1
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Peart LA, Draper M, Tarasov AI. The impact of GLP-1 signalling on the energy metabolism of pancreatic islet β-cells and extrapancreatic tissues. Peptides 2024; 178:171243. [PMID: 38788902 DOI: 10.1016/j.peptides.2024.171243] [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: 03/27/2024] [Revised: 05/19/2024] [Accepted: 05/21/2024] [Indexed: 05/26/2024]
Abstract
Glucagon-like peptide-1 signalling impacts glucose homeostasis and appetite thereby indirectly affecting substrate availability at the whole-body level. The incretin canonically produces an insulinotropic effect, thereby lowering blood glucose levels by promoting the uptake and inhibiting the production of the sugar by peripheral tissues. Likewise, GLP-1 signalling within the central nervous system reduces the appetite and food intake, whereas its gastric effect delays the absorption of nutrients, thus improving glycaemic control and reducing the risk of postprandial hyperglycaemia. We review the molecular aspects of the GLP-1 signalling, focusing on its impact on intracellular energy metabolism. Whilst the incretin exerts its effects predominantly via a Gs receptor, which decodes the incretin signal into the elevation of intracellular cAMP levels, the downstream signalling cascades within the cell, acting on fast and slow timescales, resulting in an enhancement or an attenuation of glucose catabolism, respectively.
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Affiliation(s)
- Leah A Peart
- School of Biomedical Sciences, Ulster University, Cromore Road, Coleraine, Northern Ireland BT52 1SA, UK
| | - Matthew Draper
- School of Biomedical Sciences, Ulster University, Cromore Road, Coleraine, Northern Ireland BT52 1SA, UK
| | - Andrei I Tarasov
- School of Biomedical Sciences, Ulster University, Cromore Road, Coleraine, Northern Ireland BT52 1SA, UK.
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2
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Varney MJ, Benovic JL. The Role of G Protein-Coupled Receptors and Receptor Kinases in Pancreatic β-Cell Function and Diabetes. Pharmacol Rev 2024; 76:267-299. [PMID: 38351071 PMCID: PMC10877731 DOI: 10.1124/pharmrev.123.001015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Revised: 12/01/2023] [Accepted: 12/07/2023] [Indexed: 02/16/2024] Open
Abstract
Type 2 diabetes (T2D) mellitus has emerged as a major global health concern that has accelerated in recent years due to poor diet and lifestyle. Afflicted individuals have high blood glucose levels that stem from the inability of the pancreas to make enough insulin to meet demand. Although medication can help to maintain normal blood glucose levels in individuals with chronic disease, many of these medicines are outdated, have severe side effects, and often become less efficacious over time, necessitating the need for insulin therapy. G protein-coupled receptors (GPCRs) regulate many physiologic processes, including blood glucose levels. In pancreatic β cells, GPCRs regulate β-cell growth, apoptosis, and insulin secretion, which are all critical in maintaining sufficient β-cell mass and insulin output to ensure euglycemia. In recent years, new insights into the signaling of incretin receptors and other GPCRs have underscored the potential of these receptors as desirable targets in the treatment of diabetes. The signaling of these receptors is modulated by GPCR kinases (GRKs) that phosphorylate agonist-activated GPCRs, marking the receptor for arrestin binding and internalization. Interestingly, genome-wide association studies using diabetic patient cohorts link the GRKs and arrestins with T2D. Moreover, recent reports show that GRKs and arrestins expressed in the β cell serve a critical role in the regulation of β-cell function, including β-cell growth and insulin secretion in both GPCR-dependent and -independent pathways. In this review, we describe recent insights into GPCR signaling and the importance of GRK function in modulating β-cell physiology. SIGNIFICANCE STATEMENT: Pancreatic β cells contain a diverse array of G protein-coupled receptors (GPCRs) that have been shown to improve β-cell function and survival, yet only a handful have been successfully targeted in the treatment of diabetes. This review discusses recent advances in our understanding of β-cell GPCR pharmacology and regulation by GPCR kinases while also highlighting the necessity of investigating islet-enriched GPCRs that have largely been unexplored to unveil novel treatment strategies.
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Affiliation(s)
- Matthew J Varney
- Department of Biochemistry and Molecular Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Jeffrey L Benovic
- Department of Biochemistry and Molecular Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania
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3
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Murthy MHS, Jasbi P, Lowe W, Kumar L, Olaosebikan M, Roger L, Yang J, Lewinski N, Daniels N, Cowen L, Klein-Seetharaman J. Insulin signaling and pharmacology in humans and in corals. PeerJ 2024; 12:e16804. [PMID: 38313028 PMCID: PMC10838073 DOI: 10.7717/peerj.16804] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Accepted: 12/27/2023] [Indexed: 02/06/2024] Open
Abstract
Once thought to be a unique capability of the Langerhans islets in the pancreas of mammals, insulin (INS) signaling is now recognized as an evolutionarily ancient function going back to prokaryotes. INS is ubiquitously present not only in humans but also in unicellular eukaryotes, fungi, worms, and Drosophila. Remote homologue identification also supports the presence of INS and INS receptor in corals where the availability of glucose is largely dependent on the photosynthetic activity of the symbiotic algae. The cnidarian animal host of corals operates together with a 20,000-sized microbiome, in direct analogy to the human gut microbiome. In humans, aberrant INS signaling is the hallmark of metabolic disease, and is thought to play a major role in aging, and age-related diseases, such as Alzheimer's disease. We here would like to argue that a broader view of INS beyond its human homeostasis function may help us understand other organisms, and in turn, studying those non-model organisms may enable a novel view of the human INS signaling system. To this end, we here review INS signaling from a new angle, by drawing analogies between humans and corals at the molecular level.
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Affiliation(s)
| | - Paniz Jasbi
- School of Molecular Sciences, Arizona State University, Phoenix, AZ, USA
| | - Whitney Lowe
- Departments of Chemistry & Physics, Colorado School of Mines, Golden, CO, United States
| | - Lokender Kumar
- Departments of Chemistry & Physics, Colorado School of Mines, Golden, CO, United States
| | | | - Liza Roger
- School of Molecular Sciences, Arizona State University, Phoenix, AZ, USA
- School of Ocean Futures, Arizona State University, Tempe, AZ, United States of America
| | - Jinkyu Yang
- Department of Aeronautics & Astronautics, University of Washington, Seattle, WA, USA
| | - Nastassja Lewinski
- Department of Chemical and Life Science Engineering, Virginia Commonwealth University, Richmond, VA, USA
| | - Noah Daniels
- Department of Computer Science, University of Rhode Island, Kingston, RI, USA
| | - Lenore Cowen
- Department of Computer Science, Tufts University, Medford, MA, USA
| | - Judith Klein-Seetharaman
- School of Molecular Sciences, Arizona State University, Phoenix, AZ, USA
- Departments of Chemistry & Physics, Colorado School of Mines, Golden, CO, United States
- College of Health Solutions, Arizona State University, Phoenix, AZ, United States
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4
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Folli F, Finzi G, Manfrini R, Galli A, Casiraghi F, Centofanti L, Berra C, Fiorina P, Davalli A, La Rosa S, Perego C, Higgins PB. Mechanisms of action of incretin receptor based dual- and tri-agonists in pancreatic islets. Am J Physiol Endocrinol Metab 2023; 325:E595-E609. [PMID: 37729025 PMCID: PMC10874655 DOI: 10.1152/ajpendo.00236.2023] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Revised: 09/15/2023] [Accepted: 09/16/2023] [Indexed: 09/22/2023]
Abstract
Simultaneous activation of the incretin G-protein-coupled receptors (GPCRs) via unimolecular dual-receptor agonists (UDRA) has emerged as a new therapeutic approach for type 2 diabetes. Recent studies also advocate triple agonism with molecules also capable of binding the glucagon receptor. In this scoping review, we discuss the cellular mechanisms of action (MOA) underlying the actions of these novel and therapeutically important classes of peptide receptor agonists. Clinical efficacy studies of several UDRAs have demonstrated favorable results both as monotherapies and when combined with approved hypoglycemics. Although the additive insulinotropic effects of dual glucagon-like peptide-1 receptor (GLP-1R) and glucose-dependent insulinotropic peptide receptor (GIPR) agonism were anticipated based on the known actions of either glucagon-like peptide-1 (GLP-1) or glucose-dependent insulinotropic peptide (GIP) alone, the additional benefits from GCGR were largely unexpected. Whether additional synergistic or antagonistic interactions among these G-protein receptor signaling pathways arise from simultaneous stimulation is not known. The signaling pathways affected by dual- and tri-agonism require more trenchant investigation before a comprehensive understanding of the cellular MOA. This knowledge will be essential for understanding the chronic efficacy and safety of these treatments.
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Affiliation(s)
- Franco Folli
- Dipartimento di Scienze della Salute, Università degli Studi di Milano, Milan, Italy
- Unit of Diabetes, Endocrinology and Metabolism, San Paolo Hospital, ASST Santi Paolo e Carlo, Milan, Italy
| | - Giovanna Finzi
- Unit of Pathology, Department of Oncology, ASST Sette Laghi, Varese, Italy
| | - Roberto Manfrini
- Dipartimento di Scienze della Salute, Università degli Studi di Milano, Milan, Italy
- Unit of Diabetes, Endocrinology and Metabolism, San Paolo Hospital, ASST Santi Paolo e Carlo, Milan, Italy
| | - Alessandra Galli
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, Milan, Italy
| | - Francesca Casiraghi
- Dipartimento di Scienze della Salute, Università degli Studi di Milano, Milan, Italy
| | - Lucia Centofanti
- Dipartimento di Scienze della Salute, Università degli Studi di Milano, Milan, Italy
| | - Cesare Berra
- IRCCS MultiMedica, Sesto San Giovanni, Milan, Italy
| | - Paolo Fiorina
- International Center for T1D, Pediatric Clinical Research Center Romeo ed Enrica Invernizzi, DIBIC, Università di Milano, Milan, Italy
- Nephrology Division, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States
- Division of Endocrinology, ASST Fatebenefratelli-Sacco, Milan, Italy
| | - Alberto Davalli
- Diabetes and Endocrinology Unit, Department of Internal Medicine, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Stefano La Rosa
- Unit of Pathology, Department of Medicine and Technological Innovation, University of Insubria, Varese, Italy
| | - Carla Perego
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, Milan, Italy
| | - Paul B Higgins
- Department of Life & Physical Sciences, Atlantic Technological University, Letterkenny, Ireland
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5
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Postić S, Sarikas S, Pfabe J, Pohorec V, Križančić Bombek L, Sluga N, Skelin Klemen M, Dolenšek J, Korošak D, Stožer A, Evans-Molina C, Johnson JD, Slak Rupnik M. High-resolution analysis of the cytosolic Ca 2+ events in β cell collectives in situ. Am J Physiol Endocrinol Metab 2023; 324:E42-E55. [PMID: 36449570 PMCID: PMC9829482 DOI: 10.1152/ajpendo.00165.2022] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Revised: 11/15/2022] [Accepted: 11/22/2022] [Indexed: 12/02/2022]
Abstract
The release of peptide hormones is predominantly regulated by a transient increase in cytosolic Ca2+ concentration ([Ca2+]c). To trigger exocytosis, Ca2+ ions enter the cytosol from intracellular Ca2+ stores or from the extracellular space. The molecular events of late stages of exocytosis, and their dependence on [Ca2+]c, were extensively described in isolated single cells from various endocrine glands. Notably, less work has been done on endocrine cells in situ to address the heterogeneity of [Ca2+]c events contributing to a collective functional response of a gland. For this, β cell collectives in a pancreatic islet are particularly well suited as they are the smallest, experimentally manageable functional unit, where [Ca2+]c dynamics can be simultaneously assessed on both cellular and collective level. Here, we measured [Ca2+]c transients across all relevant timescales, from a subsecond to a minute time range, using high-resolution imaging with a low-affinity Ca2+ sensor. We quantified the recordings with a novel computational framework for automatic image segmentation and [Ca2+]c event identification. Our results demonstrate that under physiological conditions the duration of [Ca2+]c events is variable, and segregated into three reproducible modes, subsecond, second, and tens of seconds time range, and are a result of a progressive temporal summation of the shortest events. Using pharmacological tools we show that activation of intracellular Ca2+ receptors is both sufficient and necessary for glucose-dependent [Ca2+]c oscillations in β cell collectives, and that a subset of [Ca2+]c events could be triggered even in the absence of Ca2+ influx across the plasma membrane. In aggregate, our experimental and analytical platform was able to readily address the involvement of intracellular Ca2+ receptors in shaping the heterogeneity of [Ca2+]c responses in collectives of endocrine cells in situ.NEW & NOTEWORTHY Physiological glucose or ryanodine stimulation of β cell collectives generates a large number of [Ca2+]c events, which can be rapidly assessed with our newly developed automatic image segmentation and [Ca2+]c event identification pipeline. The event durations segregate into three reproducible modes produced by a progressive temporal summation. Using pharmacological tools, we show that activation of ryanodine intracellular Ca2+ receptors is both sufficient and necessary for glucose-dependent [Ca2+]c oscillations in β cell collectives.
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Affiliation(s)
- Sandra Postić
- Center for physiology and pharmacology, Medical University of Vienna, Vienna, Austria
| | - Srdjan Sarikas
- Center for physiology and pharmacology, Medical University of Vienna, Vienna, Austria
| | - Johannes Pfabe
- Center for physiology and pharmacology, Medical University of Vienna, Vienna, Austria
| | - Viljem Pohorec
- Institute of Physiology, Faculty of Medicine, University of Maribor, Maribor, Slovenia
| | | | - Nastja Sluga
- Institute of Physiology, Faculty of Medicine, University of Maribor, Maribor, Slovenia
| | - Maša Skelin Klemen
- Institute of Physiology, Faculty of Medicine, University of Maribor, Maribor, Slovenia
| | - Jurij Dolenšek
- Institute of Physiology, Faculty of Medicine, University of Maribor, Maribor, Slovenia
| | - Dean Korošak
- Institute of Physiology, Faculty of Medicine, University of Maribor, Maribor, Slovenia
- Faculty of Civil Engineering, Transportation Engineering and Architecture, University of Maribor, Maribor, Slovenia
| | - Andraž Stožer
- Institute of Physiology, Faculty of Medicine, University of Maribor, Maribor, Slovenia
| | - Carmella Evans-Molina
- Center for Diabetes and Metabolic Diseases and the Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana
- Richard L. Roudebush VA Medical Center, Indianapolis, Indiana
| | - James D Johnson
- Diabetes Research Group, Life Sciences Institute, Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Marjan Slak Rupnik
- Center for physiology and pharmacology, Medical University of Vienna, Vienna, Austria
- Institute of Physiology, Faculty of Medicine, University of Maribor, Maribor, Slovenia
- Alma Mater Europaea-European Center Maribor, Maribor, Slovenia
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6
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Zaborska KE, Jordan KL, Thorson AS, Dadi PK, Schaub CM, Nakhe AY, Dickerson MT, Lynch JC, Weiss AJ, Dobson JR, Jacobson DA. Liraglutide increases islet Ca 2+ oscillation frequency and insulin secretion by activating hyperpolarization-activated cyclic nucleotide-gated channels. Diabetes Obes Metab 2022; 24:1741-1752. [PMID: 35546791 PMCID: PMC9843726 DOI: 10.1111/dom.14747] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Revised: 04/28/2022] [Accepted: 04/29/2022] [Indexed: 01/19/2023]
Abstract
AIM To determine whether hyperpolarization-activated cyclic nucleotide-gated (HCN) channels impact glucagon-like peptide-1 (GLP-1) receptor (GLP-1R) modulation of islet Ca2+ handling and insulin secretion. METHODS The impact of liraglutide (GLP-1 analogue) on islet Ca2+ handling, HCN currents and insulin secretion was monitored with fluorescence microscopy, electrophysiology and enzyme immunoassays, respectively. Furthermore, liraglutide-mediated β-to-δ-cell cross-communication was assessed following selective ablation of either mouse islet δ or β cells. RESULTS Liraglutide increased β-cell Ca2+ oscillation frequency in mouse and human islets under stimulatory glucose conditions. This was dependent in part on liraglutide activation of HCN channels, which also enhanced insulin secretion. Similarly, liraglutide activation of HCN channels also increased β-cell Ca2+ oscillation frequency in islets from rodents exposed to a diabetogenic diet. Interestingly, liraglutide accelerated Ca2+ oscillations in a majority of islet δ cells, which showed synchronized Ca2+ oscillations equivalent to β cells; therefore, we assessed if either cell type was driving this liraglutide-mediated islet Ca2+ response. Although δ-cell loss did not impact liraglutide-mediated increase in β-cell Ca2+ oscillation frequency, β-cell ablation attenuated liraglutide-facilitated acceleration of δ-cell Ca2+ oscillations. CONCLUSION The data presented here show that liraglutide-induced stimulation of islet HCN channels augments Ca2+ oscillation frequency. As insulin secretion oscillates with β-cell Ca2+ , these findings have important implications for pulsatile insulin secretion that is probably enhanced by liraglutide activation of HCN channels and therapeutics that target GLP-1Rs for treating diabetes. Furthermore, these studies suggest that liraglutide as well as GLP-1-based therapies enhance δ-cell Ca2+ oscillation frequency and somatostatin secretion kinetics in a β-cell-dependent manner.
