboratory of Biochemical Genetics and Metabolomics, Research Institute for Genetic and Molecular Epidemiology, Kursk State Medical University, 18 Yamskaya Street, 305041 Kursk, Russia
- Department of Biology, Medical Genetics and Ecology, Kursk State Medical University, 3 Karl Marx Street, 305041 Kursk, Russia
- Correspondence:
| | - Iuliia Azarova
- Laboratory of Biochemical Genetics and Metabolomics, Research Institute for Genetic and Molecular Epidemiology, Kursk State Medical University, 18 Yamskaya Street, 305041 Kursk, Russia
- Department of Biological Chemistry, Kursk State Medical University, 3 Karl Marx Street, 305041 Kursk, Russia
| | - Alexey Polonikov
- Department of Biology, Medical Genetics and Ecology, Kursk State Medical University, 3 Karl Marx Street, 305041 Kursk, Russia
- Laboratory of Statistical Genetics and Bioinformatics, Research Institute for Genetic and Molecular Epidemiology, Kursk State Medical University, 18 Yamskaya Street, 305041 Kursk, Russia
| |
Collapse
|
4
|
Ratnaparkhi A, Sudhakaran J. Neural pathways in nutrient sensing and insulin signaling. Front Physiol 2022; 13:1002183. [PMID: 36439265 PMCID: PMC9691681 DOI: 10.3389/fphys.2022.1002183] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2022] [Accepted: 10/18/2022] [Indexed: 10/29/2023] Open
Abstract
Nutrient sensing and metabolic homeostasis play an important role in the proper growth and development of an organism, and also in the energy intensive process of reproduction. Signals in response to nutritional and metabolic status is received and integrated by the brain to ensure homeostasis. In Drosophila, the fat body is one of the key organs involved in energy and nutrient sensing, storage and utilization. It also relays the nutritional status of the animal to the brain, activating specific circuits which modulate the synthesis and release of insulin-like peptides to regulate metabolism. Here, we review the molecular and cellular mechanisms involved in nutrient sensing with an emphasis on the neural pathways that modulate this process and discuss some of the open questions that need to be addressed.
Collapse
Affiliation(s)
- Anuradha Ratnaparkhi
- Department of Developmental Biology, MACS-Agharkar Research Institute, Pune, India
- Savitribai Phule Pune University, Pune, India
| | - Jyothish Sudhakaran
- Department of Developmental Biology, MACS-Agharkar Research Institute, Pune, India
| |
Collapse
|
5
|
Insulin and Its Key Role for Mitochondrial Function/Dysfunction and Quality Control: A Shared Link between Dysmetabolism and Neurodegeneration. BIOLOGY 2022; 11:biology11060943. [PMID: 35741464 PMCID: PMC9220302 DOI: 10.3390/biology11060943] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Revised: 06/01/2022] [Accepted: 06/17/2022] [Indexed: 02/07/2023]
Abstract
Insulin was discovered and isolated from the beta cells of pancreatic islets of dogs and is associated with the regulation of peripheral glucose homeostasis. Insulin produced in the brain is related to synaptic plasticity and memory. Defective insulin signaling plays a role in brain dysfunction, such as neurodegenerative disease. Growing evidence suggests a link between metabolic disorders, such as diabetes and obesity, and neurodegenerative diseases, especially Alzheimer's disease (AD). This association is due to a common state of insulin resistance (IR) and mitochondrial dysfunction. This review takes a journey into the past to summarize what was known about the physiological and pathological role of insulin in peripheral tissues and the brain. Then, it will land in the present to analyze the insulin role on mitochondrial health and the effects on insulin resistance and neurodegenerative diseases that are IR-dependent. Specifically, we will focus our attention on the quality control of mitochondria (MQC), such as mitochondrial dynamics, mitochondrial biogenesis, and selective autophagy (mitophagy), in healthy and altered cases. Finally, this review will be projected toward the future by examining the most promising treatments that target the mitochondria to cure neurodegenerative diseases associated with metabolic disorders.
Collapse
|
6
|
Dhayalan B, Glidden MD, Zaykov AN, Chen YS, Yang Y, Phillips NB, Ismail-Beigi F, Jarosinski MA, DiMarchi RD, Weiss MA. Peptide Model of the Mutant Proinsulin Syndrome. I. Design and Clinical Correlation. Front Endocrinol (Lausanne) 2022; 13:821069. [PMID: 35299972 PMCID: PMC8922534 DOI: 10.3389/fendo.2022.821069] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [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: 01/17/2022] [Indexed: 12/16/2022] Open
Abstract
The mutant proinsulin syndrome is a monogenic cause of diabetes mellitus due to toxic misfolding of insulin's biosynthetic precursor. Also designated mutant INS-gene induced diabetes of the young (MIDY), this syndrome defines molecular determinants of foldability in the endoplasmic reticulum (ER) of β-cells. Here, we describe a peptide model of a key proinsulin folding intermediate and variants containing representative clinical mutations; the latter perturb invariant core sites in native proinsulin (LeuB15→Pro, LeuA16→Pro, and PheB24→Ser). The studies exploited a 49-residue single-chain synthetic precursor (designated DesDi), previously shown to optimize in vitro efficiency of disulfide pairing. Parent and variant peptides contain a single disulfide bridge (cystine B19-A20) to provide a model of proinsulin's first oxidative folding intermediate. The peptides were characterized by circular dichroism and redox stability in relation to effects of the mutations on (a) in vitro foldability of the corresponding insulin analogs and (b) ER stress induced in cell culture on expression of the corresponding variant proinsulins. Striking correlations were observed between peptide biophysical properties, degree of ER stress and age of diabetes onset (neonatal or adolescent). Our findings suggest that age of onset reflects the extent to which nascent structure is destabilized in proinsulin's putative folding nucleus. We envisage that such peptide models will enable high-resolution structural studies of key folding determinants and in turn permit molecular dissection of phenotype-genotype relationships in this monogenic diabetes syndrome. Our companion study (next article in this issue) employs two-dimensional heteronuclear NMR spectroscopy to define site-specific perturbations in the variant peptides.
Collapse
Affiliation(s)
- Balamurugan Dhayalan
- 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
| | | | - Yen-Shan Chen
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Yanwu Yang
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Nelson B. Phillips
- Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, OH, United States
| | - Faramarz Ismail-Beigi
- 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
| | - Mark A. Jarosinski
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, United States
| | | | - Michael A. Weiss
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, United States
| |
Collapse
|
7
|
PGRMC1 acts as a size-selective cargo receptor to drive ER-phagic clearance of mutant prohormones. Nat Commun 2021; 12:5991. [PMID: 34645803 PMCID: PMC8514460 DOI: 10.1038/s41467-021-26225-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Accepted: 09/20/2021] [Indexed: 02/06/2023] Open
Abstract
The reticulon-3 (RTN3)-driven targeting complex promotes clearance of misfolded prohormones from the endoplasmic reticulum (ER) for lysosomal destruction by ER-phagy. Because RTN3 resides in the cytosolic leaflet of the ER bilayer, the mechanism of selecting misfolded prohormones as ER-phagy cargo on the luminal side of the ER membrane remains unknown. Here we identify the ER transmembrane protein PGRMC1 as an RTN3-binding partner. Via its luminal domain, PGRMC1 captures misfolded prohormones, targeting them for RTN3-dependent ER-phagy. PGRMC1 selects cargos that are smaller than the large size of other reported ER-phagy substrates. Cargos for PGRMC1 include mutant proinsulins that block secretion of wildtype proinsulin through dominant-negative interactions within the ER, causing insulin-deficiency. Chemical perturbation of PGRMC1 partially restores WT insulin storage by preventing ER-phagic degradation of WT and mutant proinsulin. Thus, PGRMC1 acts as a size-selective cargo receptor during RTN3-dependent ER-phagy, and is a potential therapeutic target for diabetes.
Collapse
|
8
|
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.
Collapse
Affiliation(s)
| | | | | | - Michael A. Weiss
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, United States
| |
Collapse
|
9
|
Dhayalan B, Chatterjee D, Chen YS, Weiss MA. Diabetes mellitus due to toxic misfolding of proinsulin variants. Mol Metab 2021:101229. [PMID: 33823319 DOI: 10.1016/j.molmet.2021.101229] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 03/10/2021] [Accepted: 03/29/2021] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Dominant mutations in the human insulin gene (INS) lead to pancreatic β-cell dysfunction and diabetes mellitus (DM) due to toxic misfolding of a mutant proinsulin. Analogous to a classical mouse model of monogenic DM ("Akita"), this syndrome highlights the susceptibility of β-cells to endoreticulum (ER) stress due to protein misfolding and aberrant aggregation. SCOPE OF REVIEW Diverse clinical mutations directly or indirectly perturb native disulfide pairing. Whereas most introduce or remove a cysteine (Cys; leading in either case to an unpaired thiol group), non-Cys-related mutations identify key determinants of folding efficiency. Studies of such mutations suggest that the hormone's evolution has been constrained not only by structure-function relationships but also by the susceptibility of its single-chain precursor to impaired foldability. An intriguing hypothesis posits that INS overexpression in response to peripheral insulin resistance likewise leads to chronic ER stress and β-cell dysfunction in the natural history of nonsyndromic Type 2 DM. MAJOR CONCLUSIONS Cryptic contributions of conserved residues to folding efficiency, as uncovered by rare genetic variants, define molecular links between biophysical principles and the emerging paradigm of Darwinian medicine: Biosynthesis of proinsulin at the edge of nonfoldability provides a key determinant of "diabesity" as a pandemic disease of civilization.
Collapse
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.
| |
Collapse
|
10
|
Wang H, Saint-Martin C, Xu J, Ding L, Wang R, Feng W, Liu M, Shu H, Fan Z, Haataja L, Arvan P, Bellanné-Chantelot C, Cui J, Huang Y. Biological behaviors of mutant proinsulin contribute to the phenotypic spectrum of diabetes associated with insulin gene mutations. Mol Cell Endocrinol 2020; 518:111025. [PMID: 32916194 PMCID: PMC7734662 DOI: 10.1016/j.mce.2020.111025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Revised: 08/30/2020] [Accepted: 08/31/2020] [Indexed: 02/06/2023]
Abstract
Insulin gene mutation is the second most common cause of neonatal diabetes (NDM). It is also one of the genes involved in maturity-onset diabetes of the young (MODY). We aim to investigate molecular behaviors of different INS gene variants that may correlate with the clinical spectrum of diabetes phenotypes. In this study, we concentrated on two previously uncharacterized MODY-causing mutants, proinsulin-p.Gly44Arg [G(B20)R] and p.Pro52Leu [P(B28)L] (a novel mutant identified in one French family), and an NDM causing proinsulin-p.(Cys96Tyr) [C(A7)Y]. We find that these proinsulin mutants exhibit impaired oxidative folding in the endoplasmic reticulum (ER) with blocked ER export, ER stress, and apoptosis. Importantly, the proinsulin mutants formed abnormal intermolecular disulfide bonds that not only involved the mutant proinsulin, but also the co-expressed WT-proinsulin, forming misfolded disulfide-linked proinsulin complexes. This impaired the intracellular trafficking of WT-proinsulin and limited the production of bioactive mature insulin. Notably, although all three mutants presented with similar defects in folding, trafficking, and dominant negative behavior, the degrees of these defects appeared to be different. Specifically, compared to MODY mutants G(B20)R and P(B28)L that partially affected folding and trafficking of co-expressed WT-proinsulin, the NDM mutant C(A7)Y resulted in an almost complete blockade of the ER export of WT-proinsulin, decreasing insulin production, inducing more severe ER stress and apoptosis. We thus demonstrate that differences in cell biological behaviors among different proinsulin mutants correlate with the spectrum of diabetes phenotypes caused by the different INS gene mutations.
