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Cheruiyot A, Hollister-Lock J, Sullivan B, Pan H, Dreyfuss JM, Bonner-Weir S, Schaffer JE. Sustained hyperglycemia specifically targets translation of mRNAs for insulin secretion. J Clin Invest 2023; 134:e173280. [PMID: 38032734 PMCID: PMC10849759 DOI: 10.1172/jci173280] [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: 06/21/2023] [Accepted: 11/28/2023] [Indexed: 12/02/2023] Open
Abstract
Pancreatic β cells are specialized for coupling glucose metabolism to insulin peptide production and secretion. Acute glucose exposure robustly and coordinately increases translation of proinsulin and proteins required for secretion of mature insulin peptide. By contrast, chronically elevated glucose levels that occur during diabetes impair β cell insulin secretion and have been shown experimentally to suppress insulin translation. Whether translation of other genes critical for insulin secretion is similarly downregulated by chronic high glucose is unknown. Here, we used high-throughput ribosome profiling and nascent proteomics in MIN6 insulinoma cells to elucidate the genome-wide impact of sustained high glucose on β cell mRNA translation. Before induction of ER stress or suppression of global translation, sustained high glucose suppressed glucose-stimulated insulin secretion and downregulated translation of not only insulin, but also mRNAs related to insulin secretory granule formation, exocytosis, and metabolism-coupled insulin secretion. Translation of these mRNAs was also downregulated in primary rat and human islets following ex vivo incubation with sustained high glucose and in an in vivo model of chronic mild hyperglycemia. Furthermore, translational downregulation decreased cellular abundance of these proteins. Our study uncovered a translational regulatory circuit during β cell glucose toxicity that impairs expression of proteins with critical roles in β cell function.
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2
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Cheruiyot A, Hollister-Lock J, Sullivan B, Pan H, Dreyfuss JM, Bonner-Weir S, Schaffer JE. Sustained hyperglycemia specifically targets translation of mRNAs for insulin secretion. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.29.560203. [PMID: 37808767 PMCID: PMC10557781 DOI: 10.1101/2023.09.29.560203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/10/2023]
Abstract
Pancreatic β-cells are specialized for coupling glucose metabolism to insulin peptide production and secretion. Acute glucose exposure robustly and coordinately increases translation of proinsulin and proteins required for secretion of mature insulin peptide. By contrast, chronically elevated glucose levels that occur during diabetes impair β-cell insulin secretion and have been shown experimentally to suppress insulin translation. Whether translation of other genes critical for insulin secretion are similarly downregulated by chronic high glucose is unknown. Here, we used high-throughput ribosome profiling and nascent proteomics in MIN6 insulinoma cells to elucidate the genome-wide impact of sustained high glucose on β-cell mRNA translation. Prior to induction of ER stress or suppression of global translation, sustained high glucose suppressed glucose-stimulated insulin secretion and downregulated translation of not only insulin, but also of mRNAs related to insulin secretory granule formation, exocytosis, and metabolism-coupled insulin secretion. Translation of these mRNAs was also downregulated in primary rat and human islets following ex-vivo incubation with sustained high glucose and in an in vivo model of chronic mild hyperglycemia. Furthermore, translational downregulation decreased cellular abundance of these proteins. Our findings uncover a translational regulatory circuit during β-cell glucose toxicity that impairs expression of proteins with critical roles in β-cell function.
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3
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Shin HC, Bochkov YA, Kim K, Gern JE, Jarjour NN, Esnault S. A motif in the 5'untranslated region of messenger RNAs regulates protein synthesis in a S6 kinase-dependent manner. Adv Biol Regul 2023; 89:100975. [PMID: 37302177 PMCID: PMC10735251 DOI: 10.1016/j.jbior.2023.100975] [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: 03/06/2023] [Accepted: 06/05/2023] [Indexed: 06/13/2023]
Abstract
The 5' untranslated regions (UTRs) in messenger RNAs (mRNAs) play an important role in the regulation of protein synthesis. We had previously identified a group of mRNAs that includes human semaphorin 7A (SEMA7A) whose translation is upregulated by the Erk/p90S6K pathway in human eosinophils, with a potential negative impact in asthma and airway inflammation. In the current study, we aimed to find a common 5'UTR regulatory cis-element, and determine its impact on protein synthesis. We identified a common and conserved 5'UTR motif GGCTG-[(C/G)T(C/G)]n-GCC that was present in this group of mRNAs. Mutations of the first two GG bases in this motif in SEMA7A 5'UTR led to a complete loss of S6K activity dependence for maximal translation. In conclusion, the newly identified 5'UTR motif present in SEMA7A has a critical role in regulating S6K-dependent protein synthesis.
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Affiliation(s)
- Hyun-Chul Shin
- Department of Chemistry Education, Korea National University of Education, Cheongju-si, Chungcheonbuk-do, Republic of Korea
| | - Yury A Bochkov
- Department of Pediatrics, School of Medicine and Public Health, University of Wisconsin, Madison, WI, USA
| | - Kangsan Kim
- Department of Chemistry Education, Korea National University of Education, Cheongju-si, Chungcheonbuk-do, Republic of Korea
| | - James E Gern
- Department of Pediatrics, School of Medicine and Public Health, University of Wisconsin, Madison, WI, USA; Department of Medicine, School of Medicine and Public Health, University of Wisconsin, Madison, WI, USA
| | - Nizar N Jarjour
- Department of Medicine, School of Medicine and Public Health, University of Wisconsin, Madison, WI, USA
| | - Stephane Esnault
- Department of Medicine, School of Medicine and Public Health, University of Wisconsin, Madison, WI, USA.
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4
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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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5
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Setting the Stage for Insulin Granule Dysfunction during Type-1-Diabetes: Is ER Stress the Culprit? Biomedicines 2022; 10:biomedicines10112695. [DOI: 10.3390/biomedicines10112695] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Revised: 10/07/2022] [Accepted: 10/19/2022] [Indexed: 11/16/2022] Open
Abstract
Type-1-diabetes (T1D) is a multifactorial disorder with a global incidence of about 8.4 million individuals in 2021. It is primarily classified as an autoimmune disorder, where the pancreatic β-cells are unable to secrete sufficient insulin. This leads to elevated blood glucose levels (hyperglycemia). The development of T1D is an intricate interplay between various risk factors, such as genetic, environmental, and cellular elements. In this review, we focus on the cellular elements, such as ER (endoplasmic reticulum) stress and its consequences for T1D pathogenesis. One of the major repercussions of ER stress is defective protein processing. A well-studied example is that of islet amyloid polypeptide (IAPP), which is known to form cytotoxic amyloid plaques when misfolded. This review discusses the possible association between ER stress, IAPP, and amyloid formation in β-cells and its consequences in T1D. Additionally, ER stress also leads to autoantigen generation. This is driven by the loss of Ca++ ion homeostasis. Imbalanced Ca++ levels lead to abnormal activation of enzymes, causing post-translational modification of β-cell proteins. These modified proteins act as autoantigens and trigger the autoimmune response seen in T1D islets. Several of these autoantigens are also crucial for insulin granule biogenesis, processing, and release. Here, we explore the possible associations between ER stress leading to defects in insulin secretion and ultimately β-cell destruction.
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Li M. The Origination of Growth Hormone/Insulin-Like Growth Factor System: A Story From Ancient Basal Chordate Amphioxus. Front Endocrinol (Lausanne) 2022; 13:825722. [PMID: 35432211 PMCID: PMC9010856 DOI: 10.3389/fendo.2022.825722] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 01/10/2022] [Indexed: 12/03/2022] Open
Abstract
The growth hormone/insulin-like growth factor (GH/IGF) system, also called the pituitary-liver axis, has a somatotrophic role in the body. Although the GH/IGF system has always been regarded as a vertebrate-specific endocrine system, its actual origin remained unknown for a long time. The basal chordate, amphioxus, occupies an evolutionary position between vertebrates and invertebrates. Impressively, most of the members of the GH/IGF system are present in the amphioxus. The GH-like molecule in the amphioxus is mainly expressed in Hatschek's pit. It functions similarly to vertebrate GH and has a GH receptor-like binding partner. The amphioxus IGF-like peptide shows mitogenic activity and an expression pattern resembling that of vertebrate IGF-I. The receptor of IGF-like peptide and IGF binding protein (IGFBP) have also been demonstrated to exist in the amphioxus. These results reveal the origin of the gene families in the GH/IGF system, providing strong evidence that this system emerged in the amphioxus.
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7
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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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8
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OKAMOTO H, TAKASAWA S. Okamoto model for necrosis and its expansions, CD38-cyclic ADP-ribose signal system for intracellular Ca 2+ mobilization and Reg (Regenerating gene protein)-Reg receptor system for cell regeneration. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2021; 97:423-461. [PMID: 34629354 PMCID: PMC8553518 DOI: 10.2183/pjab.97.022] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 06/22/2021] [Indexed: 05/03/2023]
Abstract
In pancreatic islet cell culture models and animal models, we studied the molecular mechanisms involved in the development of insulin-dependent diabetes. The diabetogenic agents, alloxan and streptozotocin, caused DNA strand breaks, which in turn activated poly(ADP-ribose) polymerase/synthetase (PARP) to deplete NAD+, thereby inhibiting islet β-cell functions such as proinsulin synthesis and ultimately leading to β-cell necrosis. Radical scavengers protected against the formation of DNA strand breaks and inhibition of proinsulin synthesis. Inhibitors of PARP prevented the NAD+ depletion, inhibition of proinsulin synthesis and β-cell death. These findings led to the proposed unifying concept for β-cell damage and its prevention (the Okamoto model). The model met one proof with PARP knockout animals and was further extended by the discovery of cyclic ADP-ribose as the second messenger for Ca2+ mobilization in glucose-induced insulin secretion and by the identification of Reg (Regenerating gene) for β-cell regeneration. Physiological and pathological events found in pancreatic β-cells have been observed in other cells and tissues.
