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Jiang C, Sun L, Wen S, Tian Y, Xu C, Xu Q, Xue H. BRIX1 promotes ribosome synthesis and enhances glycolysis by selected translation of GLUT1 in colorectal cancer. J Gene Med 2024; 26:e3632. [PMID: 38282151 DOI: 10.1002/jgm.3632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 09/25/2023] [Accepted: 10/28/2023] [Indexed: 01/30/2024] Open
Abstract
BACKGROUND Ribosome biogenesis protein BRX1 homolog (BRIX1) is critically required for the synthesis of the 60S ribosome subunit. However, the role and mechanism of BRIX1 in colorectal cancer (CRC) remain unclear. METHODS Kyoto Encyclopedia of Gene and Genome pathway and Gene Ontology analyses were used for bioinformatics analysis. The rRNA levels were detected in CRC tissues and cells. Nascent RNA synthesis was detected via cellular immunofluorescence. The correlation was analyzed between patient Positron Emission Tomography-Computed Tomography (PET-CT) values and their BRIX1 expression. The extracellular acidification rate (ECAR) and oxygen consumption rate were determined via live metabolic analyses. Polysome fractions were collected for BRIX1 mRNA used in translation. The orthotopic model and Cell Counting Kit-8 (CCK8) assay were used to assess BRIX1 function in CRC. RESULTS BRIX1 is a core protein involved in ribosome-related pathway changes in CRC. Gene Ontology analysis showed that BRIX1 was primarily enriched in ribosome assembly and ribosome biogenesis pathways. In fresh CRC tissue, rRNA levels (5S, 5.8S, 18S and 28S) were higher in the BRIX1 high-expression group than in the BRIX1 low-expression group. Similarly, BRIX1 knockdown significantly decreased rRNA levels for 5S, 5.8S, 18S and 28S in CRC cells, whereas overexpression of BRIX1 significantly increased these levels. In addition, BRIX1 knockdown inhibited nascent RNA synthesis in CRC cells. In clinical data analysis, BRIX1 expression was related to the glucose uptake in PET-CT. BRIX1 knockdown significantly decreased the ECAR value, glucose uptake and lactic acid production in CRC cells, whereas BRIX1 overexpression significantly increased these. Furthermore, BRIX1 knockdown significantly decreased the protein expression of GLUT1, whereas BRIX1 overexpression significantly increased this; however, expression of BRIX1 mRNA was unaffected in either case. Blocking glycolysis by si-GLUT1 or galactose reversed BRIX1 promotion of glycolysis and cell proliferation in CRC cells.
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Affiliation(s)
- Chunhui Jiang
- Department of Gastrointestinal Surgery, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Longci Sun
- Department of Gastrointestinal Surgery, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Siyuan Wen
- Department of Gastrointestinal Surgery, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Yuan Tian
- Department of Gastrointestinal Surgery, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Chunjie Xu
- Department of Gastrointestinal Surgery, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Qing Xu
- Department of Gastrointestinal Surgery, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Hanbing Xue
- Division of Gastroenterology and Hepatology, Key Laboratory of Gastroenterology and Hepatology, Ministry of Health, Renji Hospital, School of Medicine, Shanghai Institute of Digestive Disease, Shanghai Jiao Tong University, Shanghai, China
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2
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Xu X, Arunagiri A, Alam M, Haataja L, Evans CR, Zhao I, Castro-Gutierrez R, Russ HA, Demangel C, Qi L, Tsai B, Liu M, Arvan P. Nutrient-dependent regulation of β-cell proinsulin content. J Biol Chem 2023; 299:104836. [PMID: 37209827 PMCID: PMC10302188 DOI: 10.1016/j.jbc.2023.104836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Revised: 04/27/2023] [Accepted: 04/30/2023] [Indexed: 05/22/2023] Open
Abstract
Insulin is made from proinsulin, but the extent to which fasting/feeding controls the homeostatically regulated proinsulin pool in pancreatic β-cells remains largely unknown. Here, we first examined β-cell lines (INS1E and Min6, which proliferate slowly and are routinely fed fresh medium every 2-3 days) and found that the proinsulin pool size responds to each feeding within 1 to 2 h, affected both by the quantity of fresh nutrients and the frequency with which they are provided. We observed no effect of nutrient feeding on the overall rate of proinsulin turnover as quantified from cycloheximide-chase experiments. We show that nutrient feeding is primarily linked to rapid dephosphorylation of translation initiation factor eIF2α, presaging increased proinsulin levels (and thereafter, insulin levels), followed by its rephosphorylation during the ensuing hours that correspond to a fall in proinsulin levels. The decline of proinsulin levels is blunted by the integrated stress response inhibitor, ISRIB, or by inhibition of eIF2α rephosphorylation with a general control nonderepressible 2 (not PERK) kinase inhibitor. In addition, we demonstrate that amino acids contribute importantly to the proinsulin pool; mass spectrometry shows that β-cells avidly consume extracellular glutamine, serine, and cysteine. Finally, we show that in both rodent and human pancreatic islets, fresh nutrient availability dynamically increases preproinsulin, which can be quantified without pulse-labeling. Thus, the proinsulin available for insulin biosynthesis is rhythmically controlled by fasting/feeding cycles.