Collapse
Affiliation(s)
- Heting Wang
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
| | - Cécile Saint-Martin
- Department of Genetics, Sorbonne University, Pitié-Salpêtrière Hospital, Assistance Publique-Hôpitaux de Paris, Paris, France
| | - Jialu Xu
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
| | - Li Ding
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
| | - Ruodan Wang
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
| | - Wenli Feng
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
| | - Ming Liu
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China; Tianjin Institute of Endocrinology, Tianjin, China
| | - Hua Shu
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
| | - Zhenqian Fan
- Department of Endocrinology and Metabolism, The Second Hospital of Tianjin Medical University, Tianjin, China
| | - Leena Haataja
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Christine Bellanné-Chantelot
- Department of Genetics, Sorbonne University, Pitié-Salpêtrière Hospital, Assistance Publique-Hôpitaux de Paris, Paris, France.
| | - Jingqiu Cui
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China.
| | - Yumeng Huang
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China.
| |
Collapse
|
11
|
Arneth B. Insulin gene mutations and posttranslational and translocation defects: associations with diabetes. Endocrine 2020; 70:488-497. [PMID: 32656694 DOI: 10.1007/s12020-020-02413-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/08/2020] [Accepted: 07/01/2020] [Indexed: 02/06/2023]
Abstract
The mechanism underlying the pathogenesis of diabetes is complex and poorly understood. Recent investigations have revealed that insulin gene mutations can lead to the development of specific subtypes of diabetes. This systematic review aimed to explore the associations of insulin gene mutations and insulin translocation defects with diabetes. This review was generated using articles from PsycINFO, PubMed, Web of Science, and CINAHL. Search terms and phrases such as "diabetes," "mutations," "insulin," "preproinsulin," "INS gene," "role," "VNTR polymorphisms," and "INS promotor" were used to identify articles relevant to the research topic. The gathered data showed the significant role of insulin gene mutations and insulin translocation defects during diabetes development and progression. Genetic changes can adversely affect the development of various types of diabetes, such as neonatal diabetes mellitus and MIDY. Genetic alterations can affect insulin production, thus compromising the regulation of glucose utilization by tissues. Targeting insulin gene mutations is a potential new avenue for diagnosing and managing diabetes. There are specific subcategories of diabetes, such as MIDY and neonatal diabetes mellitus, caused by insulin gene mutations and defects in posttranslational modification. Further investigations are needed to examine the diagnostic and therapeutic potential of mutation-based biomarkers.
Collapse
Affiliation(s)
- Borros Arneth
- Institute of Laboratory Medicine and Pathobiochemistry, Molecular Diagnostics, University Hospital of Giessen and Marburg (UKGM), Justus Liebig University Giessen, Feulgenstr 12, 35332, Giessen, Germany.
| |
Collapse
|
12
|
Rege NK, Liu M, Yang Y, Dhayalan B, Wickramasinghe NP, Chen YS, Rahimi L, Guo H, Haataja L, Sun J, Ismail-Beigi F, Phillips NB, Arvan P, Weiss MA. Evolution of insulin at the edge of foldability and its medical implications. Proc Natl Acad Sci U S A 2020; 117:29618-29628. [PMID: 33154160 PMCID: PMC7703552 DOI: 10.1073/pnas.2010908117] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Proteins have evolved to be foldable, and yet determinants of foldability may be inapparent once the native state is reached. Insight has emerged from studies of diseases of protein misfolding, exemplified by monogenic diabetes mellitus due to mutations in proinsulin leading to endoplasmic reticulum stress and β-cell death. Cellular foldability of human proinsulin requires an invariant Phe within a conserved crevice at the receptor-binding surface (position B24). Any substitution, even related aromatic residue TyrB24, impairs insulin biosynthesis and secretion. As a seeming paradox, a monomeric TyrB24 insulin analog exhibits a native-like structure in solution with only a modest decrement in stability. Packing of TyrB24 is similar to that of PheB24, adjoining core cystine B19-A20 to seal the core; the analog also exhibits native self-assembly. Although affinity for the insulin receptor is decreased ∼20-fold, biological activities in cells and rats were within the range of natural variation. Together, our findings suggest that the invariance of PheB24 among vertebrate insulins and insulin-like growth factors reflects an essential role in enabling efficient protein folding, trafficking, and secretion, a function that is inapparent in native structures. In particular, we envision that the para-hydroxyl group of TyrB24 hinders pairing of cystine B19-A20 in an obligatory on-pathway folding intermediate. The absence of genetic variation at B24 and other conserved sites near this disulfide bridge-excluded due to β-cell dysfunction-suggests that insulin has evolved to the edge of foldability. Nonrobustness of a protein's fitness landscape underlies both a rare monogenic syndrome and "diabesity" as a pandemic disease of civilization.
Collapse
Affiliation(s)
- Nischay K Rege
- Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106
| | - Ming Liu
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, 300052 Tianjin, China
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI 48105
| | - Yanwu Yang
- Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202
| | - Balamurugan Dhayalan
- Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202
| | | | - Yen-Shan Chen
- Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202
| | - Leili Rahimi
- Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106
- Department of Medicine, Case Western Reserve University, Cleveland, OH 44106
| | - Huan Guo
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI 48105
| | - Leena Haataja
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI 48105
| | - Jinhong Sun
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI 48105
| | - Faramarz Ismail-Beigi
- Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106
- Department of Medicine, Case Western Reserve University, Cleveland, OH 44106
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH 44106
| | - Nelson B Phillips
- Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106
| | - Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI 48105
| | - Michael A Weiss
- Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106;
- Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202
- Department of Medicine, Case Western Reserve University, Cleveland, OH 44106
| |
Collapse
|
13
|
Identification of Ala2Thr mutation in insulin gene from a Chinese MODY10 family. Mol Cell Biochem 2020; 470:77-86. [PMID: 32405973 DOI: 10.1007/s11010-020-03748-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 05/06/2020] [Indexed: 12/26/2022]
Abstract
More than 80% of maturity-onset diabetes of the young (MODY) in Chinese is genetically unexplained. To investigate whether the insulin gene (INS) mutation is responsible for some Chinese MODY, we screened INS mutations causing MODY10 in MODY pedigrees and explored the potential pathogenic mechanisms. INS mutations were screened in 56 MODY familial probands. Structure-function characterization and clinical profiling of identified INS mutations were conducted. An INS mutation, at the position 2 alanine-to-threonine substitution (A2T), was identified and co-segregated with hyperglycemia in a MODY pedigree. The A2T mutation converted an α-helix into a β-sheet at the N-terminal of the signal peptide (SP) of preproinsulin. The A2T mutation did not affect preproinsulin translocation across endoplasmic reticulum (ER) membrane, but impaired its SP cleavage within the ER. In INS-1 cells transfected with an A2T mutant, glucose-stimulated insulin secretion (GSIS) was significantly decreased, while BiP luciferase activities were significantly increased compared to that of wild type (WT). We identified an INS-A2T mutation cosegregating with diabetes in a Chinese MODY pedigree. This mutation severely impaired SP cleavage and thus blocked the formation of proinsulin, resulting in enhanced ER stress, which may be responsible for decreased insulin secretion and subsequently, the onset of MODY10.
Collapse
|
14
|
The role of ERp44 in glucose and lipid metabolism. Arch Biochem Biophys 2019; 671:175-184. [PMID: 31283909 DOI: 10.1016/j.abb.2019.06.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Revised: 06/25/2019] [Accepted: 06/27/2019] [Indexed: 12/21/2022]
Abstract
Endoplasmic Reticulum Protein 44 (ERp44) is a member of the PDI family, named for a molecular weight of 44 kD. White adipose tissue has metabolic and endocrine functions that are important to metabolism. The role of ERp44 in glucose and lipid metabolism is not known yet. The current study was undertaken to investigate the implication of ERp44 in glucose and lipid metabolism. In this study, we generated and characterized ERp44-/- mice. We used type 2 diabetes models and ERp44 knockout mice to show the implication of ERp44 in glucose and lipid metabolism. Knockout newborns had lower blood glucose compared to wild-type. Adult knockouts had abnormal intraperitoneal, glucose, insulin and pyruvic acid tolerance. Lipocytes were smaller and fewer in knockout mice compared to wild-type. Knockouts resisted to high-fat diet-induced obesity. ERp44 expression in white adipose tissue decreased significantly in type 2 diabetes models. Results suggest that ERp44 is closely associated with glucose and lipid metabolism.
Collapse
|
15
|
Zhu R, Li X, Xu J, Barrabi C, Kekulandara D, Woods J, Chen X, Liu M. Defective endoplasmic reticulum export causes proinsulin misfolding in pancreatic β cells. Mol Cell Endocrinol 2019; 493:110470. [PMID: 31158417 PMCID: PMC6613978 DOI: 10.1016/j.mce.2019.110470] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Revised: 05/30/2019] [Accepted: 05/30/2019] [Indexed: 02/06/2023]
Abstract
Endoplasmic reticulum (ER) homeostasis is essential for cell function. Increasing evidence indicates that, efficient protein ER export is important for ER homeostasis. However, the consequence of impaired ER export remains largely unknown. Herein, we found that defective ER protein transport caused by either Sar1 mutants or brefeldin A impaired proinsulin oxidative folding in the ER of β-cells. Misfolded proinsulin formed aberrant disulfide-linked dimers and high molecular weight proinsulin complexes, and induced ER stress. Limiting proinsulin load to the ER alleviated ER stress, indicating that misfolded proinsulin is a direct cause of ER stress. This study revealed significance of efficient ER export in maintaining ER protein homeostasis and native folding of proinsulin. Given the fact that proinsulin misfolding plays an important role in diabetes, this study suggests that enhancing ER export may be a potential therapeutic target to prevent/delay β-cell failure caused by proinsulin misfolding and ER stress.
Collapse
Affiliation(s)
- Ruimin Zhu
- Department of Physiology, School of Medicine, Wayne State University, Detroit, MI, USA; Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin 300052, China
| | - Xin Li
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin 300052, China
| | - Jialu Xu
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin 300052, China
| | - Cesar Barrabi
- Department of Physiology, School of Medicine, Wayne State University, Detroit, MI, USA
| | - Dilini Kekulandara
- Department of Physiology, School of Medicine, Wayne State University, Detroit, MI, USA
| | - James Woods
- Department of Physiology, School of Medicine, Wayne State University, Detroit, MI, USA
| | - Xuequn Chen
- Department of Physiology, School of Medicine, Wayne State University, Detroit, MI, USA.
| | - Ming Liu
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin 300052, China.
| |
Collapse
|
16
|
Vakilian M, Tahamtani Y, Ghaedi K. A review on insulin trafficking and exocytosis. Gene 2019; 706:52-61. [DOI: 10.1016/j.gene.2019.04.063] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 04/22/2019] [Accepted: 04/23/2019] [Indexed: 12/21/2022]
|
17
|
Cunningham CN, Williams JM, Knupp J, Arunagiri A, Arvan P, Tsai B. Cells Deploy a Two-Pronged Strategy to Rectify Misfolded Proinsulin Aggregates. Mol Cell 2019; 75:442-456.e4. [PMID: 31176671 DOI: 10.1016/j.molcel.2019.05.011] [Citation(s) in RCA: 66] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 04/17/2019] [Accepted: 05/08/2019] [Indexed: 02/06/2023]
Abstract
Insulin gene coding sequence mutations are known to cause mutant INS-gene-induced diabetes of youth (MIDY), yet the cellular pathways needed to prevent misfolded proinsulin accumulation remain incompletely understood. Here, we report that Akita mutant proinsulin forms detergent-insoluble aggregates that entrap wild-type (WT) proinsulin in the endoplasmic reticulum (ER), thereby blocking insulin production. Two distinct quality-control mechanisms operate together to combat this insult: the ER luminal chaperone Grp170 prevents proinsulin aggregation, while the ER membrane morphogenic protein reticulon-3 (RTN3) disposes of aggregates via ER-coupled autophagy (ER-phagy). We show that enhanced RTN-dependent clearance of aggregated Akita proinsulin helps to restore ER export of WT proinsulin, which can promote WT insulin production, potentially alleviating MIDY. We also find that RTN3 participates in the clearance of other mutant prohormone aggregates. Together, these results identify a series of substrates of RTN3-mediated ER-phagy, highlighting RTN3 in the disposal of pathogenic prohormone aggregates.
