1
|
Blanc M, Habbouche L, Xiao P, Lebeaupin C, Janona M, Vaillant N, Irondelle M, Gilleron J, Murcy F, Rousseau D, Luci C, Barouillet T, Marchetti S, Lacas-Gervais S, Yvan-Charvet L, Gual P, Cardozo AK, Bailly-Maitre B. Bax Inhibitor-1 preserves pancreatic β-cell proteostasis by limiting proinsulin misfolding and programmed cell death. Cell Death Dis 2024; 15:334. [PMID: 38744890 PMCID: PMC11094198 DOI: 10.1038/s41419-024-06701-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Revised: 04/17/2024] [Accepted: 04/22/2024] [Indexed: 05/16/2024]
Abstract
The prevalence of diabetes steadily increases worldwide mirroring the prevalence of obesity. Endoplasmic reticulum (ER) stress is activated in diabetes and contributes to β-cell dysfunction and apoptosis through the activation of a terminal unfolded protein response (UPR). Our results uncover a new role for Bax Inhibitor-One (BI-1), a negative regulator of inositol-requiring enzyme 1 (IRE1α) in preserving β-cell health against terminal UPR-induced apoptosis and pyroptosis in the context of supraphysiological loads of insulin production. BI-1-deficient mice experience a decline in endocrine pancreatic function in physiological and pathophysiological conditions, namely obesity induced by high-fat diet (HFD). We observed early-onset diabetes characterized by hyperglycemia, reduced serum insulin levels, β-cell loss, increased pancreatic lipases and pro-inflammatory cytokines, and the progression of metabolic dysfunction. Pancreatic section analysis revealed that BI-1 deletion overburdens unfolded proinsulin in the ER of β-cells, confirmed by ultrastructural signs of ER stress with overwhelmed IRE1α endoribonuclease (RNase) activity in freshly isolated islets. ER stress led to β-cell dysfunction and islet loss, due to an increase in immature proinsulin granules and defects in insulin crystallization with the presence of Rod-like granules. These results correlated with the induction of autophagy, ER phagy, and crinophagy quality control mechanisms, likely to alleviate the atypical accumulation of misfolded proinsulin in the ER. In fine, BI-1 in β-cells limited IRE1α RNase activity from triggering programmed β-cell death through apoptosis and pyroptosis (caspase-1, IL-1β) via NLRP3 inflammasome activation and metabolic dysfunction. Pharmaceutical IRE1α inhibition with STF-083010 reversed β-cell failure and normalized the metabolic phenotype. These results uncover a new protective role for BI-1 in pancreatic β-cell physiology as a stress integrator to modulate the UPR triggered by accumulating unfolded proinsulin in the ER, as well as autophagy and programmed cell death, with consequences on β-cell function and insulin secretion. In pancreatic β-cells, BI-1-/- deficiency perturbs proteostasis with proinsulin misfolding, ER stress, terminal UPR with overwhelmed IRE1α/XBP1s/CHOP activation, inflammation, β-cell programmed cell death, and diabetes.
Collapse
Affiliation(s)
- Marina Blanc
- Institut National de la Santé et de la Recherche Médicale (Inserm) U1065, Université Côte d'Azur (UCA), Centre Méditerranéen de Médecine Moléculaire (C3M), Atip-Avenir, Fédération Hospitalo-Universitaire (FHU) Oncoage, Team "Hematometabolism and Metainflammation (HEMAMETABO), 06204, Nice, France
| | - Lama Habbouche
- Institut National de la Santé et de la Recherche Médicale (Inserm) U1065, Université Côte d'Azur (UCA), Centre Méditerranéen de Médecine Moléculaire (C3M), Atip-Avenir, Fédération Hospitalo-Universitaire (FHU) Oncoage, Team "Hematometabolism and Metainflammation (HEMAMETABO), 06204, Nice, France
| | - Peng Xiao
- Inflammation and Cell Death Signalling group, Signal Transduction and Metabolism Laboratory, Université libre de Bruxelles (ULB), Bruxelles, Belgique
| | - Cynthia Lebeaupin
- Degenerative Diseases Program, Sanford Burnham Prebys, La Jolla, CA, 92037, USA
| | - Marion Janona
- Institut National de la Santé et de la Recherche Médicale (Inserm) U1065, Université Côte d'Azur (UCA), Centre Méditerranéen de Médecine Moléculaire (C3M), Atip-Avenir, Fédération Hospitalo-Universitaire (FHU) Oncoage, Team "Hematometabolism and Metainflammation (HEMAMETABO), 06204, Nice, France
| | - Nathalie Vaillant
- Institut National de la Santé et de la Recherche Médicale (Inserm) U1065, Université Côte d'Azur (UCA), Centre Méditerranéen de Médecine Moléculaire (C3M), Atip-Avenir, Fédération Hospitalo-Universitaire (FHU) Oncoage, Team "Hematometabolism and Metainflammation (HEMAMETABO), 06204, Nice, France
| | - Marie Irondelle
- Institut National de la Santé et de la Recherche Médicale (Inserm) U1065, Université Côte d'Azur (UCA), Centre Méditerranéen de Médecine Moléculaire (C3M), Atip-Avenir, Fédération Hospitalo-Universitaire (FHU) Oncoage, Team "Hematometabolism and Metainflammation (HEMAMETABO), 06204, Nice, France
| | - Jérôme Gilleron
- Université Côte d'Azur, Institut National de la Santé et de la Recherche Médicale (Inserm) U1065, Adipo-Cible Research Study Group, Centre Méditerranéen de Médecine Moléculaire (C3M), Team «Insulin Resistance in Obesity and type 2 Diabetes», Nice, France
| | - Florent Murcy
- Institut National de la Santé et de la Recherche Médicale (Inserm) U1065, Université Côte d'Azur (UCA), Centre Méditerranéen de Médecine Moléculaire (C3M), Atip-Avenir, Fédération Hospitalo-Universitaire (FHU) Oncoage, Team "Hematometabolism and Metainflammation (HEMAMETABO), 06204, Nice, France
| | - Déborah Rousseau
- Institut National de la Santé et de la Recherche Médicale (Inserm) U1065, Université Côte d'Azur, Centre Méditerranéen de Médecine Moléculaire (C3M), Team «Chronic Liver Diseases Associated with Obesity and Alcohol», Nice, France
| | - Carmelo Luci
- Institut National de la Santé et de la Recherche Médicale (Inserm) U1065, Université Côte d'Azur, Centre Méditerranéen de Médecine Moléculaire (C3M), Team «Chronic Liver Diseases Associated with Obesity and Alcohol», Nice, France
| | - Thibault Barouillet
- Institut National de la Santé et de la Recherche Médicale (Inserm) U1065, Université Côte d'Azur (UCA), Centre Méditerranéen de Médecine Moléculaire (C3M), Atip-Avenir, Fédération Hospitalo-Universitaire (FHU) Oncoage, Team "Hematometabolism and Metainflammation (HEMAMETABO), 06204, Nice, France
| | - Sandrine Marchetti
- Institut National de la Santé et de la Recherche Médicale (Inserm) U1065, Université Côte d'Azur, Centre Méditerranéen de Médecine Moléculaire (C3M), Team «Metabolism, cancer and immune responses», Nice, France
| | - Sandra Lacas-Gervais
- Université Côte d'Azur, Centre Commun de Microscopie Appliquée, CCMA, Nice, France
| | - Laurent Yvan-Charvet
- Institut National de la Santé et de la Recherche Médicale (Inserm) U1065, Université Côte d'Azur (UCA), Centre Méditerranéen de Médecine Moléculaire (C3M), Atip-Avenir, Fédération Hospitalo-Universitaire (FHU) Oncoage, Team "Hematometabolism and Metainflammation (HEMAMETABO), 06204, Nice, France
| | - Philippe Gual
- Institut National de la Santé et de la Recherche Médicale (Inserm) U1065, Université Côte d'Azur, Centre Méditerranéen de Médecine Moléculaire (C3M), Team «Chronic Liver Diseases Associated with Obesity and Alcohol», Nice, France
| | - Alessandra K Cardozo
- Inflammation and Cell Death Signalling group, Signal Transduction and Metabolism Laboratory, Université libre de Bruxelles (ULB), Bruxelles, Belgique
| | - Béatrice Bailly-Maitre
- Institut National de la Santé et de la Recherche Médicale (Inserm) U1065, Université Côte d'Azur (UCA), Centre Méditerranéen de Médecine Moléculaire (C3M), Atip-Avenir, Fédération Hospitalo-Universitaire (FHU) Oncoage, Team "Hematometabolism and Metainflammation (HEMAMETABO), 06204, Nice, France.