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Affiliation(s)
- Xiaoxi Xu
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical Center, Ann Arbor, Michigan, USA; Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
| | - Anoop Arunagiri
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical Center, Ann Arbor, Michigan, USA
| | - Maroof Alam
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical Center, Ann Arbor, Michigan, USA
| | - Leena Haataja
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical Center, Ann Arbor, Michigan, USA
| | - Charles R Evans
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical Center, Ann Arbor, Michigan, USA
| | - Ivy Zhao
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical Center, Ann Arbor, Michigan, USA
| | - Roberto Castro-Gutierrez
- Department of Pharmacology & Therapeutics, University of Florida College of Medicine, Gainesville, Florida, USA; Diabetes Institute, University of Florida College of Medicine, Gainesville, Florida, USA
| | - Holger A Russ
- Department of Pharmacology & Therapeutics, University of Florida College of Medicine, Gainesville, Florida, USA; Diabetes Institute, University of Florida College of Medicine, Gainesville, Florida, USA
| | - Caroline Demangel
- Immunobiology and Therapy Unit, Institut Pasteur, Inserm U1224, Université Paris Cité, Paris, France
| | - Ling Qi
- Departments of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Billy Tsai
- Departments of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Ming Liu
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China.
| | - Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical Center, Ann Arbor, Michigan, USA; Departments of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA.
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3
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Kahn SE, Chen YC, Esser N, Taylor AJ, van Raalte DH, Zraika S, Verchere CB. The β Cell in Diabetes: Integrating Biomarkers With Functional Measures. Endocr Rev 2021; 42:528-583. [PMID: 34180979 PMCID: PMC9115372 DOI: 10.1210/endrev/bnab021] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Indexed: 02/08/2023]
Abstract
The pathogenesis of hyperglycemia observed in most forms of diabetes is intimately tied to the islet β cell. Impairments in propeptide processing and secretory function, along with the loss of these vital cells, is demonstrable not only in those in whom the diagnosis is established but typically also in individuals who are at increased risk of developing the disease. Biomarkers are used to inform on the state of a biological process, pathological condition, or response to an intervention and are increasingly being used for predicting, diagnosing, and prognosticating disease. They are also proving to be of use in the different forms of diabetes in both research and clinical settings. This review focuses on the β cell, addressing the potential utility of genetic markers, circulating molecules, immune cell phenotyping, and imaging approaches as biomarkers of cellular function and loss of this critical cell. Further, we consider how these biomarkers complement the more long-established, dynamic, and often complex measurements of β-cell secretory function that themselves could be considered biomarkers.
