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Mesto N, Movassat J, Tourrel-Cuzin C. P2-type purinergic signaling in the regulation of pancreatic β-cell functional plasticity as a promising novel therapeutic approach for the treatment of type 2 diabetes? Front Endocrinol (Lausanne) 2022; 13:1099152. [PMID: 37065173 PMCID: PMC10099247 DOI: 10.3389/fendo.2022.1099152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Accepted: 11/29/2022] [Indexed: 12/13/2022] Open
Abstract
Diabetes Mellitus is a metabolic disorder characterized by a chronic hyperglycemia due to an impaired insulin secretion and a decreased in peripheral insulin sensitivity. This disease is a major public health problem due to it sharp prevalence. Therefore, it is crucial to readapt therapeutic approaches for the treatment of this pathology. One of the strategies would be through P2-type purinergic receptors pathway via ATP binding. In addition to its well-known role as an intracellular energy intermediary in numerous biochemical and physiological processes, ATP is also an important extracellular signaling molecule. ATP mediates its effects by binding and activating two classes of P2 purinoreceptors: P2X receptors that are ligand-gated ion channel receptors, existing in seven isoforms (P2X 1 to 7) and P2Y receptors that are G-protein coupled receptors, existing in eight isoforms (P2Y 1/2/4/6/11/12/13/14). These receptors are ubiquitously distributed and involved in numerous physiological processes in several tissues. The concept of purinergic signaling, originally formulated by Geoffrey Burnstock (1929-2020), was also found to mediate various responses in the pancreas. Several studies have shown that P2 receptors are expressed in the endocrine pancreas, notably in β cells, where ATP could modulate their function but also their plasticity and thus play a physiological role in stimulating insulin secretion to face some metabolic demands. In this review, we provide a historical perspective and summarize current knowledge on P2-type purinergic signaling in the regulation of pancreatic β-cell functional plasticity, which would be a promising novel therapeutic approach for the treatment of type 2 diabetes.
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Langlhofer G, Kogel A, Schaefer M. Glucose-induced [Ca2+]i oscillations in β cells are composed of trains of spikes within a subplasmalemmal microdomain. Cell Calcium 2021; 99:102469. [PMID: 34509871 DOI: 10.1016/j.ceca.2021.102469] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 08/31/2021] [Accepted: 09/01/2021] [Indexed: 10/20/2022]
Abstract
Electrical activity and oscillations of cytosolic Ca2+ concentrations ([Ca2+]i) that trigger insulin release in response to glucose are key functions of pancreatic β cells. Although oscillatory Ca2+ signals have been intensively studied in β cells, their lower frequency did not match that of electrical activity. In addition, the measured peak [Ca2+]i did not reach levels that are typically required by synaptotagmins to elicit the release of insulin-containing vesicles in live-cell experiments. We therefore sought to resolve the Ca2+ dynamics in the subplasmalemmal microdomain that is critical for triggering fast exocytosis. Applying total internal reflection fluorescence (TIRF) microscopy in insulin-producing INS-1E and primary mouse β cells, we resolved extraordinary fast trains of Ca2+ spiking (frequency > 3 s-1) in response to glucose exposure. Using a low-affinity [Ca2+]i indicator dye, we provide experimental evidence that Ca2+ spikes reach low micromolar apparent concentrations in the vicinity of the plasma membrane. Analysis of Ca2+ spikes evoked by repeated depolarization for 10 ms closely matched the Ca2+ dynamics observed upon glucose application. To our knowledge, this is the first study that experimentally demonstrates Ca2+ spikes in β cells with velocities that resemble those of bursting or continuously appearing trains of action potentials (APs) in non-patched cells.
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Affiliation(s)
- Georg Langlhofer
- Rudolf-Boehm-Institute for Pharmacology and Toxicology, University of Leipzig, Leipzig, Germany
| | - Alexander Kogel
- Rudolf-Boehm-Institute for Pharmacology and Toxicology, University of Leipzig, Leipzig, Germany
| | - Michael Schaefer
- Rudolf-Boehm-Institute for Pharmacology and Toxicology, University of Leipzig, Leipzig, Germany.
