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Hastoy B, Godazgar M, Clark A, Nylander V, Spiliotis I, van de Bunt M, Chibalina MV, Barrett A, Burrows C, Tarasov AI, Scharfmann R, Gloyn AL, Rorsman P. Electrophysiological properties of human beta-cell lines EndoC-βH1 and -βH2 conform with human beta-cells. Sci Rep 2018; 8:16994. [PMID: 30451893 PMCID: PMC6242937 DOI: 10.1038/s41598-018-34743-7] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Accepted: 10/19/2018] [Indexed: 12/30/2022] Open
Abstract
Limited access to human islets has prompted the development of human beta cell models. The human beta cell lines EndoC-βH1 and EndoC-βH2 are increasingly used by the research community. However, little is known of their electrophysiological and secretory properties. Here, we monitored parameters that constitute the glucose-triggering pathway of insulin release. Both cell lines respond to glucose (6 and 20 mM) with 2- to 3-fold stimulation of insulin secretion which correlated with an elevation of [Ca2+]i, membrane depolarisation and increased action potential firing. Similar to human primary beta cells, KATP channel activity is low at 1 mM glucose and is further reduced upon increasing glucose concentration; an effect that was mimicked by the KATP channel blocker tolbutamide. The upstroke of the action potentials reflects the activation of Ca2+ channels with some small contribution of TTX-sensitive Na+ channels. The repolarisation involves activation of voltage-gated Kv2.2 channels and large-conductance Ca2+-activated K+ channels. Exocytosis presented a similar kinetics to human primary beta cells. The ultrastructure of these cells shows insulin vesicles composed of an electron-dense core surrounded by a thin clear halo. We conclude that the EndoC-βH1 and -βH2 cells share many features of primary human β-cells and thus represent a useful experimental model.
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Affiliation(s)
- Benoît Hastoy
- 0000 0004 1936 8948grid.4991.5Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Mahdieh Godazgar
- 0000 0004 1936 8948grid.4991.5Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Anne Clark
- 0000 0004 1936 8948grid.4991.5Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Vibe Nylander
- 0000 0004 1936 8948grid.4991.5Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Ioannis Spiliotis
- 0000 0004 1936 8948grid.4991.5Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Martijn van de Bunt
- 0000 0004 1936 8948grid.4991.5Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom ,0000 0004 1936 8948grid.4991.5Wellcome Centre for Human Genetics, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Margarita V. Chibalina
- 0000 0004 1936 8948grid.4991.5Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Amy Barrett
- 0000 0004 1936 8948grid.4991.5Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Carla Burrows
- 0000 0004 1936 8948grid.4991.5Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Andrei I. Tarasov
- 0000 0004 1936 8948grid.4991.5Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Raphael Scharfmann
- 0000 0001 2188 0914grid.10992.33INSERM U1016, Cochin Institute, Université Paris Descartes, Paris, France
| | - Anna L. Gloyn
- 0000 0004 1936 8948grid.4991.5Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom ,0000 0004 1936 8948grid.4991.5Wellcome Centre for Human Genetics, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom ,0000 0004 0488 9484grid.415719.fNational Institute for Health Research (NIHR) Oxford Biomedical Research Centre, Churchill Hospital, Oxford, United Kingdom
| | - Patrik Rorsman
- 0000 0004 1936 8948grid.4991.5Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom ,0000 0004 0488 9484grid.415719.fNational Institute for Health Research (NIHR) Oxford Biomedical Research Centre, Churchill Hospital, Oxford, United Kingdom ,0000 0000 9919 9582grid.8761.8Department of Physiology, Institute of Neuroscience and Physiology, University of Goteborg, Goteborg, Sweden
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Abstract
Islet amyloid polypeptide (IAPP) forms cytotoxic oligomers and amyloid fibrils in islets in type 2 diabetes (T2DM). The causal factors for amyloid formation are largely unknown. Mechanisms of molecular folding and assembly of human IAPP (hIAPP) into β-sheets, oligomers and fibrils have been assessed by detailed biophysical studies of hIAPP and non-fibrillogenic, rodent IAPP (rIAPP); cytotoxicity is associated with the early phases (oligomers/multimers) of fibrillogenesis. Interaction with synthetic membranes promotes β-sheet assembly possibly via a transient α-helical molecular conformation. Cellular hIAPP cytotoxicity can be activated from intracellular or extracellular sites. In transgenic rodents overexpressing hIAPP, intracellular pro-apoptotic signals can be generated at different points in β-cell protein synthesis. Increased cellular trafficking of proIAPP, failure of the unfolded protein response (UPR) or excess trafficking of misfolded peptide via the degradation pathways can induce apoptosis; these data indicate that defects in intracellular handling of hIAPP can induce cytotoxicity. However, there is no evidence for IAPP overexpression in T2DM. Extracellular amyloidosis is directly related to the degree of β-cell apoptosis in islets in T2DM. IAPP fragments, fibrils and multimers interact with membranes causing disruption in vivo and in vitro These findings support a role for extracellular IAPP in β-sheet conformation in cytotoxicity. Inhibitors of fibrillogenesis are useful tools to determine the aberrant mechanisms that result in hIAPP molecular refolding and islet amyloidosis. However, currently, their role as therapeutic agents remains uncertain.
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Affiliation(s)
- Daniel Raleigh
- Department of ChemistryStony Brook University, Stony Brook, New York, USA
- Research Department of Structural and Molecule BiologyUniversity College London, London, UK
| | - Xiaoxue Zhang
- Department of ChemistryStony Brook University, Stony Brook, New York, USA
| | - Benoît Hastoy
- Oxford Centre for Diabetes Endocrinology and MetabolismUniversity of Oxford, Oxford, UK
| | - Anne Clark
- Oxford Centre for Diabetes Endocrinology and MetabolismUniversity of Oxford, Oxford, UK
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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