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Ortega-Cuellar D, González-Sánchez I, Piñón-Zárate G, Cerbón MA, De la Rosa V, Franco-Juárez Y, Castell-Rodríguez A, Islas LD, Coronel-Cruz C. Protector Role of Cx30.2 in Pancreatic β-Cell against Glucotoxicity-Induced Apoptosis. BIOLOGY 2024; 13:468. [PMID: 39056663 PMCID: PMC11273625 DOI: 10.3390/biology13070468] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2024] [Revised: 06/07/2024] [Accepted: 06/16/2024] [Indexed: 07/28/2024]
Abstract
Glucotoxicity may exert its deleterious effects on pancreatic β-cell function via a myriad of mechanisms, leading to impaired insulin secretion and, eventually, type 2 diabetes. β-cell communication requires gap junction channels to be present among these cells. Gap junctions are constituted by transmembrane proteins of the connexins (Cxs) family. Two Cx genes have been identified in β cells, Cx36 and Cx30.2. We have found evidence that the glucose concentration on its own is sufficient to regulate Cx30.2 gene expression in mouse islets. In this work, we examine the involvement of the Cx30.2 protein in the survival of β cells (RIN-m5F). METHODS RIN-m5F cells were cultured in 5 mM D-glucose (normal) or 30 mM D-glucose (high glucose) for 24 h. Cx30.2 siRNAs was used to downregulate Cx30.2 expression. Apoptosis was measured by means of TUNEL, an annexin V staining method, and the cleaved form of the caspase-3 protein was determined using Western blot. RESULTS High glucose did not induce apoptosis in RIN-m5F β cells after 24 h; interestingly, high glucose increased the Cx30.2 total protein levels. Moreover, this work found that the downregulation of Cx30.2 expression in high glucose promoted apoptosis in RIN-m5F cells. CONCLUSION The data suggest that the upregulation of Cx30.2 protects β cells from hyperglycemia-induced apoptosis. Furthermore, Cx30.2 may be a promising avenue of therapeutic investigation for the treatment of glucose metabolic disorders.
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Affiliation(s)
- Daniel Ortega-Cuellar
- Laboratorio de Nutrición Experimental, Instituto Nacional de Pediatría, Secretaría de Salud, Mexico City 04530, Mexico; (D.O.-C.); (Y.F.-J.)
| | - Ignacio González-Sánchez
- Departamento de Biología, Facultad de Química, UNAM, Mexico City 04510, Mexico; (I.G.-S.); (M.A.C.)
| | - Gabriela Piñón-Zárate
- Departamento de Biología Celular y Tisular, Facultad de Medicina, UNAM, Mexico City 04510, Mexico; (G.P.-Z.); (A.C.-R.)
| | - Marco A. Cerbón
- Departamento de Biología, Facultad de Química, UNAM, Mexico City 04510, Mexico; (I.G.-S.); (M.A.C.)
| | - Víctor De la Rosa
- Departamento de Fisiología, Facultad de Medicina, UNAM, Mexico City 04510, Mexico; (V.D.l.R.); (L.D.I.)
| | - Yuliana Franco-Juárez
- Laboratorio de Nutrición Experimental, Instituto Nacional de Pediatría, Secretaría de Salud, Mexico City 04530, Mexico; (D.O.-C.); (Y.F.-J.)
| | - Andrés Castell-Rodríguez
- Departamento de Biología Celular y Tisular, Facultad de Medicina, UNAM, Mexico City 04510, Mexico; (G.P.-Z.); (A.C.-R.)
| | - León D. Islas
- Departamento de Fisiología, Facultad de Medicina, UNAM, Mexico City 04510, Mexico; (V.D.l.R.); (L.D.I.)
| | - Cristina Coronel-Cruz
- Departamento de Biología Celular y Tisular, Facultad de Medicina, UNAM, Mexico City 04510, Mexico; (G.P.-Z.); (A.C.-R.)
