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Hu M, Cebola I, Carrat G, Jiang S, Nawaz S, Khamis A, Canouil M, Froguel P, Schulte A, Solimena M, Ibberson M, Marchetti P, Cardenas-Diaz FL, Gadue PJ, Hastoy B, Almeida-Souza L, McMahon H, Rutter GA. Chromatin 3D interaction analysis of the STARD10 locus unveils FCHSD2 as a regulator of insulin secretion. Cell Rep 2021; 34:108881. [PMID: 33730570 PMCID: PMC7972990 DOI: 10.1016/j.celrep.2021.108881] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Hu M, Cebola I, Carrat G, Jiang S, Nawaz S, Khamis A, Canouil M, Froguel P, Schulte A, Solimena M, Ibberson M, Marchetti P, Cardenas-Diaz FL, Gadue PJ, Hastoy B, Almeida-Souza L, McMahon H, Rutter GA. Chromatin 3D interaction analysis of the STARD10 locus unveils FCHSD2 as a regulator of insulin secretion. Cell Rep 2021; 34:108703. [PMID: 33535042 PMCID: PMC7856552 DOI: 10.1016/j.celrep.2021.108703] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 12/10/2019] [Accepted: 01/08/2021] [Indexed: 12/26/2022] Open
Abstract
Using chromatin conformation capture, we show that an enhancer cluster in the STARD10 type 2 diabetes (T2D) locus forms a defined 3-dimensional (3D) chromatin domain. A 4.1-kb region within this locus, carrying 5 T2D-associated variants, physically interacts with CTCF-binding regions and with an enhancer possessing strong transcriptional activity. Analysis of human islet 3D chromatin interaction maps identifies the FCHSD2 gene as an additional target of the enhancer cluster. CRISPR-Cas9-mediated deletion of the variant region, or of the associated enhancer, from human pancreas-derived EndoC-βH1 cells impairs glucose-stimulated insulin secretion. Expression of both STARD10 and FCHSD2 is reduced in cells harboring CRISPR deletions, and lower expression of STARD10 and FCHSD2 is associated, the latter nominally, with the possession of risk variant alleles in human islets. Finally, CRISPR-Cas9-mediated loss of STARD10 or FCHSD2, but not ARAP1, impairs regulated insulin secretion. Thus, multiple genes at the STARD10 locus influence β cell function.
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Affiliation(s)
- Ming Hu
- Section of Cell Biology and Functional Genomics, Department of Medicine, Imperial College London, Hammersmith Hospital, Du Cane Road, London W12 0NN, UK
| | - Inês Cebola
- Section of Genetics and Genomics, Department of Metabolism, Digestion, and Reproduction, Imperial College London, Hammersmith Hospital, Du Cane Road, London W12 0NN, UK
| | - Gaelle Carrat
- Section of Cell Biology and Functional Genomics, Department of Medicine, Imperial College London, Hammersmith Hospital, Du Cane Road, London W12 0NN, UK
| | - Shuying Jiang
- Section of Cell Biology and Functional Genomics, Department of Medicine, Imperial College London, Hammersmith Hospital, Du Cane Road, London W12 0NN, UK
| | - Sameena Nawaz
- Oxford Centre for Diabetes Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Headington, Oxford OX3 7LE, UK
| | - Amna Khamis
- Université de Lille, CNRS, CHU Lille, Institut Pasteur de Lille, UMR 8199 - EGID, 59000 Lille, France
| | - Mickaël Canouil
- Université de Lille, CNRS, CHU Lille, Institut Pasteur de Lille, UMR 8199 - EGID, 59000 Lille, France
| | - Philippe Froguel
- Université de Lille, CNRS, CHU Lille, Institut Pasteur de Lille, UMR 8199 - EGID, 59000 Lille, France
| | - Anke Schulte
- Sanofi-Aventis Deutschland GmbH, 65926 Frankfurt am Main, Germany
| | - Michele Solimena
- Paul Langerhans Institute of the Helmholtz Center Munich at the University Hospital and Faculty of Medicine, TU Dresden, 01307 Dresden, Germany
| | - Mark Ibberson
- Vital-IT Group, SIB Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland
| | - Piero Marchetti
- Department of Endocrinology and Metabolism, University of Pisa, 56126 Pisa, Italy
| | - Fabian L Cardenas-Diaz
- Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA, USA; Centre for Cellular and Molecular Therapeutics, Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Paul J Gadue
- Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA, USA; Centre for Cellular and Molecular Therapeutics, Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Benoit Hastoy
- Oxford Centre for Diabetes Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Headington, Oxford OX3 7LE, UK
| | - Leonardo Almeida-Souza
- HiLIFE Institute of Biotechnology & Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
| | - Harvey McMahon
- MRC MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Guy A Rutter
- Section of Cell Biology and Functional Genomics, Department of Medicine, Imperial College London, Hammersmith Hospital, Du Cane Road, London W12 0NN, UK; Lee Kong Chian School of Medicine, Nan Yang Technological University, Singapore, Singapore.