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Affiliation(s)
- Steven E Kahn
- Division of Metabolism, Endocrinology and Nutrition, Department of Medicine, VA Puget Sound Health Care System and University of Washington, Seattle, 98108 WA, USA
| | - Yi-Chun Chen
- BC Children's Hospital Research Institute and Centre for Molecular Medicine and Therapeutics, Vancouver, BC, V5Z 4H4, Canada.,Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, V5Z 4H4, Canada.,Department of Surgery, University of British Columbia, Vancouver, BC, V5Z 4H4, Canada
| | - Nathalie Esser
- Division of Metabolism, Endocrinology and Nutrition, Department of Medicine, VA Puget Sound Health Care System and University of Washington, Seattle, 98108 WA, USA
| | - Austin J Taylor
- BC Children's Hospital Research Institute and Centre for Molecular Medicine and Therapeutics, Vancouver, BC, V5Z 4H4, Canada.,Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, V5Z 4H4, Canada.,Department of Surgery, University of British Columbia, Vancouver, BC, V5Z 4H4, Canada
| | - Daniël H van Raalte
- Department of Internal Medicine, Amsterdam University Medical Center (UMC), Vrije Universiteit (VU) University Medical Center, 1007 MB Amsterdam, The Netherlands.,Department of Experimental Vascular Medicine, Amsterdam University Medical Center (UMC), Academic Medical Center, 1007 MB Amsterdam, The Netherlands
| | - Sakeneh Zraika
- Division of Metabolism, Endocrinology and Nutrition, Department of Medicine, VA Puget Sound Health Care System and University of Washington, Seattle, 98108 WA, USA
| | - C Bruce Verchere
- BC Children's Hospital Research Institute and Centre for Molecular Medicine and Therapeutics, Vancouver, BC, V5Z 4H4, Canada.,Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, V5Z 4H4, Canada.,Department of Surgery, University of British Columbia, Vancouver, BC, V5Z 4H4, Canada
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4
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Laurenti MC, Matveyenko A, Vella A. Measurement of Pulsatile Insulin Secretion: Rationale and Methodology. Metabolites 2021; 11:409. [PMID: 34206296 PMCID: PMC8305896 DOI: 10.3390/metabo11070409] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 06/17/2021] [Accepted: 06/18/2021] [Indexed: 12/29/2022] Open
Abstract
Pancreatic β-cells are responsible for the synthesis and exocytosis of insulin in response to an increase in circulating glucose. Insulin secretion occurs in a pulsatile manner, with oscillatory pulses superimposed on a basal secretion rate. Insulin pulses are a marker of β-cell health, and secretory parameters, such as pulse amplitude, time interval and frequency distribution, are impaired in obesity, aging and type 2 diabetes. In this review, we detail the mechanisms of insulin production and β-cell synchronization that regulate pulsatile insulin secretion, and we discuss the challenges to consider when measuring fast oscillatory secretion in vivo. These include the anatomical difficulties of measuring portal vein insulin noninvasively in humans before the hormone is extracted by the liver and quickly removed from the circulation. Peripheral concentrations of insulin or C-peptide, a peptide cosecreted with insulin, can be used to estimate their secretion profile, but mathematical deconvolution is required. Parametric and nonparametric approaches to the deconvolution problem are evaluated, alongside the assumptions and trade-offs required for their application in the quantification of unknown insulin secretory rates from known peripheral concentrations. Finally, we discuss the therapeutical implication of targeting impaired pulsatile secretion and its diagnostic value as an early indicator of β-cell stress.
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Affiliation(s)
- Marcello C. Laurenti
- Division of Endocrinology, Diabetes & Metabolism, Mayo Clinic, Rochester, MN 55905, USA; (M.C.L.); (A.M.)
- Biomedical Engineering and Physiology Graduate Program, Mayo Clinic Graduate School of Biomedical Sciences, Rochester, MN 55905, USA
| | - Aleksey Matveyenko
- Division of Endocrinology, Diabetes & Metabolism, Mayo Clinic, Rochester, MN 55905, USA; (M.C.L.); (A.M.)
| | - Adrian Vella
- Division of Endocrinology, Diabetes & Metabolism, Mayo Clinic, Rochester, MN 55905, USA; (M.C.L.); (A.M.)