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2
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Maal-Bared G, Yee M, Harding EK, Ghebreselassie M, Bergamini M, Choy R, Kim E, Di Vito S, Patel M, Amirzadeh M, Grieder TE, Coles BL, Nagy JI, Bonin RP, Steenland HW, van der Kooy D. Connexin-36-positive gap junctions in ventral tegmental area GABA neurons sustain opiate dependence. Eur J Neurosci 2024; 59:3422-3444. [PMID: 38679044 DOI: 10.1111/ejn.16366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 03/20/2024] [Accepted: 04/03/2024] [Indexed: 05/01/2024]
Abstract
Drug dependence is characterized by a switch in motivation wherein a positively reinforcing substance can become negatively reinforcing. Put differently, drug use can transform from a form of pleasure-seeking to a form of relief-seeking. Ventral tegmental area (VTA) GABA neurons form an anatomical point of divergence between two double dissociable pathways that have been shown to be functionally implicated and necessary for these respective motivations to seek drugs. The tegmental pedunculopontine nucleus (TPP) is necessary for opiate conditioned place preferences (CPP) in previously drug-naïve rats and mice, whereas dopaminergic (DA) transmission in the nucleus accumbens (NAc) is necessary for opiate CPP in opiate-dependent and withdrawn (ODW) rats and mice. Here, we show that this switch in functional anatomy is contingent upon the gap junction-forming protein, connexin-36 (Cx36), in VTA GABA neurons. Intra-VTA infusions of the Cx36 blocker, mefloquine, in ODW rats resulted in a reversion to a drug-naïve-like state wherein the TPP was necessary for opiate CPP and where opiate withdrawal aversions were lost. Consistent with these data, conditional knockout mice lacking Cx36 in GABA neurons (GAD65-Cre;Cx36 fl(CFP)/fl(CFP)) exhibited a perpetual drug-naïve-like state wherein opiate CPP was always DA independent, and opiate withdrawal aversions were absent even in mice subjected to an opiate dependence and withdrawal induction protocol. Further, viral-mediated rescue of Cx36 in VTA GABA neurons was sufficient to restore their susceptibility to an ODW state wherein opiate CPP was DA dependent. Our findings reveal a functional role for VTA gap junctions that has eluded prevailing circuit models of addiction.
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Affiliation(s)
- Geith Maal-Bared
- Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
| | - Mandy Yee
- Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
| | - Erika K Harding
- Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada
| | - Martha Ghebreselassie
- Terrence Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Michael Bergamini
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
- Department of Human Biology, University of Toronto, Toronto, Ontario, Canada
| | - Roxanne Choy
- Department of Human Biology, University of Toronto, Toronto, Ontario, Canada
| | - Ethan Kim
- Department of Human Biology, University of Toronto, Toronto, Ontario, Canada
| | - Stephanie Di Vito
- Department of Human Biology, University of Toronto, Toronto, Ontario, Canada
| | - Maryam Patel
- Department of Human Biology, University of Toronto, Toronto, Ontario, Canada
| | - Mohammadreza Amirzadeh
- Terrence Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Taryn E Grieder
- Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
| | - Brenda L Coles
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - James I Nagy
- Department of Physiology and Pathophysiology, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Robert P Bonin
- Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada
| | | | - Derek van der Kooy
- Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
- Terrence Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
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3
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Puginier E, Leal-Fischer K, Gaitan J, Lallouet M, Scotti PA, Raoux M, Lang J. Extracellular electrophysiology on clonal human β-cell spheroids. Front Endocrinol (Lausanne) 2024; 15:1402880. [PMID: 38883608 PMCID: PMC11176477 DOI: 10.3389/fendo.2024.1402880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2024] [Accepted: 05/06/2024] [Indexed: 06/18/2024] Open
Abstract
Background Pancreatic islets are important in nutrient homeostasis and improved cellular models of clonal origin may very useful especially in view of relatively scarce primary material. Close 3D contact and coupling between β-cells are a hallmark of physiological function improving signal/noise ratios. Extracellular electrophysiology using micro-electrode arrays (MEA) is technically far more accessible than single cell patch clamp, enables dynamic monitoring of electrical activity in 3D organoids and recorded multicellular slow potentials (SP) provide unbiased insight in cell-cell coupling. Objective We have therefore asked whether 3D spheroids enhance clonal β-cell function such as electrical activity and hormone secretion using human EndoC-βH1, EndoC-βH5 and rodent INS-1 832/13 cells. Methods Spheroids were formed either by hanging drop or proprietary devices. Extracellular electrophysiology was conducted using multi-electrode arrays with appropriate signal extraction and hormone secretion measured by ELISA. Results EndoC-βH1 spheroids exhibited increased signals in terms of SP frequency and especially amplitude as compared to monolayers and even single cell action potentials (AP) were quantifiable. Enhanced electrical signature in spheroids was accompanied by an increase in the glucose stimulated insulin secretion index. EndoC-βH5 monolayers and spheroids gave electrophysiological profiles similar to EndoC-βH1, except for a higher electrical activity at 3 mM glucose, and exhibited moreover a biphasic profile. Again, physiological concentrations of GLP-1 increased AP frequency. Spheroids also exhibited a higher secretion index. INS-1 cells did not form stable spheroids, but overexpression of connexin 36, required for cell-cell coupling, increased glucose responsiveness, dampened basal activity and consequently augmented the stimulation index. Conclusion In conclusion, spheroid formation enhances physiological function of the human clonal β-cell lines and these models may provide surrogates for primary islets in extracellular electrophysiology.