Collapse
Affiliation(s)
- Corey N Cunningham
- Department of Cell & Developmental Biology, University of Michigan Medical School, 109 Zina Pitcher Place, BSRB 3043, Ann Arbor, MI 48109, USA; Cellular and Molecular Biology Program, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Jeffrey M Williams
- Department of Cell & Developmental Biology, University of Michigan Medical School, 109 Zina Pitcher Place, BSRB 3043, Ann Arbor, MI 48109, USA
| | - Jeffrey Knupp
- Department of Cell & Developmental Biology, University of Michigan Medical School, 109 Zina Pitcher Place, BSRB 3043, Ann Arbor, MI 48109, USA; Cellular and Molecular Biology Program, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Anoop Arunagiri
- Division of Metabolism Endocrinology & Diabetes, Comprehensive Diabetes Center, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Peter Arvan
- Cellular and Molecular Biology Program, University of Michigan Medical School, Ann Arbor, MI 48109, USA; Division of Metabolism Endocrinology & Diabetes, Comprehensive Diabetes Center, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
| | - Billy Tsai
- Department of Cell & Developmental Biology, University of Michigan Medical School, 109 Zina Pitcher Place, BSRB 3043, Ann Arbor, MI 48109, USA; Cellular and Molecular Biology Program, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
| |
Collapse
|
18
|
Liu M, Weiss MA, Arunagiri A, Yong J, Rege N, Sun J, Haataja L, Kaufman RJ, Arvan P. Biosynthesis, structure, and folding of the insulin precursor protein. Diabetes Obes Metab 2018; 20 Suppl 2:28-50. [PMID: 30230185 PMCID: PMC6463291 DOI: 10.1111/dom.13378] [Citation(s) in RCA: 118] [Impact Index Per Article: 19.7] [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: 05/04/2018] [Accepted: 05/23/2018] [Indexed: 02/06/2023]
Abstract
Insulin synthesis in pancreatic β-cells is initiated as preproinsulin. Prevailing glucose concentrations, which oscillate pre- and postprandially, exert major dynamic variation in preproinsulin biosynthesis. Accompanying upregulated translation of the insulin precursor includes elements of the endoplasmic reticulum (ER) translocation apparatus linked to successful orientation of the signal peptide, translocation and signal peptide cleavage of preproinsulin-all of which are necessary to initiate the pathway of proper proinsulin folding. Evolutionary pressures on the primary structure of proinsulin itself have preserved the efficiency of folding ("foldability"), and remarkably, these evolutionary pressures are distinct from those protecting the ultimate biological activity of insulin. Proinsulin foldability is manifest in the ER, in which the local environment is designed to assist in the overall load of proinsulin folding and to favour its disulphide bond formation (while limiting misfolding), all of which is closely tuned to ER stress response pathways that have complex (beneficial, as well as potentially damaging) effects on pancreatic β-cells. Proinsulin misfolding may occur as a consequence of exuberant proinsulin biosynthetic load in the ER, proinsulin coding sequence mutations, or genetic predispositions that lead to an altered ER folding environment. Proinsulin misfolding is a phenotype that is very much linked to deficient insulin production and diabetes, as is seen in a variety of contexts: rodent models bearing proinsulin-misfolding mutants, human patients with Mutant INS-gene-induced Diabetes of Youth (MIDY), animal models and human patients bearing mutations in critical ER resident proteins, and, quite possibly, in more common variety type 2 diabetes.
Collapse
Affiliation(s)
- Ming Liu
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China 300052
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor 48105 MI USA
| | - Michael A. Weiss
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis 46202 IN USA
- Department of Biochemistry, Case-Western Reserve University, Cleveland 44016 OH USA
| | - Anoop Arunagiri
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor 48105 MI USA
| | - Jing Yong
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92307 USA
| | - Nischay Rege
- Department of Biochemistry, Case-Western Reserve University, Cleveland 44016 OH USA
| | - Jinhong Sun
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China 300052
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor 48105 MI USA
| | - Leena Haataja
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor 48105 MI USA
| | - Randal J. Kaufman
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92307 USA
| | - Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor 48105 MI USA
| |
Collapse
|
19
|
Riahi Y, Israeli T, Cerasi E, Leibowitz G. Effects of proinsulin misfolding on β-cell dynamics, differentiation and function in diabetes. Diabetes Obes Metab 2018; 20 Suppl 2:95-103. [PMID: 30230182 DOI: 10.1111/dom.13379] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Revised: 05/17/2018] [Accepted: 05/23/2018] [Indexed: 12/12/2022]
Abstract
ER stress due to proinsulin misfolding has an important role in the pathophysiology of rare forms of permanent neonatal diabetes (PNDM) and probably also of common type 1 (T1D) and type 2 diabetes (T2D). Accumulation of misfolded proinsulin in the ER stimulates the unfolded protein response (UPR) that may eventually lead to apoptosis through a process called the terminal UPR. However, the β-cell ER has an incredible ability to cope with accumulation of misfolded proteins; therefore, it is not clear whether in common forms of diabetes the accumulation of misfolded proinsulin exceeds the point of no return in which terminal UPR is activated. Many studies showed that the UPR is altered in both T1D and T2D; however, the observed changes in the expression of different UPR markers are inconsistent and it is not clear whether they reflect an adaptive response to stress or indeed mediate the β-cell dysfunction of diabetes. Herein, we critically review the literature on the effects of proinsulin misfolding and ER stress on β-cell dysfunction and loss in diabetes with emphasis on β-cell dynamics, and discuss the gaps in understanding the role of proinsulin misfolding in the pathophysiology of diabetes.
Collapse
Affiliation(s)
- Yael Riahi
- The Diabetes Unit and the Endocrine Service, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Tal Israeli
- The Diabetes Unit and the Endocrine Service, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Erol Cerasi
- The Diabetes Unit and the Endocrine Service, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Gil Leibowitz
- The Diabetes Unit and the Endocrine Service, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| |
Collapse
|
20
|
Březina K, Duboué-Dijon E, Palivec V, Jiráček J, Křížek T, Viola CM, Ganderton TR, Brzozowski AM, Jungwirth P. Can Arginine Inhibit Insulin Aggregation? A Combined Protein Crystallography, Capillary Electrophoresis, and Molecular Simulation Study. J Phys Chem B 2018; 122:10069-10076. [DOI: 10.1021/acs.jpcb.8b06557] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- Kryštof Březina
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 542/2, 160 00 Prague, Czech Republic
| | - Elise Duboué-Dijon
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 542/2, 160 00 Prague, Czech Republic
| | - Vladimír Palivec
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 542/2, 160 00 Prague, Czech Republic
| | - Jiří Jiráček
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 542/2, 160 00 Prague, Czech Republic
| | - Tomáš Křížek
- Faculty of Science, Department of Analytical Chemistry, Charles University, Albertov 2030, 12840 Prague 2, Czech Republic
| | - Cristina M. Viola
- York Structural Biology Laboratory, Department of Chemistry, The University of York, Heslington, York YO10 5DD, United Kingdom
| | - Timothy R. Ganderton
- York Structural Biology Laboratory, Department of Chemistry, The University of York, Heslington, York YO10 5DD, United Kingdom
| | - Andrzej M. Brzozowski
- York Structural Biology Laboratory, Department of Chemistry, The University of York, Heslington, York YO10 5DD, United Kingdom
| | - Pavel Jungwirth
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 542/2, 160 00 Prague, Czech Republic
| |
Collapse
|
21
|
Abstract
Insulin is a key hormone for the regulation of metabolism in vertebrates. Insulin is produced by pancreatic islet cells in response to elevated glucose levels and leads to the uptake of glucose by tissues such as liver and adipose tissue to store energy. Insulin also has additional functions in regulating development. Previous work has shown that the proglucagon gene, which encodes hormones counter regulating insulin, is duplicated in teleost fish, and that the peptide hormones encoded by these genes have diversified in function. I sought to determine whether similar processes have occurred to insulin genes in these species. Searches of fish genomes revealed an unexpected diversity of insulin genes. A triplication of the insulin gene occurred at the origin of teleost fish, however one of these three genes, insc, has been lost in most teleost fish lineages. The two other insulin genes, insa and insb, have been retained but show differing levels of selective constraint suggesting that they might have diversified in function. Intriguingly, a duplicate copy of the insa gene, which I named insab, is found in many fish. The coding sequence encoded by insab genes is under weak selective constraint, with its predicted protein sequences losing their potential to be processed into a two-peptide hormone. However, these sequences have retained perfectly conserved cystine residues, suggesting that they maintain insulin's three-dimensional structure and therefore might modulate the processing and secretion of insulin produced by the other genes.
Collapse
Affiliation(s)
- David M Irwin
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, M5S 1A8, Canada; E-mail:.,Banting and Best Diabetes Centre, University of Toronto, Toronto, Ontario, M5S 1A8, Canada
| |
Collapse
|
22
|
Tsuchiya Y, Saito M, Kadokura H, Miyazaki JI, Tashiro F, Imagawa Y, Iwawaki T, Kohno K. IRE1-XBP1 pathway regulates oxidative proinsulin folding in pancreatic β cells. J Cell Biol 2018; 217:1287-1301. [PMID: 29507125 PMCID: PMC5881499 DOI: 10.1083/jcb.201707143] [Citation(s) in RCA: 84] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 12/06/2017] [Accepted: 01/22/2018] [Indexed: 11/22/2022] Open
Abstract
In mammalian pancreatic β cells, the IRE1α-XBP1 pathway is constitutively and highly activated under physiological conditions. To elucidate the precise role of this pathway, we constructed β cell-specific Ire1α conditional knockout (CKO) mice and established insulinoma cell lines in which Ire1α was deleted using the Cre-loxP system. Ire1α CKO mice showed the typical diabetic phenotype including impaired glycemic control and defects in insulin biosynthesis postnatally at 4-20 weeks. Ire1α deletion in pancreatic β cells in mice and insulinoma cells resulted in decreased insulin secretion, decreased insulin and proinsulin contents in cells, and decreased oxidative folding of proinsulin along with decreased expression of five protein disulfide isomerases (PDIs): PDI, PDIR, P5, ERp44, and ERp46. Reconstitution of the IRE1α-XBP1 pathway restored the proinsulin and insulin contents, insulin secretion, and expression of the five PDIs, indicating that IRE1α functions as a key regulator of the induction of catalysts for the oxidative folding of proinsulin in pancreatic β cells.