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5
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Liu M, Huang Y, Xu X, Li X, Alam M, Arunagiri A, Haataja L, Ding L, Wang S, Itkin-Ansari P, Kaufman RJ, Tsai B, Qi L, Arvan P. Normal and defective pathways in biogenesis and maintenance of the insulin storage pool. J Clin Invest 2021; 131:142240. [PMID: 33463547 PMCID: PMC7810482 DOI: 10.1172/jci142240] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Both basal and glucose-stimulated insulin release occur primarily by insulin secretory granule exocytosis from pancreatic β cells, and both are needed to maintain normoglycemia. Loss of insulin-secreting β cells, accompanied by abnormal glucose tolerance, may involve simple exhaustion of insulin reserves (which, by immunostaining, appears as a loss of β cell identity), or β cell dedifferentiation, or β cell death. While various sensing and signaling defects can result in diminished insulin secretion, somewhat less attention has been paid to diabetes risk caused by insufficiency in the biosynthetic generation and maintenance of the total insulin granule storage pool. This Review offers an overview of insulin biosynthesis, beginning with the preproinsulin mRNA (translation and translocation into the ER), proinsulin folding and export from the ER, and delivery via the Golgi complex to secretory granules for conversion to insulin and ultimate hormone storage. All of these steps are needed for generation and maintenance of the total insulin granule pool, and defects in any of these steps may, weakly or strongly, perturb glycemic control. The foregoing considerations have obvious potential relevance to the pathogenesis of type 2 diabetes and some forms of monogenic diabetes; conceivably, several of these concepts might also have implications for β cell failure in type 1 diabetes.
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Affiliation(s)
- Ming Liu
- 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
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Xiaoxi Xu
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Xin Li
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
| | - Maroof Alam
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Anoop Arunagiri
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Leena Haataja
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Li Ding
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
| | - Shusen Wang
- Organ Transplant Center, Tianjin First Central Hospital, Tianjin, China
| | | | - Randal J. Kaufman
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, USA
| | - Billy Tsai
- Department of Cell and Developmental Biology, and
| | - Ling Qi
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Peter Arvan
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan, USA
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6
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Jo S, Lockridge A, Mohan R, Esch N, Schlichting R, Panigrahy N, Essawy A, Gustafson E, Alejandro EU. Translational Factor eIF4G1 Regulates Glucose Homeostasis and Pancreatic β-Cell Function. Diabetes 2021; 70:155-170. [PMID: 33115825 PMCID: PMC7881850 DOI: 10.2337/db20-0057] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Accepted: 10/18/2020] [Indexed: 12/27/2022]
Abstract
Protein translation is essential for cell physiology, and dysregulation of this process has been linked to aging-related diseases such as type 2 diabetes. Reduced protein level of a requisite scaffolding protein of the initiation complex, eIF4G1, downstream of nutrients and insulin signaling is associated with diabetes in humans and mice. In the current study, we tested the hypothesis that eIF4G1 is critical for β-cell function and glucose homeostasis by genetically ablating eIF4G1 specifically in β-cells in vivo (βeIF4G1 knockout [KO]). Adult male and female βeIF4G1KO mice displayed glucose intolerance but normal insulin sensitivity. β-Cell mass was normal under steady state and under metabolic stress by diet-induced obesity, but we observed increases in proliferation and apoptosis in β-cells of βeIF4G1KO. We uncovered deficits in insulin secretion, partly due to reduced mitochondrial oxygen consumption rate, glucose-stimulated Ca2+ flux, and reduced insulin content associated with loss of eIF4E, the mRNA 5' cap-binding protein of the initiation complex and binding partner of eIF4G1. Genetic reconstitution of eIF4E in single β-cells or intact islets of βeIF4G1KO mice recovers insulin content, implicating an unexplored role for eIF4G1/eIF4E in insulin biosynthesis. Altogether these data demonstrate an essential role for the translational factor eIF4G1 on glucose homeostasis and β-cell function.