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Affiliation(s)
- Hiroshi OKAMOTO
- Department of Biochemistry, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
- Department of Biochemistry and Molecular Vascular Biology, Kanazawa University Graduate School of Medical Sciences, Kanazawa, Ishikawa, Japan
| | - Shin TAKASAWA
- Department of Biochemistry, Nara Medical University, Kashihara, Nara, Japan
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9
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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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10
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Sarwade RD, Khalique A, Kulkarni SD, Pandey PR, Gaikwad N, Seshadri V. Translation of insulin granule proteins are regulated by PDI and PABP. Biochem Biophys Res Commun 2020; 526:618-625. [PMID: 32248978 DOI: 10.1016/j.bbrc.2020.03.106] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 03/11/2020] [Accepted: 03/18/2020] [Indexed: 01/21/2023]
Abstract
Glucose mediated insulin biosynthesis is tightly regulated and shared between insulin granule proteins such as its processing enzymes, prohormone convertases, PC1/3 and PC2. However, the molecular players involved in the co-ordinated translation remain elusive. The trans-acting factors like PABP (Poly A Binding Protein) and PDI (Protein Disulphide Isomerize) binds to a conserved sequence in the 5'UTR of insulin mRNA and regulates its translation. Here, we demonstrate that 5'UTR of PC1/3 and PC2 also associate with PDI and PABP. We show that a' and RRM 3-4 domains of PDI and PABP respectively, are necessary for RNA binding activity to the 5'UTRs of insulin and its processing enzymes.
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Affiliation(s)
- Rucha D Sarwade
- National Centre of Cell Science, Ganeshkhind, Pune, 411007, India; Savitribai Phule Pune University, Ganeshkhind, Pune, 411007, India
| | - Abdul Khalique
- National Centre of Cell Science, Ganeshkhind, Pune, 411007, India; Savitribai Phule Pune University, Ganeshkhind, Pune, 411007, India
| | - Shardul D Kulkarni
- National Centre of Cell Science, Ganeshkhind, Pune, 411007, India; Savitribai Phule Pune University, Ganeshkhind, Pune, 411007, India
| | - Poonam R Pandey
- National Centre of Cell Science, Ganeshkhind, Pune, 411007, India; Savitribai Phule Pune University, Ganeshkhind, Pune, 411007, India
| | - Naina Gaikwad
- National Centre of Cell Science, Ganeshkhind, Pune, 411007, India; Savitribai Phule Pune University, Ganeshkhind, Pune, 411007, India
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11
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Chen B, Guo L, Chen X, El-Senousey HK, Ma M, Jebessa E, Nie Q. Cellular function of chicken FOXO3 and its associations with chicken growth. Poult Sci 2019; 98:5109-5117. [PMID: 31265733 DOI: 10.3382/ps/pez397] [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: 01/02/2019] [Accepted: 06/13/2019] [Indexed: 01/08/2023] Open
Abstract
FOXO3 belongs to the Forkhead O transcription factor family and it is an important gene in multiple biological processes, such as cell cycle control, cell proliferation, cell apoptosis, human longevity, and oxidative stress. Previous studies have shown that FOXO3 is associated with skeletal muscle growth and adipose development in mammals. However, the sequence of chicken FOXO3 is still incomplete and the cellular functions of FOXO3 in chickens are poorly understood. Thus, we obtained the full-length sequence of chicken FOXO3 by 5' rapid amplification of cDNA ends (5' RACE) and the phylogenetic tree showed that the chicken FOXO3 sequence was homologous with those in other species. Flow cytometry analysis and 5-ethynyl-2'-deoxyuridine assays showed that FOXO3 repressed cellular proliferation and induced apoptosis in a chicken hepatocellular carcinoma cell line (LMH). Mutations were screened in the second exon of FOXO3 and 13 synonymous single nucleotide polymorphisms were found in the test population. Further analysis showed that rs317670452 and rs15379317 were associated with many growth and carcass traits, such as the body weight at different ages and breast muscle weight. Our results indicate that chicken FOXO3 has similar cellular functions to those found in mammals and it is significantly associated with chicken growth.
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Affiliation(s)
- Biao Chen
- Department of Animal Genetics, Breeding and Reproduction, College of Animal Science, South China Agricultural University, Guangzhou 510642, Guangdong, China.,National-Local Joint Engineering Research Center for Livestock Breeding, Guangzhou 510642, Guangdong, China.,Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, and Key Laboratory of Chicken Genetics, Breeding and Reproduction, Ministry of Agriculture, Guangzhou 510642, Guangdong, China
| | - Lijin Guo
- Department of Animal Genetics, Breeding and Reproduction, College of Animal Science, South China Agricultural University, Guangzhou 510642, Guangdong, China.,National-Local Joint Engineering Research Center for Livestock Breeding, Guangzhou 510642, Guangdong, China.,Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, and Key Laboratory of Chicken Genetics, Breeding and Reproduction, Ministry of Agriculture, Guangzhou 510642, Guangdong, China
| | - Xiaolan Chen
- Department of Animal Genetics, Breeding and Reproduction, College of Animal Science, South China Agricultural University, Guangzhou 510642, Guangdong, China.,National-Local Joint Engineering Research Center for Livestock Breeding, Guangzhou 510642, Guangdong, China.,Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, and Key Laboratory of Chicken Genetics, Breeding and Reproduction, Ministry of Agriculture, Guangzhou 510642, Guangdong, China
| | | | - Manting Ma
- Department of Animal Genetics, Breeding and Reproduction, College of Animal Science, South China Agricultural University, Guangzhou 510642, Guangdong, China.,National-Local Joint Engineering Research Center for Livestock Breeding, Guangzhou 510642, Guangdong, China.,Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, and Key Laboratory of Chicken Genetics, Breeding and Reproduction, Ministry of Agriculture, Guangzhou 510642, Guangdong, China
| | - Endashaw Jebessa
- Department of Animal Genetics, Breeding and Reproduction, College of Animal Science, South China Agricultural University, Guangzhou 510642, Guangdong, China.,National-Local Joint Engineering Research Center for Livestock Breeding, Guangzhou 510642, Guangdong, China.,Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, and Key Laboratory of Chicken Genetics, Breeding and Reproduction, Ministry of Agriculture, Guangzhou 510642, Guangdong, China
| | - Qinghua Nie
- Department of Animal Genetics, Breeding and Reproduction, College of Animal Science, South China Agricultural University, Guangzhou 510642, Guangdong, China.,National-Local Joint Engineering Research Center for Livestock Breeding, Guangzhou 510642, Guangdong, China.,Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, and Key Laboratory of Chicken Genetics, Breeding and Reproduction, Ministry of Agriculture, Guangzhou 510642, Guangdong, China
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12
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Li Z, Zhou M, Cai Z, Liu H, Zhong W, Hao Q, Cheng D, Hu X, Hou J, Xu P, Xue Y, Zhou Y, Xu T. RNA-binding protein DDX1 is responsible for fatty acid-mediated repression of insulin translation. Nucleic Acids Res 2019; 46:12052-12066. [PMID: 30295850 PMCID: PMC6294501 DOI: 10.1093/nar/gky867] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2018] [Accepted: 09/14/2018] [Indexed: 01/13/2023] Open
Abstract
The molecular mechanism in pancreatic β cells underlying hyperlipidemia and insulin insufficiency remains unclear. Here, we find that the fatty acid-induced decrease in insulin levels occurs due to a decrease in insulin translation. Since regulation at the translational level is generally mediated through RNA-binding proteins, using RNA antisense purification coupled with mass spectrometry, we identify a novel insulin mRNA-binding protein, namely, DDX1, that is sensitive to palmitate treatment. Notably, the knockdown or overexpression of DDX1 affects insulin translation, and the knockdown of DDX1 eliminates the palmitate-induced repression of insulin translation. Molecular mechanism studies show that palmitate treatment causes DDX1 phosphorylation at S295 and dissociates DDX1 from insulin mRNA, thereby leading to the suppression of insulin translation. In addition, DDX1 may interact with the translation initiation factors eIF3A and eIF4B to regulate translation. In high-fat diet mice, the inhibition of insulin translation happens at an early prediabetic stage before the elevation of glucose levels. We speculate that the DDX1-mediated repression of insulin translation worsens the situation of insulin resistance and contributes to the elevation of blood glucose levels in obese animals.