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Affiliation(s)
- Emilie Puginier
- Univiversity of Bordeaux, CNRS, Bordeaux INP, Laboratoire de Chimie et Biologie des Membranes CBMN, UMR 5248, Pessac, Bordeaux, France
| | - Karen Leal-Fischer
- Univiversity of Bordeaux, CNRS, Bordeaux INP, Laboratoire de Chimie et Biologie des Membranes CBMN, UMR 5248, Pessac, Bordeaux, France
| | - Julien Gaitan
- Univiversity of Bordeaux, CNRS, Bordeaux INP, Laboratoire de Chimie et Biologie des Membranes CBMN, UMR 5248, Pessac, Bordeaux, France
| | - Marie Lallouet
- Univiversity of Bordeaux, CNRS, Bordeaux INP, Laboratoire de Chimie et Biologie des Membranes CBMN, UMR 5248, Pessac, Bordeaux, France
| | - Pier-Arnaldo Scotti
- Univiversity of Bordeaux, CNRS, Bordeaux INP, Laboratoire de Chimie et Biologie des Membranes CBMN, UMR 5248, Pessac, Bordeaux, France
| | - Matthieu Raoux
- Univiversity of Bordeaux, CNRS, Bordeaux INP, Laboratoire de Chimie et Biologie des Membranes CBMN, UMR 5248, Pessac, Bordeaux, France
| | - Jochen Lang
- Univiversity of Bordeaux, CNRS, Bordeaux INP, Laboratoire de Chimie et Biologie des Membranes CBMN, UMR 5248, Pessac, Bordeaux, France
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Wang B, Zhang Y. Asymmetric connections with starburst amacrine cells underlie the upward motion selectivity of J-type retinal ganglion cells. PLoS Biol 2023; 21:e3002301. [PMID: 37721959 PMCID: PMC10538761 DOI: 10.1371/journal.pbio.3002301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 09/28/2023] [Accepted: 08/17/2023] [Indexed: 09/20/2023] Open
Abstract
Motion is an important aspect of visual information. The directions of visual motion are encoded in the retina by direction-selective ganglion cells (DSGCs). ON-OFF DSGCs and ON DSGCs co-stratify with starburst amacrine cells (SACs) in the inner plexiform layer and depend on SACs for their direction selectivity. J-type retinal ganglion cells (J-RGCs), a type of OFF DSGCs in the mouse retina, on the other hand, do not co-stratify with SACs, and how direction selectivity in J-RGCs emerges has not been understood. Here, we report that both the excitatory and inhibitory synaptic inputs to J-RGCs are direction-selective (DS), with the inhibitory inputs playing a more important role for direction selectivity. The DS inhibitory inputs come from SACs, and the functional connections between J-RGCs and SACs are spatially asymmetric. Thus, J-RGCs and SACs form functionally important synaptic contacts even though their dendritic arbors show little overlap. These findings underscore the need to look beyond the neurons' stratification patterns in retinal circuit studies. Our results also highlight the critical role of SACs for retinal direction selectivity.
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Affiliation(s)
- Bo Wang
- Institute of Neuroscience, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, China
| | - Yifeng Zhang
- Institute of Neuroscience, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, China
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Shao YQ, Fan L, Wu WY, Zhu YJ, Xu HT. A developmental switch between electrical and neuropeptide communication in the ventromedial hypothalamus. Curr Biol 2022; 32:3137-3145.e3. [PMID: 35659861 DOI: 10.1016/j.cub.2022.05.029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 04/15/2022] [Accepted: 05/11/2022] [Indexed: 12/29/2022]
Abstract
Dissecting neural connectivity patterns within local brain regions is an essential step to understanding the function of the brain.1 Neural microcircuits in brain regions, such as the neocortex and the hippocampus, have been extensively studied.2 By contrast, the microcircuit in the hypothalamus remains largely uncharacterized. The hypothalamus is crucial for animals' survival and reproduction.3 Knowledge of how different hypothalamic nuclei coordinate with each other and outside brain regions for hypothalamus-related functions has been significantly advanced.4-9 Although there are limited studies on the neural microcircuit in the lateral hypothalamus (LHA)10,11 and the suprachiasmatic nucleus (SCN),12,13 the patterns of neural microcircuits in most of the given hypothalamic nuclei remain largely unknown. This study applied combinatory approaches to address the local neural circuit pattern in the ventromedial hypothalamus (VMH) and other hypothalamic nuclei. We discovered a unique neural circuit design in the VMH. Neurons in the VMH were electrically coupled at the early postnatal stage like ones in the neocortex.14 However, unlike neocortical neurons,14,15 they developed very few chemical synapses after the disappearance of electrical synapses. Instead, VMH neurons communicated with neuropeptides. The similar scarceness of synaptic connectivity found in other hypothalamic nuclei further indicated that the lack of synaptic connections is a unique feature for local neural circuits in most adult hypothalamic nuclei. Thus, our findings provide a solid synaptic basis at the cellular level to understand hypothalamic functions better.