| |
Collapse
|
2
|
Ramírez-Ponce MP, Flores JA, Barrella L, Alés E. Ketotifen is a microglial stabilizer by inhibiting secretory vesicle acidification. Life Sci 2023; 319:121537. [PMID: 36868401 DOI: 10.1016/j.lfs.2023.121537] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 02/22/2023] [Accepted: 02/24/2023] [Indexed: 03/05/2023]
Abstract
AIMS Microglia survey the brain environment by sensing alarm signals to provide the first line of defense against injury or infection after which they acquire an activated phenotype, but they also respond to chemical signals sent from brain mast cells, sentinels of the immune system, when these are degranulated in response to noxious agents. Nevertheless, excessive microglia activation damages the surrounding healthy neural tissue causing progressive loss of neurons and inducing chronic inflammation. Thus, it would be of intense interest the development and application of agents which prevent mast cell mediator release and inhibit the actions of such mediators once released on microglia. MAIN METHODS Fluorescence measurements of fura-2 and quinacrine were used to measure intracellular Ca2+ signaling and exocytotic vesicle fusion in resting and activated microglia. KEY FINDINGS We show that treatment of microglia with a cocktail of mast cell mediators induces microglia activation, phagocytosis, and exocytosis, and reveal by the first-time microglia undergo a phase of vesicular acidification just before the exocytotic fusion occurs. This acidification is an important process for vesicular maturation and contributes with ∼25 % to the content that the vesicle can store and later release by exocytosis. Pre-incubation with ketotifen, a mast cell stabilizer and H1R antagonist completely abolished histamine-mediated calcium signaling and acidification of microglial organelles, and concomitantly reduced the discharge of vesicle contents. SIGNIFICANCE These results highlight a key role for vesicle acidification in microglial physiology and provide a potential therapeutic target for diseases related to mast cell and microglia-mediated neuroinflammation.
Collapse
Affiliation(s)
| | - Juan Antonio Flores
- Dpto. de Bioquímica Médica y Biología Molecular e Inmunología, Facultad de Medicina, Universidad de Sevilla, Spain
| | - Lorenzo Barrella
- Dpto. de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Spain
| | - Eva Alés
- Dpto. de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Spain.
| |
Collapse
|
3
|
Chen CW, Guan BJ, Alzahrani MR, Gao Z, Gao L, Bracey S, Wu J, Mbow CA, Jobava R, Haataja L, Zalavadia AH, Schaffer AE, Lee H, LaFramboise T, Bederman I, Arvan P, Mathews CE, Gerling IC, Kaestner KH, Tirosh B, Engin F, Hatzoglou M. Adaptation to chronic ER stress enforces pancreatic β-cell plasticity. Nat Commun 2022; 13:4621. [PMID: 35941159 PMCID: PMC9360004 DOI: 10.1038/s41467-022-32425-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Accepted: 08/01/2022] [Indexed: 11/30/2022] Open
Abstract
Pancreatic β-cells are prone to endoplasmic reticulum (ER) stress due to their role in insulin secretion. They require sustainable and efficient adaptive stress responses to cope with this stress. Whether episodes of chronic stress directly compromise β-cell identity is unknown. We show here under reversible, chronic stress conditions β-cells undergo transcriptional and translational reprogramming associated with impaired expression of regulators of β-cell function and identity. Upon recovery from stress, β-cells regain their identity and function, indicating a high degree of adaptive plasticity. Remarkably, while β-cells show resilience to episodic ER stress, when episodes exceed a threshold, β-cell identity is gradually lost. Single cell RNA-sequencing analysis of islets from type 1 diabetes patients indicates severe deregulation of the chronic stress-adaptation program and reveals novel biomarkers of diabetes progression. Our results suggest β-cell adaptive exhaustion contributes to diabetes pathogenesis.
Collapse
Affiliation(s)
- Chien-Wen Chen
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA.
| | - Bo-Jhih Guan
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Mohammed R Alzahrani
- Department of Biochemistry, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Zhaofeng Gao
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Long Gao
- Department of Genetics and Institute for Diabetes, Obesity and Metabolism, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, 19104, USA
| | - Syrena Bracey
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Jing Wu
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Cheikh A Mbow
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Raul Jobava
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Leena Haataja
- The Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical Center, Ann Arbor, MI, 48105, USA
| | - Ajay H Zalavadia
- Lerner Research Institute, Cleveland Clinic, 9620 Carnegie Ave N Bldg, Cleveland, OH, 44106, US
| | - Ashleigh E Schaffer
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Hugo Lee
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, School of Medicine and Public Health, Madison, WI, 53706, USA
| | - Thomas LaFramboise
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Ilya Bederman
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Peter Arvan
- The Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical Center, Ann Arbor, MI, 48105, USA
| | - Clayton E Mathews
- Department of Pathology, Immunology and Laboratory Medicine, University of Florida College of Medicine, Gainesville, FL, US
| | - Ivan C Gerling
- Department of Medicine, University of Tennessee, Memphis, TN, US
| | - Klaus H Kaestner
- Department of Genetics and Institute for Diabetes, Obesity and Metabolism, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, 19104, USA
| | - Boaz Tirosh
- Department of Biochemistry, Case Western Reserve University, Cleveland, OH, 44106, USA
- The Institute for Drug Research, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Feyza Engin
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, School of Medicine and Public Health, Madison, WI, 53706, USA.