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Affiliation(s)
- Zonghong Li
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics & University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100101, China.,Jilin Province Key Laboratory on Chemistry and Biology of Changbai Mountain Natural Drugs, School of Life Sciences, Northeast Normal University, Changchun 130024, China
| | - Maoge Zhou
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics & University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100101, China
| | - Zhaokui Cai
- Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Hongyang Liu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics & University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100101, China
| | - Wen Zhong
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics & University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100101, China
| | - Qiang Hao
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics & University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100101, China
| | - Dongwan Cheng
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics & University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100101, China
| | - Xihao Hu
- Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Junjie Hou
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics & University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100101, China
| | - Pingyong Xu
- Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Yuanchao Xue
- Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Yifa Zhou
- Jilin Province Key Laboratory on Chemistry and Biology of Changbai Mountain Natural Drugs, School of Life Sciences, Northeast Normal University, Changchun 130024, China
| | - Tao Xu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics & University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100101, China
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13
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Pandey PR, Sarwade RD, Khalique A, Seshadri V. Interaction of HuDA and PABP at 5'UTR of mouse insulin2 regulates insulin biosynthesis. PLoS One 2018; 13:e0194482. [PMID: 29590218 PMCID: PMC5874046 DOI: 10.1371/journal.pone.0194482] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Accepted: 03/05/2018] [Indexed: 11/18/2022] Open
Abstract
Understanding the regulation of insulin biosynthesis is important as it plays a central role in glucose metabolism. The mouse insulin gene2 (Ins2) has two splice variants; long (Ins2L) and short (Ins2S), that differ only in their 5’UTR sequence and Ins2S is the major transcript which translate more efficiently as compared to Ins2L. Here, we show that cellular factors bind preferentially to the Ins2L 5’UTR, and that PABP and HuD can bind to Ins2 splice variants and regulate its translation. In vitro binding assay with insulin 5’UTR and different HuD isoforms indicate that the ‘N’ terminal region of HuD is important for RNA binding and insulin translation repression. Using reporter assay we showed that specifically full-length HuD A isoform represses translation of reporter containing insulin 5’UTR. We further show that PABP and HuD interact with each other in RNA-dependent manner and this interaction is affected by glucose and PDI (5’UTR associated translation activator). These results suggest that PABP interacts with HuD in basal glucose conditions making translation inhibitory complex, however upon glucose stimulation this association is affected and PABP is acted upon by PDI resulting in stimulation of insulin translation. Together, our findings snapshot the mechanism of post-transcriptional regulation of insulin biosynthesis.
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Affiliation(s)
- Poonam R. Pandey
- National Centre for Cell Science, Ganeshkhind, Pune, India
- Department of Biotechnology, Savitribai Phule Pune University, Ganeshkhind, Pune, India
| | - Rucha D. Sarwade
- National Centre for Cell Science, Ganeshkhind, Pune, India
- Department of Biotechnology, Savitribai Phule Pune University, Ganeshkhind, Pune, India
| | - Abdul Khalique
- National Centre for Cell Science, Ganeshkhind, Pune, India
- Department of Biotechnology, Savitribai Phule Pune University, Ganeshkhind, Pune, India
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14
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Arunagiri A, Haataja L, Cunningham CN, Shrestha N, Tsai B, Qi L, Liu M, Arvan P. Misfolded proinsulin in the endoplasmic reticulum during development of beta cell failure in diabetes. Ann N Y Acad Sci 2018; 1418:5-19. [PMID: 29377149 DOI: 10.1111/nyas.13531] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Revised: 09/14/2017] [Accepted: 09/25/2017] [Indexed: 02/06/2023]
Abstract
The endoplasmic reticulum (ER) is broadly distributed throughout the cytoplasm of pancreatic beta cells, and this is where all proinsulin is initially made. Healthy beta cells can synthesize 6000 proinsulin molecules per second. Ordinarily, nascent proinsulin entering the ER rapidly folds via the formation of three evolutionarily conserved disulfide bonds (B7-A7, B19-A20, and A6-A11). A modest amount of proinsulin misfolding, including both intramolecular disulfide mispairing and intermolecular disulfide-linked protein complexes, is a natural by-product of proinsulin biosynthesis, as is the case for many proteins. The steady-state level of misfolded proinsulin-a potential ER stressor-is linked to (1) production rate, (2) ER environment, (3) presence or absence of naturally occurring (mutational) defects in proinsulin, and (4) clearance of misfolded proinsulin molecules. Accumulation of misfolded proinsulin beyond a certain threshold begins to interfere with the normal intracellular transport of bystander proinsulin, leading to diminished insulin production and hyperglycemia, as well as exacerbating ER stress. This is most obvious in mutant INS gene-induced Diabetes of Youth (MIDY; an autosomal dominant disease) but also likely to occur in type 2 diabetes owing to dysregulation in proinsulin synthesis, ER folding environment, or clearance.
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Affiliation(s)
- Anoop Arunagiri
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, Michigan
| | - Leena Haataja
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, Michigan
| | - Corey N Cunningham
- Cellular and Molecular Biology Program, University of Michigan, Ann Arbor, Michigan
| | - Neha Shrestha
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - Billy Tsai
- Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, Michigan
| | - Ling Qi
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - Ming Liu
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, Michigan.,Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
| | - Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, Michigan
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15
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Fred RG, Mehrabi S, Adams CM, Welsh N. PTB and TIAR binding to insulin mRNA 3'- and 5'UTRs; implications for insulin biosynthesis and messenger stability. Heliyon 2016; 2:e00159. [PMID: 27699280 PMCID: PMC5035359 DOI: 10.1016/j.heliyon.2016.e00159] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 05/23/2016] [Accepted: 09/09/2016] [Indexed: 02/01/2023] Open
Abstract
OBJECTIVES Insulin expression is highly controlled on the posttranscriptional level. The RNA binding proteins (RBPs) responsible for this result are still largely unknown. METHODS AND RESULTS To identify RBPs that bind to insulin mRNA we performed mass spectrometry analysis on proteins that bound synthetic oligonucloetides mimicing the 5'- and the 3'-untranslated regions (UTRs) of rat and human insulin mRNA in vitro. We observed that the RBPs heterogeneous nuclear ribonucleoprotein (hnRNP) U, polypyrimidine tract binding protein (PTB), hnRNP L and T-cell restricted intracellular antigen 1-related protein (TIA-1-related protein; TIAR) bind to insulin mRNA sequences, and that the in vitro binding affinity of these RBPs changed when INS-1 cells were exposed to glucose, 3-isobutyl-1-methylxanthine (IBMX) or nitric oxide. High glucose exposure resulted in a modest increase in PTB and TIAR binding to an insulin mRNA sequence. The inducer of nitrosative stress DETAnonoate increased markedly hnRNP U and TIAR mRNA binding. An increased PTB to TIAR binding ratio in vitro correlated with higher insulin mRNA levels and insulin biosynthesis rates in INS-1 cells. To further investigate the importance of RNA-binding proteins for insulin mRNA stability, we decreased INS-1 and EndoC-βH1 cell levels of PTB and TIAR by RNAi. In both cell lines, decreased levels of PTB resulted in lowered insulin mRNA levels while decreased levels of TIAR resulted in increased insulin mRNA levels. Thapsigargin-induced stress granule formation was associated with a redistribution of TIAR from the cytosol to stress granules. CONCLUSIONS These experiments indicate that alterations in insulin mRNA stability and translation correlate with differential RBP binding. We propose that the balance between PTB on one hand and TIAR on the other participates in the control of insulin mRNA stability and utilization for insulin biosynthesis.
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Affiliation(s)
- Rikard G Fred
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Syrina Mehrabi
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Christopher M Adams
- Department of Biological and Medical Mass Spectrometry, Uppsala University, Uppsala, Sweden
| | - Nils Welsh
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
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16
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Ghislain J, Fontés G, Tremblay C, Kebede MA, Poitout V. Dual-Reporter β-Cell-Specific Male Transgenic Rats for the Analysis of β-Cell Functional Mass and Enrichment by Flow Cytometry. Endocrinology 2016; 157:1299-306. [PMID: 26671180 PMCID: PMC4769371 DOI: 10.1210/en.2015-1550] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Mouse β-cell-specific reporter lines have played a key role in diabetes research. Although the rat provides several advantages, its use has lagged behind the mouse due to the relative paucity of genetic models. In this report we describe the generation and characterization of transgenic rats expressing a Renilla luciferase (RLuc)-enhanced yellow fluorescent protein (YFP) fusion under control of a 9-kb genomic fragment from the rat ins2 gene (RIP7-RLuc-YFP). Analysis of RLuc luminescence and YFP fluorescence revealed that reporter expression is restricted to β-cells in the adult rat. Physiological characteristics including body weight, fat and lean mass, fasting and fed glucose levels, glucose and insulin tolerance, and β-cell mass were similar between two RIP7-RLuc-YFP lines and wild-type littermates. Glucose-induced insulin secretion in isolated islets was indistinguishable from controls in one of the lines, whereas surprisingly, insulin secretion was defective in the second line. Consequently, subsequent studies were limited to the former line. We asked whether transgene activity was responsive to glucose as shown previously for the ins2 gene. Exposing islets ex vivo to high glucose (16.7 mM) or in vivo infusion of glucose for 24 hours increased luciferase activity in islets, whereas the fraction of YFP-positive β-cells after glucose infusion was unchanged. Finally, we showed that fluorescence-activated cell sorting of YFP-positive islet cells can be used to enrich for β-cells. Overall, this transgenic line will enable for the first time the application of both fluorescence and bioluminescence/luminescence-based approaches for the study of rat β-cells.