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Salem V, Silva LD, Suba K, Georgiadou E, Neda Mousavy Gharavy S, Akhtar N, Martin-Alonso A, Gaboriau DCA, Rothery SM, Stylianides T, Carrat G, Pullen TJ, Singh SP, Hodson DJ, Leclerc I, Shapiro AMJ, Marchetti P, Briant LJB, Distaso W, Ninov N, Rutter GA. Leader β-cells coordinate Ca 2+ dynamics across pancreatic islets in vivo. Nat Metab 2019; 1:615-629. [PMID: 32694805 DOI: 10.1038/s42255-019-0075-2] [Citation(s) in RCA: 103] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Accepted: 05/08/2019] [Indexed: 02/06/2023]
Abstract
Pancreatic β-cells form highly connected networks within isolated islets. Whether this behaviour pertains to the situation in vivo, after innervation and during continuous perfusion with blood, is unclear. In the present study, we used the recombinant Ca2+ sensor GCaMP6 to assess glucose-regulated connectivity in living zebrafish Danio rerio, and in murine or human islets transplanted into the anterior eye chamber. In each setting, Ca2+ waves emanated from temporally defined leader β-cells, and three-dimensional connectivity across the islet increased with glucose stimulation. Photoablation of zebrafish leader cells disrupted pan-islet signalling, identifying these as likely pacemakers. Correspondingly, in engrafted mouse islets, connectivity was sustained during prolonged glucose exposure, and super-connected 'hub' cells were identified. Granger causality analysis revealed a controlling role for temporally defined leaders, and transcriptomic analyses revealed a discrete hub cell fingerprint. We thus define a population of regulatory β-cells within coordinated islet networks in vivo. This population may drive Ca2+ dynamics and pulsatile insulin secretion.
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Affiliation(s)
- Victoria Salem
- Department of Medicine, Imperial College London, London, UK.
| | - Luis Delgadillo Silva
- Center for Regenerative Therapies Dresden, Technische Universität Dresden, Dresden, Germany
| | - Kinga Suba
- Department of Medicine, Imperial College London, London, UK
| | | | | | - Nadeem Akhtar
- Center for Regenerative Therapies Dresden, Technische Universität Dresden, Dresden, Germany
| | | | - David C A Gaboriau
- Facility for Imaging by Light Microscopy, Imperial College London, London, UK
| | - Stephen M Rothery
- Facility for Imaging by Light Microscopy, Imperial College London, London, UK
| | | | - Gaelle Carrat
- Department of Medicine, Imperial College London, London, UK
| | - Timothy J Pullen
- Department of Diabetes, Faculty of Life Science and Medicine, King's College London, London, UK
| | - Sumeet Pal Singh
- Center for Regenerative Therapies Dresden, Technische Universität Dresden, Dresden, Germany
| | - David J Hodson
- Institute of Metabolism and Systems Research, University of Birmingham, Edgbaston, UK
- Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham, UK
- Centre of Membrane Proteins and Receptors, University of Birmingham and University of Nottingham, Nottingham, UK
| | | | - A M James Shapiro
- Clinical Islet Laboratory and Clinical Islet Transplant Program, University of Alberta, Edmonton, Alberta, Canada
| | | | | | | | - Nikolay Ninov
- Center for Regenerative Therapies Dresden, Technische Universität Dresden, Dresden, Germany.
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the University Hospital Carl Gustav Carus of TU Dresden, German Center for Diabetes Research, Dresden, Germany.
| | - Guy A Rutter
- Department of Medicine, Imperial College London, London, UK.