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Affiliation(s)
- Seokwon Jo
- Department of Integrative Biology and Physiology, University of Minnesota Medical School, Minneapolis, MN
| | - Amber Lockridge
- Department of Integrative Biology and Physiology, University of Minnesota Medical School, Minneapolis, MN
| | - Ramkumar Mohan
- Department of Integrative Biology and Physiology, University of Minnesota Medical School, Minneapolis, MN
| | - Nicholas Esch
- Department of Integrative Biology and Physiology, University of Minnesota Medical School, Minneapolis, MN
| | - Regina Schlichting
- Department of Integrative Biology and Physiology, University of Minnesota Medical School, Minneapolis, MN
| | - Neha Panigrahy
- Department of Integrative Biology and Physiology, University of Minnesota Medical School, Minneapolis, MN
| | - Ahmad Essawy
- Department of Integrative Biology and Physiology, University of Minnesota Medical School, Minneapolis, MN
| | - Eric Gustafson
- Department of Integrative Biology and Physiology, University of Minnesota Medical School, Minneapolis, MN
| | - Emilyn U Alejandro
- Department of Integrative Biology and Physiology, University of Minnesota Medical School, Minneapolis, MN
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7
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Insulin granule biogenesis and exocytosis. Cell Mol Life Sci 2020; 78:1957-1970. [PMID: 33146746 PMCID: PMC7966131 DOI: 10.1007/s00018-020-03688-4] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 09/11/2020] [Accepted: 10/19/2020] [Indexed: 02/06/2023]
Abstract
Insulin is produced by pancreatic β-cells, and once released to the blood, the hormone stimulates glucose uptake and suppresses glucose production. Defects in both the availability and action of insulin lead to elevated plasma glucose levels and are major hallmarks of type-2 diabetes. Insulin is stored in secretory granules that form at the trans-Golgi network. The granules undergo extensive modifications en route to their release sites at the plasma membrane, including changes in both protein and lipid composition of the granule membrane and lumen. In parallel, the insulin molecules also undergo extensive modifications that render the hormone biologically active. In this review, we summarize current understanding of insulin secretory granule biogenesis, maturation, transport, docking, priming and eventual fusion with the plasma membrane. We discuss how different pools of granules form and how these pools contribute to insulin secretion under different conditions. We also highlight the role of the β-cell in the development of type-2 diabetes and discuss how dysregulation of one or several steps in the insulin granule life cycle may contribute to disease development or progression.
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8
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Vasiljević J, Torkko JM, Knoch KP, Solimena M. The making of insulin in health and disease. Diabetologia 2020; 63:1981-1989. [PMID: 32894308 PMCID: PMC7476993 DOI: 10.1007/s00125-020-05192-7] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Accepted: 04/28/2020] [Indexed: 12/16/2022]
Abstract
The discovery of insulin in 1921 has been one of greatest scientific achievements of the 20th century. Since then, the availability of insulin has shifted the focus of diabetes treatment from trying to keep patients alive to saving and improving the life of millions. Throughout this time, basic and clinical research has advanced our understanding of insulin synthesis and action, both in healthy and pathological conditions. Yet, multiple aspects of insulin production remain unknown. In this review, we focus on the most recent findings on insulin synthesis, highlighting their relevance in diabetes. Graphical abstract.
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Affiliation(s)
- Jovana Vasiljević
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany
- German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
- Paul Langerhans Institute Dresden (PLID), Helmholtz Center Munich, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Tatzberg 47/49, 01307, Dresden, Germany
| | - Juha M Torkko
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany
- German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
- Paul Langerhans Institute Dresden (PLID), Helmholtz Center Munich, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Tatzberg 47/49, 01307, Dresden, Germany
| | - Klaus-Peter Knoch
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany
- German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
- Paul Langerhans Institute Dresden (PLID), Helmholtz Center Munich, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Tatzberg 47/49, 01307, Dresden, Germany
| | - Michele Solimena
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany.
- German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany.
- Paul Langerhans Institute Dresden (PLID), Helmholtz Center Munich, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Tatzberg 47/49, 01307, Dresden, Germany.
- Max Planck Institute of Molecular Cell Biology and Genetics (MPI-CBG), Dresden, Germany.
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9
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Regulation of β-cell function by RNA-binding proteins. Mol Metab 2013; 2:348-55. [PMID: 24327951 DOI: 10.1016/j.molmet.2013.09.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Revised: 09/15/2013] [Accepted: 09/16/2013] [Indexed: 02/05/2023] Open
Abstract
β-cells of the pancreatic islets are highly specialized and high-throughput units for the production of insulin, the key hormone for maintenance of glucose homeostasis. Elevation of extracellular glucose and/or GLP-1 levels triggers a rapid upregulation of insulin biosynthesis through the activation of post-transcriptional mechanisms. RNA-binding proteins are emerging as key factors in the regulation of these mechanisms as well as in other aspects of β-cell function and glucose homeostasis at large, and thus may be implicated in the pathogenesis of diabetes. Here we review current research in the field, with a major emphasis on RNA-binding proteins that control biosynthesis of insulin and other components of the insulin secretory granules by modulating the stability and translation of their mRNAs.