- Department of Medicine, Division of Endocrinology, Diabetes & Metabolism, University of Wisconsin-Madison, School of Medicine and Public Health, Madison, WI, 53705, USA.
| | - Maria Hatzoglou
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA.
| |
Collapse
|
4
|
Garvey RW, Lacivita E, Niso M, Duszyńska B, Harris PE, Leopoldo M. Design, synthesis, and characterization of a novel fluoroprobe for live human islet cell imaging of serotonin 5-HT1A receptor. ChemMedChem 2022; 17:e202100759. [PMID: 35286016 DOI: 10.1002/cmdc.202100759] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 03/08/2022] [Indexed: 11/09/2022]
Abstract
Mounting evidence suggests that the serotonin system serves in signal transmission to regulate insulin secretion in pancreatic islets of Langerhans. Among the 5-HT receptor subtype found in pancreatic islets, serotonin receptor 1A (5-HT 1A ) demonstrates a unique ability to inhibit beta-cell insulin secretion. We report on the design, synthesis, and characterization of two novel fluorescent probes for the 5-HT 1A receptor. The compounds were prepared by conjugating the scaffold of the 5-HT 1A receptor agonist 8-OH-DPAT with two fluorophores suitable for live-cells imaging. Compound 5a showed a high affinity for the 5-HT 1A receptor ( K i = 1.8 nM). Fluoroprobe 5a was able to label the 5-HT 1A receptor in pancreatic islet cell cultures in a selective manner, as the fluorescence emission was significantly attenuated by co-administration of the 5-HT 1A receptor antagonist WAY-100635. Thus, fluoroprobe 5a showed useful properties to further characterize this unique receptor's role.
Collapse
Affiliation(s)
- Robert W Garvey
- Columbia University, Division of Endocrinology, Department of Medicine, UNITED STATES
| | - Enza Lacivita
- Universita' degli Studi di Bari, Dipartimento di Farmacia-Scienze del Farmaco, Via Orabona, 4, 70125, Bari, ITALY
| | - Mauro Niso
- Università degli Studi di Bari Aldo Moro: Universita degli Studi di Bari Aldo Moro, Dipartimento di Farmacia -Scienze del Farmaco, Via Orabona, 4, 70125, Bari, ITALY
| | - Beata Duszyńska
- Institute of Pharmacology of the Polish Academy of Sciences: Instytut Farmakologii im Jerzego Maja Polskiej Akademii Nauk, Department of Medicinal Chemistry, Smetna, 12, 31-343, Krakow, POLAND
| | - Paul E Harris
- Columbia University, Division of Endocrinology, Department of Medicine, UNITED STATES
| | - Marcello Leopoldo
- Università degli Studi di Bari Aldo Moro: Universita degli Studi di Bari Aldo Moro, Dipartimento di Farmacia-Scienze del Farmaco, Via Orabona, 4, 70125, Bari, ITALY
| |
Collapse
|
5
|
Magrì A, Tabbì G, Di Natale G, La Mendola D, Pietropaolo A, Zoroddu MA, Peana M, Rizzarelli E. Zinc Interactions with a Soluble Mutated Rat Amylin to Mimic Whole Human Amylin: An Experimental and Simulation Approach to Understand Stoichiometry, Speciation and Coordination of the Metal Complexes. Chemistry 2020; 26:13072-13084. [DOI: 10.1002/chem.202002114] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Revised: 05/29/2020] [Indexed: 01/27/2023]
Affiliation(s)
- Antonio Magrì
- Consiglio Nazionale delle Ricerche Istituto di Cristallografia Via P. Gaifami 18 95126 Catania Italy
| | - Giovanni Tabbì
- Consiglio Nazionale delle Ricerche Istituto di Cristallografia Via P. Gaifami 18 95126 Catania Italy
| | - Giuseppe Di Natale
- Consiglio Nazionale delle Ricerche Istituto di Cristallografia Via P. Gaifami 18 95126 Catania Italy
| | - Diego La Mendola
- Dipartimento di Farmacia Università di Pisa Via Bonanno Pisano, 6 56126 Pisa Italy
- Consorzio Interuniversitario di Ricerca in Chimica dei, Metalli nei Sistemi Biologici (CIRCMSB) Via Celso Ulpiani 27 70126 Bari Italy
| | - Adriana Pietropaolo
- Dipartimento di Scienze della Salute Università “Magna Graecia” di Catanzaro Campus Universitario, Viale Europa 88100 Catanzaro Italy
| | | | - Massimiliano Peana
- Dipartimento di Chimica e Farmacia University of Sassari Via Vienna 2 07100 Sassari Italy
| | - Enrico Rizzarelli
- Consiglio Nazionale delle Ricerche Istituto di Cristallografia Via P. Gaifami 18 95126 Catania Italy
- Consorzio Interuniversitario di Ricerca in Chimica dei, Metalli nei Sistemi Biologici (CIRCMSB) Via Celso Ulpiani 27 70126 Bari Italy
- Dipartimento di Scienze Chimiche Università degli Studi di Catania Viale A. Doria 6 95125 Catania Italy
| |
Collapse
|
6
|
Fujita-Yoshigaki J, Yokoyama M, Katsumata-Kato O. Switching of cargo sorting from the constitutive to regulated secretory pathway by the addition of cystatin D sequence in salivary acinar cells. Am J Physiol Gastrointest Liver Physiol 2020; 319:G74-G86. [PMID: 32538138 DOI: 10.1152/ajpgi.00103.2020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The mechanism for segregation of cargo proteins into the regulated and constitutive secretory pathways in exocrine cells remains to be elucidated. We examined the transport of HaloTag proteins fused with full-length cystatin D (fCst5-Halo) or only its signal peptide (ssCst5-Halo) in parotid acinar cells. Although both fusion proteins were observed to be colocalized with amylase in the secretory granules, the coefficients for overlapping and correlation of fCst5-Halo with amylase were higher than those of ssCst5-Halo. The secretion of both the proteins was enhanced by the addition of the β-adrenergic receptor agonist isoproterenol as well as endogenous amylase. In contrast, unstimulated secretion of ssCst5-Halo without isoproterenol was significantly higher than that of fCst5-Halo and amylase. Simulation analysis using a mathematical model revealed that a large proportion of ssCst5-Halo was secreted through the constitutive pathway, whereas fCst5-Halo was transported into the secretory granules more efficiently. Precipitation of fCst5-Halo from cell lysates was increased at a low pH, which may mimic the milieu of the trans-Golgi networks. These data suggest that the addition of a full-length sequence of cystatin D facilitates efficient selective transport into the regulated pathway by aggregation at low pH in the trans-Golgi network.NEW & NOTEWORTHY The mechanism underlying the segregation of cargo proteins to the regulated and constitutive secretory pathways in exocrine cells remains to be solved. We analyzed unstimulated secretion in salivary acinar cells by performing double-labeling experiments using HaloTag technology and computer simulation. It revealed that the majority of HaloTag with only signal peptide sequence was secreted through the constitutive pathway and that the addition of a full-length cystatin D sequence changed its sorting to the regulated pathway.
