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Ebrahim N, Shakirova K, Dashinimaev E. PDX1 is the cornerstone of pancreatic β-cell functions and identity. Front Mol Biosci 2022; 9:1091757. [PMID: 36589234 PMCID: PMC9798421 DOI: 10.3389/fmolb.2022.1091757] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Accepted: 12/01/2022] [Indexed: 12/23/2022] Open
Abstract
Diabetes has been a worldwide healthcare problem for many years. Current methods of treating diabetes are still largely directed at symptoms, aiming to control the manifestations of the pathology. This creates an overall need to find alternative measures that can impact on the causes of the disease, reverse diabetes, or make it more manageable. Understanding the role of key players in the pathogenesis of diabetes and the related β-cell functions is of great importance in combating diabetes. PDX1 is a master regulator in pancreas organogenesis, the maturation and identity preservation of β-cells, and of their role in normal insulin function. Mutations in the PDX1 gene are correlated with many pancreatic dysfunctions, including pancreatic agenesis (homozygous mutation) and MODY4 (heterozygous mutation), while in other types of diabetes, PDX1 expression is reduced. Therefore, alternative approaches to treat diabetes largely depend on knowledge of PDX1 regulation, its interaction with other transcription factors, and its role in obtaining β-cells through differentiation and transdifferentiation protocols. In this article, we review the basic functions of PDX1 and its regulation by genetic and epigenetic factors. Lastly, we summarize different variations of the differentiation protocols used to obtain β-cells from alternative cell sources, using PDX1 alone or in combination with various transcription factors and modified culture conditions. This review shows the unique position of PDX1 as a potential target in the genetic and cellular treatment of diabetes.
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Affiliation(s)
- Nour Ebrahim
- Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Pirogov Russian National Research Medical University, Moscow, Russia,Moscow Institute of Physics and Technology (State University), Dolgoprudny, Russia
| | - Ksenia Shakirova
- Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Pirogov Russian National Research Medical University, Moscow, Russia
| | - Erdem Dashinimaev
- Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Pirogov Russian National Research Medical University, Moscow, Russia,Moscow Institute of Physics and Technology (State University), Dolgoprudny, Russia,*Correspondence: Erdem Dashinimaev,
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2
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Usher ET, Showalter SA. Biophysical insights into glucose-dependent transcriptional regulation by PDX1. J Biol Chem 2022; 298:102623. [PMID: 36272648 PMCID: PMC9691942 DOI: 10.1016/j.jbc.2022.102623] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Revised: 10/13/2022] [Accepted: 10/14/2022] [Indexed: 11/22/2022] Open
Abstract
The pancreatic and duodenal homeobox 1 (PDX1) is a central regulator of glucose-dependent transcription of insulin in pancreatic β cells. PDX1 transcription factor activity is integral to the development and sustained health of the pancreas; accordingly, deciphering the complex network of cellular cues that lead to PDX1 activation or inactivation is an important step toward understanding the etiopathologies of pancreatic diseases and the development of novel therapeutics. Despite nearly 3 decades of research into PDX1 control of Insulin expression, the molecular mechanisms that dictate the function of PDX1 in response to glucose are still elusive. The transcriptional activation functions of PDX1 are regulated, in part, by its two intrinsically disordered regions, which pose a barrier to its structural and biophysical characterization. Indeed, many studies of PDX1 interactions, clinical mutations, and posttranslational modifications lack molecular level detail. Emerging methods for the quantitative study of intrinsically disordered regions and refined models for transactivation now enable us to validate and interrogate the biochemical and biophysical features of PDX1 that dictate its function. The goal of this review is to summarize existing PDX1 studies and, further, to generate a comprehensive resource for future studies of transcriptional control via PDX1.
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Affiliation(s)
- Emery T Usher
- Center for Eukaryotic Gene Regulation, Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, USA
| | - Scott A Showalter
- Center for Eukaryotic Gene Regulation, Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, USA; Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania, USA.
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3
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Berger C, Zdzieblo D. Glucose transporters in pancreatic islets. Pflugers Arch 2020; 472:1249-1272. [PMID: 32394191 PMCID: PMC7462922 DOI: 10.1007/s00424-020-02383-4] [Citation(s) in RCA: 64] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Revised: 04/20/2020] [Accepted: 04/22/2020] [Indexed: 02/07/2023]
Abstract
The fine-tuning of glucose uptake mechanisms is rendered by various glucose transporters with distinct transport characteristics. In the pancreatic islet, facilitative diffusion glucose transporters (GLUTs), and sodium-glucose cotransporters (SGLTs) contribute to glucose uptake and represent important components in the glucose-stimulated hormone release from endocrine cells, therefore playing a crucial role in blood glucose homeostasis. This review summarizes the current knowledge about cell type-specific expression profiles as well as proven and putative functions of distinct GLUT and SGLT family members in the human and rodent pancreatic islet and further discusses their possible involvement in onset and progression of diabetes mellitus. In context of GLUTs, we focus on GLUT2, characterizing the main glucose transporter in insulin-secreting β-cells in rodents. In addition, we discuss recent data proposing that other GLUT family members, namely GLUT1 and GLUT3, render this task in humans. Finally, we summarize latest information about SGLT1 and SGLT2 as representatives of the SGLT family that have been reported to be expressed predominantly in the α-cell population with a suggested functional role in the regulation of glucagon release.
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Affiliation(s)
- Constantin Berger
- Tissue Engineering & Regenerative Medicine, University Hospital Würzburg, Röntgenring 11, 97070, Würzburg, Germany
| | - Daniela Zdzieblo
- Tissue Engineering & Regenerative Medicine, University Hospital Würzburg, Röntgenring 11, 97070, Würzburg, Germany.
- Fraunhofer Institute for Silicate Research (ISC), Translational Center Regenerative Therapies, Neunerplatz 2, 97082, Würzburg, Germany.
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Aydin S, Sağraç D, Şahin F. Differentiation Potential of Mesenchymal Stem Cells into Pancreatic β-Cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1247:135-156. [PMID: 32002800 DOI: 10.1007/5584_2019_476] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Stem cells having the capability to differentiate into other type of cells and renewing themselves, gained so much importance in recent years. Investigations in stem cells revealed that mesenchymal stem cells can successfully differentiate into other type of cells like adipocytes, hepatocytes, osteocytes, neurocytes and chondrocytes. In addition, these cells can also differentiate into insulin-producing beta cells. Insulin is a crucial hormone for glucose balance of the body. Insufficiency or unavailability of insulin is called diabetes. External insulin intake, as well as pancreas or islet transplantation, is the most basic treatment of diabetes. In vivo and in vitro studies demonstrate that stem cell therapy is also used in the cure of diabetes. Differentiation process of stem cells into beta cells releasing insulin is quite complicated. There are many different reports for the differentiation of stem cells in the literature. The success of differentiation of stem cells into beta cells depends on several factors like the source of stem cells, chemicals added into the differentiation medium and the duration of differentiation protocol. Distinct studies for the differentiation of stem cells into insulin-secreting cells are available in the literature. Moreover, thanks to the superior differentiation capacity of stem cells, they are being preferred in clinical studies. Stem cells were clinically used to heal diabetic ulcer, to increase c-peptide level and insulin secretion in both type 1 and type 2 diabetes. Mesenchymal stem cells having high differentiation potential to insulin-secreting cells are encouraging vehicles for both in vivo and in vitro studies together with clinical trials for diabetes mellitus.
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Affiliation(s)
- Safa Aydin
- Department of Genetics and Bioengineering, Faculty of Engineering, Yeditepe University, İstanbul, Turkey.
| | - Derya Sağraç
- Department of Genetics and Bioengineering, Faculty of Engineering, Yeditepe University, İstanbul, Turkey
| | - Fikrettin Şahin
- Department of Genetics and Bioengineering, Faculty of Engineering, Yeditepe University, İstanbul, Turkey
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Kitamoto T, Sakurai K, Lee EY, Yokote K, Accili D, Miki T. Distinct roles of systemic and local actions of insulin on pancreatic β-cells. Metabolism 2018; 82:100-110. [PMID: 29320716 PMCID: PMC7391221 DOI: 10.1016/j.metabol.2017.12.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Revised: 12/16/2017] [Accepted: 12/31/2017] [Indexed: 12/23/2022]
Abstract
OBJECTIVE Pancreatic β-cell mass and function are critical in glucose homeostasis. Their regulatory mechanisms have been studied principally under experimental conditions of reduced β-cell numbers, such as β-cell ablation and partial pancreatectomy. In the present study, we generated an opposite mouse model with an excessive amount of ectopic β-cells, and analyzed its consequence on β-cell mass and survival. METHODS Mice underwent sub-renal transplantation (SRT) of pseudo-islets generated from a pancreatic β-cell line MIN6 or intra-pancreatic transplantation (IPT) of MIN6 cells, and morphological and functional changes of their endocrine pancreata were analyzed. Cellular fate of pancreatic β-cells after transplantation was traced using RipCre:Rosa26-tdTomato mice. By using MIN6 cells, we evaluated the roles of extracellular glucose, membrane potential, and insulin signaling on β-cell survival. RESULTS SRT mice developed severe, progressive hypoglycemia associated with marked reduction in insulin-positive (Ins+) cell mass and apparent increase in apoptotic Ins+ cells. In in vitro experiments of MIN6 cells, insulin signaling blockade potently induced cell death, suggesting that local insulin action is required for β-cell survival. In fact, IPT (i.e. transplantation close to endogenous β-cells) resulted in fewer apoptotic Ins+ cells compared with those induced by SRT. On the other hand, β-cell mass was decreased in proportion to the decrease in blood glucose levels in both SRT and IPT mice, suggesting a contribution of hypoglycemia induced by systemic hyperinsulinemia. CONCLUSION Insulin plays distinct roles in β-cell survival and β-cell mass regulation through its local and systemic actions on β-cells, respectively.
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Affiliation(s)
- Takumi Kitamoto
- Department of Medical Physiology, Chiba University, Graduate School of Medicine, Chiba 260-8670, Japan; Department of Clinical Cell Biology and Medicine, Chiba University, Graduate School of Medicine, Chiba 260-8670, Japan; Division of Endocrinology, Department of Medicine, Columbia University, New York 10032, USA
| | - Kenichi Sakurai
- Center for Preventive Medical Sciences, Chiba University, Chiba 263-8522, Japan
| | - Eun Young Lee
- Department of Medical Physiology, Chiba University, Graduate School of Medicine, Chiba 260-8670, Japan
| | - Koutaro Yokote
- Department of Clinical Cell Biology and Medicine, Chiba University, Graduate School of Medicine, Chiba 260-8670, Japan
| | - Domenico Accili
- Division of Endocrinology, Department of Medicine, Columbia University, New York 10032, USA
| | - Takashi Miki
- Department of Medical Physiology, Chiba University, Graduate School of Medicine, Chiba 260-8670, Japan.
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Choi J, Kobayashi H, Okuda H, Harada KH, Takeda M, Fujimoto H, Yamane S, Tanaka D, Youssefian S, Inagaki N, Koizumi A. β-cell-specific overexpression of adiponectin receptor 1 does not improve diabetes mellitus in Akita mice. PLoS One 2018; 13:e0190863. [PMID: 29304075 PMCID: PMC5755906 DOI: 10.1371/journal.pone.0190863] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2017] [Accepted: 12/21/2017] [Indexed: 01/09/2023] Open
Abstract
Adiponectin, a metabolically-active cytokine secreted from adipose tissue, is reported to have anti-apoptotic effects on β-cells as well as anti-hyperglycemic effects through adiponectin receptor signaling. However, the anti-apoptotic effects of adiponectin on β-cells have not been confirmed in established diabetic models, and the anti-hyperglycemic effects and their associated signal cascades remain controversial. To investigate the effects of adiponectin on β-cell protection and its down-stream signaling events, we have generated β-cell-specific rat insulin promoter (RIP)-AdipoR1 transgenic mice (AdipoR1 mice), in which the adiponectin receptor, AdipoR1, is overexpressed in β-cells in a manner synchronous with insulin demand. AdipoR1 mice were then mated with Akita mice, a diabetes model in which β-cell apoptosis results from endoplasmic reticulum (ER) stress. AdipoR1 protein expression and localization in islets from AdipoR1 mice as well as in an AdipoR1-transfected mouse insulinoma cell line were confirmed, as was the activation of both AMPK and Akt in AdipoR1 mice by adiponectin. Nevertheless, there were no significant differences in Ad lib feed and fasting blood glucose levels, or in glucose tolerance tests, between Akita mice [Ins2Akita (C96Y) +/- mouse model] and AdipoR1/Akita and from 4 weeks to 10 weeks of age. Similarly, pancreatic insulin contents of AdipoR1/Akita mice were not significantly different from those in Akita mice from 15 to 20 weeks of age, but they were significantly lower than in wild-type mice. Immunostaining for insulin and subsequent electron microscopy showed that β-cell destruction in AdipoR1/Akita mice was not markedly improved in comparison with that in Akita mice. Serum adiponectin concentrations were confirmed to be extremely high (> 30 μg / ml) compared with the Kd value (0.06 μg / ml) in all mouse groups at 15 to 20 weeks of age. Therefore, although the physiological levels of adiponectin are sufficient to activate AMPK and Akt when AdipoR1 is overexpressed in β-cells, yet adiponectin cannot protect β-cells in Akita mice from ER stress-induced destruction.