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10
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Bensellam M, Laybutt DR, Jonas JC. The molecular mechanisms of pancreatic β-cell glucotoxicity: recent findings and future research directions. Mol Cell Endocrinol 2012; 364:1-27. [PMID: 22885162 DOI: 10.1016/j.mce.2012.08.003] [Citation(s) in RCA: 208] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Revised: 07/11/2012] [Accepted: 08/01/2012] [Indexed: 02/06/2023]
Abstract
It is well established that regular physiological stimulation by glucose plays a crucial role in the maintenance of the β-cell differentiated phenotype. In contrast, prolonged or repeated exposure to elevated glucose concentrations both in vitro and in vivo exerts deleterious or toxic effects on the β-cell phenotype, a concept termed as glucotoxicity. Evidence indicates that the latter may greatly contribute to the pathogenesis of type 2 diabetes. Through the activation of several mechanisms and signaling pathways, high glucose levels exert deleterious effects on β-cell function and survival and thereby, lead to the worsening of the disease over time. While the role of high glucose-induced β-cell overstimulation, oxidative stress, excessive Unfolded Protein Response (UPR) activation, and loss of differentiation in the alteration of the β-cell phenotype is well ascertained, at least in vitro and in animal models of type 2 diabetes, the role of other mechanisms such as inflammation, O-GlcNacylation, PKC activation, and amyloidogenesis requires further confirmation. On the other hand, protein glycation is an emerging mechanism that may play an important role in the glucotoxic deterioration of the β-cell phenotype. Finally, our recent evidence suggests that hypoxia may also be a new mechanism of β-cell glucotoxicity. Deciphering these molecular mechanisms of β-cell glucotoxicity is a mandatory first step toward the development of therapeutic strategies to protect β-cells and improve the functional β-cell mass in type 2 diabetes.
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Affiliation(s)
- Mohammed Bensellam
- Université catholique de Louvain, Institut de recherche expérimentale et clinique, Pôle d'endocrinologie, diabète et nutrition, Brussels, Belgium
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11
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Kulkarni SD, Muralidharan B, Panda AC, Bakthavachalu B, Vindu A, Seshadri V. Glucose-stimulated translation regulation of insulin by the 5' UTR-binding proteins. J Biol Chem 2011; 286:14146-56. [PMID: 21357685 DOI: 10.1074/jbc.m110.190553] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Insulin is the key regulator of glucose homeostasis in mammals, and glucose-stimulated insulin biosynthesis is essential for maintaining glucose levels in a narrow range in mammals. Glucose specifically promotes the translation of insulin in pancreatic β-islet, and the untranslated regions of insulin mRNA play a role in such regulation. Specific factors in the β-islets bind to the insulin 5' UTR and regulate its translation. In the present study we identify protein-disulfide isomerase (PDI) as a key regulator of glucose-stimulated insulin biosynthesis. We show that both in vitro and in vivo PDI can specifically associate with the 5' UTR of insulin mRNA. Immunodepletion of PDI from the islet extract results in loss of glucose-stimulated translation indicating a critical role for PDI in insulin biosynthesis. Similarly, transient overexpression of PDI resulted in specific translation activation by glucose. We show that the RNA binding activity of PDI is mediated through PABP. PDI catalyzes the reduction of the PABP disulfide bond resulting in specific binding of PABP to the insulin 5' UTR. We also show that glucose stimulation of the islets results in activation of a specific kinase that can phosphorylate PDI. These findings identify PDI and PABP as important players in glucose homeostasis.