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Affiliation(s)
- Karolina E Zaborska
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee
| | - Kelli L Jordan
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee
| | - Ariel S Thorson
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee
| | - Prasanna K Dadi
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee
| | - Charles M Schaub
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee
| | - Arya Y Nakhe
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee
| | - Matthew T Dickerson
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee
| | - Joshua C Lynch
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee
| | - Adam J Weiss
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee
| | - Jordyn R Dobson
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee
| | - David A Jacobson
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee
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7
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Pani P, Bal NC. Avian adjustments to cold and non-shivering thermogenesis: whats, wheres and hows. Biol Rev Camb Philos Soc 2022; 97:2106-2126. [PMID: 35899483 DOI: 10.1111/brv.12885] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Revised: 06/27/2022] [Accepted: 06/28/2022] [Indexed: 11/28/2022]
Abstract
Avian cold adaptation is hallmarked by innovative strategies of both heat conservation and thermogenesis. While minimizing heat loss can reduce the thermogenic demands of body temperature maintenance, it cannot eliminate the requirement for thermogenesis. Shivering and non-shivering thermogenesis (NST) are the two synergistic mechanisms contributing to endothermy. Birds are of particular interest in studies of NST as they lack brown adipose tissue (BAT), the major organ of NST in mammals. Critical analysis of the existing literature on avian strategies of cold adaptation suggests that skeletal muscle is the principal site of NST. Despite recent progress, isolating the mechanisms involved in avian muscle NST has been difficult as shivering and NST co-exist with its primary locomotory function. Herein, we re-evaluate various proposed molecular bases of avian skeletal muscle NST. Experimental evidence suggests that sarco(endo)plasmic reticulum Ca2+ -ATPase (SERCA) and ryanodine receptor 1 (RyR1) are key in avian muscle NST, through their mediation of futile Ca2+ cycling and thermogenesis. More recent studies have shown that SERCA regulation by sarcolipin (SLN) facilitates muscle NST in mammals; however, its role in birds is unclear. Ca2+ signalling in the muscle seems to be common to contraction, shivering and NST, but elucidating its roles will require more precise measurement of local Ca2+ levels inside avian myofibres. The endocrine control of avian muscle NST is still poorly defined. A better understanding of the mechanistic details of avian muscle NST will provide insights into the roles of these processes in regulatory thermogenesis, which could further inform our understanding of the evolution of endothermy among vertebrates.
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Affiliation(s)
- Punyadhara Pani
- School of Biotechnology, KIIT University, Bhubaneswar, Odisha, 751024, India
| | - Naresh C Bal
- School of Biotechnology, KIIT University, Bhubaneswar, Odisha, 751024, India
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8
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Zhang T, Ruan HZ, Wang YC, Shao YQ, Zhou W, Weng SJ, Zhong YM. Signaling Mechanism for Modulation by GLP-1 and Exendin-4 of GABA Receptors on Rat Retinal Ganglion Cells. Neurosci Bull 2022; 38:622-636. [PMID: 35278196 PMCID: PMC9206055 DOI: 10.1007/s12264-022-00826-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 11/10/2021] [Indexed: 11/29/2022] Open
Abstract
Glucagon-like peptide-1 (GLP-1) is expressed in retinal neurons, but its role in the retina is largely unknown. Here, we demonstrated that GLP-1 or the GLP-1 receptor (GLP-1R; a G protein-coupled receptor) agonist exendin-4 suppressed γ-aminobutyric acid receptor (GABAR)-mediated currents through GLP-1Rs in isolated rat retinal ganglion cells (GCs). Pre-incubation with the stimulatory G protein (Gs) inhibitor NF 449 abolished the exendin-4 effect. The exendin-4-induced suppression was mimicked by perfusion with 8-Br-cAMP (a cAMP analog), but was eliminated by the protein kinase A (PKA) inhibitor Rp-cAMP/KT-5720. The exendin-4 effect was accompanied by an increase in [Ca2+]i of GCs through the IP3-sensitive pathway and was blocked in Ca2+-free solution. Furthermore, when the activity of calmodulin (CaM) and CaM-dependent protein kinase II (CaMKII) was inhibited, the exendin-4 effect was eliminated. Consistent with this, exendin-4 suppressed GABAR-mediated light-evoked inhibitory postsynaptic currents in GCs in rat retinal slices. These results suggest that exendin-4-induced suppression may be mediated by a distinct Gs/cAMP-PKA/IP3/Ca2+/CaM/CaMKII signaling pathway, following the activation of GLP-1Rs.
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Affiliation(s)
- Tao Zhang
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, 200032, China
| | - Hang-Ze Ruan
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, 200032, China
| | - Yong-Chen Wang
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, 200032, China
| | - Yu-Qi Shao
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, 200032, China
| | - Wei Zhou
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, 200032, China
| | - Shi-Jun Weng
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, 200032, China
| | - Yong-Mei Zhong
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, 200032, China.
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9
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Stožer A, Paradiž Leitgeb E, Pohorec V, Dolenšek J, Križančić Bombek L, Gosak M, Skelin Klemen M. The Role of cAMP in Beta Cell Stimulus-Secretion and Intercellular Coupling. Cells 2021; 10:1658. [PMID: 34359828 PMCID: PMC8304079 DOI: 10.3390/cells10071658] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Revised: 06/18/2021] [Accepted: 06/28/2021] [Indexed: 12/22/2022] Open
Abstract
Pancreatic beta cells secrete insulin in response to stimulation with glucose and other nutrients, and impaired insulin secretion plays a central role in development of diabetes mellitus. Pharmacological management of diabetes includes various antidiabetic drugs, including incretins. The incretin hormones, glucagon-like peptide-1 and gastric inhibitory polypeptide, potentiate glucose-stimulated insulin secretion by binding to G protein-coupled receptors, resulting in stimulation of adenylate cyclase and production of the secondary messenger cAMP, which exerts its intracellular effects through activation of protein kinase A or the guanine nucleotide exchange protein 2A. The molecular mechanisms behind these two downstream signaling arms are still not fully elucidated and involve many steps in the stimulus-secretion coupling cascade, ranging from the proximal regulation of ion channel activity to the central Ca2+ signal and the most distal exocytosis. In addition to modifying intracellular coupling, the effect of cAMP on insulin secretion could also be at least partly explained by the impact on intercellular coupling. In this review, we systematically describe the possible roles of cAMP at these intra- and inter-cellular signaling nodes, keeping in mind the relevance for the whole organism and translation to humans.
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Affiliation(s)
- Andraž Stožer
- Institute of Physiology, Faculty of Medicine, University of Maribor, SI-2000 Maribor, Slovenia; (A.S.); (E.P.L.); (V.P.); (J.D.); (L.K.B.); (M.G.)
| | - Eva Paradiž Leitgeb
- Institute of Physiology, Faculty of Medicine, University of Maribor, SI-2000 Maribor, Slovenia; (A.S.); (E.P.L.); (V.P.); (J.D.); (L.K.B.); (M.G.)
| | - Viljem Pohorec
- Institute of Physiology, Faculty of Medicine, University of Maribor, SI-2000 Maribor, Slovenia; (A.S.); (E.P.L.); (V.P.); (J.D.); (L.K.B.); (M.G.)
| | - Jurij Dolenšek
- Institute of Physiology, Faculty of Medicine, University of Maribor, SI-2000 Maribor, Slovenia; (A.S.); (E.P.L.); (V.P.); (J.D.); (L.K.B.); (M.G.)
- Faculty of Natural Sciences and Mathematics, University of Maribor, SI-2000 Maribor, Slovenia
| | - Lidija Križančić Bombek
- Institute of Physiology, Faculty of Medicine, University of Maribor, SI-2000 Maribor, Slovenia; (A.S.); (E.P.L.); (V.P.); (J.D.); (L.K.B.); (M.G.)
| | - Marko Gosak
- Institute of Physiology, Faculty of Medicine, University of Maribor, SI-2000 Maribor, Slovenia; (A.S.); (E.P.L.); (V.P.); (J.D.); (L.K.B.); (M.G.)
- Faculty of Natural Sciences and Mathematics, University of Maribor, SI-2000 Maribor, Slovenia
| | - Maša Skelin Klemen
- Institute of Physiology, Faculty of Medicine, University of Maribor, SI-2000 Maribor, Slovenia; (A.S.); (E.P.L.); (V.P.); (J.D.); (L.K.B.); (M.G.)
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10
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Ježek P, Holendová B, Jabůrek M, Tauber J, Dlasková A, Plecitá-Hlavatá L. The Pancreatic β-Cell: The Perfect Redox System. Antioxidants (Basel) 2021; 10:antiox10020197. [PMID: 33572903 PMCID: PMC7912581 DOI: 10.3390/antiox10020197] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 01/20/2021] [Accepted: 01/25/2021] [Indexed: 12/12/2022] Open
Abstract
Pancreatic β-cell insulin secretion, which responds to various secretagogues and hormonal regulations, is reviewed here, emphasizing the fundamental redox signaling by NADPH oxidase 4- (NOX4-) mediated H2O2 production for glucose-stimulated insulin secretion (GSIS). There is a logical summation that integrates both metabolic plus redox homeostasis because the ATP-sensitive K+ channel (KATP) can only be closed when both ATP and H2O2 are elevated. Otherwise ATP would block KATP, while H2O2 would activate any of the redox-sensitive nonspecific calcium channels (NSCCs), such as TRPM2. Notably, a 100%-closed KATP ensemble is insufficient to reach the -50 mV threshold plasma membrane depolarization required for the activation of voltage-dependent Ca2+ channels. Open synergic NSCCs or Cl- channels have to act simultaneously to reach this threshold. The resulting intermittent cytosolic Ca2+-increases lead to the pulsatile exocytosis of insulin granule vesicles (IGVs). The incretin (e.g., GLP-1) amplification of GSIS stems from receptor signaling leading to activating the phosphorylation of TRPM channels and effects on other channels to intensify integral Ca2+-influx (fortified by endoplasmic reticulum Ca2+). ATP plus H2O2 are also required for branched-chain ketoacids (BCKAs); and partly for fatty acids (FAs) to secrete insulin, while BCKA or FA β-oxidation provide redox signaling from mitochondria, which proceeds by H2O2 diffusion or hypothetical SH relay via peroxiredoxin "redox kiss" to target proteins.
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11
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Bai J, Xue N, Lawal O, Nyati A, Santos‐Sacchi J, Navaratnam D. Calcium-induced calcium release in proximity to hair cell BK channels revealed by PKA activation. Physiol Rep 2020; 8:e14449. [PMID: 32748549 PMCID: PMC7399380 DOI: 10.14814/phy2.14449] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Revised: 04/07/2020] [Accepted: 04/08/2020] [Indexed: 11/24/2022] Open
Abstract
Large-conductance calcium-activated potassium (BK) channels play a critical role in electrical resonance, a mechanism of frequency selectivity in chicken hair cells. We determine that BK currents are dependent on inward flow of Ca2+ , and intracellular buffering of Ca2+ . Entry of Ca2+ is further amplified locally by calcium-induced Ca2+ release (CICR) in close proximity to plasma membrane BK channels. Ca2+ imaging reveals peripheral clusters of high concentrations of Ca2+ that are suprathreshold to that needed to activate BK channels. Protein kinase A (PKA) activation increases the size of BK currents likely by recruiting more BK channels due to spatial spread of high Ca2+ concentrations in turn from increasing CICR. STORM imaging confirms the presence of nanodomains with ryanodine and IP3 receptors in close proximity to the Slo subunit of BK channels. Together, these data require a rethinking of how electrical resonance is brought about and suggest effects of CICR in synaptic release. Both genders were included in this study.
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Affiliation(s)
- Jun‐ping Bai
- Department of NeurologyYale School of MedicineNew HavenCTUSA
| | - Na Xue
- Department of Otolaryngology‐Head and Neck SurgeryShanghai Ninth People's HospitalShanghai Jiaotong University School of MedicineShanghaiChina
| | - Omolara Lawal
- Department of NeurologyYale School of MedicineNew HavenCTUSA
| | - Anda Nyati
- Undergraduate ProgramJohns Hopkins UniversityBaltimoreMDUSA
| | - Joseph Santos‐Sacchi
- Department of SurgeryYale School of MedicineNew HavenCTUSA
- Department of Cell and Molecular PhysiologyYale School of MedicineNew HavenCTUSA
- Department of NeuroscienceYale School of MedicineNew HavenCTUSA
| | - Dhasakumar Navaratnam
- Department of NeurologyYale School of MedicineNew HavenCTUSA
- Department of SurgeryYale School of MedicineNew HavenCTUSA
- Department of NeuroscienceYale School of MedicineNew HavenCTUSA
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12
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Germano JDF, Huang C, Sin J, Song Y, Tucker KC, Taylor DJR, Saadaeijahromi H, Stotland A, Piplani H, Gottlieb RA, Mentzer RM, Andres AM. Intermittent Use of a Short-Course Glucagon-like Peptide-1 Receptor Agonist Therapy Limits Adverse Cardiac Remodeling via Parkin-dependent Mitochondrial Turnover. Sci Rep 2020; 10:8284. [PMID: 32427925 PMCID: PMC7237417 DOI: 10.1038/s41598-020-64924-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Accepted: 04/06/2020] [Indexed: 12/11/2022] Open
Abstract
Given that adverse remodeling is the leading cause of heart failure and death in the USA, there is an urgent unmet need to develop new methods in dealing with this devastating disease. Here we evaluated the efficacy of a short-course glucagon-like peptide-1 receptor agonist therapy-specifically 2-quinoxalinamine, 6,7-dichloro-N-(1,1-dimethylethyl)-3-(methylsulfonyl)-,6,7-dichloro-2-methylsulfonyl-3-N-tert-butylaminoquinoxaline (DMB; aka Compound 2) - in attenuating adverse LV remodeling. We also examined the role, if any, of mitochondrial turnover in this process. Wild-type, Parkin knockout and MitoTimer-expressing mice were subjected to permanent coronary artery ligation, then treated briefly with DMB. LV remodeling and cardiac function were assessed by histology and echocardiography. Autophagy and mitophagy markers were examined by western blot and mitochondrial biogenesis was inferred from MitoTimer protein fluorescence and qPCR. We found that DMB given post-infarction significantly reduced adverse LV remodeling and the decline of cardiac function. This paralleled an increase in autophagy, mitophagy and mitochondrial biogenesis. The salutary effects of the drug were lost in Parkin knockout mice, implicating Parkin-mediated mitophagy as part of its mechanism of action. Our findings suggest that enhancing Parkin-associated mitophagy and mitochondrial biogenesis after infarction is a viable target for therapeutic mitigation of adverse remodeling.