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Affiliation(s)
- Jungmi Choi
- Department of Health and Environmental Science, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Hatasu Kobayashi
- Department of Health and Environmental Science, Graduate School of Medicine, Kyoto University, Kyoto, Japan
- Department of Biomedical Sciences, College of Life and Health Sciences, Chubu University, Kasugai, Japan
| | - Hiroko Okuda
- Department of Health and Environmental Science, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Kouji H. Harada
- Department of Health and Environmental Science, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Midori Takeda
- Department of Health and Environmental Science, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | | | - Shunsuke Yamane
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Daisuke Tanaka
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Shohab Youssefian
- Laboratory of Molecular Biosciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Nobuya Inagaki
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Akio Koizumi
- Department of Health and Environmental Science, Graduate School of Medicine, Kyoto University, Kyoto, Japan
- * E-mail:
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Ardestani A, Maedler K. MST1: a promising therapeutic target to restore functional beta cell mass in diabetes. Diabetologia 2016; 59:1843-9. [PMID: 27053234 DOI: 10.1007/s00125-016-3892-9] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Accepted: 12/23/2015] [Indexed: 12/31/2022]
Abstract
The loss of insulin-producing beta cells by apoptosis is a hallmark of all forms of diabetes mellitus. Strategies to prevent beta cell apoptosis and dysfunction are urgently needed to restore the insulin-producing cells and to prevent severe diabetes progression. We recently identified the serine/threonine kinase known as mammalian sterile 20-like kinase 1 (MST1) as a critical regulator of apoptotic beta cell death and dysfunction. MST1 activates several apoptotic signalling pathways, which further stimulate its own cleavage, leading to a vicious cycle of cell death. This led us to hypothesise that MST1 signalling is central to the initiation of beta cell death in diabetes. We found that MST1 is strongly activated in a diabetic beta cell and induces not only its death but also directly impairs insulin secretion through promoting proteasomal degradation of key beta cell transcription factor, pancreatic and duodenal homeobox 1 (PDX1), which is critical for insulin production.Pre-clinical studies in various animal models of diabetes have reported that MST1 deficiency remarkably restores normoglycaemia and beta cell function and prevents the development of diabetes. Importantly, MST1 deficiency can revert fully diabetic beta cells to a non-diabetic state. MST1 may serve as a target for the development of novel therapies for diabetes that trigger the cause of the disease, namely, the destruction of the beta cells. The major current focus of our investigation is to identify and test the efficacy of potent inhibitors of this death signalling pathway to protect beta cells against the effects of autoimmune attack in type 1 diabetes and to preserve beta cell mass and function in type 2 diabetes. This review summarises a presentation given at the 'Can we make a better beta cell?' symposium at the 2015 annual meeting of the EASD. It is accompanied by two other reviews on topics from this symposium (by Heiko Lickert and colleagues, DOI: 10.1007/s00125-016-3949-9 , and by Harry Heimberg and colleagues, DOI: 10.1007/s00125-016-3879-6 ) and a commentary by the Session Chair, Shanta Persaud (DOI: 10.1007/s00125-016-3870-2 ).
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Affiliation(s)
- Amin Ardestani
- Islet Biology Laboratory, Centre for Biomolecular Interactions Bremen, University of Bremen, Leobener Straße NW2, Room B2080, 28359, Bremen, Germany.
| | - Kathrin Maedler
- Islet Biology Laboratory, Centre for Biomolecular Interactions Bremen, University of Bremen, Leobener Straße NW2, Room B2080, 28359, Bremen, Germany.
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Niu G, McQuilling JP, Zhou Y, Opara EC, Orlando G, Soker S. In Vitro Proliferation of Porcine Pancreatic Islet Cells for β-Cell Therapy Applications. J Diabetes Res 2016; 2016:5807876. [PMID: 28050568 PMCID: PMC5168554 DOI: 10.1155/2016/5807876] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Revised: 11/04/2016] [Accepted: 11/13/2016] [Indexed: 11/29/2022] Open
Abstract
β-Cell replacement through transplantation is the only curative treatment to establish a long-term stable euglycemia in diabetic patients. Owing to the shortage of donor tissue, attempts are being made to develop alternative sources of insulin-secreting cells. Stem cells differentiation and reprograming as well as isolating pancreatic progenitors from different sources are some examples; however, no approach has yet yielded a clinically relevant solution. Dissociated islet cells that are cultured in cell numbers by in vitro proliferation provide a promising platform for redifferentiation towards β-cells phenotype. In this study, we cultured islet-derived cells in vitro and examined the expression of β-cell genes during the proliferation. Islets were isolated from porcine pancreases and enzymatically digested to dissociate the component cells. The cells proliferated well in tissue culture plates and were subcultured for no more than 5 passages. Only 10% of insulin expression, as measured by PCR, was preserved in each passage. High glucose media enhanced insulin expression by about 4-18 fold, suggesting a glucose-dependent effect in the proliferated islet-derived cells. The islet-derived cells also expressed other pancreatic genes such as Pdx1, NeuroD, glucagon, and somatostatin. Taken together, these results indicate that pancreatic islet-derived cells, proliferated in vitro, retained the expression capacity for key pancreatic genes, thus suggesting that the cells may be redifferentiated into insulin-secreting β-like cells.
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Affiliation(s)
- Guoguang Niu
- Wake Forest Institute for Regenerative Medicine, Wake Forest Baptist Medical Center, Medical Center Boulevard, Winston-Salem, NC 27157, USA
| | - John P. McQuilling
- Wake Forest Institute for Regenerative Medicine, Wake Forest Baptist Medical Center, Medical Center Boulevard, Winston-Salem, NC 27157, USA
| | - Yu Zhou
- Wake Forest Institute for Regenerative Medicine, Wake Forest Baptist Medical Center, Medical Center Boulevard, Winston-Salem, NC 27157, USA
| | - Emmanuel C. Opara
- Wake Forest Institute for Regenerative Medicine, Wake Forest Baptist Medical Center, Medical Center Boulevard, Winston-Salem, NC 27157, USA
| | - Giuseppe Orlando
- Wake Forest Institute for Regenerative Medicine, Wake Forest Baptist Medical Center, Medical Center Boulevard, Winston-Salem, NC 27157, USA
| | - Shay Soker
- Wake Forest Institute for Regenerative Medicine, Wake Forest Baptist Medical Center, Medical Center Boulevard, Winston-Salem, NC 27157, USA
- Virginia Tech, Wake Forest University School of Biomedical Engineering and Sciences, 320 ICTAS, Stanger St., Virginia Tech, Blacksburg, VA 24060, USA
- *Shay Soker:
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Huang HH, Stehno-Bittel L. Differences in insulin biosynthesis pathway between small and large islets do not correspond to insulin secretion. Islets 2015; 7:e1129097. [PMID: 26752360 PMCID: PMC4878277 DOI: 10.1080/19382014.2015.1129097] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
In a variety of mammalian species, small islets secrete more insulin per volume than large islets. This difference may be due to diffusional limitations of large islets, or inherent differences in the insulin production pathways. The purpose of this study was to identify possible differences in the early phase of glucose-stimulated insulin biosynthesis between large and small islets. Isolated small and large rat islets were challenged with 30 minutes of high glucose. The expression of insulin gene transcription factors (MafA, NeuroD/ Beta2, and PDX-1), preproinsulin mRNA, proinsulin and insulin were compared between large and small islets. Under basal (low glucose) conditions, MafA and NeuroD had higher mRNA levels and greater protein amounts in large islets compared to small when normalized to GAPDH levels. 30 minutes of high glucose stimulation failed to alter the mRNA or subsequent protein levels of either gene. However, 30 minutes of high glucose suppressed activated PDX-1 protein levels in both small and large islets. High glucose stimulation did not statistically alter the preproinsulin mRNA (insulin 1 and insulin 2) levels. At the translational level, high glucose increased the proinsulin levels, and large islets showed a higher proinsulin content per cell than small islets. Insulin content per cell was not significantly different between small and large islets under basal or high glucose levels. The results fail to explain the higher level of insulin secretion noted in small versus large islets and may suggest that possible differences lie downstream in the secretory pathway rather than insulin biosynthesis.
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Affiliation(s)
- Han-Hung Huang
- Department of Physical Therapy Angelo State University; Texas Tech System; San Angelo, TX USA
| | - Lisa Stehno-Bittel
- Department of Physical Therapy and Rehabilitation Science; University of Kansas Medical Center; Kansas City, KS USA
- Likarda, LLC; Kansas City, KS USA
- Correspondence to: Lisa Stehno-Bittel;
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Patel MS, Srinivasan M, Strutt B, Mahmood S, Hill DJ. Featured Article: Beta cell specific pyruvate dehydrogenase alpha gene deletion results in a reduced islet number and β-cell mass postnatally. Exp Biol Med (Maywood) 2014; 239:975-985. [PMID: 24845368 DOI: 10.1177/1535370214531895] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The ability of pancreatic β-cells to undertake glucose-stimulated insulin secretion (GSIS) depends on the generation of adenosine triphosphate (ATP) within the mitochondria from pyruvate, a major rate-limiting enzyme being pyruvate dehydrogenase (PDH) complex (PDC). However, glucose metabolism also controls β-cell mass. To examine the role of PDC in the regulation of pancreatic β-cell development and maturation, we generated β-cell-targeted PDHα subunit knock-out male mice (β-PDHKO) and compared these with control males (β-PDHCT) from birth until 6-8 weeks age. Pancreas morphology, transcription factor expression, pancreatic insulin content, and circulating glucose and insulin values were compared. Compared to β-PDHCT male mice, β-PDHKO animals had significantly reduced pancreatic insulin content from birth, a lower serum insulin content from day 15, and relative hyperglycemia from day 30. Isolated islets from β-PDHKO mice demonstrated a reduced GSIS. The number of islets per pancreatic area, mean islet area, and the proportion of islet cells that were β-cells were all reduced in β-PDHKO animals. Similarly the number of insulin-immunopositive, extra-islet small endocrine cell clusters, a possible source of β-cell progenitors, was lower in β-PDHKO mice. Analysis of pancreatic expression of transcription factors responsible for β-cell lineage commitment, proliferation, and maturation, Pdx1, Neurogenin3, and NeuroD1 showed that mRNA abundance was reduced in the β-PDHKO. This demonstrates that PDC is not only required for insulin expression and glucose-stimulated secretion, but also directly influences β-cell growth and maturity, and positions glucose metabolism as a direct regulator of β-cell mass and plasticity.
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Affiliation(s)
- Mulchand S Patel
- Department of Biochemistry, School of Medicine and Biomedical Sciences, University at Buffalo, State University of New York, Buffalo 14214, NY
| | - Malathi Srinivasan
- Department of Biochemistry, School of Medicine and Biomedical Sciences, University at Buffalo, State University of New York, Buffalo 14214, NY
| | - Brenda Strutt
- Lawson Research Institute, St. Joseph's Health Centre, London, Ontario N6A 4V2, Canada
| | - Saleh Mahmood
- Department of Biochemistry, School of Medicine and Biomedical Sciences, University at Buffalo, State University of New York, Buffalo 14214, NY
| | - David J Hill
- Lawson Research Institute, St. Joseph's Health Centre, London, Ontario N6A 4V2, Canada Department of Medicine, Physiology, and Paediatrics, University of Western Ontario, London, Ontario N6A 3K7, Canada
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Semache M, Ghislain J, Zarrouki B, Tremblay C, Poitout V. Pancreatic and duodenal homeobox-1 nuclear localization is regulated by glucose in dispersed rat islets but not in insulin-secreting cell lines. Islets 2014; 6:e982376. [PMID: 25437380 PMCID: PMC4588559 DOI: 10.4161/19382014.2014.982376] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The transcription factor Pancreatic and Duodenal Homeobox-1 (PDX-1) plays a major role in the development and function of pancreatic β-cells and its mutation results in diabetes. In adult β-cells, glucose stimulates transcription of the insulin gene in part by regulating PDX-1 expression, stability and activity. Glucose is also thought to modulate PDX-1 nuclear translocation but in vitro studies examining nucleo-cytoplasmic shuttling of endogenous or ectopically expressed PDX-1 in insulin-secreting cell lines have led to conflicting results. Here we show that endogenous PDX-1 undergoes translocation from the cytoplasm to the nucleus in response to glucose in dispersed rat islets but not in insulin-secreting MIN6, HIT-T15, or INS832/13 cells. Interestingly, however, we found that a PDX-1-GFP fusion protein can shuttle from the cytoplasm to the nucleus in response to glucose stimulation in HIT-T15 cells. Our results suggest that the regulation of endogenous PDX-1 sub-cellular localization by glucose is observed in primary islets and that care should be taken when interpreting data from insulin-secreting cell lines.