Collapse
Affiliation(s)
- Yuichi Tsuchiya
- Graduate School of Biological Sciences and Institute for Research Initiatives, Nara Institute of Science and Technology, Ikoma, Japan
| | - Michiko Saito
- Graduate School of Biological Sciences and Institute for Research Initiatives, Nara Institute of Science and Technology, Ikoma, Japan.,Bio-science Research Center, Kyoto Pharmaceutical University, Kyoto, Japan
| | - Hiroshi Kadokura
- Graduate School of Biological Sciences and Institute for Research Initiatives, Nara Institute of Science and Technology, Ikoma, Japan.,Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Japan
| | - Jun-Ichi Miyazaki
- Division of Stem Cell Regulation Research, Osaka University Graduate School of Medicine, Suita, Japan
| | - Fumi Tashiro
- Division of Stem Cell Regulation Research, Osaka University Graduate School of Medicine, Suita, Japan
| | - Yusuke Imagawa
- Graduate School of Biological Sciences and Institute for Research Initiatives, Nara Institute of Science and Technology, Ikoma, Japan.,Department of Molecular and Cellular Biology, Research Center, Osaka International Cancer Institute, Osaka, Japan
| | - Takao Iwawaki
- Division of Cell Medicine, Department of Life Science, Medical Research Institute, Kanazawa Medical University, Uchinada, Japan
| | - Kenji Kohno
- Graduate School of Biological Sciences and Institute for Research Initiatives, Nara Institute of Science and Technology, Ikoma, Japan
| |
Collapse
|
23
|
Sowers CR, Wang R, Bourne RA, McGrath BC, Hu J, Bevilacqua SC, Paton JC, Paton AW, Collardeau-Frachon S, Nicolino M, Cavener DR. The protein kinase PERK/EIF2AK3 regulates proinsulin processing not via protein synthesis but by controlling endoplasmic reticulum chaperones. J Biol Chem 2018; 293:5134-5149. [PMID: 29444822 DOI: 10.1074/jbc.m117.813790] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Revised: 02/06/2018] [Indexed: 11/06/2022] Open
Abstract
Loss-of-function mutations of the protein kinase PERK (EIF2AK3) in humans and mice cause permanent neonatal diabetes and severe proinsulin aggregation in the endoplasmic reticulum (ER), highlighting the essential role of PERK in insulin production in pancreatic β cells. As PERK is generally known as a translational regulator of the unfolded protein response (UPR), the underlying cause of these β cell defects has often been attributed to derepression of proinsulin synthesis, resulting in proinsulin overload in the ER. Using high-resolution imaging and standard protein fractionation and immunological methods we have examined the PERK-dependent phenotype more closely. We found that whereas proinsulin aggregation requires new protein synthesis, global protein and proinsulin synthesis are down-regulated in PERK-inhibited cells, strongly arguing against proinsulin overproduction being the root cause of their aberrant ER phenotype. Furthermore, we show that PERK regulates proinsulin proteostasis by modulating ER chaperones, including BiP and ERp72. Transgenic overexpression of BiP and BiP knockdown (KD) both promoted proinsulin aggregation, whereas ERp72 overexpression and knockdown rescued it. These findings underscore the importance of ER chaperones working in concert to achieve control of insulin production and identify a role for PERK in maintaining a functional balance among these chaperones.
Collapse
Affiliation(s)
- Carrie R Sowers
- From the Department of Biology, Penn State University, University Park, Pennsylvania 16802
| | - Rong Wang
- From the Department of Biology, Penn State University, University Park, Pennsylvania 16802
| | - Rebecca A Bourne
- From the Department of Biology, Penn State University, University Park, Pennsylvania 16802
| | - Barbara C McGrath
- From the Department of Biology, Penn State University, University Park, Pennsylvania 16802
| | - Jingjie Hu
- From the Department of Biology, Penn State University, University Park, Pennsylvania 16802
| | - Sarah C Bevilacqua
- From the Department of Biology, Penn State University, University Park, Pennsylvania 16802
| | - James C Paton
- the Department of Molecular and Cellular Biology, Research Centre for Infectious Diseases, University of Adelaide, Adelaide 5005, Australia
| | - Adrienne W Paton
- the Department of Molecular and Cellular Biology, Research Centre for Infectious Diseases, University of Adelaide, Adelaide 5005, Australia
| | - Sophie Collardeau-Frachon
- the Department of Pathology, Hôpital-Femme-Mère-Enfant, Hospices Civils de Lyon, Université Claude Bernard Lyon I and CarMeN, INSERM Unit U1060, 69677 Bron, France, and
| | - Marc Nicolino
- the Service d'endocrinologie et de diabétologie pédiatriques et maladies héréditaires du métabolisme, Hôpital Femme-Mère-Enfant, Hospices Civils de Lyon, F-69677 Bron, France
| | - Douglas R Cavener
- From the Department of Biology, Penn State University, University Park, Pennsylvania 16802,
| |
Collapse
|
24
|
Arunagiri A, Haataja L, Cunningham CN, Shrestha N, Tsai B, Qi L, Liu M, Arvan P. Misfolded proinsulin in the endoplasmic reticulum during development of beta cell failure in diabetes. Ann N Y Acad Sci 2018; 1418:5-19. [PMID: 29377149 DOI: 10.1111/nyas.13531] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Revised: 09/14/2017] [Accepted: 09/25/2017] [Indexed: 02/06/2023]
Abstract
The endoplasmic reticulum (ER) is broadly distributed throughout the cytoplasm of pancreatic beta cells, and this is where all proinsulin is initially made. Healthy beta cells can synthesize 6000 proinsulin molecules per second. Ordinarily, nascent proinsulin entering the ER rapidly folds via the formation of three evolutionarily conserved disulfide bonds (B7-A7, B19-A20, and A6-A11). A modest amount of proinsulin misfolding, including both intramolecular disulfide mispairing and intermolecular disulfide-linked protein complexes, is a natural by-product of proinsulin biosynthesis, as is the case for many proteins. The steady-state level of misfolded proinsulin-a potential ER stressor-is linked to (1) production rate, (2) ER environment, (3) presence or absence of naturally occurring (mutational) defects in proinsulin, and (4) clearance of misfolded proinsulin molecules. Accumulation of misfolded proinsulin beyond a certain threshold begins to interfere with the normal intracellular transport of bystander proinsulin, leading to diminished insulin production and hyperglycemia, as well as exacerbating ER stress. This is most obvious in mutant INS gene-induced Diabetes of Youth (MIDY; an autosomal dominant disease) but also likely to occur in type 2 diabetes owing to dysregulation in proinsulin synthesis, ER folding environment, or clearance.
Collapse
Affiliation(s)
- Anoop Arunagiri
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, Michigan
| | - Leena Haataja
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, Michigan
| | - Corey N Cunningham
- Cellular and Molecular Biology Program, University of Michigan, Ann Arbor, Michigan
| | - Neha Shrestha
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - Billy Tsai
- Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, Michigan
| | - Ling Qi
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - Ming Liu
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, Michigan.,Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
| | - Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, Michigan
| |
Collapse
|
25
|
Computational study of the activity, dynamics, energetics and conformations of insulin analogues using molecular dynamics simulations: Application to hyperinsulinemia and the critical residue B26. Biochem Biophys Rep 2017; 11:182-190. [PMID: 28955783 PMCID: PMC5614686 DOI: 10.1016/j.bbrep.2017.04.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Accepted: 04/13/2017] [Indexed: 12/15/2022] Open
Abstract
Due to the increasing prevalence of diabetes, finding therapeutic analogues for insulin has become an urgent issue. While many experimental studies have been performed towards this end, they have limited scope to examine all aspects of the effect of a mutation. Computational studies can help to overcome these limitations, however, relatively few studies that focus on insulin analogues have been performed to date. Here, we present a comprehensive computational study of insulin analogues-three mutant insulins that have been identified with hyperinsulinemia and three mutations on the critical B26 residue that exhibit similar binding affinity to the insulin receptor-using molecular dynamics simulations with the aim of predicting how mutations of insulin affect its activity, dynamics, energetics and conformations. The time evolution of the conformers is studied in long simulations. The probability density function and potential of mean force calculations are performed on each insulin analogue to unravel the effect of mutations on the dynamics and energetics of insulin activation. Our conformational study can decrypt the key features and molecular mechanisms that are responsible for an enhanced or reduced activity of an insulin analogue. We find two key results: 1) hyperinsulinemia may be due to the drastically reduced activity (and binding affinity) of the mutant insulins. 2) Y26BS and Y26BE are promising therapeutic candidates for insulin as they are more active than WT-insulin. The analysis in this work can be readily applied to any set of mutations on insulin to guide development of more effective therapeutic analogues.
Collapse
|
26
|
Qi L, Tsai B, Arvan P. New Insights into the Physiological Role of Endoplasmic Reticulum-Associated Degradation. Trends Cell Biol 2017; 27:430-440. [PMID: 28131647 DOI: 10.1016/j.tcb.2016.12.002] [Citation(s) in RCA: 156] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Revised: 12/04/2016] [Accepted: 12/23/2016] [Indexed: 12/13/2022]
Abstract
Many human diseases are associated with mutations causing protein misfolding and aggregation in the endoplasmic reticulum (ER). ER-associated degradation (ERAD) is a principal quality-control mechanism responsible for targeting misfolded ER proteins for cytosolic degradation. However, despite years of effort, the physiological role of ERAD in vivo remains largely unknown. Several recent studies have reported intriguing phenotypes of mice deficient for ERAD function in specific cell types. These studies highlight that mammalian ERAD has been designed to perform a wide-range of cell-type-specific functions in vivo in a substrate-dependent manner.
Collapse
Affiliation(s)
- Ling Qi
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48105, USA; Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, MI 48105, USA.
| | - Billy Tsai
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48105, USA
| | - Peter Arvan
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48105, USA; Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, MI 48105, USA
| |
Collapse
|
27
|
Tang W, Yuan Q, Xu B, Osei K, Wang J. Exenatide substantially improves proinsulin conversion and cell survival that augment Ins2 +/Akita beta cell function. Mol Cell Endocrinol 2017; 439:297-307. [PMID: 27658750 DOI: 10.1016/j.mce.2016.09.015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Revised: 09/16/2016] [Accepted: 09/16/2016] [Indexed: 02/06/2023]
Abstract
Proinsulin folding imperfections cause extensive beta-cell defects known in diabetes. Here, we investigated whether exenatide can alleviate such defects in proinsulin conversion, beta-cell survival, and insulin secretion, in the Ins2+/Akita beta-cells that have a spontaneous mutation (Cys 96 Tyr) in the insulin 2 gene caused dominant negative misfolding problem. 15 or 120 min exenatide administration substantially improves glucose-stimulated insulin secretion, marked in the secreted insulin levels and proinsulin/insulin ratio. This improvement is mainly due to enhanced conversion of proinsulin to insulin, having nothing to do with the prohormone convertase PC1/3 and PC2 levels. The 15 min improvement is calcium-independent. The 120 min improvement is linked to calcium and/or cAMP dependent mechanisms. This efficacy is validated during longer treatment and in Akita islets. Exenatide improves Ins2+/Akita beta-cell survival and Akita mouse's glucose tolerance. The results suggest a potential of incretin mimetics in alleviating defective proinsulin conversion and other proinsulin misfolding consequences.
Collapse
Affiliation(s)
- Wei Tang
- Department of Endocrinology, Jiangsu Province Geriatric Institute Islet Cell Senescence and Function Research Laboratory, Jiangsu Province Official Hospital, 65 Jiangsu Road, Nanjing 210024, China.
| | - Qingxin Yuan
- Department of Endocrinology, First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu 210029, China
| | - Bo Xu
- State Key Laboratory of Reproductive Medicine, Institute of Toxicology, Nanjing Medical University, Nanjing 211166, China
| | - Kwame Osei
- Division of Endocrinology, Diabetes, and Metabolism, Department of Internal Medicine, The Ohio State University, Columbus, OH 43210, USA
| | - Jie Wang
- Division of Endocrinology, Diabetes, and Metabolism, Department of Internal Medicine, The Ohio State University, Columbus, OH 43210, USA; Division of Endocrinology, Jiangsu Province Hospital on Integration of Chinese and Western Medicine, Nanjing University of Chinese and Western Medicine, Nanjing, Jiangsu 210028, China.
| |
Collapse
|
28
|
Moritani M, Yokota I, Horikawa R, Urakami T, Nishii A, Kawamura T, Kikuchi N, Kikuchi T, Ogata T, Sugihara S, Amemiya S. Identification of monogenic gene mutations in Japanese subjects diagnosed with type 1B diabetes between >5 and 15.1 years of age. J Pediatr Endocrinol Metab 2016; 29:1047-54. [PMID: 27398945 DOI: 10.1515/jpem-2016-0030] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Accepted: 05/09/2016] [Indexed: 02/06/2023]
Abstract
BACKGROUND Monogenic mutations, such as those in the potassium inwardly-rectifying channel, subfamily J, member 11 (KCNJ11) and insulin (INS) genes, are identified in young patients with type 1B diabetes (non-autoimmune-mediated). We recently reported the results of a test for monogenic forms of diabetes in Japanese children who were diagnosed with type 1B diabetes at <5 years of age. In this study, we tested for monogenic forms of diabetes in Japanese children aged >5 to ≤15.1 years at the diagnosis of type 1B diabetes. METHODS Thirty-two Japanese children (eight males, 24 females) with type 1 diabetes negative for glutamate decarboxylase (GAD) 65 and/or IA-2A autoantibodies and who were aged >5 to 15.1 years at diagnosis were recruited from 16 independent hospitals participating in the Japanese Study Group of Insulin Therapy for Childhood and Adolescent Diabetes (JSGIT). We performed mutational analyses of genes with a high frequency of mutation [INS, KCNJ11, hepatocyte nuclear factor 1 alpha (HNF1α) and hepatocyte nuclear factor 4 alpha (HNF4α)]. RESULTS We identified one missense mutation (G32S) in the INS gene and two mutations (R131Q and R203S) in the HNF1α gene that could be associated with diabetes. No missense change was found in the KCNJ11 gene. CONCLUSIONS Our results suggest that although mutations in the INS gene can be detected in Japanese patients aged >5 years at diagnosis, the frequency of mutations decrease in older age groups. Conversely, the frequency of the mutation in the HNF1α gene increased in patients diagnosed at age 5 or older. Clinicians should consider the possibility of maturity onset diabetes of the young (MODY) in children diagnosed with type 1B diabetes.