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Affiliation(s)
| | - Chengqun Huang
- Cedars Sinai Medical Center, Smidt Heart Institute, Los Angeles, USA
| | - Jon Sin
- Cedars Sinai Medical Center, Smidt Heart Institute, Los Angeles, USA
| | - Yang Song
- Cedars Sinai Medical Center, Smidt Heart Institute, Los Angeles, USA
| | - Kyle C Tucker
- Cedars Sinai Medical Center, Smidt Heart Institute, Los Angeles, USA
| | - David J R Taylor
- Cedars Sinai Medical Center, Smidt Heart Institute, Los Angeles, USA
| | | | | | - Honit Piplani
- Cedars Sinai Medical Center, Smidt Heart Institute, Los Angeles, USA
| | | | - Robert M Mentzer
- Cedars Sinai Medical Center, Smidt Heart Institute, Los Angeles, USA
| | - Allen M Andres
- Cedars Sinai Medical Center, Smidt Heart Institute, Los Angeles, USA. .,University of California, San Diego, Department of Medicine, San Diego, USA.
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13
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Minami A, Fujita Y, Shimba S, Shiratori M, Kaneko YK, Sawatani T, Otsubo T, Ikeda K, Kanazawa H, Mikami Y, Sekita R, Kurebayashi Y, Takahashi T, Miyagi T, Ishikawa T, Suzuki T. The sialidase inhibitor 2,3-dehydro-2-deoxy-N-acetylneuraminic acid is a glucose-dependent potentiator of insulin secretion. Sci Rep 2020; 10:5198. [PMID: 32251344 PMCID: PMC7089948 DOI: 10.1038/s41598-020-62203-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Accepted: 03/06/2020] [Indexed: 12/12/2022] Open
Abstract
Sialidase cleaves sialic acid residues from a sialoglycoconjugate: oligosaccharides, glycolipids and glycoproteins that contain sialic acid. Histochemical imaging of the mouse pancreas using a benzothiazolylphenol-based sialic acid derivative (BTP3-Neu5Ac), a highly sensitive histochemical imaging probe used to assess sialidase activity, showed that pancreatic islets have intense sialidase activity. The sialidase inhibitor 2,3-dehydro-2-deoxy-N-acetylneuraminic acid (DANA) remarkably enhances glutamate release from hippocampal neurons. Since there are many similar processes between synaptic vesicle exocytosis and secretory granule exocytosis, we investigated the effect of DANA on insulin release from β-cells. Insulin release was induced in INS-1D cells by treatment with 8.3 mM glucose, and the release was enhanced by treatment with DANA. In a mouse intraperitoneal glucose tolerance test, the increase in serum insulin levels was enhanced by intravenous injection with DANA. However, under fasting conditions, insulin release was not enhanced by treatment with DANA. Calcium oscillations induced by 8.3 mM glucose treatment of INS-1D cells were not affected by DANA. Blood insulin levels in sialidase isozyme Neu3-deficient mice were significantly higher than those in WT mice under ad libitum feeding conditions, but the levels were not different under fasting conditions. These results indicate that DANA is a glucose-dependent potentiator of insulin secretion. The sialidase inhibitor may be useful for anti-diabetic treatment with a low risk of hypoglycemia.
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Affiliation(s)
- Akira Minami
- Department of Biochemistry, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, 422-8526, Japan.
| | - Yuka Fujita
- Department of Biochemistry, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, 422-8526, Japan
| | - Sumika Shimba
- Department of Biochemistry, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, 422-8526, Japan
| | - Mako Shiratori
- Department of Biochemistry, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, 422-8526, Japan
| | - Yukiko K Kaneko
- Department of Pharmacology, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, 422-8526, Japan
| | - Toshiaki Sawatani
- Department of Pharmacology, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, 422-8526, Japan
| | - Tadamune Otsubo
- Department of Organic Chemistry, School of Pharmaceutical Sciences, Hiroshima International University, Hiroshima, 737-0112, Japan
| | - Kiyoshi Ikeda
- Department of Organic Chemistry, School of Pharmaceutical Sciences, Hiroshima International University, Hiroshima, 737-0112, Japan
| | - Hiroaki Kanazawa
- Department of Functional Anatomy, School of Nursing, University of Shizuoka, Shizuoka, 422-8526, Japan
| | - Yasuyo Mikami
- Department of Biochemistry, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, 422-8526, Japan
| | - Risa Sekita
- Department of Biochemistry, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, 422-8526, Japan
| | - Yuuki Kurebayashi
- Department of Biochemistry, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, 422-8526, Japan
| | - Tadanobu Takahashi
- Department of Biochemistry, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, 422-8526, Japan
| | - Taeko Miyagi
- Miyagi Cancer Center Research Institute, Natori, 981-1293, Japan
| | - Tomohisa Ishikawa
- Department of Pharmacology, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, 422-8526, Japan
| | - Takashi Suzuki
- Department of Biochemistry, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, 422-8526, Japan.
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14
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Idevall-Hagren O, Tengholm A. Metabolic regulation of calcium signaling in beta cells. Semin Cell Dev Biol 2020; 103:20-30. [PMID: 32085965 DOI: 10.1016/j.semcdb.2020.01.008] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 01/10/2020] [Accepted: 01/28/2020] [Indexed: 12/22/2022]
Abstract
The cytoplasmic Ca2+ concentration ([Ca2+]cyt) regulates a vast number of cellular functions, including insulin secretion from beta cells. The major physiological insulin secretagogue, glucose, triggers [Ca2+]cyt oscillations in beta cells. Synchronization of the oscillations among the beta cells within an islet underlies the generation of pulsatile insulin secretion. This review describes the mechanisms generating [Ca2+]cyt oscillations, the interactions between [Ca2+]cyt and cell metabolism, as well as the contribution of various organelles to the shaping of [Ca2+]cyt signals and insulin secretion. It also discusses how Ca2+ signals are coordinated and spread throughout the islets and data indicating that altered Ca2+ signaling is associated with beta cell dysfunction and development of type 2 diabetes.
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Affiliation(s)
- Olof Idevall-Hagren
- Department of Medical Cell Biology, Uppsala University, Biomedical Centre, Box 571, SE-751 23 Uppsala, Sweden
| | - Anders Tengholm
- Department of Medical Cell Biology, Uppsala University, Biomedical Centre, Box 571, SE-751 23 Uppsala, Sweden.
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15
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Zhang IX, Raghavan M, Satin LS. The Endoplasmic Reticulum and Calcium Homeostasis in Pancreatic Beta Cells. Endocrinology 2020; 161:bqz028. [PMID: 31796960 PMCID: PMC7028010 DOI: 10.1210/endocr/bqz028] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2019] [Accepted: 12/01/2019] [Indexed: 12/14/2022]
Abstract
The endoplasmic reticulum (ER) mediates the first steps of protein assembly within the secretory pathway and is the site where protein folding and quality control are initiated. The storage and release of Ca2+ are critical physiological functions of the ER. Disrupted ER homeostasis activates the unfolded protein response (UPR), a pathway which attempts to restore cellular equilibrium in the face of ER stress. Unremitting ER stress, and insufficient compensation for it results in beta-cell apoptosis, a process that has been linked to both type 1 diabetes (T1D) and type 2 diabetes (T2D). Both types are characterized by progressive beta-cell failure and a loss of beta-cell mass, although the underlying causes are different. The reduction of mass occurs secondary to apoptosis in the case of T2D, while beta cells undergo autoimmune destruction in T1D. In this review, we examine recent findings that link the UPR pathway and ER Ca2+ to beta cell dysfunction. We also discuss how UPR activation in beta cells favors cell survival versus apoptosis and death, and how ER protein chaperones are involved in regulating ER Ca2+ levels. Abbreviations: BiP, Binding immunoglobulin Protein ER; endoplasmic reticulum; ERAD, ER-associated protein degradation; IFN, interferon; IL, interleukin; JNK, c-Jun N-terminal kinase; KHE, proton-K+ exchanger; MODY, maturity-onset diabetes of young; PERK, PRKR-like ER kinase; SERCA, Sarco/Endoplasmic Reticulum Ca2+-ATPases; T1D, type 1 diabetes; T2D, type 2 diabetes; TNF, tumor necrosis factor; UPR, unfolded protein response; WRS, Wolcott-Rallison syndrome.
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Affiliation(s)
- Irina X Zhang
- Department of Pharmacology and Brehm Diabetes Research Center, University of Michigan, Ann Arbor, MI
| | - Malini Raghavan
- Department of Microbiology and Immunology Michigan Medicine, University of Michigan, Ann Arbor, MI
| | - Leslie S Satin
- Department of Pharmacology and Brehm Diabetes Research Center, University of Michigan, Ann Arbor, MI
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16
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Expression of the Inositol 1,4,5-Trisphosphate Receptor and the Ryanodine Receptor Ca 2+-Release Channels in the Beta-Cells and Alpha-Cells of the Human Islets of Langerhans. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1131:271-279. [PMID: 31646514 DOI: 10.1007/978-3-030-12457-1_11] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Calcium signaling regulates secretion of hormones and many other cellular processes in the islets of Langerhans. The three subtypes of the inositol 1,4,5-trisphosphate receptors (IP3Rs), inositol 1,4,5-trisphosphate receptor type 1 (IP3R1), 1,4,5-trisphosphate receptor type 2 (IP3R2), 1,4,5-trisphosphate receptor type 3 (IP3R3), and the three subtypes of the ryanodine receptors (RyRs), ryanodine receptor 1 (RyR1), ryanodine receptor 2 (RyR2) and ryanodine receptor 3 (RyR3) are the main intracellular Ca2+-release channels. The identity and the relative levels of expression of these channels in the alpha-cells, and the beta-cells of the human islets of Langerhans are unknown. We have analyzed the RNA sequencing data obtained from highly purified human alpha-cells and beta-cells for quantitatively identifying the mRNA of the intracellular Ca2+-release channels in these cells. We found that among the three IP3Rs the IP3R3 is the most abundantly expressed one in the beta-cells, whereas IP3R1 is the most abundantly expressed one in the alpha-cells. In addition to the IP3R3, beta-cells also expressed the IP3R2, at a lower level. Among the RyRs, the RyR2 was the most abundantly expressed one in the beta-cells, whereas the RyR1 was the most abundantly expressed one in the alpha-cells. Information on the relative abundance of the different intracellular Ca2+-release channels in the human alpha-cells and the beta-cells may help the understanding of their roles in the generation of Ca2+ signals and many other related cellular processes in these cells.
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17
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Islam MS. Stimulus-Secretion Coupling in Beta-Cells: From Basic to Bedside. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1131:943-963. [PMID: 31646540 DOI: 10.1007/978-3-030-12457-1_37] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Insulin secretion in humans is usually induced by mixed meals, which upon ingestion, increase the plasma concentration of glucose, fatty acids, amino acids, and incretins like glucagon-like peptide 1. Beta-cells can stay in the off-mode, ready-mode or on-mode; the mode-switching being determined by the open state probability of the ATP-sensitive potassium channels, and the activity of enzymes like glucokinase, and glutamate dehydrogenase. Mitochondrial metabolism is critical for insulin secretion. A sound understanding of the intermediary metabolism, electrophysiology, and cell signaling is essential for comprehension of the entire spectrum of the stimulus-secretion coupling. Depolarization brought about by inhibition of the ATP sensitive potassium channel, together with the inward depolarizing currents through the transient receptor potential (TRP) channels, leads to electrical activities, opening of the voltage-gated calcium channels, and exocytosis of insulin. Calcium- and cAMP-signaling elicited by depolarization, and activation of G-protein-coupled receptors, including the free fatty acid receptors, are intricately connected in the form of networks at different levels. Activation of the glucagon-like peptide 1 receptor augments insulin secretion by amplifying calcium signals by calcium induced calcium release (CICR). In the treatment of type 2 diabetes, use of the sulfonylureas that act on the ATP sensitive potassium channel, damages the beta cells, which eventually fail; these drugs do not improve the cardiovascular outcomes. In contrast, drugs acting through the glucagon-like peptide-1 receptor protect the beta-cells, and improve cardiovascular outcomes. The use of the glucagon-like peptide 1 receptor agonists is increasing and that of sulfonylurea is decreasing. A better understanding of the stimulus-secretion coupling may lead to the discovery of other molecular targets for development of drugs for the prevention and treatment of type 2 diabetes.
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Affiliation(s)
- Md Shahidul Islam
- Department of Clinical Science and Education, Södersjukhuset, Research Center, Karolinska Institutet, Stockholm, Sweden. .,Department of Emergency Care and Internal Medicine, Uppsala University Hospital, Uppsala University, Uppsala, Sweden.
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18
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Grandl G, Novikoff A, DiMarchi R, Tschöp MH, Müller TD. Gut Peptide Agonism in the Treatment of Obesity and Diabetes. Compr Physiol 2019; 10:99-124. [PMID: 31853954 DOI: 10.1002/cphy.c180044] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Obesity is a global healthcare challenge that gives rise to devastating diseases such as the metabolic syndrome, type-2 diabetes (T2D), and a variety of cardiovascular diseases. The escalating prevalence of obesity has led to an increased interest in pharmacological options to counteract excess weight gain. Gastrointestinal hormones such as glucagon, amylin, and glucagon-like peptide-1 (GLP-1) are well recognized for influencing food intake and satiety, but the therapeutic potential of these native peptides is overall limited by a short half-life and an often dose-dependent appearance of unwanted effects. Recent clinical success of chemically optimized GLP-1 mimetics with improved pharmacokinetics and sustained action has propelled pharmacological interest in using bioengineered gut hormones to treat obesity and diabetes. In this article, we summarize the basic biology and signaling mechanisms of selected gut peptides and discuss how they regulate systemic energy and glucose metabolism. Subsequently, we focus on the design and evaluation of unimolecular drugs that combine the beneficial effects of selected gut hormones into a single entity to optimize the beneficial impact on systems metabolism. © 2020 American Physiological Society. Compr Physiol 10:99-124, 2020.
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Affiliation(s)
- Gerald Grandl
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München - German Research Center for Environmental Health (GmbH), Neuherberg, Germany.,German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Aaron Novikoff
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München - German Research Center for Environmental Health (GmbH), Neuherberg, Germany.,German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Richard DiMarchi
- Department of Chemistry, Indiana University, Bloomington, Indiana, USA
| | - Matthias H Tschöp
- German Center for Diabetes Research (DZD), Neuherberg, Germany.,Division of Metabolic Diseases, Technische Universität München, Munich, Germany
| | - Timo D Müller
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München - German Research Center for Environmental Health (GmbH), Neuherberg, Germany.,German Center for Diabetes Research (DZD), Neuherberg, Germany.,Department of Pharmacology and Experimental Therapy, Institute of Experimental and Clinical Pharmacology and Toxicology, Eberhard Karls University Hospitals and Clinics, Tübingen, Germany
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19
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Müller TD, Finan B, Bloom SR, D'Alessio D, Drucker DJ, Flatt PR, Fritsche A, Gribble F, Grill HJ, Habener JF, Holst JJ, Langhans W, Meier JJ, Nauck MA, Perez-Tilve D, Pocai A, Reimann F, Sandoval DA, Schwartz TW, Seeley RJ, Stemmer K, Tang-Christensen M, Woods SC, DiMarchi RD, Tschöp MH. Glucagon-like peptide 1 (GLP-1). Mol Metab 2019; 30:72-130. [PMID: 31767182 PMCID: PMC6812410 DOI: 10.1016/j.molmet.2019.09.010] [Citation(s) in RCA: 862] [Impact Index Per Article: 172.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 09/10/2019] [Accepted: 09/22/2019] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND The glucagon-like peptide-1 (GLP-1) is a multifaceted hormone with broad pharmacological potential. Among the numerous metabolic effects of GLP-1 are the glucose-dependent stimulation of insulin secretion, decrease of gastric emptying, inhibition of food intake, increase of natriuresis and diuresis, and modulation of rodent β-cell proliferation. GLP-1 also has cardio- and neuroprotective effects, decreases inflammation and apoptosis, and has implications for learning and memory, reward behavior, and palatability. Biochemically modified for enhanced potency and sustained action, GLP-1 receptor agonists are successfully in clinical use for the treatment of type-2 diabetes, and several GLP-1-based pharmacotherapies are in clinical evaluation for the treatment of obesity. SCOPE OF REVIEW In this review, we provide a detailed overview on the multifaceted nature of GLP-1 and its pharmacology and discuss its therapeutic implications on various diseases. MAJOR CONCLUSIONS Since its discovery, GLP-1 has emerged as a pleiotropic hormone with a myriad of metabolic functions that go well beyond its classical identification as an incretin hormone. The numerous beneficial effects of GLP-1 render this hormone an interesting candidate for the development of pharmacotherapies to treat obesity, diabetes, and neurodegenerative disorders.