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Izzi‐Engbeaya C, Comninos AN, Clarke SA, Jomard A, Yang L, Jones S, Abbara A, Narayanaswamy S, Eng PC, Papadopoulou D, Prague JK, Bech P, Godsland IF, Bassett P, Sands C, Camuzeaux S, Gomez‐Romero M, Pearce JTM, Lewis MR, Holmes E, Nicholson JK, Tan T, Ratnasabapathy R, Hu M, Carrat G, Piemonti L, Bugliani M, Marchetti P, Johnson PR, Hughes SJ, James Shapiro AM, Rutter GA, Dhillo WS. The effects of kisspeptin on β-cell function, serum metabolites and appetite in humans. Diabetes Obes Metab 2018; 20:2800-2810. [PMID: 29974637 PMCID: PMC6282711 DOI: 10.1111/dom.13460] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Revised: 06/22/2018] [Accepted: 06/29/2018] [Indexed: 02/06/2023]
Abstract
AIMS To investigate the effect of kisspeptin on glucose-stimulated insulin secretion and appetite in humans. MATERIALS AND METHODS In 15 healthy men (age: 25.2 ± 1.1 years; BMI: 22.3 ± 0.5 kg m-2 ), we compared the effects of 1 nmol kg-1 h-1 kisspeptin versus vehicle administration on glucose-stimulated insulin secretion, metabolites, gut hormones, appetite and food intake. In addition, we assessed the effect of kisspeptin on glucose-stimulated insulin secretion in vitro in human pancreatic islets and a human β-cell line (EndoC-βH1 cells). RESULTS Kisspeptin administration to healthy men enhanced insulin secretion following an intravenous glucose load, and modulated serum metabolites. In keeping with this, kisspeptin increased glucose-stimulated insulin secretion from human islets and a human pancreatic cell line in vitro. In addition, kisspeptin administration did not alter gut hormones, appetite or food intake in healthy men. CONCLUSIONS Collectively, these data demonstrate for the first time a beneficial role for kisspeptin in insulin secretion in humans in vivo. This has important implications for our understanding of the links between reproduction and metabolism in humans, as well as for the ongoing translational development of kisspeptin-based therapies for reproductive and potentially metabolic conditions.
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Affiliation(s)
- Chioma Izzi‐Engbeaya
- Section of Endocrinology and Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Department of MedicineImperial College LondonLondonUK
| | - Alexander N. Comninos
- Section of Endocrinology and Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Department of MedicineImperial College LondonLondonUK
- Department of EndocrinologyImperial College Healthcare NHS TrustLondonUK
| | - Sophie A. Clarke
- Section of Endocrinology and Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Department of MedicineImperial College LondonLondonUK
| | - Anne Jomard
- Section of Endocrinology and Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Department of MedicineImperial College LondonLondonUK
| | - Lisa Yang
- Section of Endocrinology and Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Department of MedicineImperial College LondonLondonUK
| | - Sophie Jones
- Section of Endocrinology and Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Department of MedicineImperial College LondonLondonUK
| | - Ali Abbara
- Section of Endocrinology and Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Department of MedicineImperial College LondonLondonUK
| | - Shakunthala Narayanaswamy
- Section of Endocrinology and Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Department of MedicineImperial College LondonLondonUK
| | - Pei Chia Eng
- Section of Endocrinology and Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Department of MedicineImperial College LondonLondonUK
| | - Deborah Papadopoulou
- Section of Endocrinology and Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Department of MedicineImperial College LondonLondonUK
| | - Julia K. Prague
- Section of Endocrinology and Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Department of MedicineImperial College LondonLondonUK
| | - Paul Bech
- Section of Endocrinology and Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Department of MedicineImperial College LondonLondonUK
| | - Ian F. Godsland
- Section of Metabolic Medicine, Department of Medicine, Imperial College LondonSt Mary's HospitalLondonUK
| | | | - Caroline Sands
- The MRC‐NIHR National Phenome Centre and Imperial BRC Clinical Phenotyping Centre, Division of Computational, Systems and Digestive Medicine, Department of Surgery and CancerLondonUK
| | - Stephane Camuzeaux
- The MRC‐NIHR National Phenome Centre and Imperial BRC Clinical Phenotyping Centre, Division of Computational, Systems and Digestive Medicine, Department of Surgery and CancerLondonUK
| | - Maria Gomez‐Romero
- The MRC‐NIHR National Phenome Centre and Imperial BRC Clinical Phenotyping Centre, Division of Computational, Systems and Digestive Medicine, Department of Surgery and CancerLondonUK
| | - Jake T. M. Pearce