Collapse
|
29
|
Fang J, Liu M, Zhang X, Sakamoto T, Taatjes DJ, Jena BP, Sun F, Woods J, Bryson T, Kowluru A, Zhang K, Chen X. COPII-Dependent ER Export: A Critical Component of Insulin Biogenesis and β-Cell ER Homeostasis. Mol Endocrinol 2015; 29:1156-69. [PMID: 26083833 DOI: 10.1210/me.2015-1012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Pancreatic β-cells possess a highly active protein synthetic and export machinery in the endoplasmic reticulum (ER) to accommodate the massive production of proinsulin. ER homeostasis is vital for β-cell functions and is maintained by the delicate balance between protein synthesis, folding, export, and degradation. Disruption of ER homeostasis by diabetes-causing factors leads to β-cell death. Among the 4 components to maintain ER homeostasis in β-cells, the role of ER export in insulin biogenesis is the least understood. To address this knowledge gap, the present study investigated the molecular mechanism of proinsulin ER export in MIN6 cells and primary islets. Two inhibitory mutants of the secretion-associated RAS-related protein (Sar)1 small GTPase, known to specifically block coat protein complex II (COPII)-dependent ER export, were overexpressed in β-cells using recombinant adenoviruses. Results from this approach, as well as small interfering RNA-mediated Sar1 knockdown, demonstrated that defective Sar1 function blocked proinsulin ER export and abolished its conversion to mature insulin in MIN6 cells, isolated mouse, and human islets. It is further revealed, using an in vitro vesicle formation assay, that proinsulin was packaged into COPII vesicles in a GTP- and Sar1-dependent manner. Blockage of COPII-dependent ER exit by Sar1 mutants strongly induced ER morphology change, ER stress response, and β-cell apoptosis. These responses were mediated by the PKR (double-stranded RNA-dependent kinase)-like ER kinase (PERK)/eukaryotic translation initiation factor 2α (p-eIF2α) and inositol-requiring protein 1 (IRE1)/x-box binding protein 1 (Xbp1) pathways but not via activating transcription factor 6 (ATF6). Collectively, results from the study demonstrate that COPII-dependent ER export plays a vital role in insulin biogenesis, ER homeostasis, and β-cell survival.
Collapse
Affiliation(s)
- Jingye Fang
- Department of Physiology (J.F., B.P.J., F.S., J.W., T.B., X.C.) and Center for Molecular Medicine and Genetics (X.Z., K.Z.), School of Medicine, Department of Physics and Astronomy (T.S.), College of Liberal Arts and Sciences, and Department of Pharmaceutical Sciences (A.K.), Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, and John D. Dingell VA Medical Center (A.K.), Detroit, Michigan 48201; Department of Internal Medicine (M.L.), University of Michigan, Ann Arbor, Michigan 48109; and Department of Pathology (D.J.T.), Microscopy Imaging Center, University of Vermont College of Medicine, Burlington, Vermont 05405
| | - Ming Liu
- Department of Physiology (J.F., B.P.J., F.S., J.W., T.B., X.C.) and Center for Molecular Medicine and Genetics (X.Z., K.Z.), School of Medicine, Department of Physics and Astronomy (T.S.), College of Liberal Arts and Sciences, and Department of Pharmaceutical Sciences (A.K.), Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, and John D. Dingell VA Medical Center (A.K.), Detroit, Michigan 48201; Department of Internal Medicine (M.L.), University of Michigan, Ann Arbor, Michigan 48109; and Department of Pathology (D.J.T.), Microscopy Imaging Center, University of Vermont College of Medicine, Burlington, Vermont 05405
| | - Xuebao Zhang
- Department of Physiology (J.F., B.P.J., F.S., J.W., T.B., X.C.) and Center for Molecular Medicine and Genetics (X.Z., K.Z.), School of Medicine, Department of Physics and Astronomy (T.S.), College of Liberal Arts and Sciences, and Department of Pharmaceutical Sciences (A.K.), Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, and John D. Dingell VA Medical Center (A.K.), Detroit, Michigan 48201; Department of Internal Medicine (M.L.), University of Michigan, Ann Arbor, Michigan 48109; and Department of Pathology (D.J.T.), Microscopy Imaging Center, University of Vermont College of Medicine, Burlington, Vermont 05405
| | - Takeshi Sakamoto
- Department of Physiology (J.F., B.P.J., F.S., J.W., T.B., X.C.) and Center for Molecular Medicine and Genetics (X.Z., K.Z.), School of Medicine, Department of Physics and Astronomy (T.S.), College of Liberal Arts and Sciences, and Department of Pharmaceutical Sciences (A.K.), Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, and John D. Dingell VA Medical Center (A.K.), Detroit, Michigan 48201; Department of Internal Medicine (M.L.), University of Michigan, Ann Arbor, Michigan 48109; and Department of Pathology (D.J.T.), Microscopy Imaging Center, University of Vermont College of Medicine, Burlington, Vermont 05405
| | - Douglas J Taatjes
- Department of Physiology (J.F., B.P.J., F.S., J.W., T.B., X.C.) and Center for Molecular Medicine and Genetics (X.Z., K.Z.), School of Medicine, Department of Physics and Astronomy (T.S.), College of Liberal Arts and Sciences, and Department of Pharmaceutical Sciences (A.K.), Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, and John D. Dingell VA Medical Center (A.K.), Detroit, Michigan 48201; Department of Internal Medicine (M.L.), University of Michigan, Ann Arbor, Michigan 48109; and Department of Pathology (D.J.T.), Microscopy Imaging Center, University of Vermont College of Medicine, Burlington, Vermont 05405
| | - Bhanu P Jena
- Department of Physiology (J.F., B.P.J., F.S., J.W., T.B., X.C.) and Center for Molecular Medicine and Genetics (X.Z., K.Z.), School of Medicine, Department of Physics and Astronomy (T.S.), College of Liberal Arts and Sciences, and Department of Pharmaceutical Sciences (A.K.), Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, and John D. Dingell VA Medical Center (A.K.), Detroit, Michigan 48201; Department of Internal Medicine (M.L.), University of Michigan, Ann Arbor, Michigan 48109; and Department of Pathology (D.J.T.), Microscopy Imaging Center, University of Vermont College of Medicine, Burlington, Vermont 05405
| | - Fei Sun
- Department of Physiology (J.F., B.P.J., F.S., J.W., T.B., X.C.) and Center for Molecular Medicine and Genetics (X.Z., K.Z.), School of Medicine, Department of Physics and Astronomy (T.S.), College of Liberal Arts and Sciences, and Department of Pharmaceutical Sciences (A.K.), Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, and John D. Dingell VA Medical Center (A.K.), Detroit, Michigan 48201; Department of Internal Medicine (M.L.), University of Michigan, Ann Arbor, Michigan 48109; and Department of Pathology (D.J.T.), Microscopy Imaging Center, University of Vermont College of Medicine, Burlington, Vermont 05405
| | - James Woods
- Department of Physiology (J.F., B.P.J., F.S., J.W., T.B., X.C.) and Center for Molecular Medicine and Genetics (X.Z., K.Z.), School of Medicine, Department of Physics and Astronomy (T.S.), College of Liberal Arts and Sciences, and Department of Pharmaceutical Sciences (A.K.), Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, and John D. Dingell VA Medical Center (A.K.), Detroit, Michigan 48201; Department of Internal Medicine (M.L.), University of Michigan, Ann Arbor, Michigan 48109; and Department of Pathology (D.J.T.), Microscopy Imaging Center, University of Vermont College of Medicine, Burlington, Vermont 05405
| | - Tim Bryson
- Department of Physiology (J.F., B.P.J., F.S., J.W., T.B., X.C.) and Center for Molecular Medicine and Genetics (X.Z., K.Z.), School of Medicine, Department of Physics and Astronomy (T.S.), College of Liberal Arts and Sciences, and Department of Pharmaceutical Sciences (A.K.), Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, and John D. Dingell VA Medical Center (A.K.), Detroit, Michigan 48201; Department of Internal Medicine (M.L.), University of Michigan, Ann Arbor, Michigan 48109; and Department of Pathology (D.J.T.), Microscopy Imaging Center, University of Vermont College of Medicine, Burlington, Vermont 05405
| | - Anjaneyulu Kowluru
- Department of Physiology (J.F., B.P.J., F.S., J.W., T.B., X.C.) and Center for Molecular Medicine and Genetics (X.Z., K.Z.), School of Medicine, Department of Physics and Astronomy (T.S.), College of Liberal Arts and Sciences, and Department of Pharmaceutical Sciences (A.K.), Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, and John D. Dingell VA Medical Center (A.K.), Detroit, Michigan 48201; Department of Internal Medicine (M.L.), University of Michigan, Ann Arbor, Michigan 48109; and Department of Pathology (D.J.T.), Microscopy Imaging Center, University of Vermont College of Medicine, Burlington, Vermont 05405
| | - Kezhong Zhang
- Department of Physiology (J.F., B.P.J., F.S., J.W., T.B., X.C.) and Center for Molecular Medicine and Genetics (X.Z., K.Z.), School of Medicine, Department of Physics and Astronomy (T.S.), College of Liberal Arts and Sciences, and Department of Pharmaceutical Sciences (A.K.), Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, and John D. Dingell VA Medical Center (A.K.), Detroit, Michigan 48201; Department of Internal Medicine (M.L.), University of Michigan, Ann Arbor, Michigan 48109; and Department of Pathology (D.J.T.), Microscopy Imaging Center, University of Vermont College of Medicine, Burlington, Vermont 05405
| | - Xuequn Chen
- Department of Physiology (J.F., B.P.J., F.S., J.W., T.B., X.C.) and Center for Molecular Medicine and Genetics (X.Z., K.Z.), School of Medicine, Department of Physics and Astronomy (T.S.), College of Liberal Arts and Sciences, and Department of Pharmaceutical Sciences (A.K.), Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, and John D. Dingell VA Medical Center (A.K.), Detroit, Michigan 48201; Department of Internal Medicine (M.L.), University of Michigan, Ann Arbor, Michigan 48109; and Department of Pathology (D.J.T.), Microscopy Imaging Center, University of Vermont College of Medicine, Burlington, Vermont 05405
| |
Collapse
|
30
|
Sun J, Cui J, He Q, Chen Z, Arvan P, Liu M. Proinsulin misfolding and endoplasmic reticulum stress during the development and progression of diabetes. Mol Aspects Med 2015; 42:105-18. [PMID: 25579745 PMCID: PMC4404191 DOI: 10.1016/j.mam.2015.01.001] [Citation(s) in RCA: 119] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Revised: 12/31/2014] [Accepted: 01/02/2015] [Indexed: 02/06/2023]
Abstract
To maintain copious insulin granule stores in the face of ongoing metabolic demand, pancreatic beta cells must produce large quantities of proinsulin, the insulin precursor. Proinsulin biosynthesis can account for up to 30-50% of total cellular protein synthesis of beta cells. This puts pressure on the beta cell secretory pathway, especially the endoplasmic reticulum (ER), where proinsulin undergoes its initial folding, including the formation of three evolutionarily conserved disulfide bonds. In normal beta cells, up to 20% of newly synthesized proinsulin may fail to reach its native conformation, suggesting that proinsulin is a misfolding-prone protein. Misfolded proinsulin molecules can either be refolded to their native structure or degraded through ER associated degradation (ERAD) and autophagy. These degraded molecules decrease proinsulin yield but do not otherwise compromise beta cell function. However, under certain pathological conditions, proinsulin misfolding increases, exceeding the genetically determined threshold of beta cells to handle the misfolded protein load. This results in accumulation of misfolded proinsulin in the ER - a causal factor leading to beta cell failure and diabetes. In patients with Mutant INS-gene induced diabetes of Youth (MIDY), increased proinsulin misfolding due to insulin gene mutations is the primary defect operating as a "first hit" to beta cells. Additionally, increased proinsulin misfolding can be secondary to an unfavorable ER folding environment due to genetic and/or environmental factors. Under these conditions, increased wild-type proinsulin misfolding becomes a "second hit" to the ER and beta cells, aggravating beta cell failure and diabetes. In this article, we describe our current understanding of the normal proinsulin folding pathway in the ER, and then review existing links between proinsulin misfolding, ER dysfunction, and beta cell failure in the development and progression of type 2, type 1, and some monogenic forms of diabetes.