Collapse
Affiliation(s)
- Junko Fujita-Yoshigaki
- Department of Physiology, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba, Japan.,Research Institute of Oral Science, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba, Japan
| | - Megumi Yokoyama
- Department of Physiology, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba, Japan.,Research Institute of Oral Science, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba, Japan
| | - Osamu Katsumata-Kato
- Department of Physiology, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba, Japan.,Research Institute of Oral Science, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba, Japan
| |
Collapse
|
7
|
Pecic S, Milosavic N, Rayat G, Maffei A, Harris PE. A novel optical tracer for VMAT2 applied to live cell measurements of vesicle maturation in cultured human β-cells. Sci Rep 2019; 9:5403. [PMID: 30932004 PMCID: PMC6443945 DOI: 10.1038/s41598-019-41891-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Accepted: 03/19/2019] [Indexed: 02/03/2023] Open
Abstract
The islet β-cells integrate external signals to modulate insulin secretion to better regulate blood glucose levels during periods of changing metabolic demand. The vesicular monoamine transporter type 2 (VMAT2), an important regulator of CNS neurotransmission, has an analogous role in the endocrine pancreas as a key control point of insulin secretion, with additional roles in regulating β-cell differentiation and proliferation. Here we report on the synthesis and biological characterisation of a fluorescent ligand for VMAT2 suitable for live cell imaging. Staining for VMAT2 and dopamine in live β-cell cultures show colocalisation in specific vesicles and reveal a heterogeneous population with respect to cell size, shape, vesicle number, size, and contents. Staining for VMAT2 and zinc ion, as a surrogate for insulin, reveals a wide range of vesicle sizes. Immunohistochemistry shows larger β-cell vesicles enriched for proinsulin, whereas smaller vesicles predominantly contain the processed mature insulin. In β-cell cultures obtained from nondiabetic donors, incubation at non-stimulatory glucose concentrations promotes a shift in vesicle diameter towards the more mature insulin vesicles at the expense of the larger immature insulin secretory vesicle population. We anticipate that this probe will be a useful reagent to identify living β-cells within complex mixtures for further manipulation and characterisation.
Collapse
Affiliation(s)
- Stevan Pecic
- Department of Chemistry and Biochemistry, California State University, Fullerton, California, USA
| | - Nenad Milosavic
- Division of Experimental Therapeutics, Department of Medicine, Columbia University Medical Centre, New York, New York, USA
| | - Gina Rayat
- Alberta Diabetes Institute, Ray Rajotte Surgical-Medical Research Institute, Department of Surgery, University of Alberta, Edmonton, AB, T6G 2E1, Canada
| | - Antonella Maffei
- Division of Endocrinology, Department of Medicine and Naomi Berrie Diabetes Center, Columbia University Medical Centre, New York, New York, USA
| | - Paul E Harris
- Division of Endocrinology, Department of Medicine and Naomi Berrie Diabetes Center, Columbia University Medical Centre, New York, New York, USA.
| |
Collapse
|
8
|
Proton pumping V-ATPase inhibitor bafilomycin A1 affects Rab7 lysosomal localization and abolishes anterograde trafficking of osteoclast secretory lysosomes. Biochem Biophys Res Commun 2019; 510:421-426. [DOI: 10.1016/j.bbrc.2019.01.118] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Accepted: 01/26/2019] [Indexed: 01/03/2023]
|
9
|
Kotuniak R, Fra̧czyk T, Skrobecki P, Płonka D, Bal W. Gly-His-Thr-Asp-Amide, an Insulin-Activating Peptide from the Human Pancreas Is a Strong Cu(II) but a Weak Zn(II) Chelator. Inorg Chem 2018; 57:15507-15516. [DOI: 10.1021/acs.inorgchem.8b02841] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Radosław Kotuniak
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland
| | - Tomasz Fra̧czyk
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland
- Department of Immunology, Transplantology and Internal Medicine, Medical University of Warsaw, Nowogrodzka 59, 02-006 Warsaw, Poland
| | - Piotr Skrobecki
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland
| | - Dawid Płonka
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland
| | - Wojciech Bal
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland
| |
Collapse
|
10
|
Valproate inhibits glucose-stimulated insulin secretion in beta cells. Histochem Cell Biol 2018; 150:395-401. [PMID: 30145684 DOI: 10.1007/s00418-018-1713-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/20/2018] [Indexed: 10/28/2022]
Abstract
Valproate (VPA), an FDA approved anti-epileptic drug with a half-life of 12-18 h in humans, has been shown to perturb the vacuolar proton pump (vH+-ATPase) function in yeasts by inhibiting myo-inositol phosphate synthase, the first and rate-limiting enzyme in inositol biosynthesis, thereby resulting in inositol depletion. vH+-ATPase transfers protons (H+) across cell membranes, which help maintain pH gradients within cells necessary for various cellular functions including secretion. This proton pump has a membrane (V0) and a soluble cytosolic (V1) domain, with C-subunit associated with V1. In secretory cells such as neurons and insulin-secreting beta cells, vH+-ATPase acidifies vesicles essential for secretion. In this study, we demonstrate that exposure of insulin-secreting Min6 cells to a clinical dose of VPA results in inositol depletion and loss of co-localization of subunit C of vH+-ATPase with insulin-secreting granules. Consequently, a reduction of glucose-stimulated insulin secretion is observed following VPA exposure. These results merit caution and the reassessment of the clinical use of VPA.
Collapse
|
11
|
Harrison MA, Muench SP. The Vacuolar ATPase - A Nano-scale Motor That Drives Cell Biology. Subcell Biochem 2018; 87:409-459. [PMID: 29464568 DOI: 10.1007/978-981-10-7757-9_14] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The vacuolar H+-ATPase (V-ATPase) is a ~1 MDa membrane protein complex that couples the hydrolysis of cytosolic ATP to the transmembrane movement of protons. In essentially all eukaryotic cells, this acid pumping function plays critical roles in the acidification of endosomal/lysosomal compartments and hence in transport, recycling and degradative pathways. It is also important in acid extrusion across the plasma membrane of some cells, contributing to homeostatic control of cytoplasmic pH and maintenance of appropriate extracellular acidity. The complex, assembled from up to 30 individual polypeptides, operates as a molecular motor with rotary mechanics. Historically, structural inferences about the eukaryotic V-ATPase and its subunits have been made by comparison to the structures of bacterial homologues. However, more recently, we have developed a much better understanding of the complete structure of the eukaryotic complex, in particular through advances in cryo-electron microscopy. This chapter explores these recent developments, and examines what they now reveal about the catalytic mechanism of this essential proton pump and how its activity might be regulated in response to cellular signals.