- The MRC‐NIHR National Phenome Centre and Imperial BRC Clinical Phenotyping Centre, Division of Computational, Systems and Digestive Medicine, Department of Surgery and CancerLondonUK
| | - Matthew R. Lewis
- The MRC‐NIHR National Phenome Centre and Imperial BRC Clinical Phenotyping Centre, Division of Computational, Systems and Digestive Medicine, Department of Surgery and CancerLondonUK
| | - Elaine Holmes
- The MRC‐NIHR National Phenome Centre and Imperial BRC Clinical Phenotyping Centre, Division of Computational, Systems and Digestive Medicine, Department of Surgery and CancerLondonUK
| | - Jeremy K. Nicholson
- The MRC‐NIHR National Phenome Centre and Imperial BRC Clinical Phenotyping Centre, Division of Computational, Systems and Digestive Medicine, Department of Surgery and CancerLondonUK
| | - Tricia Tan
- Section of Endocrinology and Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Department of MedicineImperial College LondonLondonUK
| | - Risheka Ratnasabapathy
- Section of Endocrinology and Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Department of MedicineImperial College LondonLondonUK
| | - Ming Hu
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of MedicineImperial College LondonLondonUK
- Imperial Pancreatic Islet Biology and Diabetes ConsortiumHammersmith Hospital, Imperial College LondonLondonUK
| | - Gaelle Carrat
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of MedicineImperial College LondonLondonUK
- Imperial Pancreatic Islet Biology and Diabetes ConsortiumHammersmith Hospital, Imperial College LondonLondonUK
| | - Lorenzo Piemonti
- Diabetes Research Institute (SR‐DRI), IRCCS San Raffaele Scientific InstituteMilanItaly
- Faculty of MedicineVita‐Salute San Raffaele UniversityMilanItaly
| | - Marco Bugliani
- Department of Clinical and Experimental Medicine, Islet Cell LaboratoryUniversity of PisaPisaItaly
| | - Piero Marchetti
- Department of Clinical and Experimental Medicine, Islet Cell LaboratoryUniversity of PisaPisaItaly
| | - Paul R. Johnson
- Nuffield Department of Surgical SciencesUniversity of OxfordOxfordUK
- Oxford Centre for Diabetes, Endocrinology, and MetabolismUniversity of OxfordOxfordUK
- National Institute of Health Research Oxford Biomedical Research Centre, Churchill HospitalOxfordUK
| | - Stephen J. Hughes
- Nuffield Department of Surgical SciencesUniversity of OxfordOxfordUK
- Oxford Centre for Diabetes, Endocrinology, and MetabolismUniversity of OxfordOxfordUK
- National Institute of Health Research Oxford Biomedical Research Centre, Churchill HospitalOxfordUK
| | - A. M. James Shapiro
- Clinical Islet Laboratory and Clinical Islet Transplant ProgramUniversity of AlbertaEdmontonCanada
| | - Guy A. Rutter
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of MedicineImperial College LondonLondonUK
- Imperial Pancreatic Islet Biology and Diabetes ConsortiumHammersmith Hospital, Imperial College LondonLondonUK
| | - Waljit S. Dhillo
- Section of Endocrinology and Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Department of MedicineImperial College LondonLondonUK
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Ratnasabapathy R, Ma Y, Izzi-Engbeaya C, Nguyen-Tu MS, Richardson E, Hussain S, De BI, Holton C, Norton M, Carrat G, Schwappach B, Rutter GA, Dhillo WS, Gardiner JV. Hypothalamic arcuate glucokinase and its downstream pathways are critical in glucose homeostasis. ACTA ACUST UNITED AC 2018. [DOI: 10.1530/endoabs.59.oc3.5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Ma Y, Ratnasabapathy R, Izzi-Engbeaya C, Nguyen-Tu MS, Richardson E, Hussain S, De Backer I, Holton C, Norton M, Carrat G, Schwappach B, Rutter GA, Dhillo WS, Gardiner J. Hypothalamic arcuate nucleus glucokinase regulates insulin secretion and glucose homeostasis. Diabetes Obes Metab 2018; 20:2246-2254. [PMID: 29748994 PMCID: PMC6099255 DOI: 10.1111/dom.13359] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Revised: 04/30/2018] [Accepted: 05/09/2018] [Indexed: 01/08/2023]
Abstract
AIMS To investigate the role of arcuate glucokinase (GK) in the regulation of glucose homeostasis. MATERIALS AND METHODS A recombinant adeno-associated virus expressing either GK or an antisense GK construct was used to alter GK activity specifically in the hypothalamic arcuate nucleus (arc). GK activity in this nucleus was also increased by stereotactic injection of the GK activator, compound A. The effect of altered arc GK activity on glucose homeostasis was subsequently investigated using glucose and insulin tolerance tests. RESULTS Increased GK activity specifically within the arc increased insulin secretion and improved glucose tolerance in rats during oral glucose tolerance tests. Decreased GK activity in this nucleus reduced insulin secretion and increased glucose levels during the same tests. Insulin sensitivity was not affected in either case. The effect of arc GK was maintained in a model of type 2 diabetes. CONCLUSIONS These results demonstrate a role for arc GK in systemic glucose homeostasis.