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Key Words
- ANOVA, analysis of variance
- BSA, bovine serum albumin
- DAPI, 4′, 6-diamidino-2-phenylindole
- DMEM, dulbecco's modified eagle medium
- EDTA, ethylenediaminetetraacetic acid
- GFP, green fluorescent protein
- HDAC, histone deacetylase
- HIT-T15
- INS832/13
- KRBH, krebs ringer bicarbonate hepes
- MIN6
- MODY, maturity-onset diabetes of the young
- PDX-1
- PDX-1, pancreatic and duodenal homeobox-1
- SEM, standard error of the mean
- SUMO, small ubiquitin-like modifier
- T2D, type 2 diabetes
- ZDF, zucker diabetic fatty
- glucose
- glucose-stimulated insulin secretion
- nucleo-cytoplasmic shuttling
- pancreatic β cells
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Affiliation(s)
- Meriem Semache
- Montreal Diabetes Research Center; CRCHUM; Montreal, QC, Canada
- Department of Biochemistry; University of Montreal; QC, Canada
| | - Julien Ghislain
- Montreal Diabetes Research Center; CRCHUM; Montreal, QC, Canada
| | - Bader Zarrouki
- Montreal Diabetes Research Center; CRCHUM; Montreal, QC, Canada
- Department of Medicine; University of Montreal; QC, Canada
| | | | - Vincent Poitout
- Montreal Diabetes Research Center; CRCHUM; Montreal, QC, Canada
- Department of Biochemistry; University of Montreal; QC, Canada
- Department of Medicine; University of Montreal; QC, Canada
- Correspondence to: Vincent Poitout;
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Semache M, Zarrouki B, Fontés G, Fogarty S, Kikani C, Chawki MB, Rutter J, Poitout V. Per-Arnt-Sim kinase regulates pancreatic duodenal homeobox-1 protein stability via phosphorylation of glycogen synthase kinase 3β in pancreatic β-cells. J Biol Chem 2013; 288:24825-33. [PMID: 23853095 DOI: 10.1074/jbc.m113.495945] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
In pancreatic β-cells, glucose induces the binding of the transcription factor pancreatic duodenal homeobox-1 (PDX-1) to the insulin gene promoter to activate insulin gene transcription. At low glucose levels, glycogen synthase kinase 3β (GSK3β) is known to phosphorylate PDX-1 on C-terminal serine residues, which triggers PDX-1 proteasomal degradation. We previously showed that the serine/threonine Per-Arnt-Sim domain-containing kinase (PASK) regulates insulin gene transcription via PDX-1. However, the mechanisms underlying this regulation are unknown. In this study, we aimed to identify the role of PASK in the regulation of PDX-1 phosphorylation, protein expression, and stability in insulin-secreting cells and isolated rodent islets of Langerhans. We observed that glucose induces a decrease in overall PDX-1 serine phosphorylation and that overexpression of WT PASK mimics this effect. In vitro, PASK directly phosphorylates GSK3β on its inactivating phosphorylation site Ser(9). Overexpression of a kinase-dead (KD), dominant negative version of PASK blocks glucose-induced Ser(9) phosphorylation of GSK3β. Accordingly, GSK3β Ser(9) phosphorylation is reduced in islets from pask-null mice. Overexpression of WT PASK or KD GSK3β protects PDX-1 from degradation and results in increased PDX-1 protein abundance. Conversely, overexpression of KD PASK blocks glucose-induction of PDX-1 protein. We conclude that PASK phosphorylates and inactivates GSK3β, thereby preventing PDX-1 serine phosphorylation and alleviating GSK3β-mediated PDX-1 protein degradation in pancreatic β-cells.
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Affiliation(s)
- Meriem Semache
- Montreal Diabetes Research Center, CRCHUM, Quebec City H1W4A4, Canada
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13
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Lipopolysaccharides impair insulin gene expression in isolated islets of Langerhans via Toll-Like Receptor-4 and NF-κB signalling. PLoS One 2012; 7:e36200. [PMID: 22558381 PMCID: PMC3338606 DOI: 10.1371/journal.pone.0036200] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2012] [Accepted: 04/03/2012] [Indexed: 12/12/2022] Open
Abstract
Background Type 2 diabetes is characterized by pancreatic β-cell dysfunction and is associated with low-grade inflammation. Recent observations suggest that the signalling cascade activated by lipopolysaccharides (LPS) binding to Toll-Like Receptor 4 (TLR4) exerts deleterious effects on pancreatic β-cell function; however, the molecular mechanisms of these effects are incompletely understood. In this study, we tested the hypothesis that LPS alters insulin gene expression via TLR4 and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) in islets. Methodology/Principal Findings A 24-h exposure of isolated human, rat and mouse islets of Langerhans to LPS dose-dependently reduced insulin gene expression. This was associated in mouse and rat islets with decreased mRNA expression of pancreas-duodenum homebox-1 (PDX-1) and mammalian homologue of avian MafA/l-Maf (MafA). Accordingly, LPS exposure also decreased glucose-induced insulin secretion. LPS repression of insulin, PDX-1 and MafA expression, as well as its inhibition of insulin secretion, were not observed in islets from TLR4-deficient mice. LPS inhibition of β-cell gene expression in rat islets was prevented by inhibition of the NF-κB pathway, but not the p38 mitogen-activated protein kinase (p38 MAPK) pathway. Conclusions/Significance Our findings demonstrate that LPS inhibit β-cell gene expression in a TLR4-dependent manner and via NF-κB signaling in pancreatic islets, suggesting a novel mechanism by which the gut microbiota might affect pancreatic β-cell function.
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14
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Cho IS, Jung M, Kwon KS, Moon E, Cho JH, Yoon KH, Kim JW, Lee YD, Kim SS, Suh-Kim H. Deregulation of CREB signaling pathway induced by chronic hyperglycemia downregulates NeuroD transcription. PLoS One 2012; 7:e34860. [PMID: 22509362 PMCID: PMC3318007 DOI: 10.1371/journal.pone.0034860] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Accepted: 03/08/2012] [Indexed: 01/05/2023] Open
Abstract
CREB mediates the transcriptional effects of glucose and incretin hormones in insulin-target cells and insulin-producing β-cells. Although the inhibition of CREB activity is known to decrease the β-cell mass, it is still unknown what factors inversely alter the CREB signaling pathway in β-cells. Here, we show that β-cell dysfunctions occurring in chronic hyperglycemia are not caused by simple inhibition of CREB activity but rather by the persistent activation of CREB due to decreases in protein phophatase PP2A. When freshly isolated rat pancreatic islets were chronically exposed to 25 mM (high) glucose, the PP2A activity was reduced with a concomitant increase in active pCREB. Brief challenges with 15 mM glucose or 30 µM forskolin after 2 hour fasting further increased the level of pCREB and consequently induced the persistent expression of ICER. The excessively produced ICER was sufficient to repress the transcription of NeuroD, insulin, and SUR1 genes. In contrast, when islets were grown in 5 mM (low) glucose, CREB was transiently activated in response to glucose or forskolin stimuli. Thus, ICER expression was transient and insufficient to repress those target genes. Importantly, overexpression of PP2A reversed the adverse effects of chronic hyperglycemia and successfully restored the transient activation of CREB and ICER. Conversely, depletion of PP2A with siRNA was sufficient to disrupt the negative feedback regulation of CREB and induce hyperglycemic phenotypes even under low glucose conditions. Our findings suggest that the failure of the negative feedback regulation of CREB is the primary cause for β-cell dysfunctions under conditions of pathogenic hyperglycemia, and PP2A can be a novel target for future therapies aiming to protect β-cells mass in the late transitional phase of non-insulin dependent type 2 diabetes (NIDDM).
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Affiliation(s)
- In-Su Cho
- Department of Anatomy, Ajou University, Suwon, South Korea
- Graduate Neuroscience Program, Ajou University, Suwon, South Korea
- BK21, Division of Cell Transformation and Restoration, Ajou University, Suwon, South Korea
| | - Miyoung Jung
- Department of Biological Sciences, Ajou University, Suwon, South Korea
| | - Ki-Sun Kwon
- Aging Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon, South Korea
| | - Eunpyo Moon
- Department of Biological Sciences, Ajou University, Suwon, South Korea
| | - Jang-Hyeon Cho
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Kun-Ho Yoon
- Department of Endocrinology, Catholic University, School of Medicine, Seoul, South Korea
| | - Ji-Won Kim
- Department of Endocrinology, Catholic University, School of Medicine, Seoul, South Korea
| | - Young-Don Lee
- Department of Anatomy, Ajou University, Suwon, South Korea
- Molecular Science and Technology, Ajou University, Suwon, South Korea
- Control for Cell Death Regulating Biodrug, Ajou University, Suwon, South Korea
| | - Sung-Soo Kim
- Department of Anatomy, Ajou University, Suwon, South Korea
- Control for Cell Death Regulating Biodrug, Ajou University, Suwon, South Korea
- * E-mail: (HS-K); (S-SK)
| | - Haeyoung Suh-Kim
- Department of Anatomy, Ajou University, Suwon, South Korea
- Graduate Neuroscience Program, Ajou University, Suwon, South Korea
- BK21, Division of Cell Transformation and Restoration, Ajou University, Suwon, South Korea
- * E-mail: (HS-K); (S-SK)
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15
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Noordeen NA, Meur G, Rutter GA, Leclerc I. Glucose-induced nuclear shuttling of ChREBP is mediated by sorcin and Ca(2+) ions in pancreatic β-cells. Diabetes 2012; 61:574-85. [PMID: 22338092 PMCID: PMC3282809 DOI: 10.2337/db10-1329] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Carbohydrate-responsive element-binding protein (ChREBP) is a regulator of pancreatic β-cell gene expression and an important mediator of glucotoxicity. Glucose increases the activity and nuclear localization of ChREBP by still ill-defined mechanisms. Here we reveal, using both MIN6 and primary mouse β-cells, a unique mechanism behind ChREBP nuclear translocation. At low glucose concentrations, ChREBP interacts with sorcin, a penta EF hand Ca(2+) binding protein, and is sequestered in the cytosol. Sorcin overexpression inhibits ChREBP nuclear accumulation at high glucose and reduced the activity of L-type pyruvate kinase (L-PK) and TxNIP promoters, two well-characterized ChREBP target genes. Sorcin inactivation by RNA interference increases ChREBP nuclear localization and in vivo binding to the L-PK promoter at low glucose concentrations. Ca(2+) influx was essential for this process since Ca(2+) chelation with EGTA, or pharmacological inhibition with diazoxide and nifedipine, blocked the effects of glucose. Conversely, mobilization of intracellular Ca(2+) with ATP caused the nuclear accumulation of ChREBP. Finally, sorcin silencing inhibited ATP-induced increases in intracellular Ca(2+) and glucose-stimulated insulin secretion. We therefore conclude that sorcin retains ChREBP in the cytosol at low glucose concentrations and may act as a Ca(2+) sensor for glucose-induced nuclear translocation and the activation of ChREBP-dependent genes.
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Affiliation(s)
| | | | - Guy A. Rutter
- Corresponding authors: Guy A. Rutter, , and Isabelle Leclerc,
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16
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Dai C, Brissova M, Hang Y, Thompson C, Poffenberger G, Shostak A, Chen Z, Stein R, Powers AC. Islet-enriched gene expression and glucose-induced insulin secretion in human and mouse islets. Diabetologia 2012; 55:707-18. [PMID: 22167125 PMCID: PMC3268985 DOI: 10.1007/s00125-011-2369-0] [Citation(s) in RCA: 121] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Accepted: 10/11/2011] [Indexed: 12/23/2022]
Abstract
AIMS/HYPOTHESIS Our understanding of the transcription factors that control the development and function of rodent islet beta cells is advancing rapidly, yet less is known of the role they play in similar processes in human islets. METHODS To characterise the abundance and regulation of key proteins involved in glucose-regulated insulin secretion in human islets, we examined the expression of MAFA, MAFB, GLUT2 (also known as SLC2A2), βGK (also known as GCK) and PDX1 in isolated, highly purified human islets with an intact insulin secretory pattern. We also assessed these features in islets from two different mouse strains (C57BL/6J and FVB). RESULTS Compared with mouse islets, human islets secreted more insulin at baseline glucose (5.6 mmol/l), but less upon stimulation with high glucose (16.7 mmol/l) or high glucose plus 3-isobutyl-1-methyl-xanthine. Human islets had relatively more MAFB than PDX1 mRNA, while mouse islets had relatively more Pdx1 than Mafb mRNA. However, v-maf musculoaponeurotic fibrosarcoma oncogene homologue (MAF) B protein was found in human islet alpha and beta cells. This is unusual as this regulator is only produced in islet alpha cells in adult mice. The expression of insulin, MAFA, βGK and PDX1 was not glucose-regulated in human islets with an intact insulin secretory pattern. CONCLUSIONS/INTERPRETATION Our results suggest that human islets have a distinctive distribution and function of key regulators of the glucose-stimulated insulin secretion pathway, emphasising the urgent need to understand the processes that regulate human islet beta cell function.