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Affiliation(s)
- T D Müller
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Neuherberg, Germany; German Center for Diabetes Research (DZD), Neuherberg, Germany; Department of Pharmacology and Experimental Therapy, Institute of Experimental and Clinical Pharmacology and Toxicology, Eberhard Karls University Hospitals and Clinics, Tübingen, Germany.
| | - B Finan
- Novo Nordisk Research Center Indianapolis, Indianapolis, IN, USA
| | - S R Bloom
- Division of Diabetes, Endocrinology and Metabolism, Imperial College London, London, UK
| | - D D'Alessio
- Division of Endocrinology, Duke University Medical Center, Durham, NC, USA
| | - D J Drucker
- The Department of Medicine, Lunenfeld-Tanenbaum Research Institute, Mt. Sinai Hospital, University of Toronto, Ontario, M5G1X5, Canada
| | - P R Flatt
- SAAD Centre for Pharmacy & Diabetes, Ulster University, Coleraine, Northern Ireland, UK
| | - A Fritsche
- German Center for Diabetes Research (DZD), Neuherberg, Germany; Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany; Division of Endocrinology, Diabetology, Vascular Disease, Nephrology and Clinical Chemistry, Department of Internal Medicine, University of Tübingen, Tübingen, Germany
| | - F Gribble
- Metabolic Research Laboratories and Medical Research Council Metabolic Diseases Unit, Wellcome Trust-Medical Research Council, Institute of Metabolic Science, Addenbrooke's Hospital, University of Cambridge, Cambridge, CB2 0QQ, UK
| | - H J Grill
- Institute of Diabetes, Obesity and Metabolism, Department of Psychology, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - J F Habener
- Laboratory of Molecular Endocrinology, Massachusetts General Hospital, Harvard University, Boston, MA, USA
| | - J J Holst
- Novo Nordisk Foundation Center for Basic Metabolic Research, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - W Langhans
- Physiology and Behavior Laboratory, ETH Zurich, Schwerzenbach, Switzerland
| | - J J Meier
- Diabetes Division, St Josef Hospital, Ruhr-University Bochum, Bochum, Germany
| | - M A Nauck
- Diabetes Center Bochum-Hattingen, St Josef Hospital (Ruhr-Universität Bochum), Bochum, Germany
| | - D Perez-Tilve
- Department of Internal Medicine, University of Cincinnati-College of Medicine, Cincinnati, OH, USA
| | - A Pocai
- Cardiovascular & ImmunoMetabolism, Janssen Research & Development, Welsh and McKean Roads, Spring House, PA, 19477, USA
| | - F Reimann
- Metabolic Research Laboratories and Medical Research Council Metabolic Diseases Unit, Wellcome Trust-Medical Research Council, Institute of Metabolic Science, Addenbrooke's Hospital, University of Cambridge, Cambridge, CB2 0QQ, UK
| | - D A Sandoval
- Department of Surgery, University of Michigan Medical School, Ann Arbor, MI, USA
| | - T W Schwartz
- Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, DL-2200, Copenhagen, Denmark; Department of Biomedical Sciences, University of Copenhagen, DK-2200, Copenhagen, Denmark
| | - R J Seeley
- Department of Surgery, University of Michigan Medical School, Ann Arbor, MI, USA
| | - K Stemmer
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Neuherberg, Germany; German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - M Tang-Christensen
- Obesity Research, Global Drug Discovery, Novo Nordisk A/S, Måløv, Denmark
| | - S C Woods
- Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati, Cincinnati, OH, USA
| | - R D DiMarchi
- Novo Nordisk Research Center Indianapolis, Indianapolis, IN, USA; Department of Chemistry, Indiana University, Bloomington, IN, USA
| | - M H Tschöp
- German Center for Diabetes Research (DZD), Neuherberg, Germany; Division of Metabolic Diseases, Department of Medicine, Technische Universität München, Munich, Germany; Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Neuherberg, Germany
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20
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Smith NK, Hackett TA, Galli A, Flynn CR. GLP-1: Molecular mechanisms and outcomes of a complex signaling system. Neurochem Int 2019; 128:94-105. [PMID: 31002893 PMCID: PMC7081944 DOI: 10.1016/j.neuint.2019.04.010] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 03/26/2019] [Accepted: 04/15/2019] [Indexed: 12/15/2022]
Abstract
Meal ingestion provokes the release of hormones and transmitters, which in turn regulate energy homeostasis and feeding behavior. One such hormone, glucagon-like peptide-1 (GLP-1), has received significant attention in the treatment of obesity and diabetes due to its potent incretin effect. In addition to the peripheral actions of GLP-1, this hormone is able to alter behavior through the modulation of multiple neural circuits. Recent work that focused on elucidating the mechanisms and outcomes of GLP-1 neuromodulation led to the discovery of an impressive array of GLP-1 actions. Here, we summarize the many levels at which the GLP-1 signal adapts to different systems, with the goal being to provide a background against which to guide future research.
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Affiliation(s)
- Nicholas K Smith
- Vanderbilt Brain Institute, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Troy A Hackett
- Department of Hearing and Speech Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Aurelio Galli
- Department of Surgery, University of Alabama at Birmingham, Birmingham, AL, USA.
| | - Charles R Flynn
- Department of Surgery, Vanderbilt University Medical Center, Nashville, TN, USA.
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21
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Pratt EPS, Harvey KE, Salyer AE, Hockerman GH. Regulation of cAMP accumulation and activity by distinct phosphodiesterase subtypes in INS-1 cells and human pancreatic β-cells. PLoS One 2019; 14:e0215188. [PMID: 31442224 PMCID: PMC6707593 DOI: 10.1371/journal.pone.0215188] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2019] [Accepted: 08/11/2019] [Indexed: 01/09/2023] Open
Abstract
Pancreatic β-cells express multiple phosphodiesterase (PDE) subtypes, but the specific roles for each in β-cell function, particularly in humans, is not clear. We evaluated the cellular role of PDE1, PDE3, and PDE4 activity in the rat insulinoma cell line INS-1 and in primary human β-cells using subtype-selective PDE inhibitors. Using a genetically encoded, FRET-based cAMP sensor, we found that the PDE1 inhibitor 8MM-IBMX, elevated cAMP levels in the absence of glucose to a greater extent than either the PDE3 inhibitor cilostamide or the PDE4 inhibitor rolipram. In 18 mM glucose, PDE1 inhibition elevated cAMP levels to a greater extent than PDE3 inhibition in INS-1 cells, while PDE4 inhibition was without effect. Inhibition of PDE1 or PDE4, but not PDE3, potentiated glucose-stimulated insulin secretion in INS-1 cells. PDE1 inhibition, but not PDE3 or PDE4 inhibition, reduced palmitate-induced caspase-3/7 activation, and enhanced CREB phosphorylation in INS-1 cells. In human β-cells, only PDE3 or PDE4 inhibition increased cAMP levels in 1.7 mM glucose, but PDE1, PDE3, or PDE4 inhibition potentiated cAMP levels in 16.7 mM glucose. Inhibition of PDE1 or PDE4 increased cAMP levels to a greater extent in 16.7 mM glucose than in 1.7 mM glucose in human β-cells. In contrast, elevation of cAMP levels by PDE3 inhibition was not different at these glucose concentrations. PDE1 inhibition also potentiated insulin secretion from human islets, suggesting that the role of PDE1 may be conserved between INS-1 cells and human pancreatic β-cells. Our results suggest that inhibition of PDE1 may be a useful strategy to potentiate glucose-stimulated insulin secretion, and to protect β-cells from the toxic effects of excess fatty acids.
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Affiliation(s)
- Evan P. S. Pratt
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN, United States of America
- Purdue University Interdisciplinary Life Science Program, Purdue University, West Lafayette, IN, United States of America
| | - Kyle E. Harvey
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN, United States of America
| | - Amy E. Salyer
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN, United States of America
| | - Gregory H. Hockerman
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN, United States of America
- * E-mail:
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22
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Tomas A, Jones B, Leech C. New Insights into Beta-Cell GLP-1 Receptor and cAMP Signaling. J Mol Biol 2019; 432:1347-1366. [PMID: 31446075 DOI: 10.1016/j.jmb.2019.08.009] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2019] [Revised: 08/06/2019] [Accepted: 08/13/2019] [Indexed: 12/14/2022]
Abstract
Harnessing the translational potential of the GLP-1/GLP-1R system in pancreatic beta cells has led to the development of established GLP-1R-based therapies for the long-term preservation of beta cell function. In this review, we discuss recent advances in the current research on the GLP-1/GLP-1R system in beta cells, including the regulation of signaling by endocytic trafficking as well as the application of concepts such as signal bias, allosteric modulation, dual agonism, polymorphic receptor variants, spatial compartmentalization of cAMP signaling and new downstream signaling targets involved in the control of beta cell function.
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Affiliation(s)
- Alejandra Tomas
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, London, W12 0NN, UK.
| | - Ben Jones
- Section of Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, London, W12 0NN, UK
| | - Colin Leech
- Department of Surgery, State University of New York, Upstate Medical University, Syracuse, NY, 13210, USA
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23
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Sarmiento BE, Santos Menezes LF, Schwartz EF. Insulin Release Mechanism Modulated by Toxins Isolated from Animal Venoms: From Basic Research to Drug Development Prospects. Molecules 2019; 24:E1846. [PMID: 31091684 PMCID: PMC6571724 DOI: 10.3390/molecules24101846] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 04/23/2019] [Accepted: 05/09/2019] [Indexed: 12/12/2022] Open
Abstract
Venom from mammals, amphibians, snakes, arachnids, sea anemones and insects provides diverse sources of peptides with different potential medical applications. Several of these peptides have already been converted into drugs and some are still in the clinical phase. Diabetes type 2 is one of the diseases with the highest mortality rate worldwide, requiring specific attention. Diverse drugs are available (e.g., Sulfonylureas) for effective treatment, but with several adverse secondary effects, most of them related to the low specificity of these compounds to the target. In this context, the search for specific and high-affinity compounds for the management of this metabolic disease is growing. Toxins isolated from animal venom have high specificity and affinity for different molecular targets, of which the most important are ion channels. This review will present an overview about the electrical activity of the ion channels present in pancreatic β cells that are involved in the insulin secretion process, in addition to the diversity of peptides that can interact and modulate the electrical activity of pancreatic β cells. The importance of prospecting bioactive peptides for therapeutic use is also reinforced.
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Affiliation(s)
- Beatriz Elena Sarmiento
- Departamento de Ciências Fisiológicas, Instituto de Ciências Biológicas, Universidade de Brasília, Brasília, DF 70910-900, Brazil.
| | - Luis Felipe Santos Menezes
- Departamento de Ciências Fisiológicas, Instituto de Ciências Biológicas, Universidade de Brasília, Brasília, DF 70910-900, Brazil.
| | - Elisabeth F Schwartz
- Departamento de Ciências Fisiológicas, Instituto de Ciências Biológicas, Universidade de Brasília, Brasília, DF 70910-900, Brazil.
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24
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Yamamoto WR, Bone RN, Sohn P, Syed F, Reissaus CA, Mosley AL, Wijeratne AB, True JD, Tong X, Kono T, Evans-Molina C. Endoplasmic reticulum stress alters ryanodine receptor function in the murine pancreatic β cell. J Biol Chem 2019; 294:168-181. [PMID: 30420428 PMCID: PMC6322901 DOI: 10.1074/jbc.ra118.005683] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2018] [Revised: 11/08/2018] [Indexed: 01/23/2023] Open
Abstract
Alterations in endoplasmic reticulum (ER) calcium (Ca2+) levels diminish insulin secretion and reduce β-cell survival in both major forms of diabetes. The mechanisms responsible for ER Ca2+ loss in β cells remain incompletely understood. Moreover, a specific role for either ryanodine receptor (RyR) or inositol 1,4,5-triphosphate receptor (IP3R) dysfunction in the pathophysiology of diabetes remains largely untested. To this end, here we applied intracellular and ER Ca2+ imaging techniques in INS-1 β cells and isolated islets to determine whether diabetogenic stressors alter RyR or IP3R function. Our results revealed that the RyR is sensitive mainly to ER stress-induced dysfunction, whereas cytokine stress specifically alters IP3R activity. Consistent with this observation, pharmacological inhibition of the RyR with ryanodine and inhibition of the IP3R with xestospongin C prevented ER Ca2+ loss under ER and cytokine stress conditions, respectively. However, RyR blockade distinctly prevented β-cell death, propagation of the unfolded protein response (UPR), and dysfunctional glucose-induced Ca2+ oscillations in tunicamycin-treated INS-1 β cells and mouse islets and Akita islets. Monitoring at the single-cell level revealed that ER stress acutely increases the frequency of intracellular Ca2+ transients that depend on both ER Ca2+ leakage from the RyR and plasma membrane depolarization. Collectively, these findings indicate that RyR dysfunction shapes ER Ca2+ dynamics in β cells and regulates both UPR activation and cell death, suggesting that RyR-mediated loss of ER Ca2+ may be an early pathogenic event in diabetes.
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Affiliation(s)
- Wataru R Yamamoto
- Departments of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Robert N Bone
- Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Paul Sohn
- Departments of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Farooq Syed
- Herman B. Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Christopher A Reissaus
- Herman B. Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Amber L Mosley
- Departments of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Aruna B Wijeratne
- Departments of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Jason D True
- Departments of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Xin Tong
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee 37235
| | - Tatsuyoshi Kono
- Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Carmella Evans-Molina
- Departments of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana 46202; Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana 46202; Departments of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202; Herman B. Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana 46202; Roudebush Veterans Affairs Medical Center, Indianapolis, Indiana 46202.
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25
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Rowlands J, Heng J, Newsholme P, Carlessi R. Pleiotropic Effects of GLP-1 and Analogs on Cell Signaling, Metabolism, and Function. Front Endocrinol (Lausanne) 2018; 9:672. [PMID: 30532733 PMCID: PMC6266510 DOI: 10.3389/fendo.2018.00672] [Citation(s) in RCA: 159] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Accepted: 10/29/2018] [Indexed: 12/22/2022] Open
Abstract
The incretin hormone Glucagon-Like Peptide-1 (GLP-1) is best known for its "incretin effect" in restoring glucose homeostasis in diabetics, however, it is now apparent that it has a broader range of physiological effects in the body. Both in vitro and in vivo studies have demonstrated that GLP-1 mimetics alleviate endoplasmic reticulum stress, regulate autophagy, promote metabolic reprogramming, stimulate anti-inflammatory signaling, alter gene expression, and influence neuroprotective pathways. A substantial body of evidence has accumulated with respect to how GLP-1 and its analogs act to restore and maintain normal cellular functions. These findings have prompted several clinical trials which have reported GLP-1 analogs improve cardiac function, restore lung function and reduce mortality in patients with obstructive lung disease, influence blood pressure and lipid storage, and even prevent synaptic loss and neurodegeneration. Mechanistically, GLP-1 elicits its effects via acute elevation in cAMP levels, and subsequent protein kinase(s) activation, pathways well-defined in pancreatic β-cells which stimulate insulin secretion in conjunction with elevated Ca2+ and ATP. More recently, new studies have shed light on additional downstream pathways stimulated by chronic GLP-1 exposure, findings which have direct relevance to our understanding of the potential therapeutic effects of longer lasting analogs recently developed for clinical use. In this review, we provide a comprehensive description of the diverse roles for GLP-1 across multiple tissues, describe downstream pathways stimulated by acute and chronic exposure, and discuss novel pleiotropic applications of GLP-1 mimetics in the treatment of human disease.