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Affiliation(s)
- Julien Ghislain
- Montreal Diabetes Research Center (J.G., G.F., C.T., M.A.K., V.P.), Centre de Recherche du Centre Hospitalier de l'Université de Montréal (J.G., G.F., C.T., M.A.K., V.P.), and Departments of Medicine (V.P.) and Biochemistry (V.P.), University of Montreal, Montréal, Québec, Canada H2X 0A9
| | - Ghislaine Fontés
- Montreal Diabetes Research Center (J.G., G.F., C.T., M.A.K., V.P.), Centre de Recherche du Centre Hospitalier de l'Université de Montréal (J.G., G.F., C.T., M.A.K., V.P.), and Departments of Medicine (V.P.) and Biochemistry (V.P.), University of Montreal, Montréal, Québec, Canada H2X 0A9
| | - Caroline Tremblay
- Montreal Diabetes Research Center (J.G., G.F., C.T., M.A.K., V.P.), Centre de Recherche du Centre Hospitalier de l'Université de Montréal (J.G., G.F., C.T., M.A.K., V.P.), and Departments of Medicine (V.P.) and Biochemistry (V.P.), University of Montreal, Montréal, Québec, Canada H2X 0A9
| | - Melkam A Kebede
- Montreal Diabetes Research Center (J.G., G.F., C.T., M.A.K., V.P.), Centre de Recherche du Centre Hospitalier de l'Université de Montréal (J.G., G.F., C.T., M.A.K., V.P.), and Departments of Medicine (V.P.) and Biochemistry (V.P.), University of Montreal, Montréal, Québec, Canada H2X 0A9
| | - Vincent Poitout
- Montreal Diabetes Research Center (J.G., G.F., C.T., M.A.K., V.P.), Centre de Recherche du Centre Hospitalier de l'Université de Montréal (J.G., G.F., C.T., M.A.K., V.P.), and Departments of Medicine (V.P.) and Biochemistry (V.P.), University of Montreal, Montréal, Québec, Canada H2X 0A9
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17
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Alarcon C, Boland BB, Uchizono Y, Moore PC, Peterson B, Rajan S, Rhodes OS, Noske AB, Haataja L, Arvan P, Marsh BJ, Austin J, Rhodes CJ. Pancreatic β-Cell Adaptive Plasticity in Obesity Increases Insulin Production but Adversely Affects Secretory Function. Diabetes 2016; 65:438-50. [PMID: 26307586 PMCID: PMC4747460 DOI: 10.2337/db15-0792] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Accepted: 08/17/2015] [Indexed: 12/17/2022]
Abstract
Pancreatic β-cells normally produce adequate insulin to control glucose homeostasis, but in obesity-related diabetes, there is a presumed deficit in insulin production and secretory capacity. In this study, insulin production was assessed directly in obese diabetic mouse models, and proinsulin biosynthesis was found to be contrastingly increased, coupled with a significant expansion of the rough endoplasmic reticulum (without endoplasmic reticulum stress) and Golgi apparatus, increased vesicular trafficking, and a depletion of mature β-granules. As such, β-cells have a remarkable capacity to produce substantial quantities of insulin in obesity, which are then made available for immediate secretion to meet increased metabolic demand, but this comes at the price of insulin secretory dysfunction. Notwithstanding, it can be restored. Upon exposing isolated pancreatic islets of obese mice to normal glucose concentrations, β-cells revert back to their typical morphology with restoration of regulated insulin secretion. These data demonstrate an unrealized dynamic adaptive plasticity of pancreatic β-cells and underscore the rationale for transient β-cell rest as a treatment strategy for obesity-linked diabetes.
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Affiliation(s)
- Cristina Alarcon
- Kovler Diabetes Center, Department of Medicine, Section of Endocrinology, Diabetes and Metabolism, The University of Chicago, Chicago, IL
| | - Brandon B Boland
- Kovler Diabetes Center, Department of Medicine, Section of Endocrinology, Diabetes and Metabolism, The University of Chicago, Chicago, IL
| | - Yuji Uchizono
- Kovler Diabetes Center, Department of Medicine, Section of Endocrinology, Diabetes and Metabolism, The University of Chicago, Chicago, IL
| | - Patrick C Moore
- Kovler Diabetes Center, Department of Medicine, Section of Endocrinology, Diabetes and Metabolism, The University of Chicago, Chicago, IL
| | - Bryan Peterson
- Kovler Diabetes Center, Department of Medicine, Section of Endocrinology, Diabetes and Metabolism, The University of Chicago, Chicago, IL
| | - Suryalekha Rajan
- Kovler Diabetes Center, Department of Medicine, Section of Endocrinology, Diabetes and Metabolism, The University of Chicago, Chicago, IL
| | - Olivia S Rhodes
- Kovler Diabetes Center, Department of Medicine, Section of Endocrinology, Diabetes and Metabolism, The University of Chicago, Chicago, IL
| | - Andrew B Noske
- Institute for Molecular Bioscience, Queensland Bioscience Precinct, The University of Queensland, Brisbane, Queensland, Australia
| | - Leena Haataja
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI
| | - Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI
| | - Bradly J Marsh
- Institute for Molecular Bioscience, Queensland Bioscience Precinct, The University of Queensland, Brisbane, Queensland, Australia
| | - Jotham Austin
- Advanced Electron Microscope Core Facility, The University of Chicago, Chicago, IL
| | - Christopher J Rhodes
- Kovler Diabetes Center, Department of Medicine, Section of Endocrinology, Diabetes and Metabolism, The University of Chicago, Chicago, IL
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18
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Hasnain SZ, Prins JB, McGuckin MA. Oxidative and endoplasmic reticulum stress in β-cell dysfunction in diabetes. J Mol Endocrinol 2016; 56:R33-54. [PMID: 26576641 DOI: 10.1530/jme-15-0232] [Citation(s) in RCA: 179] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 11/17/2015] [Indexed: 12/12/2022]
Abstract
The inability of pancreatic β-cells to make sufficient insulin to control blood sugar is a central feature of the aetiology of most forms of diabetes. In this review we focus on the deleterious effects of oxidative stress and endoplasmic reticulum (ER) stress on β-cell insulin biosynthesis and secretion and on inflammatory signalling and apoptosis with a particular emphasis on type 2 diabetes (T2D). We argue that oxidative stress and ER stress are closely entwined phenomena fundamentally involved in β-cell dysfunction by direct effects on insulin biosynthesis and due to consequences of the ER stress-induced unfolded protein response. We summarise evidence that, although these phenomenon can be driven by intrinsic β-cell defects in rare forms of diabetes, in T2D β-cell stress is driven by a range of local environmental factors including increased drivers of insulin biosynthesis, glucolipotoxicity and inflammatory cytokines. We describe our recent findings that a range of inflammatory cytokines contribute to β-cell stress in diabetes and our discovery that interleukin 22 protects β-cells from oxidative stress regardless of the environmental triggers and can correct much of diabetes pathophysiology in animal models. Finally we summarise evidence that β-cell dysfunction is reversible in T2D and discuss therapeutic opportunities for relieving oxidative and ER stress and restoring glycaemic control.
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Affiliation(s)
- Sumaira Z Hasnain
- ImmunityInfection and Inflammation Program, Mater Research Institute, Translational Research Institute, University of Queensland, 37 Kent Street, Woolloongabba, Brisbane, Queensland 4102, AustraliaMetabolic Diseases ProgramMater Research Institute, The University of Queensland, Translational Research Institute, 37 Kent Street, Woolloongabba, Brisbane, Queensland 4102, Australia
| | - Johannes B Prins
- ImmunityInfection and Inflammation Program, Mater Research Institute, Translational Research Institute, University of Queensland, 37 Kent Street, Woolloongabba, Brisbane, Queensland 4102, AustraliaMetabolic Diseases ProgramMater Research Institute, The University of Queensland, Translational Research Institute, 37 Kent Street, Woolloongabba, Brisbane, Queensland 4102, Australia
| | - Michael A McGuckin
- ImmunityInfection and Inflammation Program, Mater Research Institute, Translational Research Institute, University of Queensland, 37 Kent Street, Woolloongabba, Brisbane, Queensland 4102, AustraliaMetabolic Diseases ProgramMater Research Institute, The University of Queensland, Translational Research Institute, 37 Kent Street, Woolloongabba, Brisbane, Queensland 4102, Australia
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19
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Bogari NM, Rayes HH, Mostafa F, Abdel-Latif AM, Ramadan A, Al-Allaf FA, Taher MM, Fawzy A. A novel SNP in 3' UTR of INS gene: A case report of neonatal diabetes mellitus. Diabetes Res Clin Pract 2015. [PMID: 26212367 DOI: 10.1016/j.diabres.2015.06.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Neonatal diabetes mellitus (NDM) is a rare condition with a prevalence of 1 in 300,000 live births. We have found 3 known SNPs in 5'UTR and a novel SNP in 3' UTR in the INS gene. These SNPs were present in 9-month-old girl from Saudi Arabia and also present in the father and mother. The novel SNP we found is not present in 1000 Genome project or other databases. Further, the newly identified 3' UTR mutation in the INS gene may abolish the polyadenylation signal and result in severe RNA instability.