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Affiliation(s)
- Yin-Qi Shao
- Institute of Neuroscience and State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Liu Fan
- Institute of Neuroscience and State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Wen-Yan Wu
- Institute of Neuroscience and State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yi-Jun Zhu
- Institute of Neuroscience and State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Hua-Tai Xu
- Institute of Neuroscience and State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai 201210, China.
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Gässler A, Quiclet C, Kluth O, Gottmann P, Schwerbel K, Helms A, Stadion M, Wilhelmi I, Jonas W, Ouni M, Mayer F, Spranger J, Schürmann A, Vogel H. Overexpression of Gjb4 impairs cell proliferation and insulin secretion in primary islet cells. Mol Metab 2020; 41:101042. [PMID: 32565358 PMCID: PMC7365933 DOI: 10.1016/j.molmet.2020.101042] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 06/16/2020] [Indexed: 12/20/2022] Open
Abstract
OBJECTIVE Altered gene expression contributes to the development of type 2 diabetes (T2D); thus, the analysis of differentially expressed genes between diabetes-susceptible and diabetes-resistant mouse models is an important tool for the determination of candidate genes that participate in the pathology. Based on RNA-seq and array data comparing pancreatic gene expression of diabetes-prone New Zealand Obese (NZO) mice and diabetes-resistant B6.V-ob/ob (B6-ob/ob) mice, the gap junction protein beta 4 (Gjb4) was identified as a putative novel T2D candidate gene. METHODS Gjb4 was overexpressed in primary islet cells derived from C57BL/6 (B6) mice and INS-1 cells via adenoviral-mediated infection. The proliferation rate of cells was assessed by BrdU incorporation, and insulin secretion was measured under low (2.8 mM) and high (20 mM) glucose concentration. INS-1 cell apoptosis rate was determined by Western blotting assessing cleaved caspase 3 levels. RESULTS Overexpression of Gjb4 in primary islet cells significantly inhibited the proliferation by 47%, reduced insulin secretion of primary islets (46%) and INS-1 cells (51%), and enhanced the rate of apoptosis by 63% in INS-1 cells. Moreover, an altered expression of the miR-341-3p contributes to the Gjb4 expression difference between diabetes-prone and diabetes-resistant mice. CONCLUSIONS The gap junction protein Gjb4 is highly expressed in islets of diabetes-prone NZO mice and may play a role in the development of T2D by altering islet cell function, inducing apoptosis and inhibiting proliferation.