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12
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Martens GA, Pipeleers D. Glucose, regulator of survival and phenotype of pancreatic beta cells. VITAMINS AND HORMONES 2009; 80:507-39. [PMID: 19251048 DOI: 10.1016/s0083-6729(08)00617-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The key role of glucose in regulating insulin release by the pancreatic beta cell population is not only dependent on acute stimulus-secretion coupling mechanisms but also on more long-term influences on beta cell survival and phenotype. Glucose serves as a major survival factor for beta cells via at least three actions: it prevents an oxidative redox state, it suppresses a mitochondrial apoptotic program that is triggered at reduced mitochondrial metabolic activity and it induces genes needed for the cellular responsiveness to glucose and to growth factors. Glucose-regulated pathways may link protein synthetic and proliferative activities, making glucose a permissive factor for beta cell proliferation, in check with metabolic needs. Conditions of inadequate glucose metabolism in beta cells are not only leading to deregulation of acute secretory responses but should also be considered as causes for increased apoptosis and reduced formation of beta cells, and loss of their normal differentiated state.
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Süss C, Czupalla C, Winter C, Pursche T, Knoch KP, Schroeder M, Hoflack B, Solimena M. Rapid changes of mRNA-binding protein levels following glucose and 3-isobutyl-1-methylxanthine stimulation of insulinoma INS-1 cells. Mol Cell Proteomics 2008; 8:393-408. [PMID: 18854578 DOI: 10.1074/mcp.m800157-mcp200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Glucose and cAMP-inducing agents such as 3-isobutyl-1-methylxanthine (IBMX) rapidly change the expression profile of insulin-producing pancreatic beta-cells mostly through post-transcriptional mechanisms. A thorough analysis of these changes, however, has not yet been performed. By combining two-dimensional differential gel electrophoresis and mass spectrometry, we identified 165 spots, corresponding to 78 proteins, whose levels significantly change after stimulation of the beta-cell model INS-1 cells with 25 mM glucose + 1 mM IBMX for 2 h. Changes in the expression of selected proteins were verified by one- and two-dimensional immunoblotting. Most of the identified proteins are novel targets of rapid regulation in beta-cells. The transcription inhibitor actinomycin D failed to block changes in two-thirds of the spots, supporting their post-transcriptional regulation. More spots changed in response to IBMX than to glucose alone conceivably because of phosphorylation. Fourteen mRNA- binding proteins responded to stimulation, thus representing the most prominent class of rapidly regulated proteins. Bioinformatics analysis indicated that the mRNA 5'- and 3'-untranslated regions of 22 regulated proteins contain potential binding sites for polypyrimidine tract-binding protein 1, which promotes mRNA stability and translation in stimulated beta-cells. Overall our findings support the idea that mRNA-binding proteins play a major role in rapid adaptive changes in insulin-producing cells following their stimulation with glucose and cAMP-elevating agents.
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Affiliation(s)
- Christin Süss
- Experimental Diabetology, Dresden University of Technology, Dresden, Germany
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Muralidharan B, Bakthavachalu B, Pathak A, Seshadri V. A minimal element in 5'UTR of insulin mRNA mediates its translational regulation by glucose. FEBS Lett 2007; 581:4103-8. [PMID: 17686473 DOI: 10.1016/j.febslet.2007.07.050] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2007] [Revised: 07/16/2007] [Accepted: 07/24/2007] [Indexed: 11/17/2022]
Abstract
Glucose induced translation of insulin in pancreatic beta cells is mediated by the 5'UTR of insulin mRNA. We determined the minimal sequence/structure in the 5'UTR of rat insulin gene1 for this regulation. We show that specific factors in the pancreatic islets bind to the 5'UTR of the insulin mRNA upon glucose stimulation. We identified a minimal 29-nucleotide element in the 5'UTR that is sufficient to form the complex, and confer glucose mediated translation activation. Conserved residues in the predicted stem loop region of the un-translated region (UTR) seem to be important for the complex formation and the translation regulation.