Collapse
Affiliation(s)
- Michael A Harrison
- School of Biomedical Sciences, Faculty of Biological Sciences, The University of Leeds, Leeds, UK.
| | - Steven P Muench
- School of Biomedical Sciences, Faculty of Biological Sciences, The University of Leeds, Leeds, UK
| |
Collapse
|
12
|
Erthal LCS, Marques AF, Almeida FCL, Melo GLM, Carvalho CM, Palmieri LC, Cabral KMS, Fontes GN, Lima LMTR. Regulation of the assembly and amyloid aggregation of murine amylin by zinc. Biophys Chem 2016; 218:58-70. [PMID: 27693831 DOI: 10.1016/j.bpc.2016.09.008] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2016] [Revised: 09/10/2016] [Accepted: 09/17/2016] [Indexed: 11/17/2022]
Abstract
The secretory granule of the pancreatic β-cells is a zinc-rich environment copopulated with the hormones amylin and insulin. The human amylin is shown to interact with zinc ions with major contribution from the single histidine residue, which is absent in amylin from other species such as cat, rhesus and rodents. We report here the interaction of murine amylin with zinc ions in vitro. The self-assembly of murine amylin is tightly regulated by zinc and pH. Ion mobility mass spectrometry revealed zinc interaction with monomers and oligomers. Nuclear magnetic resonance confirms the binding of zinc to murine amylin. The aggregation process of murine amylin into amyloid fibrils is accelerated by zinc. Collectively these data suggest a general role of zinc in the modulation of amylin variants oligomerization and amyloid fibril formation.
Collapse
Affiliation(s)
- Luiza C S Erthal
- School of Pharmacy, Federal University of Rio de Janeiro - UFRJ, CCS, Bss24, Ilha do Fundão, 21941-590 Rio de Janeiro, Brazil
| | - Adriana F Marques
- School of Pharmacy, Federal University of Rio de Janeiro - UFRJ, CCS, Bss24, Ilha do Fundão, 21941-590 Rio de Janeiro, Brazil
| | - Fábio C L Almeida
- School of Pharmacy, Federal University of Rio de Janeiro - UFRJ, CCS, Bss24, Ilha do Fundão, 21941-590 Rio de Janeiro, Brazil
| | - Gustavo L M Melo
- School of Pharmacy, Federal University of Rio de Janeiro - UFRJ, CCS, Bss24, Ilha do Fundão, 21941-590 Rio de Janeiro, Brazil
| | - Camila M Carvalho
- School of Pharmacy, Federal University of Rio de Janeiro - UFRJ, CCS, Bss24, Ilha do Fundão, 21941-590 Rio de Janeiro, Brazil
| | - Leonardo C Palmieri
- School of Pharmacy, Federal University of Rio de Janeiro - UFRJ, CCS, Bss24, Ilha do Fundão, 21941-590 Rio de Janeiro, Brazil
| | - Katia M S Cabral
- School of Pharmacy, Federal University of Rio de Janeiro - UFRJ, CCS, Bss24, Ilha do Fundão, 21941-590 Rio de Janeiro, Brazil
| | - Giselle N Fontes
- Laboratory for Macromolecules (LAMAC-DIMAV), Brazilian National Institute of Metrology, Quality and Technology - INMETRO, Av. N. Sa. das Graças, 50 - Xerém, Duque de Caxias-RJ, 25250-020 Rio de Janeiro, Brazil
| | - Luís Maurício T R Lima
- School of Pharmacy, Federal University of Rio de Janeiro - UFRJ, CCS, Bss24, Ilha do Fundão, 21941-590 Rio de Janeiro, Brazil; Laboratory for Macromolecules (LAMAC-DIMAV), Brazilian National Institute of Metrology, Quality and Technology - INMETRO, Av. N. Sa. das Graças, 50 - Xerém, Duque de Caxias-RJ, 25250-020 Rio de Janeiro, Brazil; National Institute of Science and Technology for Structural Biology and Bioimaging (INBEB-INCT), Federal University of Rio de Janeiro, Rio de Janeiro 21941-590, Brazil.
| |
Collapse
|
13
|
Kelly AC, Steyn LV, Kitzmann JP, Anderson MJ, Mueller KR, Hart NJ, Lynch RM, Papas KK, Limesand SW. Function and expression of sulfonylurea, adrenergic, and glucagon-like peptide 1 receptors in isolated porcine islets. Xenotransplantation 2014; 21:385-91. [PMID: 24801676 DOI: 10.1111/xen.12101] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Accepted: 03/14/2014] [Indexed: 11/29/2022]
Abstract
The scarcity of human cadaveric pancreata limits large-scale application of islet transplantation for patients with diabetes. Islets isolated from pathogen-free pigs provide an economical and abundant alternative source assuming immunologic barriers are appropriate. Membrane receptors involved in insulin secretion that also have potential as imaging targets were investigated in isolated porcine islets. Quantitative (q)PCR revealed that porcine islets express mRNA transcripts for sulfonylurea receptor 1 (Sur1), inward rectifying potassium channel (Kir6.2, associated with Sur1), glucagon-like peptide 1 receptor (GLP1R), and adrenergic receptor alpha 2A (ADRα2A). Receptor function was assessed in static incubations with stimulatory glucose concentrations, and in the presence of receptor agonists. Glibenclamide, an anti-diabetic sulfonylurea, and exendin-4, a GLP-1 mimetic, potentiated glucose-stimulated insulin secretion >2-fold. Conversely, epinephrine maximally reduced insulin secretion 72 ± 9% (P < 0.05) and had a half maximal inhibitory concentration of 60 nm in porcine islets (95% confidence interval of 45-830 nm). The epinephrine action was inhibited by the ADRα2A antagonist yohimbine. Our findings demonstrate that porcine islets express and are responsive to both stimulatory and inhibitory membrane localized receptors, which can be used as imaging targets after transplantation or to modify insulin secretion.