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Affiliation(s)
- Neda M Bogari
- Department of Medical Genetics, Faculty of Medicine, Umm Al-Qura University, Makkah 21955, Saudi Arabia.
| | - Husni H Rayes
- Department of Pediatrics, Maternity and Children's Hospital, Makkah 21955, Saudi Arabia
| | - Fakri Mostafa
- Department of Pediatrics, Maternity and Children's Hospital, Makkah 21955, Saudi Arabia
| | - Azza M Abdel-Latif
- Division of Human Genetics & Genome Research; Department of Molecular Genetics and Enzymology, National Research Centre, 33 Bohouth St. Dokki, Giza, Egypt
| | - Abeer Ramadan
- Division of Human Genetics & Genome Research; Department of Molecular Genetics and Enzymology, National Research Centre, 33 Bohouth St. Dokki, Giza, Egypt
| | - Faisal A Al-Allaf
- Department of Medical Genetics, Faculty of Medicine, Umm Al-Qura University, Makkah 21955, Saudi Arabia; Science and Technology Unit, Umm Al-Qura University, Makkah 21955, Saudi Arabia; Molecular Diagnostics Unit, Department of Laboratory Medicine and Blood Bank, King Abdullah Medical City, Makkah 21955, Saudi Arabia
| | - Mohiuddin M Taher
- Science and Technology Unit, Umm Al-Qura University, Makkah 21955, Saudi Arabia.
| | - Ahmed Fawzy
- Division of Human Genetics & Genome Research; Department of Molecular Genetics and Enzymology, National Research Centre, 33 Bohouth St. Dokki, Giza, Egypt.
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20
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Handorf AM, Sollinger HW, Alam T. Genetic Engineering of Surrogate <i>β</i> Cells for Treatment of Type 1 Diabetes Mellitus. ACTA ACUST UNITED AC 2015. [DOI: 10.4236/jdm.2015.54037] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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21
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Modi H, Cornu M, Thorens B. Glutamine stimulates biosynthesis and secretion of insulin-like growth factor 2 (IGF2), an autocrine regulator of beta cell mass and function. J Biol Chem 2014; 289:31972-31982. [PMID: 25271169 DOI: 10.1074/jbc.m114.587733] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
IGF2 is an autocrine ligand for the beta cell IGF1R receptor and GLP-1 increases the activity of this autocrine loop by enhancing IGF1R expression, a mechanism that mediates the trophic effects of GLP-1 on beta cell mass and function. Here, we investigated the regulation of IGF2 biosynthesis and secretion. We showed that glutamine rapidly and strongly induced IGF2 mRNA translation using reporter constructs transduced in MIN6 cells and primary islet cells. This was followed by rapid secretion of IGF2 via the regulated pathway, as revealed by the presence of mature IGF2 in insulin granule fractions and by inhibition of secretion by nimodipine and diazoxide. When maximally stimulated by glutamine, the amount of secreted IGF2 rapidly exceeded its initial intracellular pool and tolbutamide, and high K(+) increased IGF2 secretion only marginally. This indicates that the intracellular pool of IGF2 is small and that sustained secretion requires de novo synthesis. The stimulatory effect of glutamine necessitates its metabolism but not mTOR activation. Finally, exposure of insulinomas or beta cells to glutamine induced Akt phosphorylation, an effect that was dependent on IGF2 secretion, and reduced cytokine-induced apoptosis. Thus, glutamine controls the activity of the beta cell IGF2/IGF1R autocrine loop by increasing the biosynthesis and secretion of IGF2. This autocrine loop can thus integrate changes in feeding and metabolic state to adapt beta cell mass and function.
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Affiliation(s)
- Honey Modi
- Center for Integrative Genomics, University of Lausanne, CH-1015 Lausanne, Switzerland
| | - Marion Cornu
- Center for Integrative Genomics, University of Lausanne, CH-1015 Lausanne, Switzerland
| | - Bernard Thorens
- Center for Integrative Genomics, University of Lausanne, CH-1015 Lausanne, Switzerland.
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22
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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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23
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Kaihara KA, Dickson LM, Jacobson DA, Tamarina N, Roe MW, Philipson LH, Wicksteed B. β-Cell-specific protein kinase A activation enhances the efficiency of glucose control by increasing acute-phase insulin secretion. Diabetes 2013; 62:1527-36. [PMID: 23349500 PMCID: PMC3636652 DOI: 10.2337/db12-1013] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Acute insulin secretion determines the efficiency of glucose clearance. Moreover, impaired acute insulin release is characteristic of reduced glucose control in the prediabetic state. Incretin hormones, which increase β-cell cAMP, restore acute-phase insulin secretion and improve glucose control. To determine the physiological role of the cAMP-dependent protein kinase (PKA), a mouse model was developed to increase PKA activity specifically in the pancreatic β-cells. In response to sustained hyperglycemia, PKA activity potentiated both acute and sustained insulin release. In contrast, a glucose bolus enhanced acute-phase insulin secretion alone. Acute-phase insulin secretion was increased 3.5-fold, reducing circulating glucose to 58% of levels in controls. Exendin-4 increased acute-phase insulin release to a similar degree as PKA activation. However, incretins did not augment the effects of PKA on acute-phase insulin secretion, consistent with incretins acting primarily via PKA to potentiate acute-phase insulin secretion. Intracellular calcium signaling was unaffected by PKA activation, suggesting that the effects of PKA on acute-phase insulin secretion are mediated by the phosphorylation of proteins involved in β-cell exocytosis. Thus, β-cell PKA activity transduces the cAMP signal to dramatically increase acute-phase insulin secretion, thereby enhancing the efficiency of insulin to control circulating glucose.
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Affiliation(s)
- Kelly A. Kaihara
- Kovler Diabetes Center, Section of Adult and Pediatric Endocrinology, Diabetes and Metabolism, Department of Medicine, The University of Chicago, Chicago, Illinois
| | - Lorna M. Dickson
- Kovler Diabetes Center, Section of Adult and Pediatric Endocrinology, Diabetes and Metabolism, Department of Medicine, The University of Chicago, Chicago, Illinois
| | - David A. Jacobson
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee
| | - Natalia Tamarina
- Kovler Diabetes Center, Section of Adult and Pediatric Endocrinology, Diabetes and Metabolism, Department of Medicine, The University of Chicago, Chicago, Illinois
| | - Michael W. Roe
- Department of Medicine, Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, New York
| | - Louis H. Philipson
- Kovler Diabetes Center, Section of Adult and Pediatric Endocrinology, Diabetes and Metabolism, Department of Medicine, The University of Chicago, Chicago, Illinois
| | - Barton Wicksteed
- Kovler Diabetes Center, Section of Adult and Pediatric Endocrinology, Diabetes and Metabolism, Department of Medicine, The University of Chicago, Chicago, Illinois
- Corresponding author: Barton Wicksteed,
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Du X, Ounissi-Benkalha H, Loder MK, Rutter GA, Polychronakos C. Overexpression of ZAC impairs glucose-stimulated insulin translation and secretion in clonal pancreatic beta-cells. Diabetes Metab Res Rev 2012; 28:645-53. [PMID: 22865650 PMCID: PMC6101213 DOI: 10.1002/dmrr.2325] [Citation(s) in RCA: 9] [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] [Indexed: 12/25/2022]
Abstract
BACKGROUND ZAC (Zinc finger protein that regulates apoptosis and cell-cycle arrest) is a candidate gene for transient neonatal diabetes mellitus (TNDM). This condition involves severe insulin deficiency at birth that reverses over weeks or months but may relapse with diabetes recurring in later life. ZAC overexpression in transgenic mice has previously been shown to result in complex changes in both beta-cell mass and possibly function. The present study therefore aimed to examine the role of ZAC in beta-cell function in vitro, independent of the confounder of a reduced beta-cell mass at birth. METHODS Overexpression of ZAC was achieved through the tetracycline-regulatable system in the beta-cell line, INS-1. RESULTS We found that ZAC overexpression exerted no significant effect on proliferation in this transformed cell line at any of the glucose concentrations examined. By contrast, glucose-stimulated insulin secretion was impaired through a mechanism downstream of cytosolic Ca(2+) increases. Furthermore, glucose-stimulated proinsulin biosynthesis was inhibited despite an increase in insulin transcript level. Finally, we found that glucose downregulated ZAC expression in both INS-1 cells and primary mouse islets. CONCLUSIONS These results indicate that ZAC is a negative regulator of the acute stimulatory effects of glucose on beta-cells, and provide a possible explanation for both insulin deficiency in the neonate and the later relapse of diabetes in patients with transient neonatal diabetes mellitus cases.