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Affiliation(s)
- Anneke Gässler
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke, Arthur-Scheunert-Allee 114-116, D-14558, Nuthetal, Germany; German Center for Diabetes Research (DZD), Ingolstädter Landstraße 1, D-85764, München-Neuherberg, Germany; Department of Endocrinology and Metabolism, Charité-Universitätsmedizin Berlin, Charitéplatz 1, D-10117, Berlin, Germany
| | - Charline Quiclet
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke, Arthur-Scheunert-Allee 114-116, D-14558, Nuthetal, Germany; German Center for Diabetes Research (DZD), Ingolstädter Landstraße 1, D-85764, München-Neuherberg, Germany
| | - Oliver Kluth
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke, Arthur-Scheunert-Allee 114-116, D-14558, Nuthetal, Germany; German Center for Diabetes Research (DZD), Ingolstädter Landstraße 1, D-85764, München-Neuherberg, Germany
| | - Pascal Gottmann
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke, Arthur-Scheunert-Allee 114-116, D-14558, Nuthetal, Germany; German Center for Diabetes Research (DZD), Ingolstädter Landstraße 1, D-85764, München-Neuherberg, Germany
| | - Kristin Schwerbel
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke, Arthur-Scheunert-Allee 114-116, D-14558, Nuthetal, Germany; German Center for Diabetes Research (DZD), Ingolstädter Landstraße 1, D-85764, München-Neuherberg, Germany
| | - Anett Helms
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke, Arthur-Scheunert-Allee 114-116, D-14558, Nuthetal, Germany; German Center for Diabetes Research (DZD), Ingolstädter Landstraße 1, D-85764, München-Neuherberg, Germany
| | - Mandy Stadion
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke, Arthur-Scheunert-Allee 114-116, D-14558, Nuthetal, Germany; German Center for Diabetes Research (DZD), Ingolstädter Landstraße 1, D-85764, München-Neuherberg, Germany
| | - Ilka Wilhelmi
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke, Arthur-Scheunert-Allee 114-116, D-14558, Nuthetal, Germany; German Center for Diabetes Research (DZD), Ingolstädter Landstraße 1, D-85764, München-Neuherberg, Germany
| | - Wenke Jonas
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke, Arthur-Scheunert-Allee 114-116, D-14558, Nuthetal, Germany; German Center for Diabetes Research (DZD), Ingolstädter Landstraße 1, D-85764, München-Neuherberg, Germany
| | - Meriem Ouni
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke, Arthur-Scheunert-Allee 114-116, D-14558, Nuthetal, Germany; German Center for Diabetes Research (DZD), Ingolstädter Landstraße 1, D-85764, München-Neuherberg, Germany
| | - Frank Mayer
- University Outpatient Clinic, Centre of Sports Medicine, University of Potsdam, Am Neuen Palais 10, D-14469, Potsdam, Germany
| | - Joachim Spranger
- Department of Endocrinology and Metabolism, Charité-Universitätsmedizin Berlin, Charitéplatz 1, D-10117, Berlin, Germany
| | - Annette Schürmann
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke, Arthur-Scheunert-Allee 114-116, D-14558, Nuthetal, Germany; German Center for Diabetes Research (DZD), Ingolstädter Landstraße 1, D-85764, München-Neuherberg, Germany; Institute of Nutritional Sciences, University of Potsdam, D-14558, Nuthetal, Germany
| | - Heike Vogel
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke, Arthur-Scheunert-Allee 114-116, D-14558, Nuthetal, Germany; German Center for Diabetes Research (DZD), Ingolstädter Landstraße 1, D-85764, München-Neuherberg, Germany; Molecular and Clinical Life Science of Metabolic Diseases, University of Potsdam, Arthur-Scheunert-Allee 114-116, D-14558, Nuthetal, Germany.
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Lall VK, Bruce G, Voytenko L, Drinkhill M, Wellershaus K, Willecke K, Deuchars J, Deuchars SA. Physiologic regulation of heart rate and blood pressure involves connexin 36-containing gap junctions. FASEB J 2017; 31:3966-3977. [PMID: 28533325 PMCID: PMC5566179 DOI: 10.1096/fj.201600919rr] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 05/01/2017] [Indexed: 01/15/2023]
Abstract
Chronically elevated sympathetic nervous activity underlies many cardiovascular diseases. Elucidating the mechanisms contributing to sympathetic nervous system output may reveal new avenues of treatment. The contribution of the gap junctional protein connexin 36 (Cx36) to the regulation of sympathetic activity and thus blood pressure and heart rate was determined using a mouse with specific genetic deletion of Cx36. Ablation of the Cx36 protein was confirmed in sympathetic preganglionic neurons of Cx36-knockout (KO) mice. Telemetric analysis from conscious Cx36 KO mice revealed higher variance in heart rate and blood pressure during rest and activity compared to wild-type (WT) mice, and smaller responses to chemoreceptor activation when anesthetized. In the working heart-brain stem preparation of the Cx36-KO mouse, respiratory-coupled sympathetic nerve discharge was attenuated and responses to chemoreceptor stimulation and noxious stimulation were blunted compared to WT mice. Using whole cell patch recordings, sympathetic preganglionic neurons in spinal cord slices of Cx36-KO mice displayed lower levels of spikelet activity compared to WT mice, indicating reduced gap junction coupling between neurons. Cx36 deletion therefore disrupts normal regulation of sympathetic outflow with effects on cardiovascular parameters.-Lall, V. K., Bruce, G., Voytenko, L., Drinkhill, M., Wellershaus, K., Willecke, K., Deuchars, J., Deuchars, S. A. Physiologic regulation of heart rate and blood pressure involves connexin 36-containing gap junctions.