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Affiliation(s)
- Yue Ma
- Section of Endocrinology and Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Imperial College London, London, UK
| | - Risheka Ratnasabapathy
- Section of Endocrinology and Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Imperial College London, London, UK
| | - Chioma Izzi-Engbeaya
- Section of Endocrinology and Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Imperial College London, London, UK
| | - Marie-Sophie Nguyen-Tu
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Imperial College London, London, UK
| | - Errol Richardson
- Section of Endocrinology and Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Imperial College London, London, UK
| | - Sufyan Hussain
- Section of Endocrinology and Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Imperial College London, London, UK
| | - Ivan De Backer
- Section of Endocrinology and Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Imperial College London, London, UK
| | - Christopher Holton
- Section of Endocrinology and Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Imperial College London, London, UK
| | - Mariana Norton
- Section of Endocrinology and Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Imperial College London, London, UK
| | - Gaelle Carrat
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Imperial College London, London, UK
| | - Blanche Schwappach
- Department of Molecular Biology, Centre for Biochemistry and Molecular Cell Biology, Heart Research Centre Göttingen, University Medicine Göttingen, Göttingen, Germany
| | - Guy A Rutter
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Imperial College London, London, UK
| | - Waljit S Dhillo
- Section of Endocrinology and Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Imperial College London, London, UK
| | - James Gardiner
- Section of Endocrinology and Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Imperial College London, London, UK
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Labasque M, Meffre J, Carrat G, Becamel C, Bockaert J, Marin P. Constitutive activity of serotonin 2C receptors at G protein-independent signaling: modulation by RNA editing and antidepressants. Mol Pharmacol 2010; 78:818-26. [PMID: 20699324 DOI: 10.1124/mol.110.066035] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Serotonin (5-HT)(2C) receptor is a G(q)-coupled receptor exhibiting a high degree of constitutive activity toward phospholipase C effector pathway, a process regulated by receptor mRNA editing. In addition to G protein-dependent signaling, 5-HT(2C) receptors also activate the extracellular signal-regulated kinase (ERK) 1/2 pathway independently of receptor coupling to G proteins. Constitutive activity at ERK signaling has not yet been explored. Transient expression of unedited 5-HT(2C-INI) receptors in human embryonic kidney (HEK) 293 cells resulted in a marked increase in ERK1/2 phosphorylation compared with nontransfected cells. No increase in ERK1/2 phosphorylation was measured in cells expressing fully edited (5-HT(2C-VGV)) receptors. Basal ERK1/2 phosphorylation in 5-HT(2C-INI) receptor-expressing cells was abolished by 5-methyl-1-(3-pyridylcarbamoyl)-1,2,3,5-tetrahydropyrrolo[2,3-f]indole (SB206,553), a 5-HT(2C) inverse agonist toward phospholipase C. This effect was prevented by the neutral antagonist 6-chloro-5-methyl-1-[6-(2-methylpyridin-3-yloxy)pyridin-3-ylcarbamoyl]indoline (SB242,084), which alone did not alter basal activity. Similar observations were made in vivo in mouse choroid plexus, a structure rich in constitutively active 5-HT(2C) receptors. Reminiscent of agonist-induced ERK1/2 phosphorylation, basal activity in HEK 293 cells was unaffected by cellular depletion of Gα(q/11) and Gα(13) proteins but strongly reduced in cells expressing a dominant-negative β-arrestin or depleted of β-arrestin by RNA interference and in cells expressing a dominant-negative calmodulin or a 5-HT(2C-INI) receptor mutant not capable of interacting with calmodulin. The tetracyclic antidepressants mirtazapine and mianserin likewise reduced basal ERK activation. On the other hand, the m-chlorophenylpiperazine derivative trazodone and the selective serotonin reuptake inhibitor fluoxetine were inactive alone but blocked 5-HT-induced ERK1/2 phosphorylation. Together, these data provide the first evidence of constitutive activity of a G protein-coupled receptor toward G-independent, β-arrestin-dependent, receptor signaling.
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Affiliation(s)
- Marilyne Labasque
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5203, Institut de Génomique Fonctionnelle, Université Montpellier 1 and 2, Montpellier, France
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