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Affiliation(s)
- Xiaoyu Du
- Division of Pediatric Endocrinology, McGill University Health Center Research Institute (Children's Hospital), Montreal, QC, Canada
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25
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Arvan P, Pietropaolo M, Ostrov D, Rhodes CJ. Islet autoantigens: structure, function, localization, and regulation. Cold Spring Harb Perspect Med 2012; 2:cshperspect.a007658. [PMID: 22908193 DOI: 10.1101/cshperspect.a007658] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Islet autoantigens associated with autoimmune type 1 diabetes (T1D) are expressed in pancreatic β cells, although many show wider patterns of expression in the neuroendocrine system. Within pancreatic β cells, every T1D autoantigen is in one way or another linked to the secretory pathway. Together, these autoantigens play diverse roles in glucose regulation, metabolism of biogenic amines, as well as the regulation, formation, and packaging of secretory granules. The mechanism(s) by which immune tolerance to islet-cell antigens is lost during the development of T1D, remains unclear. Antigenic peptide creation for immune presentation may potentially link to the secretory biology of β cells in a number of ways, including proteasomal digestion of misfolded products, exocytosis and endocytosis of cell-surface products, or antigen release from dying β cells during normal or pathological turnover. In this context, we evaluate the biochemical nature and immunogenicity of the major autoantigens in T1D including (pro)insulin, GAD65, ZnT8, IA2, and ICA69.
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Affiliation(s)
- Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI 48105, USA.
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26
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Lee EK, Kim W, Tominaga K, Martindale JL, Yang X, Subaran SS, Carlson OD, Mercken EM, Kulkarni RN, Akamatsu W, Okano H, Perrone-Bizzozero NI, de Cabo R, Egan JM, Gorospe M. RNA-binding protein HuD controls insulin translation. Mol Cell 2012; 45:826-35. [PMID: 22387028 PMCID: PMC3319250 DOI: 10.1016/j.molcel.2012.01.016] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Revised: 11/21/2011] [Accepted: 01/03/2012] [Indexed: 11/18/2022]
Abstract
Although expression of the mammalian RNA-binding protein HuD was considered to be restricted to neurons, we report that HuD is present in pancreatic β cells, where its levels are controlled by the insulin receptor pathway. We found that HuD associated with a 22-nucleotide segment of the 5' untranslated region (UTR) of preproinsulin (Ins2) mRNA. Modulating HuD abundance did not alter Ins2 mRNA levels, but HuD overexpression decreased Ins2 mRNA translation and insulin production, and conversely, HuD silencing enhanced Ins2 mRNA translation and insulin production. Following treatment with glucose, HuD rapidly dissociated from Ins2 mRNA and enabled insulin biosynthesis. Importantly, HuD-knockout mice displayed higher insulin levels in pancreatic islets, while HuD-overexpressing mice exhibited lower insulin levels in islets and in plasma. In sum, our results identify HuD as a pivotal regulator of insulin translation in pancreatic β cells.
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Affiliation(s)
- Eun Kyung Lee
- Laboratory of Molecular Biology and Immunology, National Institute on Aging-Intramural Research Program, NIH, Baltimore, MD 21224, USA
- Department of Biochemistry, College of Medicine, The Catholic University of Korea, Seoul 137-701, South Korea
| | - Wook Kim
- Laboratory of Clinical Investigation, National Institute on Aging-Intramural Research Program, NIH, Baltimore, MD 21224, USA
| | - Kumiko Tominaga
- Laboratory of Molecular Biology and Immunology, National Institute on Aging-Intramural Research Program, NIH, Baltimore, MD 21224, USA
| | - Jennifer L. Martindale
- Laboratory of Molecular Biology and Immunology, National Institute on Aging-Intramural Research Program, NIH, Baltimore, MD 21224, USA
| | - Xiaoling Yang
- Laboratory of Molecular Biology and Immunology, National Institute on Aging-Intramural Research Program, NIH, Baltimore, MD 21224, USA
| | - Sarah S. Subaran
- Laboratory of Clinical Investigation, National Institute on Aging-Intramural Research Program, NIH, Baltimore, MD 21224, USA
| | - Olga D. Carlson
- Laboratory of Clinical Investigation, National Institute on Aging-Intramural Research Program, NIH, Baltimore, MD 21224, USA
| | - Evi M. Mercken
- Laboratory of Experimental Gerontology, National Institute on Aging-Intramural Research Program, NIH, Baltimore, MD 21224, USA
| | - Rohit N. Kulkarni
- Department of Islet Cell Biology and Regenerative Medicine, Joslin Diabetes Center and Department of Medicine, Harvard Medical School, Boston, MA 02215, USA
| | - Wado Akamatsu
- Department of Physiology, Graduate School of Medicine, Keio University, Shinjuku, Tokyo 160-8582, Japan
| | - Hideyuki Okano
- Department of Physiology, Graduate School of Medicine, Keio University, Shinjuku, Tokyo 160-8582, Japan
| | - Nora I. Perrone-Bizzozero
- Department of Neurosciences, School of Medicine, University of New Mexico, Albuquerque, NM 87131, USA
| | - Rafael de Cabo
- Laboratory of Experimental Gerontology, National Institute on Aging-Intramural Research Program, NIH, Baltimore, MD 21224, USA
| | - Josephine M. Egan
- Laboratory of Clinical Investigation, National Institute on Aging-Intramural Research Program, NIH, Baltimore, MD 21224, USA
| | - Myriam Gorospe
- Laboratory of Molecular Biology and Immunology, National Institute on Aging-Intramural Research Program, NIH, Baltimore, MD 21224, USA
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Staley CA, Huang A, Nattestad M, Oshiro KT, Ray LE, Mulye T, Li ZH, Le T, Stephens JJ, Gomez SR, Moy AD, Nguyen JC, Franz AH, Lin-Cereghino J, Lin-Cereghino GP. Analysis of the 5' untranslated region (5'UTR) of the alcohol oxidase 1 (AOX1) gene in recombinant protein expression in Pichia pastoris. Gene 2012; 496:118-27. [PMID: 22285974 DOI: 10.1016/j.gene.2012.01.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2011] [Revised: 12/31/2011] [Accepted: 01/05/2012] [Indexed: 11/17/2022]
Abstract
Pichia pastoris is a methylotrophic yeast that has been genetically engineered to express over one thousand heterologous proteins valued for industrial, pharmaceutical and basic research purposes. In most cases, the 5' untranslated region (UTR) of the alcohol oxidase 1 (AOX1) gene is fused to the coding sequence of the recombinant gene for protein expression in this yeast. Because the effect of the AOX1 5'UTR on protein expression is not known, site-directed mutagenesis was performed in order to decrease or increase the length of this region. Both of these types of changes were shown to affect translational efficiency, not transcript stability. While increasing the length of the 5'UTR clearly decreased expression of a β-galactosidase reporter in a proportional manner, a deletion analysis demonstrated that the AOX1 5'UTR contains a complex mixture of both positive and negative cis-acting elements, suggesting that the construction of a synthetic 5'UTR optimized for a higher level of expression may be challenging.
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Affiliation(s)
- Chris A Staley
- Department of Biological Sciences, University of the Pacific, Stockton, CA 95211, USA
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28
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Lombardi A, Ulianich L, Treglia AS, Nigro C, Parrillo L, Lofrumento DD, Nicolardi G, Garbi C, Beguinot F, Miele C, Di Jeso B. Increased hexosamine biosynthetic pathway flux dedifferentiates INS-1E cells and murine islets by an extracellular signal-regulated kinase (ERK)1/2-mediated signal transmission pathway. Diabetologia 2012; 55:141-53. [PMID: 22006246 DOI: 10.1007/s00125-011-2315-1] [Citation(s) in RCA: 30] [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: 04/29/2011] [Accepted: 08/25/2011] [Indexed: 11/26/2022]
Abstract
AIMS/HYPOTHESIS Beta cell failure is caused by loss of cell mass, mostly by apoptosis, but also by simple dysfunction (decline of glucose-stimulated insulin secretion, downregulation of specific gene expression). Apoptosis and dysfunction are caused, at least in part, by lipoglucotoxicity. The mechanisms implicated are oxidative stress, increase in the hexosamine biosynthetic pathway (HBP) flux and endoplasmic reticulum (ER) stress. Oxidative stress plays a role in glucotoxicity-induced beta cell dedifferentiation, while glucotoxicity-induced ER stress has been mostly linked to beta cell apoptosis. We sought to clarify whether ER stress caused by increased HBP flux participates in a dedifferentiating response of beta cells, in the absence of relevant apoptosis. METHODS We used INS-1E cells and murine islets. We analysed the unfolded protein response and the expression profile of beta cells by real-time RT-PCR and western blot. The signal transmission pathway elicited by ER stress was investigated by real-time RT-PCR and immunofluorescence. RESULTS Glucosamine and high glucose induced ER stress, but did not decrease cell viability in INS-1E cells. ER stress caused dedifferentiation of beta cells, as shown by downregulation of beta cell markers and of the transcription factor, pancreatic and duodenal homeobox 1. Glucose-stimulated insulin secretion was inhibited. These effects were prevented by the chemical chaperone, 4-phenyl butyric acid. The extracellular signal-regulated kinase (ERK) signal transmission pathway was implicated, since its inhibition prevented the effects induced by glucosamine and high glucose. CONCLUSIONS/INTERPRETATION Glucotoxic ER stress dedifferentiates beta cells, in the absence of apoptosis, through a transcriptional response. These effects are mediated by the activation of ERK1/2.