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Affiliation(s)
- Varinder K Lall
- Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - Gareth Bruce
- Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - Larysa Voytenko
- Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - Mark Drinkhill
- Division of Cardiovascular and Diabetes Research, Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, United Kingdom
| | - Kerstin Wellershaus
- Life and Medical Sciences Institute (LIMES), University of Bonn, Bonn, Germany
| | - Klaus Willecke
- Life and Medical Sciences Institute (LIMES), University of Bonn, Bonn, Germany
| | - Jim Deuchars
- Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - Susan A Deuchars
- Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom;
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8
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Nagy JI, Rash JE. Cx36, Cx43 and Cx45 in mouse and rat cerebellar cortex: species-specific expression, compensation in Cx36 null mice and co-localization in neurons vs. glia. Eur J Neurosci 2017; 46:1790-1804. [PMID: 28561933 DOI: 10.1111/ejn.13614] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Revised: 05/13/2017] [Accepted: 05/24/2017] [Indexed: 12/13/2022]
Abstract
Electrical synapses formed by connexin36 (Cx36)-containing gap junctions between interneurons in the cerebellar cortex have been well characterized, including those formed between basket cells and between Golgi cells, and there is gene reporter-based evidence for the expression of connexin45 (Cx45) in the cerebellar molecular layer. Here, we used immunofluorescence approaches to further investigate expression patterns of Cx36 and Cx45 in this layer and to examine localization relationships of these connexins with each other and with glial connexin43 (Cx43). In mice, strain differences were found, such that punctate labelling for Cx36 was differentially distributed in the molecular layer of C57BL/6 vs. CD1 mice. In mice with EGFP reporter representing Cx36 expression, Cx36-puncta were localized to processes of stellate cells and other cerebellar interneurons. Punctate labelling of Cx45 was faint in the molecular layer of wild-type mice and was increased in intensity in mice with Cx36 gene ablation. The vast majority of Cx36-puncta co-localized with Cx45-puncta, which in turn was associated with the scaffolding protein zonula occludens-1. In rats, Cx45-puncta were also co-localized with Cx36-puncta and additionally occurred along Bergmann glial processes adjacent to Cx43-puncta. The results indicate strain and species differences in Cx36 as well as Cx45 expression, possible compensatory processes after loss of Cx36 expression and localization of Cx45 to both neuronal and Bergmann glial gap junctions. Further, expression of both Cx43 and Cx45 in Bergmann glia of rat may contribute to the complex properties of junctional coupling between these cells and perhaps to their reported coupling with Purkinje cells.
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Affiliation(s)
- J I Nagy
- Department of Physiology and Pathophysiology, Faculty of Medicine, University of Manitoba, 745 Bannatyne Ave, Winnipeg, MB, R3E 0J9, Canada
| | - J E Rash
- Department of Biomedical Sciences, and Program in Molecular, Cellular and Integrative Neurosciences, Colorado State University, Fort Collins, CO, USA
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Meda P. Gap junction proteins are key drivers of endocrine function. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1860:124-140. [PMID: 28284720 DOI: 10.1016/j.bbamem.2017.03.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Revised: 03/03/2017] [Accepted: 03/06/2017] [Indexed: 01/07/2023]
Abstract
It has long been known that the main secretory cells of exocrine and endocrine glands are connected by gap junctions, made by a variety of connexin species that ensure their electrical and metabolic coupling. Experiments in culture systems and animal models have since provided increasing evidence that connexin signaling contributes to control the biosynthesis and release of secretory products, as well as to the life and death of secretory cells. More recently, genetic studies have further provided the first lines of evidence that connexins also control the function of human glands, which are central to the pathogenesis of major endocrine diseases. Here, we summarize the recent information gathered on connexin signaling in these systems, since the last reviews on the topic, with particular regard to the pancreatic beta cells which produce insulin, and the renal cells which produce renin. These cells are keys to the development of various forms of diabetes and hypertension, respectively, and combine to account for the exploding, worldwide prevalence of the metabolic syndrome. This article is part of a Special Issue entitled: Gap Junction Proteins edited by Jean Claude Herve.
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Affiliation(s)
- Paolo Meda
- Department of Cell Physiology and Metabolism, University of Geneva Medical School, Switzerland.