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Affiliation(s)
| | | | - Philip Newsholme
- School of Pharmacy and Biomedical Sciences, Curtin Health Innovation Research Institute, Perth, WA, Australia
| | - Rodrigo Carlessi
- School of Pharmacy and Biomedical Sciences, Curtin Health Innovation Research Institute, Perth, WA, Australia
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26
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Coskun T, Sloop KW, Loghin C, Alsina-Fernandez J, Urva S, Bokvist KB, Cui X, Briere DA, Cabrera O, Roell WC, Kuchibhotla U, Moyers JS, Benson CT, Gimeno RE, D'Alessio DA, Haupt A. LY3298176, a novel dual GIP and GLP-1 receptor agonist for the treatment of type 2 diabetes mellitus: From discovery to clinical proof of concept. Mol Metab 2018; 18:3-14. [PMID: 30473097 PMCID: PMC6308032 DOI: 10.1016/j.molmet.2018.09.009] [Citation(s) in RCA: 397] [Impact Index Per Article: 66.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Revised: 09/26/2018] [Accepted: 09/28/2018] [Indexed: 12/15/2022] Open
Abstract
OBJECTIVE A novel dual GIP and GLP-1 receptor agonist, LY3298176, was developed to determine whether the metabolic action of GIP adds to the established clinical benefits of selective GLP-1 receptor agonists in type 2 diabetes mellitus (T2DM). METHODS LY3298176 is a fatty acid modified peptide with dual GIP and GLP-1 receptor agonist activity designed for once-weekly subcutaneous administration. LY3298176 was characterised in vitro, using signaling and functional assays in cell lines expressing recombinant or endogenous incretin receptors, and in vivo using body weight, food intake, insulin secretion and glycemic profiles in mice. A Phase 1, randomised, placebo-controlled, double-blind study was comprised of three parts: a single-ascending dose (SAD; doses 0.25-8 mg) and 4-week multiple-ascending dose (MAD; doses 0.5-10 mg) studies in healthy subjects (HS), followed by a 4-week multiple-dose Phase 1 b proof-of-concept (POC; doses 0.5-15 mg) in patients with T2DM (ClinicalTrials.gov no. NCT02759107). Doses higher than 5 mg were attained by titration, dulaglutide (DU) was used as a positive control. The primary objective was to investigate safety and tolerability of LY3298176. RESULTS LY3298176 activated both GIP and GLP-1 receptor signaling in vitro and showed glucose-dependent insulin secretion and improved glucose tolerance by acting on both GIP and GLP-1 receptors in mice. With chronic administration to mice, LY3298176 potently decreased body weight and food intake; these effects were significantly greater than the effects of a GLP-1 receptor agonist. A total of 142 human subjects received at least 1 dose of LY3298176, dulaglutide, or placebo. The PK profile of LY3298176 was investigated over a wide dose range (0.25-15 mg) and supports once-weekly administration. In the Phase 1 b trial of diabetic subjects, LY3298176 doses of 10 mg and 15 mg significantly reduced fasting serum glucose compared to placebo (least square mean [LSM] difference [95% CI]: -49.12 mg/dL [-78.14, -20.12] and -43.15 mg/dL [-73.06, -13.21], respectively). Reductions in body weight were significantly greater with the LY3298176 1.5 mg, 4.5 mg and 10 mg doses versus placebo in MAD HS (LSM difference [95% CI]: -1.75 kg [-3.38, -0.12], -5.09 kg [-6.72, -3.46] and -4.61 kg [-6.21, -3.01], respectively) and doses of 10 mg and 15 mg had a relevant effect in T2DM patients (LSM difference [95% CI]: -2.62 kg [-3.79, -1.45] and -2.07 kg [-3.25, -0.88], respectively. The most frequent side effects reported with LY3298176 were gastrointestinal (vomiting, nausea, decreased appetite, diarrhoea, and abdominal distension) in both HS and patients with T2DM; all were dose-dependent and considered mild to moderate in severity. CONCLUSIONS Based on these results, the pharmacology of LY3298176 translates from preclinical to clinical studies. LY3298176 has the potential to deliver clinically meaningful improvement in glycaemic control and body weight. The data warrant further clinical evaluation of LY3298176 for the treatment of T2DM and potentially obesity.
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Affiliation(s)
- Tamer Coskun
- Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN, USA
| | - Kyle W Sloop
- Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN, USA
| | - Corina Loghin
- Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN, USA
| | | | - Shweta Urva
- Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN, USA
| | - Krister B Bokvist
- Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN, USA
| | - Xuewei Cui
- Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN, USA
| | - Daniel A Briere
- Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN, USA
| | - Over Cabrera
- Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN, USA
| | - William C Roell
- Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN, USA
| | - Uma Kuchibhotla
- Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN, USA
| | - Julie S Moyers
- Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN, USA
| | - Charles T Benson
- Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN, USA
| | - Ruth E Gimeno
- Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN, USA
| | - David A D'Alessio
- Division of Endocrinology, Metabolism, and Nutrition, Duke University Medical Center, Durham, NC, USA
| | - Axel Haupt
- Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN, USA.
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27
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Treatments for diabetes mellitus type II: New perspectives regarding the possible role of calcium and cAMP interaction. Eur J Pharmacol 2018; 830:9-16. [PMID: 29679542 DOI: 10.1016/j.ejphar.2018.04.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 03/29/2018] [Accepted: 04/03/2018] [Indexed: 12/18/2022]
Abstract
Diabetes mellitus (DM) is among the top ten causes of death worldwide. It is considered to be one of the major global epidemics of the 21st century, with a significant impact on public health budgets. DM is a metabolic disorder with multiple etiologies. Its pathophysiology is marked by dysfunction of pancreatic β-cells which compromises the synthesis and secretion of insulin along with resistance to insulin action in peripheral tissues (muscle and adipose). Subjects presenting insulin resistance in DM type 2 often also exhibit increased insulin secretion and hyperinsulinemia. Insulin secretion is controlled by several factors such as nutrients, hormones, and neural factors. Exocytosis of insulin granules has, as its main stimulus, increased intracellular calcium ([Ca+2]i) and it is further amplified by cyclic AMP (cAMP). In the event of this hyperfunction, it is very common for β-cells to go into exhaustion leading to failure or death. Several animal studies have demonstrated pleiotropic effects of L-type Ca2+ channel blockers (CCBs). In animal models of obesity and diabetes, treatment with CCBs promoted restoration of insulin secretion, glycemic control, and reduction of pancreatic β-cell apoptosis. In addition, hypertensive individuals treated with CCBs presented a lower incidence of DM when compared with other antihypertensive agents. In this review, we propose that pharmacological manipulation of the Ca2+/cAMP interaction system could lead to important targets for pharmacological improvement of insulin secretion in DM type 2.
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28
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Robichaux WG, Cheng X. Intracellular cAMP Sensor EPAC: Physiology, Pathophysiology, and Therapeutics Development. Physiol Rev 2018; 98:919-1053. [PMID: 29537337 PMCID: PMC6050347 DOI: 10.1152/physrev.00025.2017] [Citation(s) in RCA: 138] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 09/05/2017] [Accepted: 09/06/2017] [Indexed: 12/13/2022] Open
Abstract
This review focuses on one family of the known cAMP receptors, the exchange proteins directly activated by cAMP (EPACs), also known as the cAMP-regulated guanine nucleotide exchange factors (cAMP-GEFs). Although EPAC proteins are fairly new additions to the growing list of cAMP effectors, and relatively "young" in the cAMP discovery timeline, the significance of an EPAC presence in different cell systems is extraordinary. The study of EPACs has considerably expanded the diversity and adaptive nature of cAMP signaling associated with numerous physiological and pathophysiological responses. This review comprehensively covers EPAC protein functions at the molecular, cellular, physiological, and pathophysiological levels; and in turn, the applications of employing EPAC-based biosensors as detection tools for dissecting cAMP signaling and the implications for targeting EPAC proteins for therapeutic development are also discussed.
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Affiliation(s)
- William G Robichaux
- Department of Integrative Biology and Pharmacology, Texas Therapeutics Institute, The Brown Foundation Institute of Molecular Medicine, The University of Texas Health Science Center , Houston, Texas
| | - Xiaodong Cheng
- Department of Integrative Biology and Pharmacology, Texas Therapeutics Institute, The Brown Foundation Institute of Molecular Medicine, The University of Texas Health Science Center , Houston, Texas
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29
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Podewin T, Ast J, Broichhagen J, Fine NHF, Nasteska D, Leippe P, Gailer M, Buenaventura T, Kanda N, Jones BJ, M’Kadmi C, Baneres JL, Marie J, Tomas A, Trauner D, Hoffmann-Röder A, Hodson DJ. Conditional and Reversible Activation of Class A and B G Protein-Coupled Receptors Using Tethered Pharmacology. ACS CENTRAL SCIENCE 2018; 4:166-179. [PMID: 29532016 PMCID: PMC5832994 DOI: 10.1021/acscentsci.7b00237] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Indexed: 05/21/2023]
Abstract
Understanding the activation and internalization of G protein-coupled receptors (GPCRs) using conditional approaches is paramount to developing new therapeutic strategies. Here, we describe the design, synthesis, and testing of ExONatide, a benzylguanine-linked peptide agonist of the glucagon-like peptide-1 receptor (GLP-1R), a class B GPCR required for maintenance of glucose levels in humans. ExONatide covalently binds to SNAP-tagged GLP-1R-expressing cells, leading to prolonged cAMP generation, Ca2+ rises, and intracellular retention of the receptor. These effects were readily switched OFF following cleavage of the introduced disulfide bridge using the cell-permeable reducing agent beta-mercaptoethanol (BME). A similar approach could be extended to a class A GPCR using GhrelON, a benzylguanine-linked peptide agonist of the growth hormone secretagogue receptor 1a (GHS-R1a), which is involved in food intake and growth. Thus, ExONatide and GhrelON allow SNAP-tag-directed activation of class A and B GPCRs involved in gut hormone signaling in a reversible manner. This tactic, termed reductively cleavable agONist (RECON), may be useful for understanding GLP-1R and GHS-R1a function both in vitro and in vivo, with applicability across GPCRs.
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Affiliation(s)
- Tom Podewin
- Department
of Chemistry and Center for Integrated Protein Science, LMU Munich, 81377 Munich, Germany
| | - Julia Ast
- Institute
of Metabolism and Systems Research (IMSR), University of Birmingham, B15 2TT, Birmingham, United Kingdom
- Centre
for Endocrinology, Diabetes and Metabolism, Birmingham
Health Partners, Birmingham, B15 2TH, United Kingdom, and COMPARE University of Birmingham and University of Nottingham
Midlands
| | - Johannes Broichhagen
- Department
of Chemistry and Center for Integrated Protein Science, LMU Munich, 81377 Munich, Germany
| | - Nicholas H. F. Fine
- Institute
of Metabolism and Systems Research (IMSR), University of Birmingham, B15 2TT, Birmingham, United Kingdom
- Centre
for Endocrinology, Diabetes and Metabolism, Birmingham
Health Partners, Birmingham, B15 2TH, United Kingdom, and COMPARE University of Birmingham and University of Nottingham
Midlands
| | - Daniela Nasteska
- Institute
of Metabolism and Systems Research (IMSR), University of Birmingham, B15 2TT, Birmingham, United Kingdom
- Centre
for Endocrinology, Diabetes and Metabolism, Birmingham
Health Partners, Birmingham, B15 2TH, United Kingdom, and COMPARE University of Birmingham and University of Nottingham
Midlands
| | - Philipp Leippe
- Department
of Chemistry and Center for Integrated Protein Science, LMU Munich, 81377 Munich, Germany
| | - Manuel Gailer
- Department
of Chemistry and Center for Integrated Protein Science, LMU Munich, 81377 Munich, Germany
| | - Teresa Buenaventura
- Section
of Cell Biology and Functional Genomics, Department of Medicine, Imperial College London, London, W12 0NN, United Kingdom
| | - Nisha Kanda
- Section
of Cell Biology and Functional Genomics, Department of Medicine, Imperial College London, London, W12 0NN, United Kingdom
| | - Ben J. Jones
- Section
of Investigative Medicine, Division of Diabetes, Endocrinology and
Metabolism, Imperial College London, London, W12 0NN, United Kingdom
| | - Celine M’Kadmi
- Institut des Biomolécules
Max Mousseron, UMR 5247 CNRS-Université Montpellier-ENSCM,
Faculté de Pharmacie, 15 Avenue
Charles Flahault, BP 14491, 34093 Montpellier Cedex 05, France
| | - Jean-Louis Baneres
- Institut des Biomolécules
Max Mousseron, UMR 5247 CNRS-Université Montpellier-ENSCM,
Faculté de Pharmacie, 15 Avenue
Charles Flahault, BP 14491, 34093 Montpellier Cedex 05, France
| | - Jacky Marie
- Institut des Biomolécules
Max Mousseron, UMR 5247 CNRS-Université Montpellier-ENSCM,
Faculté de Pharmacie, 15 Avenue
Charles Flahault, BP 14491, 34093 Montpellier Cedex 05, France
| | - Alejandra Tomas
- Section
of Cell Biology and Functional Genomics, Department of Medicine, Imperial College London, London, W12 0NN, United Kingdom
| | - Dirk Trauner
- Department
of Chemistry and Center for Integrated Protein Science, LMU Munich, 81377 Munich, Germany
- (D.T.) E-mail:
| | - Anja Hoffmann-Röder
- Department
of Chemistry and Center for Integrated Protein Science, LMU Munich, 81377 Munich, Germany
- (A.H.-R.) E-mail:
| | - David J. Hodson
- Institute
of Metabolism and Systems Research (IMSR), University of Birmingham, B15 2TT, Birmingham, United Kingdom
- Centre
for Endocrinology, Diabetes and Metabolism, Birmingham
Health Partners, Birmingham, B15 2TH, United Kingdom, and COMPARE University of Birmingham and University of Nottingham
Midlands
- (D.J.H.)
E-mail:
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30
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Arden C. A role for Glucagon-Like Peptide-1 in the regulation of β-cell autophagy. Peptides 2018; 100:85-93. [PMID: 29412836 DOI: 10.1016/j.peptides.2017.12.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Revised: 12/04/2017] [Accepted: 12/04/2017] [Indexed: 12/11/2022]
Abstract
Autophagy is a highly conserved intracellular recycling pathway that serves to recycle damaged organelles/proteins or superfluous nutrients during times of nutritional stress to provide energy to maintain intracellular homeostasis and sustain core metabolic functions. Under these conditions, autophagy functions as a cell survival mechanism but impairment of this pathway can lead to pro-death stimuli. Due to their role in synthesising and secreting insulin, pancreatic β-cells have a high requirement for robust degradation pathways. Recent research suggests that functional autophagy is required to maintain β-cell survival and function in response to high fat diet suggesting a pro-survival role. However, a role for autophagy has also been implicated in the pathogenesis of type 2 diabetes. Thus, the pro-survival vs pro-death role of autophagy in regulating β-cell mass requires discussion. Emerging evidence suggests that Glucagon-Like Peptide-1 (GLP-1) may exert beneficial effects on glucose homeostasis via autophagy-dependent pathways both in pancreatic β-cells and in other cell types. The aim of the current review is to: i) summarise the literature surrounding β-cell autophagy and its pro-death vs pro-survival role in regulating β-cell mass; ii) review the literature describing the impact of GLP-1 on β-cell autophagy and in other cell types; iii) discuss the potential underlying mechanisms.