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Affiliation(s)
- C. Dai
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Vanderbilt University, 7435 MRBIV, Nashville, TN 37232 USA
| | - M. Brissova
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Vanderbilt University, 7435 MRBIV, Nashville, TN 37232 USA
| | - Y. Hang
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN USA
| | - C. Thompson
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Vanderbilt University, 7435 MRBIV, Nashville, TN 37232 USA
| | - G. Poffenberger
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Vanderbilt University, 7435 MRBIV, Nashville, TN 37232 USA
| | - A. Shostak
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Vanderbilt University, 7435 MRBIV, Nashville, TN 37232 USA
| | - Z. Chen
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Vanderbilt University, 7435 MRBIV, Nashville, TN 37232 USA
| | - R. Stein
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN USA
| | - A. C. Powers
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Vanderbilt University, 7435 MRBIV, Nashville, TN 37232 USA
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN USA
- VA Tennessee Valley Healthcare System, Nashville, TN USA
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17
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Meur G, Qian Q, da Silva Xavier G, Pullen TJ, Tsuboi T, McKinnon C, Fletcher L, Tavaré JM, Hughes S, Johnson P, Rutter GA. Nucleo-cytosolic shuttling of FoxO1 directly regulates mouse Ins2 but not Ins1 gene expression in pancreatic beta cells (MIN6). J Biol Chem 2011; 286:13647-56. [PMID: 21335550 PMCID: PMC3075709 DOI: 10.1074/jbc.m110.204248] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2010] [Revised: 02/14/2011] [Indexed: 01/26/2023] Open
Abstract
The Forkhead box transcription factor FoxO1 regulates metabolic gene expression in mammals. FoxO1 activity is tightly controlled by phosphatidylinositol 3-kinase (PI3K) signaling, resulting in its phosphorylation and nuclear exclusion. We sought here to determine the mechanisms involved in glucose and insulin-stimulated nuclear shuttling of FoxO1 in pancreatic β cells and its consequences for preproinsulin (Ins1, Ins2) gene expression. Nuclear-localized endogenous FoxO1 translocated to the cytosol in response to elevated glucose (3 versus 16.7 mM) in human islet β cells. Real-time confocal imaging of nucleo-cytosolic shuttling of a FoxO1-EGFP chimera in primary mouse and clonal MIN6 β cells revealed a time-dependent glucose-responsive nuclear export, also mimicked by exogenous insulin, and blocked by suppressing insulin secretion. Constitutively active PI3K or protein kinase B/Akt exerted similar effects, while inhibitors of PI3K, but not of glycogen synthase kinase-3 or p70 S6 kinase, blocked nuclear export. FoxO1 overexpression reversed the activation by glucose of pancreatic duodenum homeobox-1 (Pdx1) transcription. Silencing of FoxO1 significantly elevated the expression of mouse Ins2, but not Ins1, mRNA at 3 mM glucose. Putative FoxO1 binding sites were identified in the distal promoter of rodent Ins2 genes and direct binding of FoxO1 to the Ins2 promoter was demonstrated by chromatin immunoprecipitation. A 915-bp glucose-responsive Ins2 promoter was inhibited by constitutively active FoxO1, an effect unaltered by simultaneous overexpression of PDX1. We conclude that nuclear import of FoxO1 contributes to the suppression of Pdx1 and Ins2 gene expression at low glucose, the latter via a previously unsuspected and direct physical interaction with the Ins2 promoter.
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Affiliation(s)
- Gargi Meur
- From the Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Faculty of Medicine, Imperial College London, London SW7 2AZ, United Kingdom
| | - Qingwen Qian
- From the Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Faculty of Medicine, Imperial College London, London SW7 2AZ, United Kingdom
| | - Gabriela da Silva Xavier
- From the Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Faculty of Medicine, Imperial College London, London SW7 2AZ, United Kingdom
| | - Timothy J. Pullen
- From the Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Faculty of Medicine, Imperial College London, London SW7 2AZ, United Kingdom
| | - Takashi Tsuboi
- the Department of Life Sciences, University of Tokyo, Tokyo 153-8902, Japan
| | - Caroline McKinnon
- From the Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Faculty of Medicine, Imperial College London, London SW7 2AZ, United Kingdom
- the Henry Wellcome Laboratories for Integrated Cell Signalling and Department of Biochemistry, School of Medical Sciences, University Walk, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Laura Fletcher
- the Henry Wellcome Laboratories for Integrated Cell Signalling and Department of Biochemistry, School of Medical Sciences, University Walk, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Jeremy M. Tavaré
- the Henry Wellcome Laboratories for Integrated Cell Signalling and Department of Biochemistry, School of Medical Sciences, University Walk, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Stephen Hughes
- the Nuffield Department of Surgery, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom, and
| | - Paul Johnson
- the Nuffield Department of Surgery, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom, and
| | - Guy A. Rutter
- From the Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Faculty of Medicine, Imperial College London, London SW7 2AZ, United Kingdom
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18
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Ardestani A, Sauter NS, Paroni F, Dharmadhikari G, Cho JH, Lupi R, Marchetti P, Oberholzer J, Conte JK, Maedler K. Neutralizing interleukin-1beta (IL-1beta) induces beta-cell survival by maintaining PDX1 protein nuclear localization. J Biol Chem 2011; 286:17144-55. [PMID: 21393239 DOI: 10.1074/jbc.m110.210526] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The transcription factor PDX1 plays a critical role during β-cell development and in glucose-induced insulin gene transcription in adult β-cells. Acute glucose exposure leads to translocalization of PDX1 to the nucleoplasm, whereas under conditions of oxidative stress, PDX1 shuttles from the nucleus to the cytosol. Here we show that cytosolic PDX1 expression correlated with β-cell failure in diabetes. In isolated islets from patients with type 2 diabetes and from diabetic mice, we found opposite regulation of insulin and PDX1 mRNA; insulin was decreased in diabetes, but PDX1 was increased. This suggests that elevated PDX1 mRNA levels may be insufficient to regulate insulin. In diabetic islets, PDX1 protein was localized in the cytosol, whereas in non-diabetic controls, PDX1 was in the nucleus. In contrast, overexpression of either IL-1 receptor antagonist or shuttling-deficient PDX1 restored β-cell survival and function and PDX1 nuclear localization. Our results show that nuclear localization of PDX1 is essential for a functional β-cell and provides a novel mechanism of the protective effect of IL-1 receptor antagonist on β-cell survival and function.
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Affiliation(s)
- Amin Ardestani
- Islet Biology Laboratory, Centre for Biomolecular Interactions Bremen 28355, University of Bremen, Leobener Strasse NW2, Rm. B2080, 28359 Bremen, Germany
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19
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Ryu GR, Yoo JM, Lee E, Ko SH, Ahn YB, Song KH. Decreased Expression and Induced Nucleocytoplasmic Translocation of Pancreatic and Duodenal Homeobox 1 in INS-1 Cells Exposed to High Glucose and Palmitate. Diabetes Metab J 2011; 35:65-71. [PMID: 21537415 PMCID: PMC3080567 DOI: 10.4093/dmj.2011.35.1.65] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2010] [Accepted: 09/28/2010] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND Type 2 diabetes mellitus (T2DM) is often accompanied by increased levels of circulating fatty acid. Elevations in fatty acids and glucose for prolonged periods of time have been suggested to cause progressive dysfunction or apoptosis of pancreatic beta cells in T2DM. However, the precise mechanism of this adverse effect is not well understood. METHODS INS-1 rat-derived insulin-secreting cells were exposed to 30 mM glucose and 0.25 mM palmitate for 48 hours. RESULTS The production of reactive oxygen species increased significantly. Pancreatic and duodenal homeobox 1 (Pdx1) expression was down-regulated, as assessed by reverse transcription-polymerase chain reaction and Western blot analyses. The promoter activities of insulin and Pdx1 were also diminished. Of note, there was nucleocytoplasmic translocation of Pdx1, which was partially prevented by treatment with an antioxidant, N-acetyl-L-cysteine. CONCLUSION Our data suggest that prolonged exposure of beta cells to elevated levels of glucose and palmitate negatively affects Pdx1 expression via oxidative stress.
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Affiliation(s)
- Gyeong Ryul Ryu
- Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea
| | - Jun Mo Yoo
- Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea
| | - Esder Lee
- Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea
| | - Seung-Hyun Ko
- Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea
| | - Yu-Bae Ahn
- Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea
| | - Ki-Ho Song
- Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea
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20
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Stein R. Insulin Gene Transcription: Factors Involved in Cell Type–Specific and Glucose‐Regulated Expression in Islet β Cells are Also Essential During Pancreatic Development. Compr Physiol 2011. [DOI: 10.1002/cphy.cp070202] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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21
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Wolf G, Hessabi B, Karkour A, Henrion U, Dahlhaus M, Ostmann A, Giese B, Fraunholz M, Grabarczyk P, Jack R, Walther R. The activation of the rat insulin gene II by BETA2 and PDX-1 in rat insulinoma cells is repressed by Pax6. Mol Endocrinol 2010; 24:2331-42. [PMID: 20943817 DOI: 10.1210/me.2009-0220] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The transcriptional transactivator Pax6 binds the pancreatic islet cell-specific enhancer sequence (PISCES) of the rat insulin I gene. However the human, mouse, and rat insulin gene II promoters do not contain a PISCES element. To analyze the role of Pax6 in those PISCES-less promoters, we investigated its influence on rat insulin gene II expression and included in our studies the main activators: pancreatic and duodenal homeobox protein-1 (PDX-1) and BETA2/E47. Luciferase assays, Northern blots, and RIA were used to study effects of Pax6 overexpression, gel shift and chromatin precipitation assays to study its binding to the DNA, and yeast two-hybrid assays and glutathione S transferase capture assays to investigate its interactions with PDX-1 and BETA2. Finally, glucose-dependent intracellular transport of Pax6 was demonstrated by fluorescence microscopy. Overexpression of Pax6 prevents activation of the rat insulin II gene by BETA2 and PDX-1 and hence suppresses insulin synthesis and secretion. In vitro, Pax6 binds to the A-boxes, thereby blocking binding of PDX-1, and at the same time, its paired domain interacts with BETA2. Fluorescence microscopy demonstrated that the nuclear-cytoplasmic localization of Pax6 and PDX-1 are oppositely regulated by glucose. From the results, it is suggested that at low concentrations of glucose, Pax6 is localized in the nucleus and prevents the activation of the insulin gene by occupying the PDX-1 binding site and by interacting with BETA2.
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Affiliation(s)
- Gabriele Wolf
- Department of Medical Biochemistry and Molecular Biology, University of Greifswald, Klinikum, Greifswald, Germany
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22
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An R, da Silva Xavier G, Semplici F, Vakhshouri S, Hao HX, Rutter J, Pagano MA, Meggio F, Pinna LA, Rutter GA. Pancreatic and duodenal homeobox 1 (PDX1) phosphorylation at serine-269 is HIPK2-dependent and affects PDX1 subnuclear localization. Biochem Biophys Res Commun 2010; 399:155-61. [PMID: 20637728 PMCID: PMC2958310 DOI: 10.1016/j.bbrc.2010.07.035] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2010] [Accepted: 07/12/2010] [Indexed: 01/04/2023]
Abstract
Pancreatic and duodenal homeobox 1 (PDX1) regulates pancreatic development and mature beta-cell function. We demonstrate by mass spectrometry that serine residue at position 269 in the C-terminal domain of PDX1 is phosphorylated in beta-cells. Besides we show that the degree of phosphorylation, assessed with a phospho-Ser-269-specific antibody, is decreased by elevated glucose concentrations in both MIN6 beta-cells and primary mouse pancreatic islets. Homeodomain interacting protein kinase 2 (HIPK2) phosphorylates PDX1 in vitro; phosphate incorporation substantially decreases in PDX1 S269A mutant. Silencing of HIPK2 led to a 51+/-0.2% decrease in Ser-269 phosphorylation in MIN6 beta-cells. Mutation of Ser-269 to phosphomimetic residue glutamic acid (S269E) or de-phosphomimetic residue alanine (S269A) exerted no effect on PDX1 half-life. Instead, PDX1 S269E mutant displayed abnormal changes in subnuclear localization in response to high glucose. Our results suggest that HIPK2-mediated phosphorylation of PDX1 at Ser-269 might be a regulatory mechanism connecting signals generated by changes in extracellular glucose concentration to downstream effectors via changes in subnuclear localization of PDX1, thereby influencing islet cell differentiation and function.