Collapse
Affiliation(s)
- Jinhong Sun
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, MI 48105, USA
| | - Jingqiu Cui
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin 300052, China
| | - Qing He
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin 300052, China
| | - Zheng Chen
- School of Life Sciences, Northeast Normal University, Changchun, Jilin 130024, China
| | - Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, MI 48105, USA.
| | - Ming Liu
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, MI 48105, USA; Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin 300052, China.
| |
Collapse
|
31
|
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.
Collapse
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
| |
Collapse
|
32
|
Vashisth H. Theoretical and computational studies of peptides and receptors of the insulin family. MEMBRANES 2015; 5:48-83. [PMID: 25680077 PMCID: PMC4384091 DOI: 10.3390/membranes5010048] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Accepted: 01/28/2015] [Indexed: 01/05/2023]
Abstract
Synergistic interactions among peptides and receptors of the insulin family are required for glucose homeostasis, normal cellular growth and development, proliferation, differentiation and other metabolic processes. The peptides of the insulin family are disulfide-linked single or dual-chain proteins, while receptors are ligand-activated transmembrane glycoproteins of the receptor tyrosine kinase (RTK) superfamily. Binding of ligands to the extracellular domains of receptors is known to initiate signaling via activation of intracellular kinase domains. While the structure of insulin has been known since 1969, recent decades have seen remarkable progress on the structural biology of apo and liganded receptor fragments. Here, we review how this useful structural information (on ligands and receptors) has enabled large-scale atomically-resolved simulations to elucidate the conformational dynamics of these biomolecules. Particularly, applications of molecular dynamics (MD) and Monte Carlo (MC) simulation methods are discussed in various contexts, including studies of isolated ligands, apo-receptors, ligand/receptor complexes and intracellular kinase domains. The review concludes with a brief overview and future outlook for modeling and computational studies in this family of proteins.
Collapse
Affiliation(s)
- Harish Vashisth
- Department of Chemical Engineering, University of New Hampshire, 33 Academic Way, Durham, NH 03824, USA.
| |
Collapse
|
33
|
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.
Collapse
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.
| |
Collapse
|
34
|
Ittner AA, Bertz J, Chan TYB, van Eersel J, Polly P, Ittner LM. The nucleotide exchange factor SIL1 is required for glucose-stimulated insulin secretion from mouse pancreatic beta cells in vivo. Diabetologia 2014; 57:1410-9. [PMID: 24733160 DOI: 10.1007/s00125-014-3230-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Accepted: 03/13/2014] [Indexed: 01/06/2023]
Abstract
AIMS/HYPOTHESIS Regulation of insulin secretion along the secretory pathway is incompletely understood. We addressed the expression of SIL1, a nucleotide exchange factor for the endoplasmic reticulum (ER) chaperone glucose-regulated protein 78 kD (GRP78), in pancreatic beta cells and investigated whether or not SIL1 is involved in beta cell function. METHODS SIL1 expression was analysed by immunoblotting and immunofluorescence. Metabolic and islet variables, including glucose tolerance, beta cell mass, insulin secretion, islet ultrastructure, insulin content and levels of ER stress marker proteins, were addressed in Sil1 knockout (Sil1 (-/-)) mice. Insulin, proinsulin and C-peptide release was addressed in Sil1 (-/-) islets, and SIL1 overexpression or knockdown was explored in MIN6 cells in vitro. Models of type 1 diabetes and insulin resistance were induced in Sil1 (-/-) mice by administration of streptozotocin (STZ) and a high-fat diet (HFD), respectively. RESULTS We show that SIL1 is expressed in pancreatic beta cells and is required for islet insulin content, islet sizing, glucose tolerance and glucose-stimulated insulin secretion in vivo. Levels of pancreatic ER stress markers are increased in Sil1 (-/-) mice, and Sil1 (-/-) beta cell ER is ultrastructurally compromised. Isolated Sil1 (-/-) islets show lower proinsulin and insulin content and impaired glucose-stimulated insulin secretion. Modulation of SIL1 protein levels in MIN6 cells correlates with changes in insulin content and secreted insulin. Furthermore, Sil1 (-/-) mice are more susceptible to STZ-induced type 1 diabetes with increased apoptosis. Upon HFD feeding, Sil1 (-/-) mice show markedly lower insulin secretion and exacerbated glucose intolerance compared with control mice. Surprisingly, however, HFD-fed Sil1 (-/-) mice display pronounced islet hyperplasia with low amounts of insulin in total pancreas. CONCLUSIONS/INTERPRETATION These results reveal a novel role for the nucleotide exchange factor SIL1 in pancreatic beta cell function under physiological and disease conditions such as diabetes and the metabolic syndrome.
Collapse
Affiliation(s)
- Arne A Ittner
- School of Medical Sciences, University of New South Wales, Botany Street, Kensington, Sydney, 2052, NSW, Australia,
| | | | | | | | | | | |
Collapse
|
35
|
Hara T, Mahadevan J, Kanekura K, Hara M, Lu S, Urano F. Calcium efflux from the endoplasmic reticulum leads to β-cell death. Endocrinology 2014; 155:758-68. [PMID: 24424032 PMCID: PMC3929724 DOI: 10.1210/en.2013-1519] [Citation(s) in RCA: 103] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
It has been established that intracellular calcium homeostasis is critical for survival and function of pancreatic β-cells. However, the role of endoplasmic reticulum (ER) calcium homeostasis in β-cell survival and death is not clear. Here we show that ER calcium depletion plays a critical role in β-cell death. Various pathological conditions associated with β-cell death, including ER stress, oxidative stress, palmitate, and chronic high glucose, decreased ER calcium levels and sarcoendoplasmic reticulum Ca(2+)-ATPase 2b expression, leading to β-cell death. Ectopic expression of mutant insulin and genetic ablation of WFS1, a causative gene for Wolfram syndrome, also decreased ER calcium levels and induced β-cell death. Hyperactivation of calpain-2, a calcium-dependent proapoptotic protease, was detected in β-cells undergoing ER calcium depletion. Ectopic expression of sarcoendoplasmic reticulum Ca(2+)-ATPase 2b, as well as pioglitazone and rapamycin treatment, could prevent calcium efflux from the ER and mitigate β-cell death under various stress conditions. Our results reveal a critical role of ER calcium depletion in β-cell death and indicate that identification of pathways and chemical compounds restoring ER calcium levels will lead to novel therapeutic modalities and pharmacological interventions for type 1 and type 2 diabetes and other ER-related diseases including Wolfram syndrome.
Collapse
Affiliation(s)
- Takashi Hara
- Department of Medicine (T.H., J.M., K.K., M.H., S.L., F.U.), Division of Endocrinology, Metabolism, and Lipid Research, and Department of Pathology and Immunology (F.U.), Washington University School of Medicine, St Louis, Missouri 63110; and Cardiovascular-Metabolics Research Laboratories (T.H.), Daiichi Sankyo Co, Ltd, Tokyo 103-8426, Japan
| | | | | | | | | | | |
Collapse
|
36
|
Engin F, Nguyen T, Yermalovich A, Hotamisligil GS. Aberrant islet unfolded protein response in type 2 diabetes. Sci Rep 2014; 4:4054. [PMID: 24514745 PMCID: PMC3920274 DOI: 10.1038/srep04054] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2013] [Accepted: 01/21/2014] [Indexed: 12/15/2022] Open
Abstract
The endoplasmic reticulum adapts to fluctuations in demand and copes with stress through an adaptive signaling cascade called the unfolded protein response (UPR). Accumulating evidence indicates that the canonical UPR is critical to the survival and function of insulin-producing pancreatic β-cells, and alterations in the UPR may contribute to the pathogenesis of type 2 diabetes. However, the dynamic regulation of UPR molecules in the islets of animal models and humans with type 2 diabetes remains to be elucidated. Here, we analyzed the expression of activating factor 6 (ATF6α) and spliced X-box binding protein 1 (sXBP1), and phosphorylation of eukaryotic initiation factor 2 (eIF2α), to evaluate the three distinct branches of the UPR in the pancreatic islets of mice with diet- or genetic-induced obesity and insulin resistance. ATF6 and sXBP1 expression was predominantly found in the β-cells, where hyperglycemia coincided with a decline in expression in both experimental models and in humans with type 2 diabetes. These data suggest alterations in the expression of UPR mediators may contribute to the decline in islet function in type 2 diabetes in mice and humans.
Collapse
Affiliation(s)
- Feyza Engin
- Department of Genetics and Complex Diseases, Harvard School of Public Health, Boston, MA 02115
| | - Truc Nguyen
- Department of Genetics and Complex Diseases, Harvard School of Public Health, Boston, MA 02115
| | - Alena Yermalovich
- Department of Genetics and Complex Diseases, Harvard School of Public Health, Boston, MA 02115
| | - Gökhan S Hotamisligil
- 1] Department of Genetics and Complex Diseases, Harvard School of Public Health, Boston, MA 02115 [2] Broad Institute of Harvard and MIT, Harvard School of Public Health, Boston, MA 02115
| |
Collapse
|
37
|
Wright J, Birk J, Haataja L, Liu M, Ramming T, Weiss MA, Appenzeller-Herzog C, Arvan P. Endoplasmic reticulum oxidoreductin-1α (Ero1α) improves folding and secretion of mutant proinsulin and limits mutant proinsulin-induced endoplasmic reticulum stress. J Biol Chem 2013; 288:31010-8. [PMID: 24022479 DOI: 10.1074/jbc.m113.510065] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Upon chronic up-regulation of proinsulin synthesis, misfolded proinsulin can accumulate in the endoplasmic reticulum (ER) of pancreatic β-cells, promoting ER stress and type 2 diabetes mellitus. In Mutant Ins-gene-induced Diabetes of Youth (MIDY), misfolded mutant proinsulin impairs ER exit of co-expressed wild-type proinsulin, limiting insulin production and leading to eventual β-cell death. In this study we have investigated the hypothesis that increased expression of ER oxidoreductin-1α (Ero1α), despite its established role in the generation of H2O2, might nevertheless be beneficial in limiting proinsulin misfolding and its adverse downstream consequences. Increased Ero1α expression is effective in promoting wild-type proinsulin export from cells co-expressing misfolded mutant proinsulin. In addition, we find that upon increased Ero1α expression, some of the MIDY mutants themselves are directly rescued from ER retention. Secretory rescue of proinsulin-G(B23)V is correlated with improved oxidative folding of mutant proinsulin. Indeed, using three different variants of Ero1α, we find that expression of either wild-type or an Ero1α variant lacking regulatory disulfides can rescue mutant proinsulin-G(B23)V, in parallel with its ability to provide an oxidizing environment in the ER lumen, whereas beneficial effects were less apparent for a redox-inactive form of Ero1. Increased expression of protein disulfide isomerase antagonizes the rescue provided by oxidatively active Ero1. Importantly, ER stress induced by misfolded proinsulin was limited by increased expression of Ero1α, suggesting that enhancing the oxidative folding of proinsulin may be a viable therapeutic strategy in the treatment of type 2 diabetes.