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3
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Jain S, Jacobson KA. Purinergic signaling in diabetes and metabolism. Biochem Pharmacol 2020; 187:114393. [PMID: 33359363 DOI: 10.1016/j.bcp.2020.114393] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 12/21/2020] [Accepted: 12/22/2020] [Indexed: 12/22/2022]
Abstract
Purinergic signaling, a concept originally formulated by the late Geoffrey Burnstock (1929-2020), was found to modulate pathways in every physiological system. In metabolic disorders there is a role for both adenosine receptors and P2 (nucleotide) receptors, of which there are two classes, i.e. P2Y metabotropic and P2X ionotropic receptors. The individual roles of the 19 receptors encompassed by this family have been dissected - and in many cases the effects associated with specific cell types, including adipocytes, skeletal muscle, liver cells and immune cells. It is suggested that ligands selective for each of the four adenosine receptors (A1, A2A, A2B and A3), and several of the P2 subtypes (e.g. P2Y6 or P2X7 antagonists) might have therapeutic potential for treating diabetes and obesity. This is a developing story with some conflicting conclusions relevant to drug discovery, which we summarize here.
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Affiliation(s)
- Shanu Jain
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD 20892, USA
| | - Kenneth A Jacobson
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD 20892, USA.
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4
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Rorsman P, Ashcroft FM. Pancreatic β-Cell Electrical Activity and Insulin Secretion: Of Mice and Men. Physiol Rev 2018; 98:117-214. [PMID: 29212789 PMCID: PMC5866358 DOI: 10.1152/physrev.00008.2017] [Citation(s) in RCA: 433] [Impact Index Per Article: 72.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Revised: 05/30/2017] [Accepted: 06/18/2017] [Indexed: 12/14/2022] Open
Abstract
The pancreatic β-cell plays a key role in glucose homeostasis by secreting insulin, the only hormone capable of lowering the blood glucose concentration. Impaired insulin secretion results in the chronic hyperglycemia that characterizes type 2 diabetes (T2DM), which currently afflicts >450 million people worldwide. The healthy β-cell acts as a glucose sensor matching its output to the circulating glucose concentration. It does so via metabolically induced changes in electrical activity, which culminate in an increase in the cytoplasmic Ca2+ concentration and initiation of Ca2+-dependent exocytosis of insulin-containing secretory granules. Here, we review recent advances in our understanding of the β-cell transcriptome, electrical activity, and insulin exocytosis. We highlight salient differences between mouse and human β-cells, provide models of how the different ion channels contribute to their electrical activity and insulin secretion, and conclude by discussing how these processes become perturbed in T2DM.
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Affiliation(s)
- Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, United Kingdom; Department of Neuroscience and Physiology, Metabolic Research Unit, Göteborg, Sweden; and Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Frances M Ashcroft
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, United Kingdom; Department of Neuroscience and Physiology, Metabolic Research Unit, Göteborg, Sweden; and Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
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5
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Farashi S. Interaction between pancreatic β cell and electromagnetic fields: A systematic study toward finding the natural frequency spectrum of β cell system. Electromagn Biol Med 2017; 36:341-356. [PMID: 29087732 DOI: 10.1080/15368378.2017.1389751] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Interaction between biological systems and environmental electric or magnetic fields has gained attention during the past few decades. Although there are a lot of studies that have been conducted for investigating such interaction, the reported results are considerably inconsistent. Besides the complexity of biological systems, the important reason for such inconsistent results may arise due to different excitation protocols that have been applied in different experiments. In order to investigate carefully the way that external electric or magnetic fields interact with a biological system, the parameters of excitation, such as intensity or frequency, should be selected purposefully due to the influence of these parameters on the system response. In this study, pancreatic β cell, the main player of blood glucose regulating system, is considered and the study is focused on finding the natural frequency spectrum of the system using modeling approach. Natural frequencies of a system are important characteristics of the system when external excitation is applied. The result of this study can help researchers to select proper frequency parameter for electrical excitation of β cell system. The results show that there are two distinct frequency ranges for natural frequency of β cell system, which consist of extremely low (or near zero) and 100-750 kHz frequency ranges. There are experimental works on β cell exposure to electromagnetic fields that support such finding.