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Affiliation(s)
- Rong An
- Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, London SW7 2AZ, UK
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23
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Islet beta-cell-specific MafA transcription requires the 5'-flanking conserved region 3 control domain. Mol Cell Biol 2010; 30:4234-44. [PMID: 20584984 DOI: 10.1128/mcb.01396-09] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
MafA is a key transcriptional activator of islet beta cells, and its exclusive expression within beta cells of the developing and adult pancreas is distinct among pancreatic regulators. Region 3 (base pairs -8118 to -7750 relative to the transcription start site), one of six conserved 5' cis domains of the MafA promoter, is capable of directing beta-cell-line-selective expression. Transgenic reporters of region 3 alone (R3), sequences spanning regions 1 to 6 (R1-6; base pairs -10428 to +230), and R1-6 lacking R3 (R1-6(DeltaR3)) were generated. Only the R1-6 transgene was active in MafA(+) insulin(+) cells during development and in adult cells. R1-6 also mediated glucose-induced MafA expression. Conversely, pancreatic expression was not observed with the R3 or R1-6(DeltaR3) line, although much of the nonpancreatic expression pattern was shared between the R1-6 and R1-6(DeltaR3) lines. Further support for the importance of R3 was also shown, as the islet regulators Nkx6.1 and Pax6, but not NeuroD1, activated MafA in gel shift, chromatin immunoprecipitation (ChIP), and transfection assays and in vivo mouse knockout models. Lastly, ChIP demonstrated that Pax6 and Pdx-1 also bound to R1 and R6, potentially functioning in pancreatic and nonpancreatic expression. These data highlight the nature of the cis- and trans-acting factors controlling the beta-cell-specific expression of MafA.
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Transcriptional regulation of glucose sensors in pancreatic β-cells and liver: an update. SENSORS 2010; 10:5031-53. [PMID: 22399922 PMCID: PMC3292162 DOI: 10.3390/s100505031] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/01/2010] [Revised: 05/07/2010] [Accepted: 05/13/2010] [Indexed: 01/17/2023]
Abstract
Pancreatic β-cells and the liver play a key role in glucose homeostasis. After a meal or in a state of hyperglycemia, glucose is transported into the β-cells or hepatocytes where it is metabolized. In the β-cells, glucose is metabolized to increase the ATP:ADP ratio, resulting in the secretion of insulin stored in the vesicle. In the hepatocytes, glucose is metabolized to CO(2), fatty acids or stored as glycogen. In these cells, solute carrier family 2 (SLC2A2) and glucokinase play a key role in sensing and uptaking glucose. Dysfunction of these proteins results in the hyperglycemia which is one of the characteristics of type 2 diabetes mellitus (T2DM). Thus, studies on the molecular mechanisms of their transcriptional regulations are important in understanding pathogenesis and combating T2DM. In this paper, we will review a recent update on the progress of gene regulation of glucose sensors in the liver and β-cells.
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Zhang X, Yong W, Lv J, Zhu Y, Zhang J, Chen F, Zhang R, Yang T, Sun Y, Han X. Inhibition of forkhead box O1 protects pancreatic beta-cells against dexamethasone-induced dysfunction. Endocrinology 2009; 150:4065-73. [PMID: 19443572 DOI: 10.1210/en.2009-0343] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Forkhead Box O1 (FoxO1) is a key transcription regulator of insulin/IGF-I signaling pathway, and its activity can be increased by dexamethasone (DEX) in several cell types. However, the role of FoxO1 in DEX-induced pancreatic beta-cell dysfunction has not been fully understood. Therefore, in this study, we investigated whether FoxO1 could mediate DEX-induced beta-cell dysfunction and the possible underlying mechanisms in pancreatic beta-cell line RINm5F cells and primary rat islet. We found that DEX markedly increased FoxO1 mRNA and protein expression and decreased FoxO1 phosphorylation through the Akt pathway, which resulted in an increase in active FoxO1 in RINm5F cells and isolated rat islets. Activated FoxO1 subsequently inhibited pancreatic duodenal homeobox-1 expression and induced nuclear exclusion of pancreatic duodenal homeobox-1. Knockdown of FoxO1 by RNA interference restored the expression of pancreatic duodenal homeobox-1 and prevented DEX-induced dysfunction of glucose-stimulated insulin secretion in rat islets. Together, the results of present study demonstrate that FoxO1 is integrally involved in DEX-induced inhibition of pancreatic duodenal homeobox-1 and glucose-stimulated insulin secretion dysfunction in pancreatic islet beta-cells. Inhibition of FoxO1 can effectively protect beta-cells against DEX-induced dysfunction.
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Affiliation(s)
- Xiongfei Zhang
- Key Laboratory of Human Functional Genomics of Jiangsu Province, Nanjing Medical University, Nanjing 210029, People's Republic of China
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26
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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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27
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Prokocimer M, Davidovich M, Nissim-Rafinia M, Wiesel-Motiuk N, Bar DZ, Barkan R, Meshorer E, Gruenbaum Y. Nuclear lamins: key regulators of nuclear structure and activities. J Cell Mol Med 2009; 13:1059-85. [PMID: 19210577 PMCID: PMC4496104 DOI: 10.1111/j.1582-4934.2008.00676.x] [Citation(s) in RCA: 205] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2008] [Accepted: 01/19/2009] [Indexed: 11/27/2022] Open
Abstract
The nuclear lamina is a proteinaceous structure located underneath the inner nuclear membrane (INM), where it associates with the peripheral chromatin. It contains lamins and lamin-associated proteins, including many integral proteins of the INM, chromatin modifying proteins, transcriptional repressors and structural proteins. A fraction of lamins is also present in the nucleoplasm, where it forms stable complexes and is associated with specific nucleoplasmic proteins. The lamins and their associated proteins are required for most nuclear activities, mitosis and for linking the nucleoplasm to all major cytoskeletal networks in the cytoplasm. Mutations in nuclear lamins and their associated proteins cause about 20 different diseases that are collectively called laminopathies'. This review concentrates mainly on lamins, their structure and their roles in DNA replication, chromatin organization, adult stem cell differentiation, aging, tumorogenesis and the lamin mutations leading to laminopathic diseases.
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Affiliation(s)
- Miron Prokocimer
- Department of Genetics, The Institute of Life Sciences, The Hebrew University of JerusalemJerusalem, Israel
| | - Maya Davidovich
- Department of Genetics, The Institute of Life Sciences, The Hebrew University of JerusalemJerusalem, Israel
| | - Malka Nissim-Rafinia
- Department of Genetics, The Institute of Life Sciences, The Hebrew University of JerusalemJerusalem, Israel
| | - Naama Wiesel-Motiuk
- Department of Genetics, The Institute of Life Sciences, The Hebrew University of JerusalemJerusalem, Israel
| | - Daniel Z Bar
- Department of Genetics, The Institute of Life Sciences, The Hebrew University of JerusalemJerusalem, Israel
| | - Rachel Barkan
- Department of Genetics, The Institute of Life Sciences, The Hebrew University of JerusalemJerusalem, Israel
| | - Eran Meshorer
- Department of Genetics, The Institute of Life Sciences, The Hebrew University of JerusalemJerusalem, Israel
| | - Yosef Gruenbaum
- Department of Genetics, The Institute of Life Sciences, The Hebrew University of JerusalemJerusalem, Israel
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28
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Jin CX, Li WL, Xu F, Geng ZH, He ZY, Su J, Tao XR, Ding XY, Wang X, Hu YP. Conversion of immortal liver progenitor cells into pancreatic endocrine progenitor cells by persistent expression of Pdx-1. J Cell Biochem 2008; 104:224-36. [PMID: 17979180 DOI: 10.1002/jcb.21617] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The conversion of expandable liver progenitor cells into pancreatic beta cells would provide a renewable cell source for diabetes cell therapy. Previously, we reported the establishment of liver epithelial progenitor cells (LEPCs). In this work, LEPCs were modified into EGFP/Pdx-1 LEPCs, cells with stable expression of both Pdx-1 and EGFP. Unlike previous work, with persistent expression of Pdx-1, EGFP/Pdx-1 LEPCs acquired the phenotype of pancreatic endocrine progenitor cells rather than giving rise to insulin-producing cells directly. EGFP/Pdx-1 LEPCs proliferated vigorously and expressed the crucial transcription factors involved in beta cell development, including Ngn3, NeuroD, Nkx2.2, Nkx6.1, Pax4, Pax6, Isl1, MafA and endogenous Pdx-1, but did not secrete insulin. When cultured in high glucose/low serum medium supplemented with cytokines, EGFP/Pdx-1 LEPCs stopped proliferating and gave rise to functional beta cells without any evidence of exocrine or other islet cell lineage differentiation. When transplanted into diabetic SCID mice, EGFP/Pdx-1 LEPCs ameliorated hyperglycemia by secreting insulin in a glucose regulated manner. Considering the limited availability of beta cells, we propose that our experiments will provide a framework for utilizing the immortal liver progenitor cells as a renewable cell source for the generation of functional pancreatic beta cells.
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Affiliation(s)
- Cai-Xia Jin
- Department of Cell Biology, Second Military Medical University, Shanghai 200433, P. R. China
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29
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Pannier AK, Ariazi EA, Bellis AD, Bengali Z, Jordan VC, Shea LD. Bioluminescence imaging for assessment and normalization in transfected cell arrays. Biotechnol Bioeng 2008; 98:486-97. [PMID: 17486653 PMCID: PMC2648395 DOI: 10.1002/bit.21477] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Transfected cell arrays (TCAs) represent a high-throughput technique to correlate gene expression with functional cell responses. Despite advances in TCAs, improvements are needed for the widespread application of this technology. We have developed a TCA that combines a two-plasmid system and dual-bioluminescence imaging to quantitatively normalize for variability in transfection and increase sensitivity. The two-plasmids consist of: (i) normalization plasmid present within each spot, and (ii) functional plasmid that varies between spots, responsible for the functional endpoint of the array. Bioluminescence imaging of dual-luciferase reporters (renilla, firefly luciferase) provides sensitive and quantitative detection of cellular response, with minimal post-transfection processing. The array was applied to quantify estrogen receptor alpha (ERalpha) activity in MCF-7 breast cancer cells. A plasmid containing an ERalpha-regulated promoter directing firefly luciferase expression was mixed with a normalization plasmid, complexed with cationic lipids and deposited into an array. ER induction mimicked results obtained through traditional assays methods, with estrogen inducing luciferase expression 10-fold over the antiestrogen fulvestrant or vehicle. Furthermore, the array captured a dose response to estrogen, demonstrating the sensitivity of bioluminescence quantification. This system provides a tool for basic science research, with potential application for the development of patient specific therapies.
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Affiliation(s)
- Angela K. Pannier
- Department of Interdepartmental Biological Sciences, Northwestern University, Evanston, Illinois
| | | | - Abigail D. Bellis
- Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Rd E156, Evanston, Illinois 60208-3120; telephone: 847-491-7043; fax: 847-491-3728; e-mail:
| | - Zain Bengali
- Department of Interdepartmental Biological Sciences, Northwestern University, Evanston, Illinois
| | | | - Lonnie D. Shea
- Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Rd E156, Evanston, Illinois 60208-3120; telephone: 847-491-7043; fax: 847-491-3728; e-mail:
- Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Chicago, Illinois 60611
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30
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Diraison F, Ravier MA, Richards SK, Smith RM, Shimano H, Rutter GA. SREBP1 is required for the induction by glucose of pancreatic beta-cell genes involved in glucose sensing. J Lipid Res 2008; 49:814-22. [PMID: 18178930 DOI: 10.1194/jlr.m700533-jlr200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Previous studies have reported both positive and negative effects of culture of islets at high glucose concentrations on regulated insulin secretion. Here, we have reexamined this question in mouse islets and determined the role of changes in lipid synthesis in the effects of glucose. Glucose-stimulated insulin secretion (GSIS) and gene expression were examined in islets from C57BL/6 mice or littermates deleted for sterol-regulatory element binding protein-1 (SREBP1) after 4 days of culture at high glucose concentrations. Culture of control islets at 30 versus 8 mmol/l glucose led to enhanced secretion at both basal (3 mmol/l) and stimulatory (17 mmol/l) glucose concentrations and to enhanced triacylglycerol accumulation. These changes were associated with increases in the expression of genes involved in glucose sensing (glucose transporter 2, glucokinase, sulfonylurea receptor 1, inwardly rectifying K(+) channel 6.2), differentiation (pancreatic duodenal homeobox 1), and lipogenesis (Srebp1, fatty acid synthase, acetyl-coenzyme A carboxylase 1, stearoyl-coenzyme A desaturase 1). When cultured at either 8 or 30 mmol/l glucose, SREBP1-deficient (SREBP1(-/-)) islets displayed reduced GSIS and triacylglycerol content compared with normal islets. Correspondingly, glucose induction of the above genes in control islets was no longer observed in SREBP1(-/-) mouse islets. We conclude that enhanced lipid synthesis mediated by SREBP1c-dependent genes is required for the adaptive changes in islet gene expression and insulin secretion at high glucose concentrations.