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10
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Deuchars SA. How sympathetic are your spinal cord circuits? Exp Physiol 2015; 100:365-71. [PMID: 25655449 DOI: 10.1113/ep085031] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Accepted: 01/29/2015] [Indexed: 12/21/2022]
Abstract
NEW FINDINGS What is the topic of this review? This review focuses on the role of gap junctions and interneurones in sympathetic control at the spinal cord level. What advances does it highlight? The review considers the importance of these local spinal circuits in contributing to rhythmic autonomic activity and enabling appropriate responses to homeostatic perturbations. Sympathetic control of end organs relies on the activity of sympathetic preganglionic neurones (SPNs) within the spinal cord. These SPNs exhibit heterogeneity with respect to function, neurochemistry, location, descending inputs and patterns of activity. Part of this heterogeneity is bestowed by local spinal circuitry. Our understanding of the role of these local circuits, including the significance of connections between the SPNs themselves through specialized gap junctions, is patchy. This report focuses on interneurones and gap junctions within these circuits. Gap junctions play a role in sympathetic control; they are located on SPNs in the intermediolateral cell column. Mefloquine, a chemical that blocks these gap junctions, reduces local rhythmic activity in the spinal cord slice and disrupts autonomic control in the working heart-brainstem preparation. The role that these gap junctions may play in health and disease in adult animals remains to be elucidated fully. Presympathetic interneurones are located in laminae V, VII and X and the intermediolateral cell column; those in lamina X are GABAergic and directly inhibit SPNs. The GABAergic inputs onto SPNs exert their effects through activation of synaptic and extrasynaptic receptors, which stabilize the membrane at negative potentials. The GABAergic interneurones contribute to rhythmic patterns of activity that can be generated in the spinal cord, because bicuculline reduces network oscillatory activity. These studies indicate that local spinal cord circuitry is critical in enabling appropriate levels and patterning of activity in sympathetic outflow. We need to understand how these circuits may be harnessed in the situation of spinal cord injury.
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Affiliation(s)
- Susan A Deuchars
- School of Biomedical Sciences, University of Leeds, Leeds, LS2 9JT, UK
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11
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Abstract
The pancreas produces enzymes with a digestive function and hormones with a metabolic function, which are produced by distinct cell types of acini and islets, respectively. Within these units, secretory cells coordinate their functioning by exchanging information via signals that flow in the intercellular spaces and are generated either at distance (several neural and hormonal inputs) or nearby the pancreatic cells themselves (inputs mediated by membrane ionic-specific channels and by ionic- and metabolite-permeant pannexin channels and connexin "hemichannels"). Pancreatic secretory cells further interact via the extracellular matrix of the pancreas (inputs mediated by integrins) and directly with neighboring cells, by mechanisms that do not require extracellular mediators (inputs mediated by gap and tight junction channels). Here, we review the expression and function of the connexins and pannexins that are expressed by the main secretory cells of the exocrine and endocrine pancreatic cells. Available data show that the patterns of expression of these proteins differ in acini and islets, supporting distinct functions in the physiological secretion of pancreatic enzymes and hormones. Circumstantial evidence further suggests that alterations in the signaling provided by these proteins are involved in pancreatic diseases.
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12
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Lorenzo PI, Fuente-Martín E, Brun T, Cobo-Vuilleumier N, Jimenez-Moreno CM, G Herrera Gomez I, López Noriega L, Mellado-Gil JM, Martin-Montalvo A, Soria B, Gauthier BR. PAX4 Defines an Expandable β-Cell Subpopulation in the Adult Pancreatic Islet. Sci Rep 2015; 5:15672. [PMID: 26503027 PMCID: PMC4622080 DOI: 10.1038/srep15672] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Accepted: 10/01/2015] [Indexed: 12/31/2022] Open
Abstract
PAX4 is a key regulator of pancreatic islet development whilst in adult acute overexpression protects β-cells against stress-induced apoptosis and stimulates proliferation. Nonetheless, sustained PAX4 expression promotes β-cell dedifferentiation and hyperglycemia, mimicking β-cell failure in diabetic patients. Herein, we study mechanisms that allow stringent PAX4 regulation endowing favorable β-cell adaptation in response to changing environment without loss of identity. To this end, PAX4 expression was monitored using a mouse bearing the enhanced green fluorescent protein (GFP) and cre recombinase construct under the control of the islet specific pax4 promoter. GFP was detected in 30% of islet cells predominantly composed of PAX4-enriched β-cells that responded to glucose-induced insulin secretion. Lineage tracing demonstrated that all islet cells were derived from PAX4+ progenitor cells but that GFP expression was confined to a subpopulation at birth which declined with age correlating with reduced replication. However, this GFP+ subpopulation expanded during pregnancy, a state of active β-cell replication. Accordingly, enhanced proliferation was exclusively detected in GFP+ cells consistent with cell cycle genes being stimulated in PAX4-overexpressing islets. Under stress conditions, GFP+ cells were more resistant to apoptosis than their GFP- counterparts. Our data suggest PAX4 defines an expandable β-cell sub population within adult islets.