Collapse
Affiliation(s)
- Amy C Kelly
- School of Comparative Animal and Biomedical Sciences, University of Arizona, Tucson, AZ, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Martinez-Zaguilan R, Tompkins LS, Gillies RJ, Lynch RM. Simultaneous analysis of intracellular pH and Ca²⁺ from cell populations. Methods Mol Biol 2013; 937:253-71. [PMID: 23007592 DOI: 10.1007/978-1-62703-086-1_16] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Although changes in both pH(in) and [Ca(2+)](i) have been observed in response to a variety of agonists, it is not clear whether these ionic events work independently or are coordinated to lead to a specific physiological response. One of the fundamental problems in studying these ionic events is that changes in pH(in) modify Ca(2+) regulatory mechanisms and changes in Ca(2+) may modify pH regulation. It is desirable to use a technique that allows concomitant monitoring of these two ions in cell populations with high time resolution. Furthermore, like many Ca(2+) binding proteins, all Ca(2+)-sensitive fluoroprobes are inherently sensitive to pH owing to competition of H(+) for the Ca(2+)-binding sites. This chapter describes experimental paradigms that provide optimum conditions for simultaneous measurement of pH from the fluorescence emission of snarf-1, and Ca(2+) using fura-2. The fluorescence spectra of these compounds are sufficiently different to allow simultaneous measurement of pH and Ca(2+) both in vitro and in vivo. Moreover, the ratio of the H(+)-sensitive wavelengths of snarf-1 is unaffected by Ca(2+), or the concomitant presence of fura-2 in cells. Although the fluorescence ratio of fura-2 is insensitive to the presence of snarf-1, it is affected by pH, as indicated above. We describe procedures to correct for this effect and to obtain calibration parameters for fura-2 and snarf-1 required to facilitate analysis of pH and Ca(2+) concentrations within cell populations.
Collapse
Affiliation(s)
- Raul Martinez-Zaguilan
- Department of Physiology, Texas Tech University Health Sciences Center, Lubbock, TX, USA
| | | | | | | |
Collapse
|
15
|
Hines T, Beauchamp D, Rice C. Baroreflex Control of Sympathetic Nerve Activity in Hypertensive Pregnant Rats with Reduced Uterine Perfusion. Hypertens Pregnancy 2009; 26:303-14. [PMID: 17710579 DOI: 10.1080/10641950701415598] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
OBJECTIVE Baroreflex sensitivity is reduced in women with preeclampsia. The aim of this study was to determine whether baroreflex control of renal sympathetic nerve activity (RSNA) is altered in pregnant rats with reduced uterine perfusion (a model of human preeclampsia). METHODS Uterine perfusion was reduced in the third trimester by clipping the distal aorta and uterine branches of the ovarian arteries. RSNA baroreflex parameters were compared at term gestation in rats with reduced uterine perfusion (n = 12), in normal pregnant rats (n = 14) and in nonpregnant rats (n = 14). RESULTS Reduced perfusion rats were hypertensive (123.6 +/- 2.3 mm Hg), and normal pregnant rats were hypotensive (97.7 +/- 2.2 mm Hg), compared with controls. In rats with reduced perfusion, the baroreflex was shifted to a higher set-point, and maximum and minimum RSNA were increased compared with normal pregnant rats. CONCLUSION The blunted baroreflex gain of normal pregnancy is maintained in rats with reduced uterine perfusion, but a hypertensive shift in baroreflex function exists in this rat model that is associated with a reversal of the reflex maximum and minimum RSNA observed in normal pregnancy.
Collapse
Affiliation(s)
- Tina Hines
- University of Missouri-Kansas City School of Nursing, Kansas City, Missouri 64108, USA.
| | | | | |
Collapse
|
16
|
Ravier MA, Tsuboi T, Rutter GA. Imaging a target of Ca2+ signalling: dense core granule exocytosis viewed by total internal reflection fluorescence microscopy. Methods 2008; 46:233-8. [PMID: 18854212 PMCID: PMC2597054 DOI: 10.1016/j.ymeth.2008.09.016] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2008] [Accepted: 09/12/2008] [Indexed: 12/20/2022] Open
Abstract
Ca2+ ions are the most ubiquitous second messenger found in all cells, and play a significant role in controlling regulated secretion from neurons, endocrine, neuroendocrine and exocrine cells. Here, we describe microscopic techniques to image regulated secretion, a target of Ca2+ signalling. The first of these, total internal reflection fluorescence (TIRF), is well suited for optical sectioning at cell–substrate regions with an unusually thin region of fluorescence excitation (<150 nm). It is thus particularly useful for studies of regulated hormone secretion. A brief summary of this approach is provided, as well as a description of the physical basis for the technique and the tools to implement TIRF using a standard fluorescence microscope. We also detail the different fluorescent probes which can be used to detect secretion and how to analyze the data obtained. A comparison between TIRF and other imaging modalities including confocal and multiphoton microscopy is also included.
Collapse
Affiliation(s)
- Magalie A Ravier
- Unit of Endocrinology and Metabolism, University of Louvain Faculty of Medicine, UCL 55.30 Avenue Hippocrate 55, B-1200 Brussels, Belgium
| | | | | |
Collapse
|
17
|
Erent M, Meli A, Moisoi N, Babich V, Hannah MJ, Skehel P, Knipe L, Zupancic G, Ogden D, Carter T. Rate, extent and concentration dependence of histamine-evoked Weibel-Palade body exocytosis determined from individual fusion events in human endothelial cells. J Physiol 2007; 583:195-212. [PMID: 17540703 PMCID: PMC2277235 DOI: 10.1113/jphysiol.2007.132993] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The rate, concentration dependence and extent of histamine-evoked Weibel-Palade body (WPB) exocytosis were investigated with time-resolved fluorescence microscopy in cultured human umbilical vein endothelial cells expressing WPB-targeted chimeras of enhanced green fluorescent protein (EGFP). Exocytosis of single WPBs was characterized by an increase in EGFP fluorescence, morphological changes and release of WPB contents. The fluorescence increase was due to a rise of intra-WPB pH from resting levels, estimated as pH 5.45+/-0.26 (s.d., n=144), to pH 7.40. It coincided with uptake of extracellular Alexa-647, indicating the formation of a fusion pore, prior to loss of fluorescent contents. Delays between the increase in intracellular free calcium ion concentration evoked by histamine and the first fusion event were 10.0+/-4.42 s (n=9 cells) at 0.3 microM histamine and 1.57+/-0.21 s (n=15 cells) at 100 microM histamine, indicating the existence of a slow process or processes in histamine-evoked WPB exocytosis. The maximum rates of exocytosis were 1.20+/-0.16 WPB s(-1) (n=9) at 0.3 microM and 3.66+/-0.45 WPB s(-1) at 100 microM histamine (n=15). These occurred 2-5 s after histamine addition and declined to lower rates with continued stimulation. The initial delays and maximal rate of exocytosis were unaffected by removal of external Ca2+ indicating that the initial burst of secretion is driven by Ca2+ release from internal stores, but sustained exocytosis required external Ca2+. Data were compared to exocytosis evoked by a maximal concentration of the strong secretagogue ionomycin (1 microM), for which there was a delay between calcium elevation and secretion of 1.67+/-0.24 s (n=6), and a peak fusion rate of approximately 10 WPB s(-1).