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Affiliation(s)
- Catherine Arden
- Institute of Cellular Medicine, The Medical School, Newcastle University, Newcastle upon Tyne NE2 4HH, UK.
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31
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Gumuslu E, Cine N, Ertan M, Mutlu O, Komsuoglu Celikyurt I, Ulak G. Exenatide upregulates gene expression of glucagon-like peptide-1 receptor and nerve growth factor in streptozotocin/nicotinamide-induced diabetic mice. Fundam Clin Pharmacol 2017; 32:174-180. [DOI: 10.1111/fcp.12329] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2017] [Revised: 09/15/2017] [Accepted: 10/25/2017] [Indexed: 12/25/2022]
Affiliation(s)
- Esen Gumuslu
- Department of Medical Genetics; Medical Faculty; Kocaeli University; Kocaeli 41380 Turkey
| | - Naci Cine
- Department of Medical Genetics; Medical Faculty; Kocaeli University; Kocaeli 41380 Turkey
| | - Merve Ertan
- Department of Medical Genetics; Medical Faculty; Kocaeli University; Kocaeli 41380 Turkey
| | - Oguz Mutlu
- Department of Medical Pharmacology; Psychopharmacology Lab.; Medical Faculty; Kocaeli University; Kocaeli 41380 Turkey
| | - Ipek Komsuoglu Celikyurt
- Department of Medical Pharmacology; Psychopharmacology Lab.; Medical Faculty; Kocaeli University; Kocaeli 41380 Turkey
| | - Guner Ulak
- Department of Medical Pharmacology; Psychopharmacology Lab.; Medical Faculty; Kocaeli University; Kocaeli 41380 Turkey
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32
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Seino S, Sugawara K, Yokoi N, Takahashi H. β-Cell signalling and insulin secretagogues: A path for improved diabetes therapy. Diabetes Obes Metab 2017; 19 Suppl 1:22-29. [PMID: 28880474 DOI: 10.1111/dom.12995] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Revised: 04/24/2017] [Accepted: 04/27/2017] [Indexed: 12/26/2022]
Abstract
Insulin secretagogues including sulfonylureas, glinides and incretin-related drugs such as dipeptidyl peptidase 4 (DPP-4) inhibitors and glucagon-like peptide-1 receptor agonists are widely used for treatment of type 2 diabetes. In addition, glucokinase activators and G-protein-coupled receptor 40 (GPR40) agonists also have been developed, although the drugs are not clinically usable. These different drugs exert their effects on insulin secretion by different mechanisms. Recent advances in β-cell signalling studies have not only deepened our understanding of insulin secretion but also revealed novel mechanisms of insulin secretagogues. Clarification of the signalling mechanisms of the insulin secretagogues will contribute to improved drug therapy for diabetes.
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Affiliation(s)
- Susumu Seino
- Division of Molecular and Metabolic Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Kenji Sugawara
- Division of Molecular and Metabolic Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
- Division of Diabetes and Endocrinology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Norihide Yokoi
- Division of Molecular and Metabolic Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Harumi Takahashi
- Division of Molecular and Metabolic Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
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Müller TD, Finan B, Clemmensen C, DiMarchi RD, Tschöp MH. The New Biology and Pharmacology of Glucagon. Physiol Rev 2017; 97:721-766. [PMID: 28275047 DOI: 10.1152/physrev.00025.2016] [Citation(s) in RCA: 206] [Impact Index Per Article: 29.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
In the last two decades we have witnessed sizable progress in defining the role of gastrointestinal signals in the control of glucose and energy homeostasis. Specifically, the molecular basis of the huge metabolic benefits in bariatric surgery is emerging while novel incretin-based medicines based on endogenous hormones such as glucagon-like peptide 1 and pancreas-derived amylin are improving diabetes management. These and related developments have fostered the discovery of novel insights into endocrine control of systemic metabolism, and in particular a deeper understanding of the importance of communication across vital organs, and specifically the gut-brain-pancreas-liver network. Paradoxically, the pancreatic peptide glucagon has reemerged in this period among a plethora of newly identified metabolic macromolecules, and new data complement and challenge its historical position as a gut hormone involved in metabolic control. The synthesis of glucagon analogs that are biophysically stable and soluble in aqueous solutions has promoted biological study that has enriched our understanding of glucagon biology and ironically recruited glucagon agonism as a central element to lower body weight in the treatment of metabolic disease. This review summarizes the extensive historical record and the more recent provocative direction that integrates the prominent role of glucagon in glucose elevation with its under-acknowledged effects on lipids, body weight, and vascular health that have implications for the pathophysiology of metabolic diseases, and the emergence of precision medicines to treat metabolic diseases.
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Affiliation(s)
- T D Müller
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany; German Center for Diabetes Research, Neuherberg, Germany; Department of Chemistry, Indiana University, Bloomington, Indiana; Division of Metabolic Diseases, Technische Universität München, Munich, Germany
| | - B Finan
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany; German Center for Diabetes Research, Neuherberg, Germany; Department of Chemistry, Indiana University, Bloomington, Indiana; Division of Metabolic Diseases, Technische Universität München, Munich, Germany
| | - C Clemmensen
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany; German Center for Diabetes Research, Neuherberg, Germany; Department of Chemistry, Indiana University, Bloomington, Indiana; Division of Metabolic Diseases, Technische Universität München, Munich, Germany
| | - R D DiMarchi
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany; German Center for Diabetes Research, Neuherberg, Germany; Department of Chemistry, Indiana University, Bloomington, Indiana; Division of Metabolic Diseases, Technische Universität München, Munich, Germany
| | - M H Tschöp
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany; German Center for Diabetes Research, Neuherberg, Germany; Department of Chemistry, Indiana University, Bloomington, Indiana; Division of Metabolic Diseases, Technische Universität München, Munich, Germany
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34
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Liu Y, Zhong X, Ding Y, Ren L, Bai T, Liu M, Liu Z, Guo Y, Guo Q, Zhang Y, Yang J, Zhang Y. Inhibition of voltage-dependent potassium channels mediates cAMP-potentiated insulin secretion in rat pancreatic β cells. Islets 2017; 9:11-18. [PMID: 28103136 PMCID: PMC5345751 DOI: 10.1080/19382014.2017.1280644] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Insulin secretion is essential for maintenance of glucose homeostasis. An important intracellular signal regulating insulin secretion is cAMP. In this report, we showed that an increase of cAMP induced by adenylyl cyclase (AC) activator forskolin or by cAMP analog db-cAMP not only potentiated insulin secretion but also inhibited Kv channels, and these effects were reversed by AC inhibitor SQ22536. The cAMP-mediated Kv channel inhibition resulted in prolongation of action potential duration, which partly accounts for the elevation of intracellular Ca2+ induced by activation of cAMP signaling. Taken together, the results suggest that Kv channels are involved in cAMP-potentiated insulin secretion in pancreatic β cells.
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Affiliation(s)
- Yunfeng Liu
- Department of Endocrinology, the First Hospital of Shanxi Medical University, Shanxi Medical University, Taiyuan, China
- CONTACT Yunfeng Liu Department of Endocrinology, The first Hospital of Shanxi Medical University, Taiyuan 030001, China; Yi Zhang , Department of Pharmacology, Shanxi Medical University, Taiyuan 030001, China
| | - Xiangqin Zhong
- Department of Pharmacology, Shanxi Medical University, Taiyuan, China
| | - Yaqin Ding
- Department of Pharmacology, Shanxi Medical University, Taiyuan, China
| | - Lele Ren
- Department of Pharmacology, Shanxi Medical University, Taiyuan, China
| | - Tao Bai
- Department of Endocrinology, the First Hospital of Shanxi Medical University, Shanxi Medical University, Taiyuan, China
- Department of Pharmacology, Shanxi Medical University, Taiyuan, China
- Key Laboratory of Cellular Physiology, Ministry of Education, Shanxi Medical University, Taiyuan, China
| | - Mengmeng Liu
- Department of Pharmacology, Shanxi Medical University, Taiyuan, China
| | - Zhihong Liu
- Department of Pharmacology, Shanxi Medical University, Taiyuan, China
- Key Laboratory of Cellular Physiology, Ministry of Education, Shanxi Medical University, Taiyuan, China
| | - Yangyan Guo
- Department of Pharmacology, Shanxi Medical University, Taiyuan, China
| | - Qing Guo
- Department of Pharmacology, Shanxi Medical University, Taiyuan, China
| | - Yu Zhang
- Department of Pharmacology, Shanxi Medical University, Taiyuan, China
| | - Jing Yang
- Department of Endocrinology, the First Hospital of Shanxi Medical University, Shanxi Medical University, Taiyuan, China
| | - Yi Zhang
- Department of Pharmacology, Shanxi Medical University, Taiyuan, China
- Key Laboratory of Cellular Physiology, Ministry of Education, Shanxi Medical University, Taiyuan, China
- CONTACT Yunfeng Liu Department of Endocrinology, The first Hospital of Shanxi Medical University, Taiyuan 030001, China; Yi Zhang , Department of Pharmacology, Shanxi Medical University, Taiyuan 030001, China
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Wu HY, Mao XF, Fan H, Wang YX. p38 β Mitogen-Activated Protein Kinase Signaling Mediates Exenatide-Stimulated Microglial β-Endorphin Expression. Mol Pharmacol 2017; 91:451-463. [PMID: 28202578 DOI: 10.1124/mol.116.107102] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Accepted: 02/07/2017] [Indexed: 12/14/2022] Open
Abstract
Recent discoveries established that activation of glucagon-like peptide-1 receptors (GLP-1Rs) mediates neuroprotection and antinociception through microglial β-endorphin expression. This study aimed to explore the underlying signaling mechanisms of microglial β-endorphin. GLP-1Rs and β-endorphin were coexpressed in primary cultures of microglia. Treatment with the GLP-1R agonist exenatide concentration-dependently stimulated microglial expression of the β-endorphin precursor gene proopiomelanocortin (POMC) and peptides, with EC50 values of 4.1 and 7.5 nM, respectively. Exenatide also significantly increased intracellular cAMP levels and expression of p-protein kinase A (PKA), p-p38, and p-cAMP response element binding protein (CREB) in cultured primary microglia. Furthermore, exenatide-induced microglial expression of POMC was completely blocked by reagents that specifically inhibit adenylyl cyclase and activation of PKA, p38, and CREB. In addition, knockdown of p38β (but not p38α) using short interfering RNA (siRNA) eliminated exenatide-induced microglial p38 phosphorylation and POMC expression. In contrast, lipopolysaccharide increased microglial activation of p38, and knockdown of p38α (but not p38β) partially suppressed expression of proinflammatory factors (including tumor necrosis factor-α, interleukin-1β, and interleukin-6). Exenatide-induced phosphorylation of p38 and CREB was also totally blocked by the PKA inhibitor and siRNA/p38β, but not by siRNA/p38α Seven-day intrathecal injections of siRNA/p38β (but not siRNA/p38α) completely blocked exenatide-induced spinal p38 activation, β-endorphin expression, and mechanical antiallodynia in rats with established neuropathy, although siRNA/p38β and siRNA/p38α were not antiallodynic. To our knowledge, our results are the first to show a causal relationship between the PKA-dependent p38β mitogen-activated protein kinase/CREB signal cascade and GLP-1R agonism-mediated microglial β-endorphin expression. The differential role of p38α and p38β activation in inflammation and nociception was also highlighted.
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Affiliation(s)
- Hai-Yun Wu
- King's Laboratory, Shanghai Jiao Tong University School of Pharmacy, Shanghai, China
| | - Xiao-Fang Mao
- King's Laboratory, Shanghai Jiao Tong University School of Pharmacy, Shanghai, China
| | - Hui Fan
- King's Laboratory, Shanghai Jiao Tong University School of Pharmacy, Shanghai, China
| | - Yong-Xiang Wang
- King's Laboratory, Shanghai Jiao Tong University School of Pharmacy, Shanghai, China
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Shigeto M, Cha CY, Rorsman P, Kaku K. A role of PLC/PKC-dependent pathway in GLP-1-stimulated insulin secretion. J Mol Med (Berl) 2017; 95:361-368. [PMID: 28097390 DOI: 10.1007/s00109-017-1508-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2016] [Revised: 11/19/2016] [Accepted: 11/30/2016] [Indexed: 01/11/2023]
Abstract
Glucagon-like peptide-1 (GLP-1) is an endogenous glucose-lowering hormone and GLP-1 receptor agonists are currently being used as antidiabetic drugs clinically. The canonical signalling pathway (including cAMP, Epac2, protein kinase A (PKA) and KATP channels) is almost universally accepted as the main mechanism of GLP-1-stimulated insulin secretion. This belief is based on in vitro studies that used nanomolar (1-100 nM) concentrations of GLP-1. Recently, it was found that the physiological concentrations (1-10 pM) of GLP-1 also stimulate insulin secretion from isolated islets, induce membrane depolarization and increase of intracellular [Ca2+] in isolated β cells/pancreatic islets. These responses were unaffected by PKA inhibitors and occurred without detectable increases in intracellular cAMP and PKA activity. These PKA-independent actions of GLP-1 depend on protein kinase C (PKC), involve activation of the standard GLP-1 receptor (GLP1R) and culminate in activation of phospholipase C (PLC), leading to an elevation of diacylglycerol (DAG), increased L-type Ca2+ and TRPM4/TRPM5 channel activities. Here, we review these recent data and contrast them against the effects of nanomolar concentrations of GLP-1. The differential intracellular signalling activated by low and high concentrations of GLP-1 could provide a clue to explain how GLP-1 exerts different function in the central nervous system and peripheral organs.
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Affiliation(s)
- Makoto Shigeto
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, Old Road, Oxford, OX3 7LE, UK. .,Department of Diabetes, Endocrinology and Metabolism, Kawasaki Medical School, 577 Matsushima, Kurashiki, Okayama, 701-0192, Japan.
| | - Chae Young Cha
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, Old Road, Oxford, OX3 7LE, UK
| | - Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, Old Road, Oxford, OX3 7LE, UK
| | - Kohei Kaku
- Department of Diabetes, Endocrinology and Metabolism, Kawasaki Medical School, 577 Matsushima, Kurashiki, Okayama, 701-0192, Japan
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Tang W, Yuan Q, Xu B, Osei K, Wang J. Exenatide substantially improves proinsulin conversion and cell survival that augment Ins2 +/Akita beta cell function. Mol Cell Endocrinol 2017; 439:297-307. [PMID: 27658750 DOI: 10.1016/j.mce.2016.09.015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Revised: 09/16/2016] [Accepted: 09/16/2016] [Indexed: 02/06/2023]
Abstract
Proinsulin folding imperfections cause extensive beta-cell defects known in diabetes. Here, we investigated whether exenatide can alleviate such defects in proinsulin conversion, beta-cell survival, and insulin secretion, in the Ins2+/Akita beta-cells that have a spontaneous mutation (Cys 96 Tyr) in the insulin 2 gene caused dominant negative misfolding problem. 15 or 120 min exenatide administration substantially improves glucose-stimulated insulin secretion, marked in the secreted insulin levels and proinsulin/insulin ratio. This improvement is mainly due to enhanced conversion of proinsulin to insulin, having nothing to do with the prohormone convertase PC1/3 and PC2 levels. The 15 min improvement is calcium-independent. The 120 min improvement is linked to calcium and/or cAMP dependent mechanisms. This efficacy is validated during longer treatment and in Akita islets. Exenatide improves Ins2+/Akita beta-cell survival and Akita mouse's glucose tolerance. The results suggest a potential of incretin mimetics in alleviating defective proinsulin conversion and other proinsulin misfolding consequences.