Collapse
Affiliation(s)
- Jordan Wright
- From the Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105
| | | | | | | | | | | | | | | |
Collapse
|
38
|
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.
Collapse
|
39
|
Bachar-Wikstrom E, Wikstrom JD, Ariav Y, Tirosh B, Kaiser N, Cerasi E, Leibowitz G. Stimulation of autophagy improves endoplasmic reticulum stress-induced diabetes. Diabetes 2013; 62:1227-37. [PMID: 23274896 PMCID: PMC3609555 DOI: 10.2337/db12-1474] [Citation(s) in RCA: 155] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Accumulation of misfolded proinsulin in the β-cell leads to dysfunction induced by endoplasmic reticulum (ER) stress, with diabetes as a consequence. Autophagy helps cellular adaptation to stress via clearance of misfolded proteins and damaged organelles. We studied the effects of proinsulin misfolding on autophagy and the impact of stimulating autophagy on diabetes progression in Akita mice, which carry a mutation in proinsulin, leading to its severe misfolding. Treatment of female diabetic Akita mice with rapamycin improved diabetes, increased pancreatic insulin content, and prevented β-cell apoptosis. In vitro, autophagic flux was increased in Akita β-cells. Treatment with rapamycin further stimulated autophagy, evidenced by increased autophagosome formation and enhancement of autophagosome-lysosome fusion. This was associated with attenuation of cellular stress and apoptosis. The mammalian target of rapamycin (mTOR) kinase inhibitor Torin1 mimicked the rapamycin effects on autophagy and stress, indicating that the beneficial effects of rapamycin are indeed mediated via inhibition of mTOR. Finally, inhibition of autophagy exacerbated stress and abolished the anti-ER stress effects of rapamycin. In conclusion, rapamycin reduces ER stress induced by accumulation of misfolded proinsulin, thereby improving diabetes and preventing β-cell apoptosis. The beneficial effects of rapamycin in this context strictly depend on autophagy; therefore, stimulating autophagy may become a therapeutic approach for diabetes.
Collapse
Affiliation(s)
- Etty Bachar-Wikstrom
- Endocrinology and Metabolism Service, Department of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Jakob D. Wikstrom
- Endocrinology and Metabolism Service, Department of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Yafa Ariav
- Endocrinology and Metabolism Service, Department of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Boaz Tirosh
- School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Nurit Kaiser
- Endocrinology and Metabolism Service, Department of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Erol Cerasi
- Endocrinology and Metabolism Service, Department of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Gil Leibowitz
- Endocrinology and Metabolism Service, Department of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
- Corresponding author: Gil Leibowitz,
| |
Collapse
|
40
|
Moritani M, Yokota I, Tsubouchi K, Takaya R, Takemoto K, Minamitani K, Urakami T, Kawamura T, Kikuchi N, Itakura M, Ogata T, Sugihara S, Amemiya S. Identification of INS and KCNJ11 gene mutations in type 1B diabetes in Japanese children with onset of diabetes before 5 years of age. Pediatr Diabetes 2013; 14:112-20. [PMID: 22957706 DOI: 10.1111/j.1399-5448.2012.00917.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Revised: 07/12/2012] [Accepted: 07/12/2012] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND The etiology of type 1 diabetes (T1D) is heterogeneous and is according to presence or absence of pancreatic autoantibodies divided into two subtypes: type 1A (autoimmune-mediated) and type 1B (non-autoimmune-mediated). Although several genes have been linked to type 1A diabetes, the genetic cause of type 1B diabetes in Japanese individuals is far from understood. OBJECTIVE The aim of this study was to test for monogenic forms of diabetes in auto antibody-negative Japanese children with T1D. METHODS Thirty four (19 males and 15 female) unrelated Japanese children with glutamate decarboxylase (GAD) 65 antibodies and/or IA-2A-negative T1D and diabetes diagnosed at < 5 yr of age were recruited from 17 unrelated hospitals participating in the Japanese Study Group of Insulin Therapy for children and adolescent diabetes (JSGIT). We screened the INS gene and the KCNJ11 gene which encode the ATP-sensitive potassium cannel by direct sequencing in 34 Japanese children with T1D. RESULTS We identified three novel (C31Y, C96R, and C109F) mutations and one previously reported mutation (R89C) in the INS gene in five children, in addition to one mutation in the KCNJ11 gene (H46R) in one child. These mutations are most likely pathogenic and therefore the cause of diabetes in carriers. CONCLUSION Our results suggest that monogenic forms of diabetes, particularly INS gene mutations, can be detected in Japanese patients classified with type 1B. Mutation screening, at least of the INS gene, is recommended for Japanese patients diagnosed as autoantibody negative at <5 yr of age.
Collapse
Affiliation(s)
- Maki Moritani
- Laboratory for Pediatrics Genome Medicine, Department of Clinical Research, Kagawa National Children's Hospital, Zentsuji, Kagawa, 765-8501, Japan
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
41
|
Sanlioglu AD, Altunbas HA, Balci MK, Griffith TS, Sanlioglu S. Clinical utility of insulin and insulin analogs. Islets 2013; 5:67-78. [PMID: 23584214 PMCID: PMC4204021 DOI: 10.4161/isl.24590] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Revised: 04/05/2013] [Accepted: 04/06/2013] [Indexed: 02/08/2023] Open
Abstract
Diabetes is a pandemic disease characterized by autoimmune, genetic and metabolic abnormalities. While insulin deficiency manifested as hyperglycemia is a common sequel of both Type-1 and Type-2 diabetes (T1DM and T2DM), it does not result from a single genetic defect--rather insulin deficiency results from the functional loss of pancreatic β cells due to multifactorial mechanisms. Since pancreatic β cells of patients with T1DM are destroyed by autoimmune reaction, these patients require daily insulin injections. Insulin resistance followed by β cell dysfunction and β cell loss is the characteristics of T2DM. Therefore, most patients with T2DM will require insulin treatment due to eventual loss of insulin secretion. Despite the evidence of early insulin treatment lowering macrovascular (coronary artery disease, peripheral arterial disease and stroke) and microvascular (diabetic nephropathy, neuropathy and retinopathy) complications of T2DM, controversy exists among physicians on how to initiate and intensify insulin therapy. The slow acting nature of regular human insulin makes its use ineffective in counteracting postprandial hyperglycemia. Instead, recombinant insulin analogs have been generated with a variable degree of specificity and action. Due to the metabolic variability among individuals, optimum blood glucose management is a formidable task to accomplish despite the presence of novel insulin analogs. In this article, we present a recent update on insulin analog structure and function with an overview of the evidence on the various insulin regimens clinically used to treat diabetes.
Collapse
MESH Headings
- Animals
- Diabetes Mellitus, Type 1/blood
- Diabetes Mellitus, Type 1/complications
- Diabetes Mellitus, Type 1/drug therapy
- Diabetes Mellitus, Type 1/metabolism
- Diabetes Mellitus, Type 2/blood
- Diabetes Mellitus, Type 2/complications
- Diabetes Mellitus, Type 2/drug therapy
- Diabetes Mellitus, Type 2/metabolism
- Diabetic Angiopathies/prevention & control
- Drug Monitoring
- Evidence-Based Medicine
- Humans
- Hyperglycemia/prevention & control
- Hypoglycemic Agents/administration & dosage
- Hypoglycemic Agents/chemistry
- Hypoglycemic Agents/metabolism
- Hypoglycemic Agents/therapeutic use
- Insulin/administration & dosage
- Insulin/analogs & derivatives
- Insulin/metabolism
- Insulin/therapeutic use
- Insulin, Regular, Human/administration & dosage
- Insulin, Regular, Human/analogs & derivatives
- Insulin, Regular, Human/genetics
- Insulin, Regular, Human/therapeutic use
- Recombinant Proteins/administration & dosage
- Recombinant Proteins/chemistry
- Recombinant Proteins/therapeutic use
Collapse
Affiliation(s)
- Ahter D. Sanlioglu
- Human Gene and Cell Therapy Center; Akdeniz University Faculty of Medicine; Antalya, Turkey
- Department of Medical Biology and Genetics; Akdeniz University Faculty of Medicine; Antalya, Turkey
| | - Hasan Ali Altunbas
- Human Gene and Cell Therapy Center; Akdeniz University Faculty of Medicine; Antalya, Turkey
- Department of Internal Medicine; Division of Endocrinology and Metabolism; Akdeniz University Faculty of Medicine; Antalya, Turkey
| | - Mustafa Kemal Balci
- Human Gene and Cell Therapy Center; Akdeniz University Faculty of Medicine; Antalya, Turkey
- Department of Internal Medicine; Division of Endocrinology and Metabolism; Akdeniz University Faculty of Medicine; Antalya, Turkey
| | | | - Salih Sanlioglu
- Human Gene and Cell Therapy Center; Akdeniz University Faculty of Medicine; Antalya, Turkey
- Department of Medical Biology and Genetics; Akdeniz University Faculty of Medicine; Antalya, Turkey
| |
Collapse
|
42
|
Yu P, Li Q, Liu F, Sun Y, Zhang J. Relationship between proinsulin and beta cell function in different states of glucose tolerance. Int J Diabetes Dev Ctries 2012. [DOI: 10.1007/s13410-012-0089-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
|
43
|
Yuan Q, Tang W, Zhang X, Hinson JA, Liu C, Osei K, Wang J. Proinsulin atypical maturation and disposal induces extensive defects in mouse Ins2+/Akita β-cells. PLoS One 2012; 7:e35098. [PMID: 22509386 PMCID: PMC3318013 DOI: 10.1371/journal.pone.0035098] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Accepted: 03/08/2012] [Indexed: 02/06/2023] Open
Abstract
Because of its low relative folding rate and plentiful manufacture in β-cells, proinsulin maintains a homeostatic balance of natively and plentiful non-natively folded states (i.e., proinsulin homeostasis, PIHO) through the integration of maturation and disposal processes. PIHO is susceptible to genetic and environmental influences, and its disorder has been critically linked to defects in β-cells in diabetes. To explore this hypothesis, we performed polymerase chain reaction (PCR), metabolic-labeling, immunoblotting, and histological studies to clarify what defects result from primary disorder of PIHO in model Ins2+/Akita β-cells. We used T antigen-transformed Ins2+/Akita and control Ins2+/+ β-cells established from Akita and wild-type littermate mice. In Ins2+/Akita β-cells, we found no apparent defect at the transcriptional and translational levels to contribute to reduced cellular content of insulin and its precursor and secreted insulin. Glucose response remained normal in proinsulin biosynthesis but was impaired for insulin secretion. The size and number of mature insulin granules were reduced, but the size/number of endoplasmic reticulum, Golgi, mitochondrion, and lysosome organelles and vacuoles were expanded/increased. Moreover, cell death increased, and severe oxidative stress, which manifested as increased reactive oxygen species, thioredoxin-interacting protein, and protein tyrosine nitration, occurred in Ins2+/Akita β-cells and/or islets. These data show the first clear evidence that primary PIHO imbalance induces severe oxidative stress and impairs glucose-stimulated insulin release and β-cell survival as well as producing other toxic consequences. The defects disclosed/clarified in model Ins2+/Akita β-cells further support a role of the genetic and stress-susceptible PIHO disorder in β-cell failure and diabetes.