Collapse
Affiliation(s)
- M Erent
- Medical Research Councils National Institute for Medical Research, Mill Hill, London NW7 1AA, UK
| | | | | | | | | | | | | | | | | | | |
Collapse
|
18
|
Pernas-Sueiras O, Alfonso A, Vieytes MR, Botana LM. PKC and cAMP positively modulate alkaline-induced exocytosis in the human mast cell line HMC-1. J Cell Biochem 2007; 99:1651-63. [PMID: 16823786 DOI: 10.1002/jcb.21009] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
We study in HMC-1 the activation process, measured as histamine release. We know that ammonium chloride (NH(4)Cl) and ionomycin release histamine, and the modulatory role of drugs targeting protein kinase C (PKC), adenosine 3',5'-cyclic monophosphate (cAMP), tyrosine kinase (TyrK) and phosphatidylinositol 3-kinase (PI3K) on this effect. We used Gö6976 (100 nM) and low concentration of GF 109203X (GF) (50 nM) to inhibit Ca(2+)-dependent PKC isozymes. For Ca(2+)-independent isozymes, we used 500 nM GF and 10 microM rottlerin (specifically inhibits PKCdelta). Phorbol 12-myristate 13-acetate (PMA) (100 ng/ml) was used to stimulate PKC, and genistein (10 microM) and lavendustin A (1 microM) as unspecific TyrK inhibitors. STI571 10 microM was used to specifically inhibit the activity of Kit, the receptor for stem cell factor, and 10 nM wortmannin as a PI3K inhibitor. Activation of PKC with PMA enhances histamine release in response to NH(4)Cl and ionomycin. PMA increases NH(4)Cl-induced alkalinization and ionomycin-induced Ca(2+) entry. Inhibition of PKCdelta strongly inhibits Ca(2+) entry elicited by ionomycin, but failed to modify histamine release. The effect of cAMP-active drugs was explored with the adenylate cyclase activator forskolin (30 microM), the inhibitor SQ22,536 (1 microM), the cAMP analog dibutyryl cAMP (200 microM), and the PKA blocker H89 (1 microM). Forskolin and dibutyryl cAMP do increase NH(4)Cl-induced alkalinization, and potentiate histamine release elicited by this compound. Our data indicates that alkaline-induced exocytosis is modulated by PKC and cAMP, suggesting that pH could be a modulatory signal itself.
Collapse
|
19
|
Stiernet P, Guiot Y, Gilon P, Henquin JC. Glucose Acutely Decreases pH of Secretory Granules in Mouse Pancreatic Islets. J Biol Chem 2006; 281:22142-22151. [PMID: 16760469 DOI: 10.1074/jbc.m513224200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Glucose-induced insulin secretion requires a rise in beta-cell cytosolic Ca2+ ([Ca2+]c) that triggers exocytosis and a mechanistically unexplained amplification of the action of [Ca2+]c. Insulin granules are kept acidic by luminal pumping of protons with simultaneous Cl- uptake to maintain electroneutrality. Experiments using patched, dialyzed beta-cells prompted the suggestion that acute granule acidification by glucose underlies amplification of insulin secretion. However, others found glucose to increase granular pH in intact islets. In this study, we measured islet granular pH with Lysosensor DND-160, a fluorescent dye that permits ratiometric determination of pH < 6 in acidic compartments. Stimulation of mouse islets with glucose reversibly decreased granular pH by mechanisms that are dependent on metabolism and Cl- ions but independent of changes in [Ca2+]c and protein kinase A or C activity. Granular pH was increased by concanamycin (blocker of the vesicular type H+-ATPase) > methylamine (weak base) > Cl- omission. Concanamycin and methylamine did not alter glucose-induced [Ca2+]c increase in islets but strongly inhibited the two phases of insulin secretion. Omission of Cl- did not affect the first phase but decreased the second phase of both [Ca2+]c and insulin responses. Neither experimental condition affected the [Ca2+]c rise induced by 30 mM KCl, but the insulin responses were inhibited by concanamycin > methylamine and not affected by Cl- omission. The amplification of insulin secretion by glucose was not suppressed. We conclude that an acidic granular pH is important for insulin secretion but that the acute further acidification produced by glucose is not essential for the augmentation of secretion via the amplifying pathway.
Collapse
Affiliation(s)
- Patrick Stiernet
- Units of Endocrinology and Metabolism, University of Louvain Faculty of Medicine, B-1200 Brussels, Belgium
| | - Yves Guiot
- Unit of Pathology, University of Louvain Faculty of Medicine, B-1200 Brussels, Belgium
| | - Patrick Gilon
- Units of Endocrinology and Metabolism, University of Louvain Faculty of Medicine, B-1200 Brussels, Belgium
| | - Jean-Claude Henquin
- Units of Endocrinology and Metabolism, University of Louvain Faculty of Medicine, B-1200 Brussels, Belgium.
| |
Collapse
|
20
|
Nabe K, Fujimoto S, Shimodahira M, Kominato R, Nishi Y, Funakoshi S, Mukai E, Yamada Y, Seino Y, Inagaki N. Diphenylhydantoin suppresses glucose-induced insulin release by decreasing cytoplasmic H+ concentration in pancreatic islets. Endocrinology 2006; 147:2717-27. [PMID: 16527842 DOI: 10.1210/en.2005-1260] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Diphenylhydantoin (DPH), which is clinically used in the treatment of epilepsy, inhibits glucose-induced insulin release from pancreatic islets by a mechanism that remains unknown. In the present study, DPH is shown to suppress glucose-induced insulin release concentration-dependently. In dynamic experiments, 20 microm DPH suppressed 16.7 mm glucose-induced biphasic insulin release. DPH also suppressed insulin release in the presence of 16.7 mm glucose, 200 microm diazoxide, and 30 mm K+ without affecting the intracellular Ca2+ concentration. DPH suppressed ATP content and mitochondrial membrane hyperpolarization in the presence of 16.7 mm glucose without affecting glucose utilization, glucose oxidation, and reduced nicotinamide adenine dinucleotide phosphate fluorescence. DPH increased cytoplasmic pH in the presence of high glucose, but the increase was abolished under Na+ -deprived conditions and HCO3- -deprived conditions, suggesting that Na+ and HCO3- transport across the plasma membrane are involved in the increase in cytoplasmic pH by DPH. Alkalization by adding NH4+ to the extracellular medium also suppressed insulin release, ATP content, and mitochondrial membrane hyperpolarization. Because ATP production from the mitochondrial fraction in the presence of substrates was decreased by increased pH in the medium, DPH suppresses mitochondrial ATP production by reducing the H+ gradient across mitochondrial membrane. Using permeabilized islets, the increase in pH was shown to decrease Ca2+ efficacy at a clamped concentration of ATP in the exocytotic system. Taken together, DPH inhibits glucose-induced insulin secretion not only by inhibiting mitochondrial ATP production, but also by reducing Ca2+ efficacy in the exocytotic system through its alkalizing effect on cytoplasm.