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Affiliation(s)
- Sajjad Farashi
- a Faculty of Medicine , Shahid Beheshti University of Medical Sciences , Tehran , Iran
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Brännmark C, Lövfors W, Komai AM, Axelsson T, El Hachmane MF, Musovic S, Paul A, Nyman E, Olofsson CS. Mathematical modeling of white adipocyte exocytosis predicts adiponectin secretion and quantifies the rates of vesicle exo- and endocytosis. J Biol Chem 2017; 292:20032-20043. [PMID: 28972187 DOI: 10.1074/jbc.m117.801225] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Revised: 09/22/2017] [Indexed: 11/06/2022] Open
Abstract
Adiponectin is a hormone secreted from white adipocytes and takes part in the regulation of several metabolic processes. Although the pathophysiological importance of adiponectin has been thoroughly investigated, the mechanisms controlling its release are only partly understood. We have recently shown that adiponectin is secreted via regulated exocytosis of adiponectin-containing vesicles, that adiponectin exocytosis is stimulated by cAMP-dependent mechanisms, and that Ca2+ and ATP augment the cAMP-triggered secretion. However, much remains to be discovered regarding the molecular and cellular regulation of adiponectin release. Here, we have used mathematical modeling to extract detailed information contained within our previously obtained high-resolution patch-clamp time-resolved capacitance recordings to produce the first model of adiponectin exocytosis/secretion that combines all mechanistic knowledge deduced from electrophysiological experimental series. This model demonstrates that our previous understanding of the role of intracellular ATP in the control of adiponectin exocytosis needs to be revised to include an additional ATP-dependent step. Validation of the model by introduction of data of secreted adiponectin yielded a very close resemblance between the simulations and experimental results. Moreover, we could show that Ca2+-dependent adiponectin endocytosis contributes to the measured capacitance signal, and we were able to predict the contribution of endocytosis to the measured exocytotic rate under different experimental conditions. In conclusion, using mathematical modeling of published and newly generated data, we have obtained estimates of adiponectin exo- and endocytosis rates, and we have predicted adiponectin secretion. We believe that our model should have multiple applications in the study of metabolic processes and hormonal control thereof.
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Affiliation(s)
- Cecilia Brännmark
- Department of Physiology/Metabolic Physiology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at University of Gothenburg, Medicinaregatan 11, SE-405 30 Göteborg
| | - William Lövfors
- Departments of Biomedical Engineering, SE-581 83 Linköping; Mathematics, Linköping University, SE-581 83 Linköping
| | - Ali M Komai
- Department of Physiology/Metabolic Physiology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at University of Gothenburg, Medicinaregatan 11, SE-405 30 Göteborg
| | - Tom Axelsson
- Departments of Biomedical Engineering, SE-581 83 Linköping
| | - Mickaël F El Hachmane
- Department of Physiology/Metabolic Physiology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at University of Gothenburg, Medicinaregatan 11, SE-405 30 Göteborg
| | - Saliha Musovic
- Department of Physiology/Metabolic Physiology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at University of Gothenburg, Medicinaregatan 11, SE-405 30 Göteborg
| | - Alexandra Paul
- Department of Biology and Biological Engineering, Chalmers University of Technology, Kemivägen 10 SE-412 96 Göteborg
| | - Elin Nyman
- Departments of Biomedical Engineering, SE-581 83 Linköping; Cardiovascular and Metabolic Diseases iMed Biotech Unit, AstraZeneca R&D, 431 83 Gothenburg, Sweden.
| | - Charlotta S Olofsson
- Department of Physiology/Metabolic Physiology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at University of Gothenburg, Medicinaregatan 11, SE-405 30 Göteborg.