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Affiliation(s)
- Frederique Diraison
- Department of Cell Biology, Division of Medicine, Faculty of Medicine, Imperial College, London SW72A2, UK
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31
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Doyle ME, Egan JM. Mechanisms of action of glucagon-like peptide 1 in the pancreas. Pharmacol Ther 2007; 113:546-93. [PMID: 17306374 PMCID: PMC1934514 DOI: 10.1016/j.pharmthera.2006.11.007] [Citation(s) in RCA: 485] [Impact Index Per Article: 28.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2006] [Accepted: 11/27/2006] [Indexed: 12/13/2022]
Abstract
Glucagon-like peptide 1 (GLP-1) is a hormone that is encoded in the proglucagon gene. It is mainly produced in enteroendocrine L cells of the gut and is secreted into the blood stream when food containing fat, protein hydrolysate, and/or glucose enters the duodenum. Its particular effects on insulin and glucagon secretion have generated a flurry of research activity over the past 20 years culminating in a naturally occurring GLP-1 receptor (GLP-1R) agonist, exendin 4 (Ex-4), now being used to treat type 2 diabetes mellitus (T2DM). GLP-1 engages a specific guanine nucleotide-binding protein (G-protein) coupled receptor (GPCR) that is present in tissues other than the pancreas (brain, kidney, lung, heart, and major blood vessels). The most widely studied cell activated by GLP-1 is the insulin-secreting beta cell where its defining action is augmentation of glucose-induced insulin secretion. Upon GLP-1R activation, adenylyl cyclase (AC) is activated and cAMP is generated, leading, in turn, to cAMP-dependent activation of second messenger pathways, such as the protein kinase A (PKA) and Epac pathways. As well as short-term effects of enhancing glucose-induced insulin secretion, continuous GLP-1R activation also increases insulin synthesis, beta cell proliferation, and neogenesis. Although these latter effects cannot be currently monitored in humans, there are substantial improvements in glucose tolerance and increases in both first phase and plateau phase insulin secretory responses in T2DM patients treated with Ex-4. This review will focus on the effects resulting from GLP-1R activation in the pancreas.
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Affiliation(s)
- Máire E Doyle
- Department of Pathology, Immunology & Laboratory Medicine, College of Medicine, University of Florida, Gainesville, FL, USA
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32
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An R, da Silva Xavier G, Hao HX, Semplici F, Rutter J, Rutter GA. Regulation by Per-Arnt-Sim (PAS) kinase of pancreatic duodenal homeobox-1 nuclear import in pancreatic beta-cells. Biochem Soc Trans 2007; 34:791-3. [PMID: 17052199 DOI: 10.1042/bst0340791] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The transcription factor PDX-1 (pancreatic duodenal homeobox-1) is required for normal pancreatic development and for the function of insulin-producing islet beta-cells in mammals. We have shown previously that glucose regulates insulin gene expression in part through the activation and translocation of PDX-1 from the nuclear periphery to the nucleoplasm. We have also found that PASK [PAS (Per-Arnt-Sim) kinase], a member of the nutrient-regulated family of protein kinases, is activated in response to glucose challenge in beta-cells and is involved in the regulation of expression of PDX-1. Purified PASK efficiently phosphorylated recombinant PDX-1 in vitro on a single site (Thr-152). To determine the impact of phosphorylation at this site, we generated wild-type and mutant (T152A, T152D and T152E) forms of PDX-1 and examined the distribution of each of these in clonal MIN6 beta-cells by immunocytochemical analysis. Unexpectedly, only the T152D mutation significantly affected subcellular distribution, increasing the ratio of nuclear/cytosolic labelling at low and high glucose concentrations, suggesting that phosphorylation at Thr-152 inhibits nuclear uptake in response to glucose. Based on these results, experiments to examine the contribution of Thr-152 to the overall phosphorylation of PDX-1 in intact cells will be undertaken.
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Affiliation(s)
- R An
- Henry Wellcome Signalling Laboratories and Department of Biochemistry, University of Bristol, Bristol BS8 ITD, UK
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33
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Abstract
Our understanding of metabolism is undergoing a dramatic shift. Indeed, the efforts made towards elucidating the mechanisms controlling the major regulatory pathways are now being rewarded. At the molecular level, the crucial role of transcription factors is particularly well-illustrated by the link between alterations of their functions and the occurrence of major metabolic diseases. In addition, the possibility of manipulating the ligand-dependent activity of some of these transcription factors makes them attractive as therapeutic targets. The aim of this review is to summarize recent knowledge on the transcriptional control of metabolic homeostasis. We first review data on the transcriptional regulation of the intermediary metabolism, i.e., glucose, amino acid, lipid, and cholesterol metabolism. Then, we analyze how transcription factors integrate signals from various pathways to ensure homeostasis. One example of this coordination is the daily adaptation to the circadian fasting and feeding rhythm. This section also discusses the dysregulations causing the metabolic syndrome, which reveals the intricate nature of glucose and lipid metabolism and the role of the transcription factor PPARgamma in orchestrating this association. Finally, we discuss the molecular mechanisms underlying metabolic regulations, which provide new opportunities for treating complex metabolic disorders.
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Affiliation(s)
- Béatrice Desvergne
- Center for Integrative Genomics, National Centre of Competence in Research Frontiers in Genetics, University of Lausanne, Lausanne, Switzerland
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34
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Poitout V, Hagman D, Stein R, Artner I, Robertson RP, Harmon JS. Regulation of the insulin gene by glucose and fatty acids. J Nutr 2006; 136:873-6. [PMID: 16549443 PMCID: PMC1853259 DOI: 10.1093/jn/136.4.873] [Citation(s) in RCA: 147] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The insulin gene is expressed almost exclusively in pancreatic beta-cells. Metabolic regulation of insulin gene expression enables the beta-cell to maintain adequate stores of intracellular insulin to sustain the secretory demand. Glucose is the major physiologic regulator of insulin gene expression; it coordinately controls the recruitment of transcription factors [e.g., pancreatic/duodenal homeobox-1 (PDX-1), mammalian homologue of avian MafA/L-Maf (MafA), Beta2/Neuro D (B2), the rate of transcription, and the stability of insulin mRNA. However, chronically elevated levels of glucose (glucotoxicity) and lipids (lipotoxicity) also contribute to the worsening of beta-cell function in type 2 diabetes, in part via inhibition of insulin gene expression. The mechanisms of glucotoxicity, which involve decreased binding activities of PDX-1 and MafA and increased activity of C/EBPbeta, are mediated by high-glucose-induced generation of oxidative stress. On the other hand, lipotoxicity is mediated by de novo ceramide synthesis and involves inhibition of PDX-1 nuclear translocation and MafA gene expression. Glucotoxicity and lipotoxicity have common targets, which makes their combination particularly harmful to insulin gene expression and beta-cell function in type 2 diabetes.
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Affiliation(s)
- Vincent Poitout
- Department of Medicine, University of Montréal, Montréal, QC, Canada.
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35
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Boucher MJ, Selander L, Carlsson L, Edlund H. Phosphorylation marks IPF1/PDX1 protein for degradation by glycogen synthase kinase 3-dependent mechanisms. J Biol Chem 2006; 281:6395-403. [PMID: 16407209 DOI: 10.1074/jbc.m511597200] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The transcription factor IPF1/PDX1 plays a crucial role in both pancreas development and maintenance of beta-cell function. Targeted disruption of this transcription factor in beta-cells leads to diabetes, whereas reduced expression levels affect insulin expression and secretion. Therefore, it is essential to determine molecular mechanisms underlying the regulation of this key transcription factor on mRNA levels and, most importantly, on protein levels. Here we show that a minor portion of IPF1/PDX1 is phosphorylated on serine 61 and/or serine 66 in pancreatic beta-cells. This phosphorylated form of IPF1/PDX1 preferentially accumulates following proteasome inhibition, an effect that is prevented by inhibition of glycogen synthase kinase 3 (GSK3) activity. Oxidative stress, which is associated with the diabetic state, (i) increases IPF1/PDX1 Ser61 and/or Ser66 phosphorylation and (ii) increases the degradation rate and decreases the half-life of IPF-1/PDX-1 protein. In addition, we provide evidence that GSK3 activity participates in oxidative stress-induced effects on beta-cells. Thus, this current study uncovers a new mechanism that might contribute to diminished levels of IPF1/PDX1 protein and beta-cell dysfunction during the progression of diabetes.
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Affiliation(s)
- Marie-Josée Boucher
- Umeå Center for Molecular Medicine, University of Umeå, SE-901 87 Umeå, Sweden
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36
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Kawamori D, Kaneto H, Nakatani Y, Matsuoka TA, Matsuhisa M, Hori M, Yamasaki Y. The Forkhead Transcription Factor Foxo1 Bridges the JNK Pathway and the Transcription Factor PDX-1 through Its Intracellular Translocation. J Biol Chem 2006; 281:1091-8. [PMID: 16282329 DOI: 10.1074/jbc.m508510200] [Citation(s) in RCA: 204] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
It has been shown that oxidative stress and activation of the c-Jun N-terminal kinase (JNK) pathway induce the nucleocytoplasmic translocation of the pancreatic transcription factor PDX-1, which leads to pancreatic beta-cell dysfunction. In this study, we have shown that the forkhead transcription factor Foxo1/FKHR plays a role as a mediator between the JNK pathway and PDX-1. Under oxidative stress conditions, Foxo1 changed its intracellular localization from the cytoplasm to the nucleus in the pancreatic beta-cell line HIT-T15. The overexpression of JNK also induced the nuclear localization of Foxo1, but in contrast, suppression of JNK reduced the oxidative stress-induced nuclear localization of Foxo1, suggesting the involvement of the JNK pathway in Foxo1 translocation. In addition, oxidative stress or activation of the JNK pathway decreased the activity of Akt in HIT cells, leading to the decreased phosphorylation of Foxo1 following nuclear localization. Furthermore, adenovirus-mediated Foxo1 overexpression reduced the nuclear expression of PDX-1, whereas repression of Foxo1 by Foxo1-specific small interfering RNA retained the nuclear expression of PDX-1 under oxidative stress conditions. Taken together, Foxo1 is involved in the nucleocytoplasmic translocation of PDX-1 by oxidative stress and the JNK pathway.
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Affiliation(s)
- Dan Kawamori
- Department of Internal Medicine and Therapeutics (A8), Osaka University Graduate School of Medicine, Suita City, Japan
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37
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Hagman DK, Hays LB, Parazzoli SD, Poitout V. Palmitate inhibits insulin gene expression by altering PDX-1 nuclear localization and reducing MafA expression in isolated rat islets of Langerhans. J Biol Chem 2005; 280:32413-8. [PMID: 15944145 PMCID: PMC1361267 DOI: 10.1074/jbc.m506000200] [Citation(s) in RCA: 154] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Abnormalities in lipid metabolism have been proposed as contributing factors to both defective insulin secretion from the pancreatic beta cell and peripheral insulin resistance in type 2 diabetes. Previously, we have shown that prolonged exposure of isolated rat islets of Langerhans to excessive fatty acid levels impairs insulin gene transcription. This study was designed to assess whether palmitate alters the expression and binding activity of the key regulatory factors pancreas-duodenum homeobox-1 (PDX-1), MafA, and Beta2, which respectively bind to the A3, C1, and E1 elements in the proximal region of the insulin promoter. Nuclear extracts of isolated rat islets cultured with 0.5 mm palmitate exhibited reduced binding activity to the A3 and C1 elements but not the E1 element. Palmitate did not affect the overall expression of PDX-1 but reduced its nuclear localization. In contrast, palmitate blocked the stimulation of MafA mRNA and protein expression by glucose. Combined adenovirus-mediated overexpression of PDX-1 and MafA in islets completely prevented the inhibition of insulin gene expression by palmitate. These results demonstrate that prolonged exposure of islets to palmitate inhibits insulin gene transcription by impairing nuclear localization of PDX-1 and cellular expression of MafA.