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Wicksteed B, Uchizono Y, Alarcon C, McCuaig JF, Shalev A, Rhodes CJ. A cis-element in the 5' untranslated region of the preproinsulin mRNA (ppIGE) is required for glucose regulation of proinsulin translation. Cell Metab 2007; 5:221-7. [PMID: 17339029 DOI: 10.1016/j.cmet.2007.02.007] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2006] [Revised: 02/09/2007] [Accepted: 02/16/2007] [Indexed: 10/23/2022]
Abstract
Insulin production in pancreatic beta cells is predominantly regulated through glucose control of proinsulin translation. Previously, this was shown to require sequences within the untranslated regions (UTRs) of the preproinsulin (ppI) mRNA. Here, those sequences were found to be sufficient for specific glucose-regulated proinsulin translation. Furthermore, an element 40-48 bp from the 5' end of the ppI mRNA specifically bound a factor present in islets of Langerhans. Glucose-responsive factor binding to this cis-element exhibited temporal and glucose-concentration-dependent patterns that paralleled proinsulin biosynthesis. Mutating this cis-element abolished the ability of ppI mRNA UTRs to confer glucose regulation upon translation. Like the rat 5'UTR, the human ppI 5'UTR conferred glucose regulation of translation. However alternative splicing of the human 5'UTR that disrupts the cis-element abolished glucose-regulated translation. These data indicate that glucose regulation of cis-element/trans-acting factor interaction is a key component of the mechanism by which glucose regulates insulin production.
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Affiliation(s)
- Barton Wicksteed
- Comprehensive Diabetes Center, Section of Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Chicago, IL 60637, USA
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Martens GA, Wang Q, Kerckhofs K, Stangé G, Ling Z, Pipeleers D. Metabolic activation of glucose low-responsive beta-cells by glyceraldehyde correlates with their biosynthetic activation in lower glucose concentration range but not at high glucose. Endocrinology 2006; 147:5196-204. [PMID: 16916947 DOI: 10.1210/en.2006-0580] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Insulin synthesis and release activities of beta-cells can be acutely regulated by glucose through its glycolytic and mitochondrial breakdown involving a glucokinase-dependent rate-limiting step. Isolated beta-cell populations are composed of cells with intercellular differences in acute glucose responsiveness that have been attributed to differences in glucokinase (GK) expression and activity. This study first shows that glyceraldehyde can be used as GK-bypassing oxidative substrate and then examines whether the triose can metabolically activate beta-cells with low glucose responsiveness. Glyceraldehyde 1 mm induced a similar cellular (14)CO(2) output and metabolic redox state as glucose 4 mM. Using flow cytometric analysis, glyceraldehyde (0.25-2 mM) was shown to concentration-dependently increase the percent metabolically activated cells at all tested glucose concentrations (2.5-20 mM). Its ability to activate beta-cells that are unresponsive to the prevailing glucose level was further illustrated in glucose low-responsive cells that were isolated by flow sorting. Metabolic activation by glyceraldehyde was associated with an activation of nutrient-driven translational control proteins and an increased protein synthetic response to glucose, however not beyond the maximal rates that are inducible by glucose alone. It is concluded that glucose low-responsive beta-cells can be metabolically activated by the GK-bypassing glyceraldehyde, increasing their acute biosynthetic response to glucose but not their maximal glucose-inducible biosynthetic capacity, which is considered subject to chronic regulation.
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Affiliation(s)
- G A Martens
- Diabetes Research Center, Laarbeeklaan 103, B-1090 Brussels, Belgium
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Borgonovo B, Ouwendijk J, Solimena M. Biogenesis of secretory granules. Curr Opin Cell Biol 2006; 18:365-70. [PMID: 16806882 DOI: 10.1016/j.ceb.2006.06.010] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2006] [Accepted: 06/08/2006] [Indexed: 11/22/2022]
Abstract
Secretory granules of neuroendocrine cells store and release peptide hormones and neuropeptides in response to various stimuli. Generation of granules from the Golgi complex involves the aggregation of cargo proteins and their sorting from non-regulated secretory molecules. Recent findings on knockout mice lacking individual granule constituents have challenged the hypothesis that an 'essential' protein for the assembly of these organelles exists, while studies on polypyrimidine tract-binding protein and ICA512/IA-2 have provided insight into the mechanisms for adjusting granule production in relation to stimulation and secretory activity.
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Affiliation(s)
- Barbara Borgonovo
- Experimental Diabetology, Carl Gustav Carus Medical School, Dresden University of Technology, Fetscherstrasse 74, 01307 Dresden, Germany
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