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Hastoy B, Scotti PA, Milochau A, Fezoua-Boubegtiten Z, Rodas J, Megret R, Desbat B, Laguerre M, Castano S, Perrais D, Rorsman P, Oda R, Lang J. A Central Small Amino Acid in the VAMP2 Transmembrane Domain Regulates the Fusion Pore in Exocytosis. Sci Rep 2017; 7:2835. [PMID: 28588281 PMCID: PMC5460238 DOI: 10.1038/s41598-017-03013-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Accepted: 04/27/2017] [Indexed: 11/30/2022] Open
Abstract
Exocytosis depends on cytosolic domains of SNARE proteins but the function of the transmembrane domains (TMDs) in membrane fusion remains controversial. The TMD of the SNARE protein synaptobrevin2/VAMP2 contains two highly conserved small amino acids, G100 and C103, in its central portion. Substituting G100 and/or C103 with the β-branched amino acid valine impairs the structural flexibility of the TMD in terms of α-helix/β-sheet transitions in model membranes (measured by infrared reflection-absorption or evanescent wave spectroscopy) during increase in protein/lipid ratios, a parameter expected to be altered by recruitment of SNAREs at fusion sites. This structural change is accompanied by reduced membrane fluidity (measured by infrared ellipsometry). The G100V/C103V mutation nearly abolishes depolarization-evoked exocytosis (measured by membrane capacitance) and hormone secretion (measured biochemically). Single-vesicle optical (by TIRF microscopy) and biophysical measurements of ATP release indicate that G100V/C103V retards initial fusion-pore opening, hinders its expansion and leads to premature closure in most instances. We conclude that the TMD of VAMP2 plays a critical role in membrane fusion and that the structural mobility provided by the central small amino acids is crucial for exocytosis by influencing the molecular re-arrangements of the lipid membrane that are necessary for fusion pore opening and expansion.
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Affiliation(s)
- Benoît Hastoy
- Laboratory of Membrane Chemistry and Biology (CBMN), UMR CNRS 5248, Université de Bordeaux, Allée de Geoffroy St Hilaire, 33600, Pessac, France.,Université de Bordeaux, 351 Cours de la Libération, 33400, Talence, France.,Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, OX3 7LJ, UK
| | - Pier A Scotti
- Laboratory of Membrane Chemistry and Biology (CBMN), UMR CNRS 5248, Université de Bordeaux, Allée de Geoffroy St Hilaire, 33600, Pessac, France.,Université de Bordeaux, 351 Cours de la Libération, 33400, Talence, France
| | - Alexandra Milochau
- Laboratory of Membrane Chemistry and Biology (CBMN), UMR CNRS 5248, Université de Bordeaux, Allée de Geoffroy St Hilaire, 33600, Pessac, France.,Université de Bordeaux, 351 Cours de la Libération, 33400, Talence, France
| | - Zahia Fezoua-Boubegtiten
- Laboratory of Membrane Chemistry and Biology (CBMN), UMR CNRS 5248, Université de Bordeaux, Allée de Geoffroy St Hilaire, 33600, Pessac, France.,Université de Bordeaux, 351 Cours de la Libération, 33400, Talence, France
| | - Jorge Rodas
- Université de Bordeaux, 351 Cours de la Libération, 33400, Talence, France.,Laboratoire de l'Intégration du Matériau au Système, UMR CNRS 5218, 351 Cours de la Libération, 33400 Talence, France.,Institut Polytechnique de Bordeaux, Avernue des Facultés, 33405, Talence, France
| | - Rémi Megret
- Université de Bordeaux, 351 Cours de la Libération, 33400, Talence, France.,Laboratoire de l'Intégration du Matériau au Système, UMR CNRS 5218, 351 Cours de la Libération, 33400 Talence, France.,Institut Polytechnique de Bordeaux, Avernue des Facultés, 33405, Talence, France
| | - Bernard Desbat
- Laboratory of Membrane Chemistry and Biology (CBMN), UMR CNRS 5248, Université de Bordeaux, Allée de Geoffroy St Hilaire, 33600, Pessac, France.,Université de Bordeaux, 351 Cours de la Libération, 33400, Talence, France
| | - Michel Laguerre
- Laboratory of Membrane Chemistry and Biology (CBMN), UMR CNRS 5248, Université de Bordeaux, Allée de Geoffroy St Hilaire, 33600, Pessac, France.,Université de Bordeaux, 351 Cours de la Libération, 33400, Talence, France
| | - Sabine Castano
- Laboratory of Membrane Chemistry and Biology (CBMN), UMR CNRS 5248, Université de Bordeaux, Allée de Geoffroy St Hilaire, 33600, Pessac, France.,Université de Bordeaux, 351 Cours de la Libération, 33400, Talence, France