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Affiliation(s)
- Wei Tang
- Department of Endocrinology, Jiangsu Province Geriatric Institute Islet Cell Senescence and Function Research Laboratory, Jiangsu Province Official Hospital, 65 Jiangsu Road, Nanjing 210024, China.
| | - Qingxin Yuan
- Department of Endocrinology, First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu 210029, China
| | - Bo Xu
- State Key Laboratory of Reproductive Medicine, Institute of Toxicology, Nanjing Medical University, Nanjing 211166, China
| | - Kwame Osei
- Division of Endocrinology, Diabetes, and Metabolism, Department of Internal Medicine, The Ohio State University, Columbus, OH 43210, USA
| | - Jie Wang
- Division of Endocrinology, Diabetes, and Metabolism, Department of Internal Medicine, The Ohio State University, Columbus, OH 43210, USA; Division of Endocrinology, Jiangsu Province Hospital on Integration of Chinese and Western Medicine, Nanjing University of Chinese and Western Medicine, Nanjing, Jiangsu 210028, China.
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Jandaghi P, Najafabadi HS, Bauer AS, Papadakis AI, Fassan M, Hall A, Monast A, von Knebel Doeberitz M, Neoptolemos JP, Costello E, Greenhalf W, Scarpa A, Sipos B, Auld D, Lathrop M, Park M, Büchler MW, Strobel O, Hackert T, Giese NA, Zogopoulos G, Sangwan V, Huang S, Riazalhosseini Y, Hoheisel JD. Expression of DRD2 Is Increased in Human Pancreatic Ductal Adenocarcinoma and Inhibitors Slow Tumor Growth in Mice. Gastroenterology 2016; 151:1218-1231. [PMID: 27578530 DOI: 10.1053/j.gastro.2016.08.040] [Citation(s) in RCA: 87] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Revised: 08/01/2016] [Accepted: 08/04/2016] [Indexed: 01/08/2023]
Abstract
BACKGROUND & AIMS Incidence of and mortality from pancreatic ductal adenocarcinoma (PDAC), the most common form of pancreatic cancer, are almost equivalent, so better treatments are needed. We studied gene expression profiles of PDACs and the functions of genes with altered expression to identify new therapeutic targets. METHODS We performed microarray analysis to analyze gene expression profiles of 195 PDAC and 41 non-tumor pancreatic tissue samples. We undertook an extensive analysis of the PDAC transcriptome by superimposing interaction networks of proteins encoded by aberrantly expressed genes over signaling pathways associated with PDAC development to identify factors that might alter regulation of these pathways during tumor progression. We performed tissue microarray analysis to verify changes in expression of candidate protein using an independent set of 152 samples (40 nontumor pancreatic tissues, 63 PDAC sections, and 49 chronic pancreatitis samples). We validated the functional relevance of the candidate molecule using RNA interference or pharmacologic inhibitors in pancreatic cancer cell lines and analyses of xenograft tumors in mice. RESULTS In an analysis of 38,276 human genes and loci, we identified 1676 genes that were significantly up-regulated and 1166 genes that were significantly down-regulated in PDAC compared with nontumor pancreatic tissues. One gene that was up-regulated and associated with multiple signaling pathways that are dysregulated in PDAC was G protein subunit αi2, which has not been previously associated with PDAC. G protein subunit αi2 mediates the effects of dopamine receptor D2 (DRD2) on cyclic adenosine monophosphate signaling; PDAC tissues had a slight but significant increase in DRD2 messenger RNA. Levels of DRD2 protein were substantially increased in PDACs, compared with non-tumor tissues, in tissue microarray analyses. RNA interference knockdown of DRD2 or inhibition with pharmacologic antagonists (pimozide and haloperidol) reduced proliferation of pancreatic cancer cells, induced endoplasmic reticulum stress and apoptosis, and reduced cell migration. RNA interference knockdown of DRD2 in pancreatic tumor cells reduced growth of xenograft tumors in mice, and administration of the DRD2 inhibitor haloperidol to mice with orthotopic xenograft tumors reduced final tumor size and metastasis. CONCLUSIONS In gene expression profile analysis of PDAC samples, we found the DRD2 signaling pathway to be activated. Inhibition of DRD2 in pancreatic cancer cells reduced proliferation and migration, and slowed growth of xenograft tumors in mice. DRD2 antagonists routinely used for management of schizophrenia might be tested in patients with pancreatic cancer.
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Affiliation(s)
- Pouria Jandaghi
- Functional Genome Analysis, Deutsches Krebsforschungszentrum, Heidelberg, Germany; Department of Human Genetics, McGill University, Montreal, Quebec, Canada; McGill University and Genome Quebec Innovation Centre, Montreal, Quebec, Canada
| | - Hamed S Najafabadi
- Department of Human Genetics, McGill University, Montreal, Quebec, Canada; McGill University and Genome Quebec Innovation Centre, Montreal, Quebec, Canada
| | - Andrea S Bauer
- Functional Genome Analysis, Deutsches Krebsforschungszentrum, Heidelberg, Germany
| | - Andreas I Papadakis
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada; Rosalind and Morris Goodman Cancer Research Centre, McGill University, Montreal, Quebec, Canada
| | - Matteo Fassan
- ARC-NET Center for Applied Research on Cancer, University and Azienda Ospedaliera Universitaria Integrata, Verona, Italy
| | - Anita Hall
- Rosalind and Morris Goodman Cancer Research Centre, McGill University, Montreal, Quebec, Canada; The Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada
| | - Anie Monast
- Rosalind and Morris Goodman Cancer Research Centre, McGill University, Montreal, Quebec, Canada
| | - Magnus von Knebel Doeberitz
- Department of Applied Tumor Biology, Institute of Pathology, University Hospital Heidelberg, Heidelberg, Germany
| | - John P Neoptolemos
- National Institute for Health Research, Liverpool Pancreas Biomedical Research Unit, Liverpool, UK
| | - Eithne Costello
- National Institute for Health Research, Liverpool Pancreas Biomedical Research Unit, Liverpool, UK
| | - William Greenhalf
- National Institute for Health Research, Liverpool Pancreas Biomedical Research Unit, Liverpool, UK
| | - Aldo Scarpa
- ARC-NET Center for Applied Research on Cancer, University and Azienda Ospedaliera Universitaria Integrata, Verona, Italy; Department of Pathology and Diagnostics, Università di Verona, Verona, Italy
| | - Bence Sipos
- Institute for Pathology and Neuropathology, Universitätsklinikum Tübingen, Tübingen, Germany
| | - Daniel Auld
- Department of Human Genetics, McGill University, Montreal, Quebec, Canada; McGill University and Genome Quebec Innovation Centre, Montreal, Quebec, Canada
| | - Mark Lathrop
- Department of Human Genetics, McGill University, Montreal, Quebec, Canada; McGill University and Genome Quebec Innovation Centre, Montreal, Quebec, Canada
| | - Morag Park
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada; Rosalind and Morris Goodman Cancer Research Centre, McGill University, Montreal, Quebec, Canada; Department of Pathology, McGill University, Montréal, Quebec, Canada; Department of Oncology, McGill University, Montréal, Quebec, Canada
| | - Markus W Büchler
- Department of Surgery, University Hospital Heidelberg, Heidelberg, Germany
| | - Oliver Strobel
- Department of Surgery, University Hospital Heidelberg, Heidelberg, Germany
| | - Thilo Hackert
- Department of Surgery, University Hospital Heidelberg, Heidelberg, Germany
| | - Nathalia A Giese
- Department of Surgery, University Hospital Heidelberg, Heidelberg, Germany
| | - George Zogopoulos
- Rosalind and Morris Goodman Cancer Research Centre, McGill University, Montreal, Quebec, Canada; The Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada
| | - Veena Sangwan
- Rosalind and Morris Goodman Cancer Research Centre, McGill University, Montreal, Quebec, Canada; Department of Oncology, McGill University, Montréal, Quebec, Canada
| | - Sidong Huang
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada; Rosalind and Morris Goodman Cancer Research Centre, McGill University, Montreal, Quebec, Canada
| | - Yasser Riazalhosseini
- Department of Human Genetics, McGill University, Montreal, Quebec, Canada; McGill University and Genome Quebec Innovation Centre, Montreal, Quebec, Canada.
| | - Jörg D Hoheisel
- Functional Genome Analysis, Deutsches Krebsforschungszentrum, Heidelberg, Germany
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Broichhagen J, Johnston NR, von Ohlen Y, Meyer-Berg H, Jones BJ, Bloom SR, Rutter GA, Trauner D, Hodson DJ. Allosteric Optical Control of a Class B G-Protein-Coupled Receptor. Angew Chem Int Ed Engl 2016; 55:5865-8. [PMID: 27059784 PMCID: PMC5031193 DOI: 10.1002/anie.201600957] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Indexed: 11/09/2022]
Abstract
Allosteric regulation promises to open up new therapeutic avenues by increasing drug specificity at G-protein-coupled receptors (GPCRs). However, drug discovery efforts are at present hampered by an inability to precisely control the allosteric site. Herein, we describe the design, synthesis, and testing of PhotoETP, a light-activated positive allosteric modulator of the glucagon-like peptide-1 receptor (GLP-1R), a class B GPCR involved in the maintenance of glucose homeostasis in humans. PhotoETP potentiates Ca(2+) , cAMP, and insulin responses to glucagon-like peptide-1 and its metabolites following illumination of cells with blue light. PhotoETP thus provides a blueprint for the production of small-molecule class B GPCR allosteric photoswitches, and may represent a useful tool for understanding positive cooperativity at the GLP-1R.
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Affiliation(s)
- Johannes Broichhagen
- LMU Munich, Department of Chemistry and Center for Integrated Protein Science (CIPSM), Butenandtstrasse 5-13, 81377, Munich, Germany
- École Polytechnique Fédérale de Lausanne (EPFL), Institute of Chemical Sciences and Engineering (ISIC), Laboratory of Protein Engineering (LIP), 1015, Lausanne, Switzerland
| | - Natalie R Johnston
- Imperial College London, Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Hammersmith Hospital, Du Cane Road, London, W12 0NN, UK
| | - Yorrick von Ohlen
- Imperial College London, Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Hammersmith Hospital, Du Cane Road, London, W12 0NN, UK
| | - Helena Meyer-Berg
- LMU Munich, Department of Chemistry and Center for Integrated Protein Science (CIPSM), Butenandtstrasse 5-13, 81377, Munich, Germany
| | - Ben J Jones
- Imperial College London, Section of Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, UK
| | - Stephen R Bloom
- Imperial College London, Section of Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, UK
| | - Guy A Rutter
- Imperial College London, Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Hammersmith Hospital, Du Cane Road, London, W12 0NN, UK
| | - Dirk Trauner
- LMU Munich, Department of Chemistry and Center for Integrated Protein Science (CIPSM), Butenandtstrasse 5-13, 81377, Munich, Germany.
| | - David J Hodson
- Imperial College London, Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Hammersmith Hospital, Du Cane Road, London, W12 0NN, UK. ,
- Institute of Metabolism and Systems Research (IMSR), University of Birmingham, B15 2TT, UK. ,
- Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham, B15 2TH, UK. ,
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Thompson A, Stephens JW, Bain SC, Kanamarlapudi V. Molecular Characterisation of Small Molecule Agonists Effect on the Human Glucagon Like Peptide-1 Receptor Internalisation. PLoS One 2016; 11:e0154229. [PMID: 27100083 PMCID: PMC4839733 DOI: 10.1371/journal.pone.0154229] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Accepted: 04/11/2016] [Indexed: 01/23/2023] Open
Abstract
The glucagon-like peptide receptor (GLP-1R), which is a G-protein coupled receptor (GPCR), signals through both Gαs and Gαq coupled pathways and ERK phosphorylation to stimulate insulin secretion. The aim of this study was to determine molecular details of the effect of small molecule agonists, compounds 2 and B, on GLP-1R mediated cAMP production, intracellular Ca2+ accumulation, ERK phosphorylation and its internalisation. In human GLP-1R (hGLP-1R) expressing cells, compounds 2 and B induced cAMP production but caused no intracellular Ca2+ accumulation, ERK phosphorylation or hGLP-1R internalisation. GLP-1 antagonists Ex(9-39) and JANT-4 and the orthosteric binding site mutation (V36A) in hGLP-1R failed to inhibit compounds 2 and B induced cAMP production, confirming that their binding site distinct from the GLP-1 binding site on GLP-1R. However, K334A mutation of hGLP-1R, which affects Gαs coupling, inhibited GLP-1 as well as compounds 2 and B induced cAMP production, indicating that GLP-1, compounds 2 and B binding induce similar conformational changes in the GLP-1R for Gαs coupling. Additionally, compound 2 or B binding to the hGLP-1R had significantly reduced GLP-1 induced intracellular Ca2+ accumulation, ERK phosphorylation and hGLP-1R internalisation. This study illustrates pharmacology of differential activation of GLP-1R by GLP-1 and compounds 2 and B.
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Affiliation(s)
- Aiysha Thompson
- Institute of Life Science 1, Medical School, Swansea University, Singleton Park, Swansea, United Kingdom
| | - Jeffrey W. Stephens
- Institute of Life Science 1, Medical School, Swansea University, Singleton Park, Swansea, United Kingdom
| | - Stephen C. Bain
- Institute of Life Science 1, Medical School, Swansea University, Singleton Park, Swansea, United Kingdom
| | - Venkateswarlu Kanamarlapudi
- Institute of Life Science 1, Medical School, Swansea University, Singleton Park, Swansea, United Kingdom
- * E-mail:
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41
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Broichhagen J, Johnston NR, von Ohlen Y, Meyer-Berg H, Jones BJ, Bloom SR, Rutter GA, Trauner D, Hodson DJ. Allosterische optische Steuerung eines Klasse-B-G-Protein-gekoppelten Rezeptors. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201600957] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Johannes Broichhagen
- LMU München; Department Chemie und Center for Integrated Protein Science (CIPSM); Butenandtstraße 5-13 81377 München Deutschland
- École Polytechnique Fédérale de Lausanne (EPFL); Institute of Chemical Sciences and Engineering (ISIC); Laboratory of Protein Engineering (LIP); 1015 Lausanne Schweiz
| | - Natalie R. Johnston
- Imperial College London; Section of Cell Biology and Functional Genomics; Division of Diabetes, Endocrinology and Metabolism; Department of Medicine, Hammersmith Hospital; Du Cane Road London W12 0NN Großbritannien
| | - Yorrick von Ohlen
- Imperial College London; Section of Cell Biology and Functional Genomics; Division of Diabetes, Endocrinology and Metabolism; Department of Medicine, Hammersmith Hospital; Du Cane Road London W12 0NN Großbritannien
| | - Helena Meyer-Berg
- LMU München; Department Chemie und Center for Integrated Protein Science (CIPSM); Butenandtstraße 5-13 81377 München Deutschland
| | - Ben J. Jones
- Imperial College London; Section of Investigative Medicine; Division of Diabetes, Endocrinology and Metabolism; Großbritannien
| | - Stephen R. Bloom
- Imperial College London; Section of Investigative Medicine; Division of Diabetes, Endocrinology and Metabolism; Großbritannien
| | - Guy A. Rutter
- Imperial College London; Section of Cell Biology and Functional Genomics; Division of Diabetes, Endocrinology and Metabolism; Department of Medicine, Hammersmith Hospital; Du Cane Road London W12 0NN Großbritannien
| | - Dirk Trauner
- LMU München; Department Chemie und Center for Integrated Protein Science (CIPSM); Butenandtstraße 5-13 81377 München Deutschland
| | - David J. Hodson
- Imperial College London; Section of Cell Biology and Functional Genomics; Division of Diabetes, Endocrinology and Metabolism; Department of Medicine, Hammersmith Hospital; Du Cane Road London W12 0NN Großbritannien
- Institute of Metabolism and Systems Research (IMSR); University of Birmingham; Birmingham B15 2TT Großbritannien
- Centre for Endocrinology; Diabetes and Metabolism; Birmingham Health Partners; Birmingham B15 2TH Großbritannien
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42
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Röder PV, Wu B, Liu Y, Han W. Pancreatic regulation of glucose homeostasis. Exp Mol Med 2016; 48:e219. [PMID: 26964835 PMCID: PMC4892884 DOI: 10.1038/emm.2016.6] [Citation(s) in RCA: 454] [Impact Index Per Article: 56.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Revised: 12/03/2015] [Accepted: 12/06/2015] [Indexed: 12/11/2022] Open
Abstract
In order to ensure normal body function, the human body is dependent on a tight control of its blood glucose levels. This is accomplished by a highly sophisticated network of various hormones and neuropeptides released mainly from the brain, pancreas, liver, intestine as well as adipose and muscle tissue. Within this network, the pancreas represents a key player by secreting the blood sugar-lowering hormone insulin and its opponent glucagon. However, disturbances in the interplay of the hormones and peptides involved may lead to metabolic disorders such as type 2 diabetes mellitus (T2DM) whose prevalence, comorbidities and medical costs take on a dramatic scale. Therefore, it is of utmost importance to uncover and understand the mechanisms underlying the various interactions to improve existing anti-diabetic therapies and drugs on the one hand and to develop new therapeutic approaches on the other. This review summarizes the interplay of the pancreas with various other organs and tissues that maintain glucose homeostasis. Furthermore, anti-diabetic drugs and their impact on signaling pathways underlying the network will be discussed.