Collapse
Affiliation(s)
- Koichiro Nabe
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan
| | | | | | | | | | | | | | | | | | | |
Collapse
|
21
|
Tsuboi T, Ravier MA, Parton LE, Rutter GA. Sustained exposure to high glucose concentrations modifies glucose signaling and the mechanics of secretory vesicle fusion in primary rat pancreatic beta-cells. Diabetes 2006; 55:1057-65. [PMID: 16567529 DOI: 10.2337/diabetes.55.04.06.db05-1577] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The mechanism(s) by which chronic hyperglycemia impairs glucose-stimulated insulin secretion is poorly defined. Here, we compare the "nanomechanics" of single exocytotic events in primary rat pancreatic beta-cells cultured for 48 h at optimal (10 mmol/l) or elevated (30 mmol/l) glucose concentrations. Cargo release was imaged by total internal reflection fluorescence microscopy of lumen-targeted probes (neuropeptide Y [NPY]-pH-insensitive yellow fluorescent protein [NPY-Venus] or NPY-monomeric red fluorescent protein), while the fate of the vesicle membrane was reported simultaneously with phosphatase-on-the-granule-of-insulinoma-enhanced green fluorescent protein. Under all conditions studied, exocytosis proceeded via a "cavity recapture" mechanism in which the vesicle and plasma membranes fused transiently. While essentially complete release of NPY-Venus was observed in 24 +/- 1% of glucose-stimulated exocytotic events in cells maintained at 10 mmol/l glucose, this value was reduced reversibly to 5 +/- 2% of events by culture at 30 mmol/l glucose, in line with decreases in Glut2 and glucokinase gene expression, and attenuated glucose-stimulated increases in NADPH and intracellular [Ca2+]. Since vesicle release in response to cell depolarization with KCl was not affected by culture at 30 mmol/l glucose, we conclude that hyperglycemia causes the abnormal termination of individual insulin release events principally by inhibiting glucose signaling.
Collapse
Affiliation(s)
- Takashi Tsuboi
- Department of Biochemistry, School of Medical Sciences, University of Bristol, University Walk, Bristol, BS8 1TD, UK
| | | | | | | |
Collapse
|
22
|
Sautin YY, Lu M, Gaugler A, Zhang L, Gluck SL. Phosphatidylinositol 3-kinase-mediated effects of glucose on vacuolar H+-ATPase assembly, translocation, and acidification of intracellular compartments in renal epithelial cells. Mol Cell Biol 2005; 25:575-89. [PMID: 15632060 PMCID: PMC543406 DOI: 10.1128/mcb.25.2.575-589.2005] [Citation(s) in RCA: 170] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Vacuolar H+-ATPases (V-ATPases) are a family of ATP-driven proton pumps. They maintain pH gradients between intracellular compartments and are required for proton secretion out of the cytoplasm. Mechanisms of extrinsic control of V-ATPase are poorly understood. Previous studies showed that glucose is an important regulator of V-ATPase assembly in Saccharomyces cerevisiae. Human V-ATPase directly interacts with aldolase, providing a coupling mechanism for glucose metabolism and V-ATPase function. Here we show that glucose is a crucial regulator of V-ATPase in renal epithelial cells and that the effect of glucose is mediated by phosphatidylinositol 3-kinase (PI3K). Glucose stimulates V-ATPase-dependent acidification of the intracellular compartments in human proximal tubular cells HK-2 and porcine renal epithelial cells LLC-PK1. Glucose induces rapid ATP-independent assembly of the V1 and Vo domains of V-ATPase and extensive translocation of the V-ATPase V1 and Vo domains between different membrane pools and between membranes and the cytoplasm. In HK-2 cells, glucose stimulates polarized translocation of V-ATPase to the apical plasma membrane. The effects of glucose on V-ATPase trafficking and assembly can be abolished by pretreatment with the PI3K inhibitor LY294002 and can be reproduced in glucose-deprived cells by adenoviral expression of the constitutively active catalytic subunit p110alpha of PI3K. Taken together these data provide evidence that, in renal epithelial cells, glucose plays an important role in the control of V-ATPase-dependent acidification of intracellular compartments and V-ATPase assembly and trafficking and that the effects of glucose are mediated by PI3K-dependent signaling.
Collapse
Affiliation(s)
- Yuri Y Sautin
- Department of Medicine, Division of Nephrology, Box 100224, University of Florida, 1600 SW Archer Rd., Gainesville, FL 32610-0224, USA.
| | | | | | | | | |
Collapse
|
23
|
Oliveira-Souza M, Musa-Aziz R, Malnic G, De Mello Aires M. Arginine vasopressin stimulates H+-ATPase in MDCK cells via V1 (cell Ca2+) and V2 (cAMP) receptors. Am J Physiol Renal Physiol 2004; 286:F402-8. [PMID: 12965889 DOI: 10.1152/ajprenal.00121.2003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The effect of arginine vasopressin (AVP) and/or atrial natriuretic peptide (ANP) on the regulation of intracellular pH (pHi) via H+-ATPase and of cytosolic calcium ([Ca2+]i) was investigated in Madin-Darby canine kidney (MDCK) cells by the fluorescent probes BCECF-AM and fluo-4-AM, respectively. The pHi recovery rate was examined after intracellular acidification following an NH4Cl pulse, in the presence of zero Na+ plus Schering 28080 (a specific inhibitor of H+-K+-ATPase). AVP (10-12-10-6 M) increased the rate of pHi recovery and [Ca2+]i in a dose-dependent manner. V1- or V2-receptor antagonists impaired the effect of AVP on both processes, and DDAVP (10-12-10-6 M; a V2-selective agonist) caused a dose-dependent stimulation of them. [Ca2+]i or cAMP (as increased by 10-5 M thapsigargin or 8-BrcAMP, respectively) alone had no effect on H+-ATPase, but their synergic action was necessary to stimulate H+-ATPase. In agreement with these findings, ANP (10-6 M) or dimethyl-BAPTA-AM (5 x 10-5 M), impairing the increase of [Ca2+]i in response to AVP, blocks the stimulatory effect of AVP on H+-ATPase.
Collapse
Affiliation(s)
- Maria Oliveira-Souza
- Department of Physiology and Biophysics, Instituto de Ciências Biomédicas, Univ. of São Paulo, SP 05508-900, Brazil
| | | | | | | |
Collapse
|