| | - David Perrais
- Université de Bordeaux, 351 Cours de la Libération, 33400, Talence, France.,Interdisciplinary Institute for Neuroscience, UMR CNRS 5287, 146, rue Léo-Saignat, 33077, Bordeaux, France
| | - Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, OX3 7LJ, UK
| | - Reiko Oda
- Laboratory of Membrane Chemistry and Biology (CBMN), UMR CNRS 5248, Université de Bordeaux, Allée de Geoffroy St Hilaire, 33600, Pessac, France.,Université de Bordeaux, 351 Cours de la Libération, 33400, Talence, France
| | - Jochen Lang
- Laboratory of Membrane Chemistry and Biology (CBMN), UMR CNRS 5248, Université de Bordeaux, Allée de Geoffroy St Hilaire, 33600, Pessac, France. .,Université de Bordeaux, 351 Cours de la Libération, 33400, Talence, France.
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Duvoor C, Dendi VS, Marco A, Shekhawat NS, Chada A, Ravilla R, Musham CK, Mirza W, Chaudhury A. Commentary: ATP: The crucial component of secretory vesicles: Accelerated ATP/insulin exocytosis and prediabetes. Front Physiol 2017; 8:53. [PMID: 28210227 PMCID: PMC5288386 DOI: 10.3389/fphys.2017.00053] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Accepted: 01/19/2017] [Indexed: 02/03/2023] Open
Affiliation(s)
- Chitharanjan Duvoor
- Department of Endocrinology and Internal Medicine, University of Arkansas for Medical SciencesLittle Rock, AR, USA; GIM FoundationLittle Rock, AR, USA
| | - Vijaya S Dendi
- GIM FoundationLittle Rock, AR, USA; Department of Internal Medicine and Hospital Medicine, Christus Trinity Mother Frances HospitalTyler, TX, USA
| | - Asween Marco
- GIM FoundationLittle Rock, AR, USA; Department of Policy, University of Arkansas for Little RockLittle Rock, AR, USA
| | - Nawal S Shekhawat
- GIM FoundationLittle Rock, AR, USA; Tutwiler ClinicTutwiler, MS, USA
| | - Aditya Chada
- GIM FoundationLittle Rock, AR, USA; Department of Pulmonary and Critical Care Medicine, University of Arkansas for Medical SciencesLittle Rock, AR, USA
| | - Rahul Ravilla
- GIM FoundationLittle Rock, AR, USA; Winthrop P. Rockefeller Cancer Institute, University of Arkansas for Medical SciencesLittle Rock, AR, USA
| | - Chaitanya K Musham
- GIM FoundationLittle Rock, AR, USA; St. Vincent Infirmary (Catholic Health Initiative)Little Rock, AR, USA
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Collins SC, Do HW, Hastoy B, Hugill A, Adam J, Chibalina MV, Galvanovskis J, Godazgar M, Lee S, Goldsworthy M, Salehi A, Tarasov AI, Rosengren AH, Cox R, Rorsman P. Increased Expression of the Diabetes Gene SOX4 Reduces Insulin Secretion by Impaired Fusion Pore Expansion. Diabetes 2016; 65:1952-61. [PMID: 26993066 PMCID: PMC4996324 DOI: 10.2337/db15-1489] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Accepted: 03/08/2016] [Indexed: 12/27/2022]
Abstract
The transcription factor Sox4 has been proposed to underlie the increased type 2 diabetes risk linked to an intronic single nucleotide polymorphism in CDKAL1 In a mouse model expressing a mutant form of Sox4, glucose-induced insulin secretion is reduced by 40% despite normal intracellular Ca(2+) signaling and depolarization-evoked exocytosis. This paradox is explained by a fourfold increase in kiss-and-run exocytosis (as determined by single-granule exocytosis measurements) in which the fusion pore connecting the granule lumen to the exterior expands to a diameter of only 2 nm, which does not allow the exit of insulin. Microarray analysis indicated that this correlated with an increased expression of the exocytosis-regulating protein Stxbp6. In a large collection of human islet preparations (n = 63), STXBP6 expression and glucose-induced insulin secretion correlated positively and negatively with SOX4 expression, respectively. Overexpression of SOX4 in the human insulin-secreting cell EndoC-βH2 interfered with granule emptying and inhibited hormone release, the latter effect reversed by silencing STXBP6 These data suggest that increased SOX4 expression inhibits insulin secretion and increased diabetes risk by the upregulation of STXBP6 and an increase in kiss-and-run exocytosis at the expense of full fusion. We propose that pharmacological interventions promoting fusion pore expansion may be effective in diabetes therapy.