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Affiliation(s)
- Derek K. Hagman
- From the Pacific Northwest Research Institute, Seattle, Washington 98122 and the
| | - Lori B. Hays
- From the Pacific Northwest Research Institute, Seattle, Washington 98122 and the
| | - Susan D. Parazzoli
- From the Pacific Northwest Research Institute, Seattle, Washington 98122 and the
| | - Vincent Poitout
- From the Pacific Northwest Research Institute, Seattle, Washington 98122 and the
- Department of Medicine, University of Washington, Seattle, Washington 98195
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38
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Stanojevic V, Yao KM, Thomas MK. The coactivator Bridge-1 increases transcriptional activation by pancreas duodenum homeobox-1 (PDX-1). Mol Cell Endocrinol 2005; 237:67-74. [PMID: 15885879 DOI: 10.1016/j.mce.2005.03.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2005] [Accepted: 03/07/2005] [Indexed: 11/30/2022]
Abstract
Well-orchestrated transcriptional regulation of pancreatic beta cells is essential for insulin production and glucose homeostasis. Pancreas duodenum homeobox-1 (PDX-1) is a key regulator of glucose-dependent insulin production and glucose metabolism. We find that PDX-1 interacts with the PDZ-domain coactivator Bridge-1 in yeast interaction trap assays. Rat Bridge-1 and PDX-1 interact directly in GST pull-down assays via Bridge-1 interactions with the amino-terminal transactivation domain of PDX-1. Bridge-1 also interacts with wild-type and mutant human PDX-1 (IPF-1) proteins and strongly interacts with the amino-terminal PDX-1 P63fsdelC (MODY4) mutant protein. Transcriptional activation by PDX-1 is increased by addition of Bridge-1 in multiple contexts, including synergistic activation of a Gal4 reporter by Gal4-Bridge-1 and Gal4-PDX-1 fusion proteins, activation of the somatostatin promoter TAAT1 enhancer, and synergistic activation of the rat insulin I promoter FarFlat enhancer by PDX-1, E12, and E47. We propose that the coactivator Bridge-1 modulates PDX-1 functions in the regulation of its target genes.
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Affiliation(s)
- Violeta Stanojevic
- Laboratory of Molecular Endocrinology, Massachusetts General Hospital, Wellman 340, 50 Blossom Street, Boston, MA 02114, USA
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39
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Abstract
Considerable progress has been made in the understanding of the sequential activation of signal transduction pathways and the expression of transcription factors during pancreas development. Much of this understanding has been obtained by analyses of the phenotypes of mice in which the expression of key genes has been disrupted (knockout mice). Knockout of the genes for Pdx1, Hlxb9, Isl1, or Hex results in an arrest of pancreas development at a very early stage (embryonic d 8-9). Disruption of genes encoding components of the Notch signaling pathway, e.g. Hes1 or neurogenin-3, abrogates development of the endocrine pancreas (islets of Langerhans). Disruption of transcription factor genes expressed more downstream in the developmental cascade (Beta2/NeuroD, Pax4, NKx2.2, and Nkx6.1) curtails the formation of insulin-producing beta-cells. An understanding of the importance of transcription factor genes during pancreas development has provided insights into the pathogenesis of diabetes, in which the mass of insulin-producing beta-cells is reduced.
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Affiliation(s)
- Joel F Habener
- Laboratory of Molecular Endocrinology, Massachusetts General Hospital, Howard Hughes Medical Institute, Harvard Medical School, 55 Fruit Street, WEL320, Boston, Massachusetts 02114, USA.
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40
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Mosley AL, Ozcan S. The Pancreatic Duodenal Homeobox-1 Protein (Pdx-1) Interacts with Histone Deacetylases Hdac-1 and Hdac-2 on Low Levels of Glucose. J Biol Chem 2004; 279:54241-7. [PMID: 15496408 DOI: 10.1074/jbc.m410379200] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have previously demonstrated that high concentrations of glucose stimulate insulin gene expression by causing hyperacetylation of histone H4 at the insulin gene promoter. Furthermore, we have shown that the glucose-mediated hyperacetylation of histone H4 depends on the recruitment of the histone acetyltransferase p300 by the beta cell-specific transcription factor Pdx-1. In this study, we demonstrate that the histone deacetylases Hdac-1 and Hdac-2 are rapidly recruited to the insulin promoter in the mouse insulinoma cell line MIN6 when cells are switched from high to low glucose media. Moreover, we demonstrate that the beta cell-specific homeodomain protein Pdx-1 interacts with histone deacetylases Hdac-1 and Hdac-2 at low levels of glucose. In vitro studies indicate that the interaction between Pdx-1 and Hdac-1 or Hdac-2 is direct and requires the C terminus of Pdx-1. Treatment of MIN6 cells with okadaic acid, which inhibits the activity of protein phosphatases, abolishes the interaction of Pdx-1 with Hdac-1 and Hdac-2 on low levels of glucose, suggesting the requirement of a dephosphorylation event for this interaction to occur. These data indicate that insulin gene expression is decreased on low levels of glucose by recruitment of Hdac-1 and Hdac-2 to the insulin promoter by the transcription factor Pdx-1.
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Affiliation(s)
- Amber L Mosley
- Department of Molecular and Cellular Biochemistry, Chandler Medical Center, University of Kentucky, Lexington, Kentucky 40536, USA
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León-Quinto T, Jones J, Skoudy A, Burcin M, Soria B. In vitro directed differentiation of mouse embryonic stem cells into insulin-producing cells. Diabetologia 2004; 47:1442-51. [PMID: 15309294 DOI: 10.1007/s00125-004-1458-8] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/03/2004] [Accepted: 04/19/2004] [Indexed: 11/26/2022]
Abstract
AIMS/HYPOTHESIS We recently demonstrated that insulin-producing cells derived from embryonic stem cells normalise hyperglycaemia in transplanted diabetic mice. The differentiation and selection procedure, however, was successful in less than 5% of the assays performed. Thus, to improve its effectiveness, new strategies have been developed, which increase the number of islet cells or islet progenitors. METHODS Mouse embryonic stem cells transfected with a plasmid containing the Nkx6.1 promoter gene followed by a neomycin-resistance gene, were cultured with factors known to participate in endocrine pancreatic development and factors that modulate signalling pathways involved in these processes. Neomycin was used to select the Nkx6.1-positive cells, which also express insulin. The transfected cells were differentiated using several exogenous agents, followed by selection of Nkx6.1-positive cells. The resulting cells were analysed for pancreatic gene and protein expression by immunocytochemistry, RT-PCR and radioimmunoassay. Also, proliferation assays were performed, as well as transplantation to streptozotocin-induced diabetic mice. RESULTS The protocols yielded cell cultures with approximately 20% of cells co-expressing insulin and Pdx-1. Cell trapping selection yielded an almost pure population of insulin-positive cells, which expressed the beta cell genes/proteins Pdx-1, Nkx6.1, insulin, glucokinase, GLUT-2 and Sur-1. Subsequent transplantation to streptozotocin-induced diabetic mice normalised their glycaemia during the time period of experimentation, proving the efficiency of the protocols. CONCLUSIONS/INTERPRETATION These methods were both highly efficient and very reproducible, resulting in a new strategy to obtain insulin-containing cells from stem cells with a near 100% success rate, while actively promoting the maturation of the exocytotic machinery.
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Affiliation(s)
- T León-Quinto
- Institute of Bioengineering, School of Medicine, Miguel Hernández University, San Juan Campus, Alicante, Spain
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42
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Guillemain G, Da Silva Xavier G, Rafiq I, Leturque A, Rutter GA. Importin beta1 mediates the glucose-stimulated nuclear import of pancreatic and duodenal homeobox-1 in pancreatic islet beta-cells (MIN6). Biochem J 2004; 378:219-27. [PMID: 14632628 PMCID: PMC1223942 DOI: 10.1042/bj20031549] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2003] [Revised: 11/14/2003] [Accepted: 11/24/2003] [Indexed: 11/17/2022]
Abstract
The transcription factor PDX-1 (pancreatic and duodenal homeobox-1) is essential for pancreatic development and the maintainence of expression of islet beta-cell-specific genes. In an previous study [Rafiq, Kennedy and Rutter (1998) J. Biol. Chem. 273, 23241-23247] we demonstrated that PDX-1 may be activated at elevated glucose concentrations by translocation from undefined binding sites in the cytosol and nuclear membrane into the nucleoplasm. In the present study, we show that PDX-1 interacts directly and specifically in vitro with the nuclear import receptor family member, importin beta1, and that this interaction is mediated by the PDX-1 homeodomain (amino acids 146-206). Demonstrating the functional importance of the PDX-1-importin beta1 interaction, microinjection of MIN6 beta-cells with anti-(importin beta1) antibodies blocked both the nuclear translocation of PDX-1, and the activation by glucose (30 mM versus 3 mM) of the pre-proinsulin promoter. However, treatment with extracts from pancreatic islets incubated at either low or high glucose concentrations had no impact on the ability of PDX-1 to interact with importin beta1 in vitro. Furthermore, importin beta1 also interacted with SREBP1c (sterol-regulatory-element-binding protein 1c) in vitro, and microinjection of importin beta1 antibodies blocked the activation by glucose of SREBP1c target genes. Since the subcellular distribution of SREBP1c is unaffected by glucose, these findings suggest that a redistribution of importin beta1 is unlikely to explain the glucose-stimulated nuclear uptake of PDX-1. Instead, we conclude that the uptake of PDX-1 into the nucleoplasm, as glucose concentrations increase, may be mediated by release of the factor both from sites of retention in the cytosol and from non-productive complexes with importin beta1 at the nuclear membrane.
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Affiliation(s)
- Ghislaine Guillemain
- Henry Wellcome Laboratories for Integrated Cell Signalling and Department of Biochemistry, University of Bristol, Bristol BS8 1TD, UK
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43
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Abstract
Many transcription factors are critical for ensuring proper embryonic development of the endocrine pancreas and normal islet function. The transcription factor pancreatic duodenal homeobox 1 (PDX-1) is uniformly expressed in early pancreatic buds of embryos as well as the beta and delta cells of the islets of Langerhans. PDX-1 has also been found in dispersed endocrine cells of the duodenum in adults and plays a key role in pancreas formation. It has been reported that null mutation of PDX-1 in mice results in a failure of the pancreatic bud to expand; thus, the mice die 2-3 days after birth from hyperglycemia and dehydration. Heterozygous PDX-1 mice developed a pancreas but were diabetic. It has been shown that PDX-1 is required for maintaining the pancreatic islet functions by activating gene transcriptions including insulin, somatostatin (SST), islet amyloid polypeptide, glucose transporter type 2, and glucokinase. PDX-1 serves a dual role in pancreatic development. It initially contributes to pancreatic formation during embryogenesis and subsequently regulates the pancreatic islet cell physiology in mature islet cells. Understanding the underlying molecular mechanisms of pancreas formation, especially the function of PDX-1, may contribute to the enhanced treatment and prevention of debilitating diseases such as diabetes, insulinomas, and pancreatic carcinomas.
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Affiliation(s)
- Satoshi Ashizawa
- Michael E. DeBakey Department of Surgery, Baylor College of Medicine, Houston, Texas, USA
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44
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Da Silva Xavier G, Qian Q, Cullen PJ, Rutter GA. Distinct roles for insulin and insulin-like growth factor-1 receptors in pancreatic beta-cell glucose sensing revealed by RNA silencing. Biochem J 2004; 377:149-58. [PMID: 14563207 PMCID: PMC1223855 DOI: 10.1042/bj20031260] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2003] [Revised: 10/15/2003] [Accepted: 10/17/2003] [Indexed: 01/03/2023]
Abstract
The importance of the insulin receptor (IR) and the insulin-like growth factor-1 receptor (IGF-1R) for glucose-regulated insulin secretion and gene expression in pancreatic islet beta-cells is at present unresolved. Here, we have used small interfering RNAs (siRNAs) to silence the expression of each receptor selectively in clonal MIN6 beta-cells. Reduction of IR levels by >90% completely inhibited glucose (30 mM compared with 3 mM)-induced insulin secretion, but had no effect on depolarization-stimulated secretion. IR depletion also blocked the accumulation of preproinsulin (PPI), pancreatic duodenum homoeobox-1 (PDX-1) and glucokinase (GK) mRNAs at elevated glucose concentrations, as assessed by quantitative real-time PCR analysis (TaqMan). Similarly, depletion of IGF-1R inhibited glucose-induced insulin secretion but, in contrast with the effects of IR silencing, had little impact on the regulation of gene expression by glucose. Moreover, loss of IGF-1R, but not IR, markedly inhibited glucose-stimulated increases in cytosolic and mitochondrial ATP, suggesting a role for IGF-1R in the maintenance of oxidative metabolism and in the generation of mitochondrial coupling factors. RNA silencing thus represents a useful tool for the efficient and selective inactivation of receptor tyrosine kinases in isolated beta-cells. By inhibiting glucose-stimulated insulin secretion through the inactivation of IGF-1R, this approach also demonstrates the existence of insulin-independent mechanisms whereby elevated glucose concentrations regulate PPI, PDX-1 and GK gene expression in beta-cells.