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Affiliation(s)
- Pia V Röder
- Metabolism in Human Diseases Unit, Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
- Metabolism in Human Diseases Unit, Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), Singapore 138673, Singapore. E-mail: or
| | - Bingbing Wu
- Laboratory of Metabolic Medicine, Singapore Bioimaging Consortium, A*STAR, Singapore, Singapore
| | - Yixian Liu
- Laboratory of Metabolic Medicine, Singapore Bioimaging Consortium, A*STAR, Singapore, Singapore
| | - Weiping Han
- Metabolism in Human Diseases Unit, Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
- Laboratory of Metabolic Medicine, Singapore Bioimaging Consortium, A*STAR, Singapore, Singapore
- Metabolism in Human Diseases Unit, Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), Singapore 138673, Singapore. E-mail: or
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43
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Takeda Y, Shimayoshi T, Holz GG, Noma A. Modeling analysis of inositol 1,4,5-trisphosphate receptor-mediated Ca2+ mobilization under the control of glucagon-like peptide-1 in mouse pancreatic β-cells. Am J Physiol Cell Physiol 2016; 310:C337-47. [PMID: 26741144 PMCID: PMC4888524 DOI: 10.1152/ajpcell.00234.2015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Accepted: 11/19/2015] [Indexed: 01/22/2023]
Abstract
Glucagon-like peptide-1 (GLP-1) is an intestinally derived blood glucose-lowering hormone that potentiates glucose-stimulated insulin secretion from pancreatic β-cells. The secretagogue action of GLP-1 is explained, at least in part, by its ability to stimulate cAMP production so that cAMP may facilitate the release of Ca(2+) from inositol trisphosphate receptor (IP3R)-regulated Ca(2+) stores. However, a quantitative model has yet to be provided that explains the molecular mechanisms and dynamic processes linking GLP-1-stimulated cAMP production to Ca(2+) mobilization. Here, we performed simulation studies to investigate how GLP-1 alters the abilities of Ca(2+) and IP3 to act as coagonists at IP3R Ca(2+) release channels. A new dynamic model was constructed based on the Kaftan model, which demonstrates dual steady-state allosteric regulation of the IP3R by Ca(2+) and IP3. Data obtained from β-cells were then analyzed to understand how GLP-1 facilitates IP3R-mediated Ca(2+) mobilization when UV flash photolysis is used to uncage Ca(2+) and IP3 intracellularly. When the dynamic model for IP3R activation was incorporated into a minimal cell model, the Ca(2+) transients and oscillations induced by GLP-1 were successfully reconstructed. Simulation studies indicated that transient and oscillatory responses to GLP-1 were produced by sequential positive and negative feedback regulation due to fast activation and slow inhibition of the IP3R by Ca(2+). The slow rate of Ca(2+)-dependent inhibition was revealed to provide a remarkable contribution to the time course of the decay of cytosolic Ca(2+) transients. It also served to drive and pace Ca(2+) oscillations that are significant when evaluating how GLP-1 stimulates insulin secretion.
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Affiliation(s)
- Yukari Takeda
- Department of Bioinformatics, College of Life Sciences, Ritsumeikan University, Kusatsu City, Japan;
| | - Takao Shimayoshi
- Department of Systems Science, Kyoto University, Kyoto, Japan; and
| | - George G Holz
- Departments of Medicine and Pharmacology, SUNY Upstate Medical University, Syracuse, New York
| | - Akinori Noma
- Department of Bioinformatics, College of Life Sciences, Ritsumeikan University, Kusatsu City, Japan
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44
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Markwardt ML, Seckinger KM, Rizzo MA. Regulation of Glucokinase by Intracellular Calcium Levels in Pancreatic β Cells. J Biol Chem 2015; 291:3000-9. [PMID: 26698632 DOI: 10.1074/jbc.m115.692160] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Indexed: 01/01/2023] Open
Abstract
Glucokinase (GCK) controls the rate of glucose metabolism in pancreatic β cells, and its activity is rate-limiting for insulin secretion. Posttranslational GCK activation can be stimulated through either G protein-coupled receptors or receptor tyrosine kinase signaling pathways, suggesting a common mechanism. Here we show that inhibiting Ca(2+) release from the endoplasmic reticulum (ER) decouples GCK activation from receptor stimulation. Furthermore, pharmacological release of ER Ca(2+) stimulates activation of a GCK optical biosensor and potentiates glucose metabolism, implicating rises in cytoplasmic Ca(2+) as a critical regulatory mechanism. To explore the potential for glucose-stimulated GCK activation, the GCK biosensor was optimized using circularly permuted mCerulean3 proteins. This new sensor sensitively reports activation in response to insulin, glucagon-like peptide 1, and agents that raise cAMP levels. Transient, glucose-stimulated GCK activation was observed in βTC3 and MIN6 cells. An ER-localized channelrhodopsin was used to manipulate the cytoplasmic Ca(2+) concentration in cells expressing the optimized FRET-GCK sensor. This permitted quantification of the relationship between cytoplasmic Ca(2+) concentrations and GCK activation. Half-maximal activation of the FRET-GCK sensor was estimated to occur at ∼400 nm Ca(2+). When expressed in islets, fluctuations in GCK activation were observed in response to glucose, and we estimated that posttranslational activation of GCK enhances glucose metabolism by ∼35%. These results suggest a mechanism for integrative control over GCK activation and, therefore, glucose metabolism and insulin secretion through regulation of cytoplasmic Ca(2+) levels.
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Affiliation(s)
- Michele L Markwardt
- From the University of Maryland School of Medicine, Baltimore, Maryland 21201
| | - Kendra M Seckinger
- From the University of Maryland School of Medicine, Baltimore, Maryland 21201
| | - Mark A Rizzo
- From the University of Maryland School of Medicine, Baltimore, Maryland 21201
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45
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Sugawara K, Shibasaki T, Takahashi H, Seino S. Structure and functional roles of Epac2 (Rapgef4). Gene 2015; 575:577-83. [PMID: 26390815 DOI: 10.1016/j.gene.2015.09.029] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Revised: 08/13/2015] [Accepted: 09/15/2015] [Indexed: 10/24/2022]
Abstract
Epac (exchange protein activated by cyclic-AMP) 2 is a direct target of 3'-5'-cyclic adenosine monophosphate (cAMP) and is involved in cAMP-mediated signal transduction through activation of the Ras-like small GTPase Rap. Crystallographic analyses revealed that activation of Epac2 by cAMP is accompanied by dynamic structural changes. Epac2 is expressed mainly in brain, neuroendocrine and endocrine tissues, and is involved in diverse cellular functions in the tissues. In this review, we summarize the structure and function of Epac2. We also discuss the physiological and pathophysiological roles of Epac2, and the possibility of Epac2 as a therapeutic target.
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Affiliation(s)
- Kenji Sugawara
- Division of Diabetes and Endocrinology, Kobe University Graduate School of Medicine, Kobe, Japan; Division of Molecular and Metabolic Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Tadao Shibasaki
- Division of Molecular and Metabolic Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Harumi Takahashi
- Division of Molecular and Metabolic Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Susumu Seino
- Division of Molecular and Metabolic Medicine, Kobe University Graduate School of Medicine, Kobe, Japan.
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46
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Llanos P, Contreras-Ferrat A, Barrientos G, Valencia M, Mears D, Hidalgo C. Glucose-Dependent Insulin Secretion in Pancreatic β-Cell Islets from Male Rats Requires Ca2+ Release via ROS-Stimulated Ryanodine Receptors. PLoS One 2015; 10:e0129238. [PMID: 26046640 PMCID: PMC4457734 DOI: 10.1371/journal.pone.0129238] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Accepted: 05/06/2015] [Indexed: 12/03/2022] Open
Abstract
Glucose-stimulated insulin secretion (GSIS) from pancreatic β-cells requires an increase in intracellular free Ca2+ concentration ([Ca2+]). Glucose uptake into β-cells promotes Ca2+ influx and reactive oxygen species (ROS) generation. In other cell types, Ca2+ and ROS jointly induce Ca2+ release mediated by ryanodine receptor (RyR) channels. Therefore, we explored here if RyR-mediated Ca2+ release contributes to GSIS in β-cell islets isolated from male rats. Stimulatory glucose increased islet insulin secretion, and promoted ROS generation in islets and dissociated β-cells. Conventional PCR assays and immunostaining confirmed that β-cells express RyR2, the cardiac RyR isoform. Extended incubation of β-cell islets with inhibitory ryanodine suppressed GSIS; so did the antioxidant N-acetyl cysteine (NAC), which also decreased insulin secretion induced by glucose plus caffeine. Inhibitory ryanodine or NAC did not affect insulin secretion induced by glucose plus carbachol, which engages inositol 1,4,5-trisphosphate receptors. Incubation of islets with H2O2 in basal glucose increased insulin secretion 2-fold. Inhibitory ryanodine significantly decreased H2O2-stimulated insulin secretion and prevented the 4.5-fold increase of cytoplasmic [Ca2+] produced by incubation of dissociated β-cells with H2O2. Addition of stimulatory glucose or H2O2 (in basal glucose) to β-cells disaggregated from islets increased RyR2 S-glutathionylation to similar levels, measured by a proximity ligation assay; in contrast, NAC significantly reduced the RyR2 S-glutathionylation increase produced by stimulatory glucose. We propose that RyR2-mediated Ca2+ release, induced by the concomitant increases in [Ca2+] and ROS produced by stimulatory glucose, is an essential step in GSIS.
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Affiliation(s)
- Paola Llanos
- Institute for Research in Dental Sciences, Facultad de Odontología, Universidad de Chile, Santiago, Chile
- Center of Molecular Studies of the Cell, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Ariel Contreras-Ferrat
- Institute for Research in Dental Sciences, Facultad de Odontología, Universidad de Chile, Santiago, Chile
- Center of Molecular Studies of the Cell, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Genaro Barrientos
- Physiology and Biophysics Program, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Marco Valencia
- Center of Molecular Studies of the Cell, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - David Mears
- Center of Molecular Studies of the Cell, Facultad de Medicina, Universidad de Chile, Santiago, Chile
- Human Genetics Program, Institute of Biomedical Sciences, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Cecilia Hidalgo
- Center of Molecular Studies of the Cell, Facultad de Medicina, Universidad de Chile, Santiago, Chile
- Physiology and Biophysics Program, Facultad de Medicina, Universidad de Chile, Santiago, Chile
- Biomedical Neuroscience Institute, Facultad de Medicina, Universidad de Chile, Santiago, Chile
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47
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Zibolka J, Mühlbauer E, Peschke E. Melatonin influences somatostatin secretion from human pancreatic δ-cells via MT1 and MT2 receptors. J Pineal Res 2015; 58:198-209. [PMID: 25585597 DOI: 10.1111/jpi.12206] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Accepted: 01/09/2015] [Indexed: 12/20/2022]
Abstract
Melatonin is an effector of the diurnal clock on pancreatic islets. The membrane receptor-transmitted inhibitory influence of melatonin on insulin secretion is well established and contrasts with the reported stimulation of glucagon release from α-cells. Virtually, nothing is known concerning the melatonin-mediated effects on islet δ-cells. Analysis of a human pancreatic δ-cell model, the cell line QGP-1, and the use of a somatostatin-specific radioimmunoassay showed that melatonin primarily has an inhibitory effect on somatostatin secretion in the physiological concentration range. In the pharmacological range, melatonin elicited slightly increased somatostatin release from δ-cells. Cyclic adenosine monophosphate (cAMP) is the major second messenger dose-dependently stimulating somatostatin secretion, in experiments employing the membrane-permeable 8-Br-cAMP. 8-Br-cyclic guanosine monophosphate proved to be of only minor relevance to somatostatin release. As the inhibitory effect of 1 nm melatonin was reversed after incubation of QGP-1 cells with the nonselective melatonin receptor antagonist luzindole, but not with the MT2-selective antagonist 4-P-PDOT (4-phenyl-2-propionamidotetraline), an involvement of the MT1 receptor can be assumed. Somatostatin release from the δ-cells at low glucose concentrations was significantly inhibited during co-incubation with 1 nm melatonin, an effect which was less pronounced at higher glucose levels. Transient expression experiments, overexpressing MT1, MT2, or a deletion variant as a control, indicated that the MT1 and not the MT2 receptor was the major transmitter of the inhibitory melatonin effect. These data point to a significant influence of melatonin on pancreatic δ-cells and on somatostatin release.
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Affiliation(s)
- Juliane Zibolka
- Institute of Anatomy and Cell Biology, Martin Luther University Halle-Wittenberg, Halle, Germany
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48
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Thompson A, Kanamarlapudi V. Agonist-induced internalisation of the glucagon-like peptide-1 receptor is mediated by the Gαq pathway. Biochem Pharmacol 2015; 93:72-84. [DOI: 10.1016/j.bcp.2014.10.015] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Revised: 10/27/2014] [Accepted: 10/30/2014] [Indexed: 12/12/2022]
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The regions within the N-terminus critical for human glucagon like peptide-1 receptor (hGLP-1R) cell surface expression. Sci Rep 2014; 4:7410. [PMID: 25502804 PMCID: PMC4344312 DOI: 10.1038/srep07410] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 11/20/2014] [Indexed: 11/16/2022] Open
Abstract
The hGLP-1R is a target for the treatment of type 2 diabetes and belongs to the class B family of GPCRs. Like other class B GPCRs, the GLP-1R contains an N-terminal signal peptide (SP) and undergoes N-linked glycosylation, which are important for its trafficking and maturation. This study analysed the role of the SP, the hydrophobic region after the SP (HRASP), glycosylation and the conserved residues within the N-terminus in GLP-1R trafficking. HGLP-1R targeted to the cell surface showed no SP, and the SP deleted mutant, but not the mutants defective in SP cleavage, showed cell surface expression, demonstrating the importance of SP cleavage for hGLP-1R cell surface expression. The N-terminal deletions of hGLP-1R revealed that the HRASP, not the SP, is essential for cell surface expression of GLP-1R. Further, inhibition of hGLP-1R glycosylation prevented cell surface expression of the receptor. Mutation of Trp39, Tyr69 and Tyr88, which are required for agonist binding, in the GLP-1R abolished cell surface expression of the receptor independent of the SP cleavage or N-linked glycosylation. In conclusion, the N-terminus of hGLP-1R regulates receptor trafficking and maturation. Therefore this study provides insight into the role of hGLP-1R N-terminus on the receptor cell surface expression.
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50
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Chandra V, Albagli-Curiel O, Hastoy B, Piccand J, Randriamampita C, Vaillant E, Cavé H, Busiah K, Froguel P, Vaxillaire M, Rorsman P, Polak M, Scharfmann R. RFX6 Regulates Insulin Secretion by Modulating Ca2+ Homeostasis in Human β Cells. Cell Rep 2014; 9:2206-18. [DOI: 10.1016/j.celrep.2014.11.010] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Revised: 10/09/2014] [Accepted: 11/06/2014] [Indexed: 10/24/2022] Open
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