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Affiliation(s)
- Stephan C Collins
- Oxford Centre for Diabetes, Endocrinology & Metabolism, Radcliffe Department of Medicine, Oxford, U.K. Université de Bourgogne Franche-Comté, Burgundy, France
| | - Hyun Woong Do
- Oxford Centre for Diabetes, Endocrinology & Metabolism, Radcliffe Department of Medicine, Oxford, U.K
| | - Benoit Hastoy
- Oxford Centre for Diabetes, Endocrinology & Metabolism, Radcliffe Department of Medicine, Oxford, U.K
| | - Alison Hugill
- Mammalian Genetics Unit, MRC Harwell, Oxfordshire, U.K
| | - Julie Adam
- Oxford Centre for Diabetes, Endocrinology & Metabolism, Radcliffe Department of Medicine, Oxford, U.K
| | - Margarita V Chibalina
- Oxford Centre for Diabetes, Endocrinology & Metabolism, Radcliffe Department of Medicine, Oxford, U.K
| | - Juris Galvanovskis
- Oxford Centre for Diabetes, Endocrinology & Metabolism, Radcliffe Department of Medicine, Oxford, U.K. Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy, and Genetics, University of Oxford, Oxford, U.K
| | - Mahdieh Godazgar
- Oxford Centre for Diabetes, Endocrinology & Metabolism, Radcliffe Department of Medicine, Oxford, U.K
| | - Sheena Lee
- Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy, and Genetics, University of Oxford, Oxford, U.K
| | | | - Albert Salehi
- Lund University Diabetes Centre, Department of Clinical Sciences, Skåne University Hospital Malmö, Lund University, Malmö, Sweden Department of Neuroscience and Physiology, University of Göteborg, Göteborg, Sweden
| | - Andrei I Tarasov
- Oxford Centre for Diabetes, Endocrinology & Metabolism, Radcliffe Department of Medicine, Oxford, U.K. Oxford National Institute of Health Research, Biomedical Research Centre, Churchill Hospital, Oxford, U.K
| | - Anders H Rosengren
- Lund University Diabetes Centre, Department of Clinical Sciences, Skåne University Hospital Malmö, Lund University, Malmö, Sweden
| | - Roger Cox
- Mammalian Genetics Unit, MRC Harwell, Oxfordshire, U.K
| | - Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology & Metabolism, Radcliffe Department of Medicine, Oxford, U.K. Department of Neuroscience and Physiology, University of Göteborg, Göteborg, Sweden Oxford National Institute of Health Research, Biomedical Research Centre, Churchill Hospital, Oxford, U.K
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10
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Khan S, Yan-Do R, Duong E, Wu X, Bautista A, Cheley S, MacDonald PE, Braun M. Autocrine activation of P2Y1 receptors couples Ca (2+) influx to Ca (2+) release in human pancreatic beta cells. Diabetologia 2014; 57:2535-45. [PMID: 25208758 DOI: 10.1007/s00125-014-3368-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Accepted: 08/13/2014] [Indexed: 01/26/2023]
Abstract
AIMS/HYPOTHESIS There is evidence that ATP acts as an autocrine signal in beta cells but the receptors and pathways involved are incompletely understood. Here we investigate the receptor subtype(s) and mechanism(s) mediating the effects of ATP on human beta cells. METHODS We examined the effects of purinergic agonists and antagonists on membrane potential, membrane currents, intracellular Ca(2+) ([Ca(2+)]i) and insulin secretion in human beta cells. RESULTS Extracellular application of ATP evoked small inward currents (3.4 ± 0.7 pA) accompanied by depolarisation of the membrane potential (by 14.4 ± 2.4 mV) and stimulation of electrical activity at 6 mmol/l glucose. ATP increased [Ca(2+)]i by stimulating Ca(2+) influx and evoking Ca(2+) release via InsP3-receptors in the endoplasmic reticulum (ER). ATP-evoked Ca(2+) release was sufficient to trigger exocytosis in cells voltage-clamped at -70 mV. All effects of ATP were mimicked by the P2Y(1/12/13) agonist ADP and the P2Y1 agonist