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Affiliation(s)
- Gabriela Da Silva Xavier
- Henry Wellcome Laboratories for Integrated Cell Signalling and Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK
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45
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Kawamori D, Kajimoto Y, Kaneto H, Umayahara Y, Fujitani Y, Miyatsuka T, Watada H, Leibiger IB, Yamasaki Y, Hori M. Oxidative stress induces nucleo-cytoplasmic translocation of pancreatic transcription factor PDX-1 through activation of c-Jun NH(2)-terminal kinase. Diabetes 2003; 52:2896-904. [PMID: 14633849 DOI: 10.2337/diabetes.52.12.2896] [Citation(s) in RCA: 166] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Oxidative stress is induced in pancreatic beta-cells under diabetic conditions and causes beta-cell dysfunction. Antioxidant treatment of diabetic animals leads to recovery of insulin biosynthesis and increases the expression of its controlling transcription factor, pancreatic duodenal homeobox-1 (PDX-1), in pancreatic beta-cells. Here, we show that PDX-1 is translocated from the nuclei to the cytoplasm of pancreatic beta-cells in response to oxidative stress. When oxidative stress was charged upon beta-cell-derived HIT-T15 cells, both endogenous PDX-1 and exogenously introduced green fluorescent protein-tagged PDX-1 moved from the nuclei to the cytoplasm. The addition of a dominant negative form of c-Jun NH(2)-terminal kinase (JNK) inhibited oxidative stress-induced PDX-1 translocation, suggesting an essential role of JNK in mediating this phenomenon. Whereas the nuclear localization signal (NLS) in PDX-1 was not affected by oxidative stress, leptomycin B, a specific inhibitor of the classical leucine-rich nuclear export signal (NES), inhibited nucleo-cytoplasmic translocation of PDX-1 induced by oxidative stress. Moreover, we identified an NES at position 82-94 of the mouse PDX-1 protein. Thus, our present results revealed a novel mechanism that negatively regulates PDX-1 function. The identification of the NES, which overrides the function of the NLS in an oxidative stress-responsive, JNK-dependent manner, supports the complicated regulation of PDX-1 function in vivo and may further the understanding of beta-cell pathophysiology in diabetes.
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Affiliation(s)
- Dan Kawamori
- Department of Internal Medicine and Therapeutics, Osaka University Graduate School of Medicine, Suita City, Osaka, Japan
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46
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Khoo S, Griffen SC, Xia Y, Baer RJ, German MS, Cobb MH. Regulation of insulin gene transcription by ERK1 and ERK2 in pancreatic beta cells. J Biol Chem 2003; 278:32969-77. [PMID: 12810726 DOI: 10.1074/jbc.m301198200] [Citation(s) in RCA: 127] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We show that the mitogen-activated protein kinases ERK1/2 are components of the mechanism by which glucose stimulates insulin gene expression. ERK1/2 activity is required for glucose-dependent transcription from both the full-length rat insulin I promoter and the glucose-sensitive isolated E2A3/4 promoter element in intact islets and beta cell lines. Dominant negative ERK2 and MEK inhibitors suppress glucose stimulation of the rat insulin I promoter and the E2A3/4 element. Overexpression of ERK2 is sufficient to stimulate transcription from the E2A3/4 element. The glucose-induced response is dependent upon ERK1/2 phosphorylation of a subset of transcription factors that include Beta2 (also known as NeuroD1) and PDX-1. Phosphorylation increases their functional activity and results in a cumulative transactivation of the promoter. Thus, ERK1/2 act at multiple points to transduce a glucose signal to insulin gene transcription.
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MESH Headings
- Animals
- Blotting, Northern
- Cells, Cultured
- Cricetinae
- Dimerization
- Dose-Response Relationship, Drug
- Enzyme Activation
- Enzyme Inhibitors/pharmacology
- Female
- Gene Expression Regulation, Enzymologic
- Genes, Dominant
- Genetic Vectors
- Glucose/metabolism
- Glutathione Transferase/metabolism
- Insulin/metabolism
- Islets of Langerhans/metabolism
- Male
- Mice
- Mitogen-Activated Protein Kinase 1/genetics
- Mitogen-Activated Protein Kinase 1/metabolism
- Mitogen-Activated Protein Kinase 3
- Mitogen-Activated Protein Kinases/metabolism
- Mutagenesis, Site-Directed
- Phosphorylation
- Promoter Regions, Genetic
- Protein Binding
- RNA, Messenger/metabolism
- Rats
- Rats, Sprague-Dawley
- Recombinant Proteins/metabolism
- Retroviridae/genetics
- Transcription, Genetic
- Transcriptional Activation
- Transfection
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Affiliation(s)
- Shih Khoo
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
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47
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Gao Y, Miyazaki JI, Hart GW. The transcription factor PDX-1 is post-translationally modified by O-linked N-acetylglucosamine and this modification is correlated with its DNA binding activity and insulin secretion in min6 beta-cells. Arch Biochem Biophys 2003; 415:155-63. [PMID: 12831837 DOI: 10.1016/s0003-9861(03)00234-0] [Citation(s) in RCA: 127] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The pancreatic/duodenal homeobox-1 protein (PDX-1, also called STF-1, IPF-1) is a transcription factor that plays an important role in pancreatic function and development. Here, we have overexpressed and purified PDX-1 from baculovirus/sf-9 cells, transiently transfected Cos-7 cells and native Min6 cells and demonstrated that the protein is posttranslationally modified by O-linked N-acetylglucosamine (O-GlcNAc). The approaches we used include binding of the protein to the lectin WGA, labeling with galactosyltransferase and UDP-[(3)H]gal and probing with the O-GlcNAc-specific antibody, RL-2. PNGase F treatment and structural analysis indicate that the carbohydrate is beta-linked O-GlcNAc. Mapping of [(3)H]gal-labeled tryptic peptides indicates that PDX-1 has two major sites for O-GlcNAcylation. In Min6 cells, elevated glucose concentration leads to an increase in protein O-GlcNAcylation and this hyperglycosylation correlates with an increase in DNA binding activity of PDX-1 and insulin secretion. On the other hand, the GFAT inhibitor azaserine reduces intracellular O-GlcNAc levels and profoundly attenuates glucose-stimulated insulin secretion. These data suggest that O-GlcNAcylation may be involved in the regulation of PDX-1 DNA binding activity and in glucose-stimulated insulin secretion in beta-cells.
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Affiliation(s)
- Yuan Gao
- Department of Biological Chemistry, The Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205-2185, USA
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48
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da Silva Xavier G, Leclerc I, Varadi A, Tsuboi T, Moule SK, Rutter GA. Role for AMP-activated protein kinase in glucose-stimulated insulin secretion and preproinsulin gene expression. Biochem J 2003; 371:761-74. [PMID: 12589707 PMCID: PMC1223356 DOI: 10.1042/bj20021812] [Citation(s) in RCA: 214] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2002] [Revised: 02/10/2003] [Accepted: 02/17/2003] [Indexed: 11/17/2022]
Abstract
AMP-activated protein kinase (AMPK) has recently been implicated in the control of preproinsulin gene expression in pancreatic islet beta-cells [da Silva Xavier, Leclerc, Salt, Doiron, Hardie, Kahn and Rutter (2000) Proc. Natl. Acad. Sci. U.S.A. 97, 4023-4028]. Using pharmacological and molecular strategies to regulate AMPK activity in rat islets and clonal MIN6 beta-cells, we show here that the effects of AMPK are exerted largely upstream of insulin release. Thus forced increases in AMPK activity achieved pharmacologically with 5-amino-4-imidazolecarboxamide riboside (AICAR), or by adenoviral overexpression of a truncated, constitutively active form of the enzyme (AMPK alpha 1.T(172)D), blocked glucose-stimulated insulin secretion. In MIN6 cells, activation of AMPK suppressed glucose metabolism, as assessed by changes in total, cytosolic or mitochondrial [ATP] and NAD(P)H, and reduced increases in intracellular [Ca(2+)] caused by either glucose or tolbutamide. By contrast, inactivation of AMPK by expression of a dominant-negative form of the enzyme mutated in the catalytic site (AMPK alpha 1.D(157)A) did not affect glucose-stimulated increases in [ATP], NAD(P)H or intracellular [Ca(2+)], but led to the unregulated release of insulin. These results indicate that inhibition of AMPK by glucose is essential for the activation of insulin secretion by the sugar, and may contribute to the transcriptional stimulation of the preproinsulin gene. Modulation of AMPK activity in the beta-cell may thus represent a novel therapeutic strategy for the treatment of type 2 diabetes mellitus.
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Affiliation(s)
- Gabriela da Silva Xavier
- Henry Wellcome Laboratories of Integrated Cell Signalling and Department of Biochemistry, University Walk, University of Bristol, Bristol BS8 1TD, UK
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49
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Osterhoff M, Möhlig M, Schwanstecher M, Seufert J, Ortmann J, Schatz H, Pfeiffer AFH. Ca2+/calmodulin-dependent protein kinase II delta2 regulates gene expression of insulin in INS-1 rat insulinoma cells. Cell Calcium 2003; 33:175-84. [PMID: 12600804 DOI: 10.1016/s0143-4160(02)00227-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Ca(2+)/calmodulin-dependent protein kinase II is a member of a broad family of ubiquitously expressed Ca(2+) sensing serine/threonine-kinases. Ca(2+)/calmodulin-dependent protein kinase II is highly expressed in insulin secreting cells and is associated with insulin secretory granules and has been proposed to play an important role in exocytosis or in insulin granule transport to release sites. To elucidate its function the antisense sequence of the major beta-cell subtype, Ca(2+)/calmodulin-dependent protein kinase II delta(2), was stably expressed in INS-1 rat insulinoma cells. This caused a loss of Ca(2+)/calmodulin-dependent protein kinase II delta(2) expression at the mRNA and protein level, while the expression of the 95% homologous Ca(2+)/calmodulin-dependent protein kinase II gamma and of beta-cell specific proteins such as the homeodomain factor pancreatic-duodenal homeobox factor-1 (PDX-1, also referred to as islet/duodenum homeobox-1, IDX-1, insulin promoter factor-1, IPF-1 and somatostatin transactivating factor-1, STF-1), the glucagon-like peptide-1 (GLP-1) receptor and K(ATP)-channels K(IR)6.2/SUR-1 (sulfonylurea receptor-1) was not altered. Unexpectedly, the cells showed a large reduction of insulin gene expression, which was due to reduced insulin gene transcription. Electrophoretic mobility shift assays of PDX-1 binding to the insulin promoter A1 and E2/A3A4 elements showed additional bands indicating alterations of PDX-1 complex formation. Stable over expression of Ca(2+)/calmodulin-dependent protein kinase II delta(2), by contrast, was associated with elevated expression of insulin mRNA. Therefore, we conclude that Ca(2+)/calmodulin-dependent protein kinase II delta(2) links fuel-dependent increases in intracellular Ca(2+) concentrations to transcriptional regulation of genes related to the metabolic control of insulin secretion.
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Affiliation(s)
- M Osterhoff
- Deutsches Institut für Ernährungsforschung (DIfE), D-14558, Bergholz-Rehbrücke, Germany.
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Stoffers DA, Desai BM, DeLeon DD, Simmons RA. Neonatal exendin-4 prevents the development of diabetes in the intrauterine growth retarded rat. Diabetes 2003; 52:734-40. [PMID: 12606515 DOI: 10.2337/diabetes.52.3.734] [Citation(s) in RCA: 209] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Uteroplacental insufficiency resulting in fetal growth retardation is a common complication of pregnancy and a significant cause of perinatal morbidity and mortality. Epidemiological studies show an increased incidence of type 2 diabetes in humans who were growth retarded at birth. The mechanisms by which an abnormal intrauterine milieu leads to the development of diabetes in adulthood are not known. Therefore, a rat model of uteroplacental insufficiency was developed; intrauterine growth-retarded (IUGR) rats develop diabetes with a phenotype similar to that observed in the human with type 2 diabetes. We show here that administration of a pancreatic beta-cell trophic factor, exendin-4 (Ex-4), during the prediabetic neonatal period dramatically prevents the development of diabetes in this model. This occurs because neonatal Ex-4 prevents the progressive reduction in insulin-producing beta-cell mass that is observed in IUGR rats over time. Expression of PDX, a critical regulator of pancreas development and islet differentiation, is restored to normal levels, and islet beta-cell proliferation rates are normalized by the neonatal Ex-4 treatment. These results indicate that exposure to Ex-4 in the newborn period reverses the adverse consequences of fetal programming and prevents the development of diabetes in adulthood.
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Affiliation(s)
- Doris A Stoffers
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, Clinical Research Building 611B, University of Pennsylvania School of Medicine, 415 Curie Boulevard, Philadelphia, PA 19104, USA.
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