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Affiliation(s)
- A Lombardi
- Dipartimento di Scienze e Tecnologie Biologiche e Ambientali, Università degli Studi del Salento, 73100 Lecce, Italy
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29
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A small molecule differentiation inducer increases insulin production by pancreatic β cells. Proc Natl Acad Sci U S A 2011; 108:20713-8. [PMID: 22143803 DOI: 10.1073/pnas.1118526109] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
New drugs for preserving and restoring pancreatic β-cell function are critically needed for the worldwide epidemic of type 2 diabetes and the cure for type 1 diabetes. We previously identified a family of neurogenic 3,5-disubstituted isoxazoles (Isx) that increased expression of neurogenic differentiation 1 (NeuroD1, also known as BETA2); this transcription factor functions in neuronal and pancreatic β-cell differentiation and is essential for insulin gene transcription. Here, we probed effects of Isx on human cadaveric islets and MIN6 pancreatic β cells. Isx increased the expression and secretion of insulin in islets that made little insulin after prolonged ex vivo culture and increased expression of neurogenic differentiation 1 and other regulators of islet differentiation and insulin gene transcription. Within the first few hours of exposure, Isx caused biphasic activation of ERK1/2 and increased bulk histone acetylation. Although there was little effect on histone deacetylase activity, Isx increased histone acetyl transferase activity in nuclear extracts. Reconstitution assays indicated that Isx increased the activity of the histone acetyl transferase p300 through an ERK1/2-dependent mechanism. In summary, we have identified a small molecule with antidiabetic activity, providing a tool for exploring islet function and a possible lead for therapeutic intervention in diabetes.
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30
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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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31
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Towns R, Pietropaolo M. GAD65 autoantibodies and its role as biomarker of Type 1 diabetes and Latent Autoimmune Diabetes in Adults (LADA). DRUG FUTURE 2011; 36:847. [PMID: 22869930 DOI: 10.1358/dof.2011.036.11.1710754] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
One of the hallmarks of autoimmune diabetes is the presence of adaptive responses directed to neuroendocrine proteins. One of these proteins is glutamic acid decarboxylase (GAD). While GAD is widely distributed in neuroendocrine tissues, its specific significance in diabetes has paralleled the advances in understanding humoral and cellular immunity in Type 1 diabetes (T1D) and in a subset of Type 2 diabetes (T2D), going from the seminal discoveries of islet autoantibodies to the development and standardization of bioassays as diagnostic tools, to studies on the structure of GAD and its antigenic determinants. GAD65 autoantibodies can accurately predict T1D development in combination with other surrogate humoral biomarkers and they are considered the most sensitive and specific biomarker which identifies a subset of clinically diagnosed T2D termed Latent Autoimmune Diabetes in Adults (LADA). We and others provided evidence indicating that GAD65 autoantibody detection should be part of the diagnostic assessment for clinically diagnosed T2DM mainly because it predicts the rate of progression to insulin requirement in patients affected by LADA. More recently GAD has been used as a "tolerogenic vaccine" to preserve beta cell function in autoimmune diabetes. While the results of Phase III clinical trials did not substantiate the earlier promise of Phase I and II trials, there are still many unanswered questions and approaches that need to be investigated in the applications of GAD in the therapy of T1D and LADA.
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Affiliation(s)
- Roberto Towns
- Laboratory of Immunogenetics, The Brehm Center for Diabetes Research, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan
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32
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Abstract
Eukaryotic cells respond to stress in the endoplasmic reticulum (ER) resulting from insufficient protein folding capacity or altered ER homeostasis by activating the unfolded protein response (UPR). In mammalian cells the UPR is mediated by at least three ER-localized sensors/transducers, and the cellular response and susceptibility to ER stress is likely to be cell-type specific to some degree. Here, we review the response of pancreatic β-cells or islets to ER stress induced by pharmacological agents, misfolded insulin expression, excessive nutrient exposure and in animal models of type 2 diabetes. This review highlights the particular importance of PERK-mediated translational control and the transcriptional response in pancreatic β-cells and how these relate to the highly specialized function of β-cells, namely glucose-regulated insulin secretion and production. We examine how chronic ER stress may prematurely 'age' the β-cell or cause its genetic reprogramming to either reduce its ability to mount a cell survival response to ER stress, or impair normal function. Both could contribute to β-cell failure in diabetes. We also explore the therapeutic potential of targeting the UPR to preserve β-cell function.
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Affiliation(s)
- A Volchuk
- Division of Cellular & Molecular Biology, Toronto General Research Institute, University Health Network, Toronto, Canada.
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33
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Lee EK, Gorospe M. Minireview: posttranscriptional regulation of the insulin and insulin-like growth factor systems. Endocrinology 2010; 151:1403-8. [PMID: 20032049 PMCID: PMC2850238 DOI: 10.1210/en.2009-1123] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Insulin and IGFs share structural similarities and regulate metabolic processes including glucose homeostasis. Acute alterations in glucose levels trigger rapid changes in insulin concentration and insulin signaling. These processes are tightly regulated by posttranscriptional mechanisms that alter the stability and translation of mRNAs encoding insulin and the insulin receptor. Long-term glucose homeostasis is also modulated by IGFs and IGF receptors, whose expression is likewise subject to changes in the stability and translation of the encoding mRNAs. The control of mRNA half-life and translation is governed by RNA-binding proteins and microRNAs that interact with target transcripts at the 3' and 5' untranslated regions. In this review, we describe the RNA-binding proteins and microRNAs that target the mRNAs encoding insulin, IGFs, and their receptors. We discuss how these mRNA-binding factors help to elicit timely, versatile, and tissue-specific changes in insulin and IGF function, thereby effecting critical control of energy metabolism.
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Affiliation(s)
- Eun Kyung Lee
- National Institute on Aging-Intramural Research Program, National Institutes of Health, 251 Bayview Boulevard, Baltimore, Maryland 21224, USA
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34
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Panda AC, Kulkarni SD, Muralidharan B, Bakthavachalu B, Seshadri V. Novel splice variant of mouse insulin2 mRNA: implications for insulin expression. FEBS Lett 2010; 584:1169-73. [PMID: 20153322 DOI: 10.1016/j.febslet.2010.02.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2009] [Revised: 02/04/2010] [Accepted: 02/05/2010] [Indexed: 11/29/2022]
Abstract
Insulin is a secreted peptide that controls glucose homeostasis in mammals, and insulin biosynthesis is regulated by glucose at many levels. Rodent insulin is encoded by two non-allelic genes. We have identified a novel splice variant of the insulin2 gene in mice that constitutes about 75% of total insulin2 mRNA. The alternate splicing does not alter the ORF but reduces the 5'UTR by 12 bases. A reporter gene containing the novel short 5'UTR, is more efficiently expressed in cells, suggesting that alternative splicing of insulin mRNA in mice could result in an additional level of regulation in insulin biosynthesis.
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35
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Recessive mutations in the INS gene result in neonatal diabetes through reduced insulin biosynthesis. Proc Natl Acad Sci U S A 2010; 107:3105-10. [PMID: 20133622 DOI: 10.1073/pnas.0910533107] [Citation(s) in RCA: 145] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Heterozygous coding mutations in the INS gene that encodes preproinsulin were recently shown to be an important cause of permanent neonatal diabetes. These dominantly acting mutations prevent normal folding of proinsulin, which leads to beta-cell death through endoplasmic reticulum stress and apoptosis. We now report 10 different recessive INS mutations in 15 probands with neonatal diabetes. Functional studies showed that recessive mutations resulted in diabetes because of decreased insulin biosynthesis through distinct mechanisms, including gene deletion, lack of the translation initiation signal, and altered mRNA stability because of the disruption of a polyadenylation signal. A subset of recessive mutations caused abnormal INS transcription, including the deletion of the C1 and E1 cis regulatory elements, or three different single base-pair substitutions in a CC dinucleotide sequence located between E1 and A1 elements. In keeping with an earlier and more severe beta-cell defect, patients with recessive INS mutations had a lower birth weight (-3.2 SD score vs. -2.0 SD score) and were diagnosed earlier (median 1 week vs. 10 weeks) compared to those with dominant INS mutations. Mutations in the insulin gene can therefore result in neonatal diabetes as a result of two contrasting pathogenic mechanisms. Moreover, the recessively inherited mutations provide a genetic demonstration of the essential role of multiple sequence elements that regulate the biosynthesis of insulin in man.
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36
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Won JC, Rhee BD, Ko KS. Glucose-responsive gene expression system for gene therapy. Adv Drug Deliv Rev 2009; 61:633-40. [PMID: 19394377 DOI: 10.1016/j.addr.2009.03.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2009] [Accepted: 03/25/2009] [Indexed: 12/30/2022]
Abstract
Regulation of gene expression by glucose is an important mechanism for mammals in adapting to their nutritional environment. Glucose, the primary fuel for most cells, modulates gene expression that is crucial in the cellular adaptation to glycemic variation. Transcription of the genes for insulin and glycolytic and lipogenic enzymes is stimulated by glucose in pancreatic beta-cells and liver. Recent findings further support the key role of the carbohydrate-responsive element binding protein in the regulation of glycolytic and lipogenic genes by glucose and dietary carbohydrates. Herein, we review the transcriptional regulation of glucose-responsive genes, and recent advances in the gene therapy using glucose-responsive gene expression for diabetes.