MRS-2365, whereas the P2X(1/3) agonist α,β-methyleneadenosine-5-triphosphate only had a small effect. The P2Y1 antagonists MRS-2279 and MRS-2500 hyperpolarised glucose-stimulated beta cells and lowered [Ca(2+)]i in the absence of exogenously added ATP and inhibited glucose-induced insulin secretion by 35%. In voltage-clamped cells subjected to action potential-like stimulation, MRS-2279 decreased [Ca(2+)]i and exocytosis without affecting Ca(2+) influx. CONCLUSIONS/INTERPRETATION These data demonstrate that ATP acts as a positive autocrine signal in human beta cells by activating P2Y1 receptors, stimulating electrical activity and coupling Ca(2+) influx to Ca(2+) release from ER stores.
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Affiliation(s)
- Shara Khan
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada
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11
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Lemaître F, Guille Collignon M, Amatore C. Recent advances in Electrochemical Detection of Exocytosis. Electrochim Acta 2014. [DOI: 10.1016/j.electacta.2014.02.059] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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12
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Abstract
Impaired insulin secretion from pancreatic β-cells is a major factor in the pathogenesis of type 2 diabetes. The main regulator of insulin secretion is the plasma glucose concentration. Insulin secretion is modified by other nutrients, circulating hormones and the autonomic nervous system, as well as local paracrine and autocrine signals. Autocrine signalling involves diffusible molecules that bind to receptors on the same cell from which they have been released. The first transmitter to be implicated in the autocrine regulation of β-cell function was insulin itself. The importance of autocrine insulin signalling is underscored by the finding that mice lacking insulin receptors in β-cells are glucose intolerant. In addition to insulin, β-cells secrete a variety of additional substances, including peptides (e.g. amylin, chromogranin A and B and their cleavage products), neurotransmitters (ATP and γ-aminobutyric acid) and ions (e.g. zinc). Here we review the autocrine effects of substances secreted from β-cells, with a focus on acute effects in stimulus-secretion coupling, present some novel data and discuss the general significance of autocrine signals for the regulation of insulin secretion.
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Affiliation(s)
- M Braun
- Alberta Diabetes Institute, University of Alberta, Edmonton, Canada.
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Abstract
Pancreatic β cells secrete insulin, the body's only hormone capable of lowering plasma glucose levels. Impaired or insufficient insulin secretion results in diabetes mellitus. The β cell is electrically excitable; in response to an elevation of glucose, it depolarizes and starts generating action potentials. The electrophysiology of mouse β cells and the cell's role in insulin secretion have been extensively investigated. More recently, similar studies have been performed on human β cells. These studies have revealed numerous and important differences between human and rodent β cells. Here we discuss the properties of human pancreatic β cells: their glucose sensing, the ion channel complement underlying glucose-induced electrical activity that culminates in exocytotic release of insulin, the cellular control of exocytosis, and the modulation of insulin secretion by circulating hormones and locally released neurotransmitters. Finally, we consider the pathophysiology of insulin secretion and the interactions between genetics and environmental factors that may explain the current diabetes epidemic.