Collapse
Affiliation(s)
- Qingxin Yuan
- Division of Endocrinology, Diabetes, and Metabolism, Department of Internal Medicine, The Ohio State University, Columbus, Ohio, United States of America
| | - Wei Tang
- Division of Endocrinology, Diabetes, and Metabolism, Department of Internal Medicine, The Ohio State University, Columbus, Ohio, United States of America
| | - Xiaoping Zhang
- Division of Endocrinology, Diabetes, and Metabolism, Department of Internal Medicine, The Ohio State University, Columbus, Ohio, United States of America
| | - Jack A. Hinson
- Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States of America
| | - Chao Liu
- Division of Endocrinology, Jiangsu Province Hospital on Integration of Chinese and Western Medicine, Nanjing University of Chinese and Western Medicine, Nanjing, Jiangsu, China
| | - Kwame Osei
- Division of Endocrinology, Diabetes, and Metabolism, Department of Internal Medicine, The Ohio State University, Columbus, Ohio, United States of America
| | - Jie Wang
- Division of Endocrinology, Diabetes, and Metabolism, Department of Internal Medicine, The Ohio State University, Columbus, Ohio, United States of America
- Division of Endocrinology, Jiangsu Province Hospital on Integration of Chinese and Western Medicine, Nanjing University of Chinese and Western Medicine, Nanjing, Jiangsu, China
- * E-mail:
| |
Collapse
|
44
|
Endoplasmic reticulum stress and insulin biosynthesis: a review. EXPERIMENTAL DIABETES RESEARCH 2012; 2012:509437. [PMID: 22474424 PMCID: PMC3303544 DOI: 10.1155/2012/509437] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/14/2011] [Accepted: 12/06/2011] [Indexed: 12/21/2022]
Abstract
Insulin resistance and pancreatic beta cell dysfunction are major contributors to the pathogenesis of diabetes. Various conditions play a role in the pathogenesis of pancreatic beta cell dysfunction and are correlated with endoplasmic reticulum (ER) stress. Pancreatic beta cells are susceptible to ER stress. Many studies have shown that increased ER stress induces pancreatic beta cell dysfunction and diabetes mellitus using genetic models of ER stress and by various stimuli. There are many reports indicating that ER stress plays an important role in the impairment of insulin biosynthesis, suggesting that reduction of ER stress could be a therapeutic target for diabetes. In this paper, we reviewed the relationship between ER stress and diabetes and how ER stress controls insulin biosynthesis.
Collapse
|
45
|
Hetz C, Martinon F, Rodriguez D, Glimcher LH. The unfolded protein response: integrating stress signals through the stress sensor IRE1α. Physiol Rev 2011; 91:1219-43. [PMID: 22013210 DOI: 10.1152/physrev.00001.2011] [Citation(s) in RCA: 443] [Impact Index Per Article: 34.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Stress induced by accumulation of unfolded proteins at the endoplasmic reticulum (ER) is a classic feature of secretory cells and is observed in many tissues in human diseases including cancer, diabetes, obesity, and neurodegeneration. Cellular adaptation to ER stress is achieved by the activation of the unfolded protein response (UPR), an integrated signal transduction pathway that transmits information about the protein folding status at the ER to the nucleus and cytosol to restore ER homeostasis. Inositol-requiring transmembrane kinase/endonuclease-1 (IRE1α), the most conserved UPR stress sensor, functions as an endoribonuclease that processes the mRNA of the transcription factor X-box binding protein-1 (XBP1). IRE1α signaling is a highly regulated process, controlled by the formation of a dynamic scaffold onto which many regulatory components assemble, here referred to as the UPRosome. Here we provide an overview of the signaling and regulatory mechanisms underlying IRE1α function and discuss the emerging role of the UPR in adaptation to protein folding stress in specialized secretory cells and in pathological conditions associated with alterations in ER homeostasis.
Collapse
Affiliation(s)
- Claudio Hetz
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, MA, USA.
| | | | | | | |
Collapse
|
46
|
Rajpal G, Schuiki I, Liu M, Volchuk A, Arvan P. Action of protein disulfide isomerase on proinsulin exit from endoplasmic reticulum of pancreatic β-cells. J Biol Chem 2011; 287:43-47. [PMID: 22105075 DOI: 10.1074/jbc.c111.279927] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
For insulin synthesis, the proinsulin precursor is translated at the endoplasmic reticulum (ER), folds to include its three native disulfide bonds, and is exported to secretory granules for processing and secretion. Protein disulfide isomerase (PDI) has long been assumed to assist proinsulin in this process. Herein we have examined the effect of PDI knockdown (PDI-KD) in β-cells. The data establish that upon PDI-KD, oxidation of proinsulin to form native disulfide bonds is unimpaired and in fact enhanced. This is accompanied by improved proinsulin exit from the ER and increased total insulin secretion, with no evidence of ER stress. We provide evidence for direct physical interaction between PDI and proinsulin in the ER of pancreatic β-cells, in a manner requiring the catalytic activity of PDI. In β-cells after PDI-KD, enhanced export is selective for proinsulin over other secretory proteins, but the same effect is observed for recombinant proinsulin trafficking upon PDI-KD in heterologous cells. We hypothesize that PDI exhibits unfoldase activity for proinsulin, increasing retention of proinsulin within the ER of pancreatic β-cells.
Collapse
Affiliation(s)
- Gautam Rajpal
- Division of Metabolism, Endocrinology and Diabetes and the Cellular and Molecular Biology Program, University of Michigan Medical Center, Ann Arbor, Michigan 48105-51714
| | - Irmgard Schuiki
- Division of Cellular and Molecular Biology, Toronto General Research Institute, University Health Network, Toronto, Ontario M5G 2M9, Canada
| | - Ming Liu
- Division of Metabolism, Endocrinology and Diabetes and the Cellular and Molecular Biology Program, University of Michigan Medical Center, Ann Arbor, Michigan 48105-51714
| | - Allen Volchuk
- Division of Cellular and Molecular Biology, Toronto General Research Institute, University Health Network, Toronto, Ontario M5G 2M9, Canada
| | - Peter Arvan
- Division of Metabolism, Endocrinology and Diabetes and the Cellular and Molecular Biology Program, University of Michigan Medical Center, Ann Arbor, Michigan 48105-51714.
| |
Collapse
|
47
|
Kiselar JG, Datt M, Chance MR, Weiss MA. Structural analysis of proinsulin hexamer assembly by hydroxyl radical footprinting and computational modeling. J Biol Chem 2011; 286:43710-43716. [PMID: 22033917 DOI: 10.1074/jbc.m111.297853] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mutations in the insulin gene can impair proinsulin folding and cause diabetes mellitus. Although crystal structures of insulin dimers and hexamers are well established, proinsulin is refractory to crystallization. Although an NMR structure of an engineered proinsulin monomer has been reported, structures of the wild-type monomer and hexamer remain undetermined. We have utilized hydroxyl radical footprinting and molecular modeling to characterize these structures. Differences between the footprints of insulin and proinsulin, defining a "shadow" of the connecting (C) domain, were employed to refine the model. Our results demonstrate that in its monomeric form, (i) proinsulin contains a native-like insulin moiety and (ii) the C-domain footprint resides within an adjoining segment (residues B23-B29) that is accessible to modification in insulin but not proinsulin. Corresponding oxidation rates were observed within core insulin moieties of insulin and proinsulin hexamers, suggesting that the proinsulin hexamer retains an A/B structure similar to that of insulin. Further similarities in rates of oxidation between the respective C-domains of proinsulin monomers and hexamers suggest that this loop in each case flexibly projects from an outer surface. Although dimerization or hexamer assembly would not be impaired, an ensemble of predicted C-domain positions would block hexamer-hexamer stacking as visualized in classical crystal lattices. We anticipate that protein footprinting in combination with modeling, as illustrated here, will enable comparative studies of diabetes-associated mutant proinsulins and their aberrant modes of aggregation.
Collapse
Affiliation(s)
- Janna G Kiselar
- Center for Proteomics and Bioinformatics, Case Western Reserve University, Cleveland, Ohio 44106.
| | - Manish Datt
- Center for Proteomics and Bioinformatics, Case Western Reserve University, Cleveland, Ohio 44106
| | - Mark R Chance
- Center for Proteomics and Bioinformatics, Case Western Reserve University, Cleveland, Ohio 44106; Center for Synchrotron Biosciences, Case Western Reserve University, Cleveland, Ohio 44106
| | - Michael A Weiss
- Departments of Biochemistry and Medicine, Case Western Reserve University, Cleveland, Ohio 44106
| |
Collapse
|
48
|
Burns JN, Turnage KC, Walker CA, Lieberman RL. The stability of myocilin olfactomedin domain variants provides new insight into glaucoma as a protein misfolding disorder. Biochemistry 2011; 50:5824-33. [PMID: 21612213 DOI: 10.1021/bi200231x] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Myocilin variants, localized to the olfactomedin (OLF) domain, are linked to early-onset, inherited forms of open-angle glaucoma. Disease-causing myocilin variants accumulate within trabecular meshwork cells instead of being secreted to the trabecular extracellular matrix of the eye. We hypothesize that, like in other diseases of protein misfolding, aggregation and downstream pathogenesis originate from the compromised thermal stability of mutant myocilins. In an expansion of our pilot study of four mutants, we compare 21 additional purified OLF variants by using a fluorescence stability assay and investigate the secondary structure of the most stable variants by circular dichroism. Variants with lower melting temperatures are correlated with earlier glaucoma diagnoses. The chemical chaperone trimethylamine N-oxide is capable of restoring the stability of most, but not all, variants to wild-type (WT) levels. Interestingly, three reported OLF disease variants, A427T, G246R, and A445V, exhibited properties indistinguishable from those of WT OLF, but an increased apparent aggregation propensity in vitro relative to that of WT OLF suggests that biophysical factors other than thermal stability, such as kinetics and unfolding pathways, may also be involved in myocilin glaucoma pathogenesis. Similarly, no changes from WT OLF stability and secondary structure were detected for three annotated single-nucleotide polymorphism variants. Our work provides the first quantitative demonstration of compromised stability among many identified OLF variants and places myocilin glaucoma in the context of other diseases of protein misfolding.
Collapse
Affiliation(s)
- J Nicole Burns
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States
| | | | | | | |
Collapse
|
49
|
Dual and opposing roles of the unfolded protein response regulated by IRE1alpha and XBP1 in proinsulin processing and insulin secretion. Proc Natl Acad Sci U S A 2011; 108:8885-90. [PMID: 21555585 DOI: 10.1073/pnas.1105564108] [Citation(s) in RCA: 196] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
As a key regulator of the unfolded protein response, the transcription factor XBP1 activates genes in protein secretory pathways and is required for the development of certain secretory cells. To elucidate the function of XBP1 in pancreatic β-cells, we generated β-cell-specific XBP1 mutant mice. Xbp1(f/f);RIP-cre mice displayed modest hyperglycemia and glucose intolerance resulting from decreased insulin secretion from β-cells. Ablation of XBP1 markedly decreased the number of insulin granules in β-cells, impaired proinsulin processing, increased the serum proinsulin:insulin ratio, blunted glucose-stimulated insulin secretion, and inhibited cell proliferation. Notably, XBP1 deficiency not only compromised the endoplasmic reticulum stress response in β-cells but also caused constitutive hyperactivation of its upstream activator, IRE1α, which could degrade a subset of mRNAs encoding proinsulin-processing enzymes. Hence, the combined effects of XBP1 deficiency on the canonical unfolded protein response and its negative feedback activation of IRE1α caused β-cell dysfunction in XBP1 mutant mice. These results demonstrate that IRE1α has dual and opposing roles in β-cells, and that a precisely regulated feedback circuit involving IRE1α and its product XBP1s is required to achieve optimal insulin secretion and glucose control.
Collapse
|
50
|
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).
Collapse
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
| |
Collapse
|