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Affiliation(s)
- Jong Chul Won
- Department of Internal Medicine, Sanggye Paik Hospital, Mitochondrial Research Group, Inje University College of Medicine, Seoul, Republic of Korea
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Hartley T, Brumell J, Volchuk A. Emerging roles for the ubiquitin-proteasome system and autophagy in pancreatic beta-cells. Am J Physiol Endocrinol Metab 2009; 296:E1-10. [PMID: 18812463 DOI: 10.1152/ajpendo.90538.2008] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Protein degradation in eukaryotic cells is mediated primarily by the ubiquitin-proteasome system and autophagy. Turnover of protein aggregates and other cytoplasmic components, including organelles, is another function attributed to autophagy. The ubiquitin-proteasome system and autophagy are essential for normal cell function but under certain pathological conditions can be overwhelmed, which can lead to adverse effects in cells. In this review we will focus primarily on the insulin-producing pancreatic beta-cell. Pancreatic beta-cells respond to glucose levels by both producing and secreting insulin. The inability of beta-cells to secrete sufficient insulin is a major contributory factor in the development of type 2 diabetes. The aim of this review is to examine some of the crucial roles of the ubiquitin-proteasome system and autophagy in normal pancreatic beta-cell function and how these pathways may become dysfunctional under pathological conditions associated with metabolic syndromes.
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Affiliation(s)
- Taila Hartley
- Division of Cell and Molecular Biology, Toronto General Research Institute, University Health Network, Toronto, ON, M5G 1L7 Canada
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38
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Zhang L, Lai E, Teodoro T, Volchuk A. GRP78, but Not Protein-disulfide Isomerase, Partially Reverses Hyperglycemia-induced Inhibition of Insulin Synthesis and Secretion in Pancreatic {beta}-Cells. J Biol Chem 2008; 284:5289-98. [PMID: 19103594 DOI: 10.1074/jbc.m805477200] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Chronic hyperglycemia contributes to pancreatic beta-cell dysfunction during the development of type 2 diabetes. Treatment of pancreatic beta-cells with prolonged high glucose concentrations has been shown to reduce insulin promoter activity and insulin gene expression. Here, we examined the effect of high glucose on endoplasmic reticulum (ER) stress pathway activation and insulin production in INS-1 832/13 pancreatic beta-cells. Treatment of cells with 25 mm glucose for 24-48 h decreased insulin mRNA and protein levels and reduced the proinsulin translation rate, which was accompanied by enhanced unfolded protein response pathway activation (XBP-1 mRNA splicing and increased phospho-eIF2alpha, CHOP, and active ATF6 levels). Overexpressing the ER chaperone GRP78 partially rescued high glucose-induced suppression of proinsulin levels and improved glucose-stimulated insulin secretion with no effect on insulin 2 mRNA levels. Under these conditions, there was little effect of GRP78 overexpression on ER stress markers. Knockdown of GRP78 expression under basal glucose conditions reduced cellular insulin levels and glucose-stimulated insulin secretion. Thus, GRP78 is essential for insulin biosynthesis, and enhancing chaperone capacity can improve beta-cell function in the presence of prolonged hyperglycemia. In contrast, overexpression of the ER chaperone and oxidoreductase protein-disulfide isomerase (PDI) reduced glucose-stimulated insulin secretion and induced ER stress resulting from the accumulation of proinsulin in the ER. These results suggest a role for both GRP78 and PDI in insulin biosynthesis, although an excess of PDI disrupts normal proinsulin processing.
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Affiliation(s)
- Liling Zhang
- Division of Cell and Molecular Biology, Toronto General Research Institute, University Health Network, Toronto, Ontario M5G 1L7, Canada
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39
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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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Scheuner D, Kaufman RJ. The unfolded protein response: a pathway that links insulin demand with beta-cell failure and diabetes. Endocr Rev 2008; 29:317-33. [PMID: 18436705 PMCID: PMC2528859 DOI: 10.1210/er.2007-0039] [Citation(s) in RCA: 419] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The endoplasmic reticulum (ER) is the entry site into the secretory pathway for newly synthesized proteins destined for the cell surface or released into the extracellular milieu. The study of protein folding and trafficking within the ER is an extremely active area of research that has provided novel insights into many disease processes. Cells have evolved mechanisms to modulate the capacity and quality of the ER protein-folding machinery to prevent the accumulation of unfolded or misfolded proteins. These signaling pathways are collectively termed the unfolded protein response (UPR). The UPR sensors signal a transcriptional response to expand the ER folding capacity, increase degradation of malfolded proteins, and limit the rate of mRNA translation to reduce the client protein load. Recent genetic and biochemical evidence in both humans and mice supports a requirement for the UPR to preserve ER homeostasis and prevent the beta-cell failure that may be fundamental in the etiology of diabetes. Chronic or overwhelming ER stress stimuli associated with metabolic syndrome can disrupt protein folding in the ER, reduce insulin secretion, invoke oxidative stress, and activate cell death pathways. Therapeutic interventions to prevent polypeptide-misfolding, oxidative damage, and/or UPR-induced cell death have the potential to improve beta-cell function and/or survival in the treatment of diabetes.
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Affiliation(s)
- Donalyn Scheuner
- Department of Biological Chemistry, and Howard Hughes Medical Institute, The University of Michigan Medical Center, Ann Arbor, Michigan 48109, USA.
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Uchizono Y, Alarcón C, Wicksteed BL, Marsh BJ, Rhodes CJ. The balance between proinsulin biosynthesis and insulin secretion: where can imbalance lead? Diabetes Obes Metab 2007; 9 Suppl 2:56-66. [PMID: 17919179 DOI: 10.1111/j.1463-1326.2007.00774.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Insulin is stored in pancreatic beta-cells in beta-granules. Whenever insulin is secreted in response to a nutrient secretagogue, there is a complementary increase in proinsulin biosynthesis to replenish intracellular insulin stores. This specific nutrient regulation of proinsulin biosynthesis is predominately regulated at the translational level. Recently, a highly conserved cis-element in the 5'-untranslated region (UTR) of preproinsulin mRNA, named ppIGE, has been identified that is required for specific translational regulation of proinsulin biosynthesis. This ppIGE is also found in the 5'-UTR of certain other translationally regulated beta-granule protein mRNAs, including the proinsulin processing endopeptidases, PC1/3 and PC2. This provides a mechanism whereby proinsulin processing is adaptable to changes in proinsulin biosynthesis. However, relatively few beta-granules undergo secretion, with most remaining in the storage pool for approximately 5 days. Aged beta-granules are retired by intracellular degradation mechanisms, either via crinophagy and/or autophagy, as another long-term means of maintaining beta-granule stores at optimal levels. When a disconnection between insulin production and secretion arises, as may occur in type 2 diabetes, autophagy further increases to maintain beta-granule numbers. However, if this increased autophagy becomes chronic, autophagia-mediated cell death occurs that could then contribute to beta-cell loss in type 2 diabetes.
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Affiliation(s)
- Y Uchizono
- Comprehensive Diabetes Center, Department of Medicine, Section of Endocrinology, Diabetes and Metabolism, The University of Chicago, Chicago, IL 60637, USA
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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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Lawrence MC, McGlynn K, Naziruddin B, Levy MF, Cobb MH. Differential regulation of CHOP-10/GADD153 gene expression by MAPK signaling in pancreatic beta-cells. Proc Natl Acad Sci U S A 2007; 104:11518-25. [PMID: 17615236 PMCID: PMC1913886 DOI: 10.1073/pnas.0704618104] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
CHOP-10 (GADD153/DDIT-3) is a bZIP protein involved in differentiation and apoptosis. Its expression is induced in response to stresses such as nutrient deprivation, perturbation of the endoplasmic reticulum, redox imbalance, and UV exposure. Here we show that CHOP expression is induced in cultured pancreatic beta-cells maintained in a basal glucose concentration of 5.5 mM and repressed by stimulatory glucose (>or=11 mM). Both induction and repression of CHOP are dependent on the MAPKs ERK1 and ERK2. Two regulatory composite sites containing overlapping MafA response elements (MARE) and CAAT enhancer binding (CEB) elements regulate transcription in an ERK1/2-dependent manner. One site (MARE-CEB), from -320 to -300 bp in the promoter, represses transcription. The other site (CEB-MARE), from +2,628 to +2,641 bp in the first intron of the CHOP gene, activates it. MafA can influence transcription of both sites. The MARE-CEB is repressed by MafA, whereas the CEB-MARE site, which is homologous to the A2C1 component of the glucose-sensitive RIPE3b region of the insulin gene promoter, is activated by MafA. These results indicate that ERK1/2 have dual roles in regulating CHOP gene expression via both promoter and intronic regions, depending on environmental and metabolic stresses imposed on pancreatic beta-cells.
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Affiliation(s)
- Michael C. Lawrence
- *Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390; and
| | - Kathleen McGlynn
- *Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390; and
| | - Bashoo Naziruddin
- cGMP Islet Cell Processing Laboratory, Islet Cell Transplant Program, Baylor University Medical Center, Dallas, TX 75246
| | - Marlon F. Levy
- cGMP Islet Cell Processing Laboratory, Islet Cell Transplant Program, Baylor University Medical Center, Dallas, TX 75246
| | - Melanie H. Cobb
- *Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390; and
- To whom correspondence should be addressed at:
Department of Pharmacology, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75390-9041. E-mail:
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