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Affiliation(s)
- Patrik Rorsman
- Oxford Center for Diabetes, Endocrinology and Metabolism, University of Oxford, Oxford OX3 7LJ, United Kingdom.
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14
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Hoppa MB, Jones E, Karanauskaite J, Ramracheya R, Braun M, Collins SC, Zhang Q, Clark A, Eliasson L, Genoud C, MacDonald PE, Monteith AG, Barg S, Galvanovskis J, Rorsman P. Multivesicular exocytosis in rat pancreatic beta cells. Diabetologia 2012; 55:1001-12. [PMID: 22189485 PMCID: PMC3296018 DOI: 10.1007/s00125-011-2400-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Accepted: 11/17/2011] [Indexed: 11/04/2022]
Abstract
AIMS/HYPOTHESIS To establish the occurrence, modulation and functional significance of compound exocytosis in insulin-secreting beta cells. METHODS Exocytosis was monitored in rat beta cells by electrophysiological, biochemical and optical methods. The functional assays were complemented by three-dimensional reconstruction of confocal imaging, transmission and block face scanning electron microscopy to obtain ultrastructural evidence of compound exocytosis. RESULTS Compound exocytosis contributed marginally (<5% of events) to exocytosis elicited by glucose/membrane depolarisation alone. However, in beta cells stimulated by a combination of glucose and the muscarinic agonist carbachol, 15-20% of the release events were due to multivesicular exocytosis, but the frequency of exocytosis was not affected. The optical measurements suggest that carbachol should stimulate insulin secretion by ∼40%, similar to the observed enhancement of glucose-induced insulin secretion. The effects of carbachol were mimicked by elevating [Ca(2+)](i) from 0.2 to 2 μmol/l Ca(2+). Two-photon sulforhodamine imaging revealed exocytotic events about fivefold larger than single vesicles and that these structures, once formed, could persist for tens of seconds. Cells exposed to carbachol for 30 s contained long (1-2 μm) serpentine-like membrane structures adjacent to the plasma membrane. Three-dimensional electron microscopy confirmed the existence of fused multigranular aggregates within the beta cell, the frequency of which increased about fourfold in response to stimulation with carbachol. CONCLUSIONS/INTERPRETATION Although contributing marginally to glucose-induced insulin secretion, compound exocytosis becomes quantitatively significant under conditions associated with global elevation of cytoplasmic calcium. These findings suggest that compound exocytosis is a major contributor to the augmentation of glucose-induced insulin secretion by muscarinic receptor activation.
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Affiliation(s)
- M. B. Hoppa
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Oxford, OX3 7LJ UK
| | - E. Jones
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Oxford, OX3 7LJ UK
| | - J. Karanauskaite
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Oxford, OX3 7LJ UK
| | - R. Ramracheya
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Oxford, OX3 7LJ UK
| | - M. Braun
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Oxford, OX3 7LJ UK
| | - S. C. Collins
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Oxford, OX3 7LJ UK
| | - Q. Zhang
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Oxford, OX3 7LJ UK
| | - A. Clark
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Oxford, OX3 7LJ UK
| | - L. Eliasson
- Lund University Diabetes Centre, Clinical Research Centre, Malmo, Sweden
| | - C. Genoud
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - P. E. MacDonald
- Department of Pharmacology, University of Alberta, Edmonton, Canada
| | | | - S. Barg
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - J. Galvanovskis
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Oxford, OX3 7LJ UK
| | - P. Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Oxford, OX3 7LJ UK
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15
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Levi F, Mosekilde E, Rand DA. Advancing systems medicine and therapeutics through biosimulation. Interface Focus 2010. [DOI: 10.1098/rsfs.2010.0019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Affiliation(s)
- Francis Levi
- U776, INSERM, hôpital Paul Brousse, 14-16 Avenue Paul Vaillant Couturier, Villejuif, France
| | - Erik Mosekilde
- Department of Physics, Technical University of Denmark, Fysikvej 309, Lyngby, Denmark
| | - David A. Rand
- Warwick Systems Biology Centre and Mathematics Institute, University of Warwick, Coventry House, Coventry, UK
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