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Affiliation(s)
- Petra I Lorenzo
- Pancreatic Islet Development and Regeneration Unit, Department of Stem Cells, CABIMER-Andalusian Center for Molecular Biology and Regenerative Medicine, Seville, Spain
| | - Esther Fuente-Martín
- Pancreatic Islet Development and Regeneration Unit, Department of Stem Cells, CABIMER-Andalusian Center for Molecular Biology and Regenerative Medicine, Seville, Spain
| | - Thierry Brun
- Department of Cell Physiology and Metabolism, University of Geneva, Geneva, Switzerland
| | - Nadia Cobo-Vuilleumier
- Pancreatic Islet Development and Regeneration Unit, Department of Stem Cells, CABIMER-Andalusian Center for Molecular Biology and Regenerative Medicine, Seville, Spain
| | - Carmen María Jimenez-Moreno
- Pancreatic Islet Development and Regeneration Unit, Department of Stem Cells, CABIMER-Andalusian Center for Molecular Biology and Regenerative Medicine, Seville, Spain
| | - Irene G Herrera Gomez
- Pancreatic Islet Development and Regeneration Unit, Department of Stem Cells, CABIMER-Andalusian Center for Molecular Biology and Regenerative Medicine, Seville, Spain
| | - Livia López Noriega
- Pancreatic Islet Development and Regeneration Unit, Department of Stem Cells, CABIMER-Andalusian Center for Molecular Biology and Regenerative Medicine, Seville, Spain
| | - José Manuel Mellado-Gil
- Pancreatic Islet Development and Regeneration Unit, Department of Stem Cells, CABIMER-Andalusian Center for Molecular Biology and Regenerative Medicine, Seville, Spain
| | - Alejandro Martin-Montalvo
- Pancreatic Islet Development and Regeneration Unit, Department of Stem Cells, CABIMER-Andalusian Center for Molecular Biology and Regenerative Medicine, Seville, Spain
| | - Bernat Soria
- Cellular Therapy of Diabetes Mellitus and its Complications, Department of Stem Cells, CABIMER-Andalusian Center for Molecular Biology and Regenerative Medicine, Seville, Spain.,CIBERDEM, Instituto Carlos III, Madrid, Spain
| | - Benoit R Gauthier
- Pancreatic Islet Development and Regeneration Unit, Department of Stem Cells, CABIMER-Andalusian Center for Molecular Biology and Regenerative Medicine, Seville, Spain
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13
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Pizarro-Delgado J, Deeney JT, Martín-del-Río R, Corkey BE, Tamarit-Rodriguez J. KCl -Permeabilized Pancreatic Islets: An Experimental Model to Explore the Messenger Role of ATP in the Mechanism of Insulin Secretion. PLoS One 2015; 10:e0140096. [PMID: 26444014 PMCID: PMC4596849 DOI: 10.1371/journal.pone.0140096] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Accepted: 09/22/2015] [Indexed: 11/18/2022] Open
Abstract
Our previous work has demonstrated that islet depolarization with KCl opens connexin36 hemichannels in β-cells of mouse pancreatic islets allowing the exchange of small metabolites with the extracellular medium. In this study, the opening of these hemichannels has been further characterized in rat islets and INS-1 cells. Taking advantage of hemicannels'opening, the uptake of extracellular ATP and its effect on insulin release were investigated. 70 mM KCl stimulated light emission by luciferin in dispersed rat islets cells transduced with the fire-fly luciferase gene: it was suppressed by 20 mM glucose and 50 μM mefloquine, a specific connexin36 inhibitor. Extracellular ATP was taken up or released by islets depolarized with 70 mM KCl at 5 mM glucose, depending on the external ATP concentration. 1 mM ATP restored the loss of ATP induced by the depolarization itself. ATP concentrations above 5 mM increased islet ATP content and the ATP/ADP ratio. No ATP uptake occurred in non-depolarized or KCl-depolarized islets simultaneously incubated with 50 μM mefloquine or 20 mM glucose. Extracellular ATP potentiated the secretory response induced by 70 mM KCl at 5 mM glucose in perifused rat islets: 5 mM ATP triggered a second phase of insulin release after the initial peak triggered by KCl-depolarization itself; at 10 mM, it increased both the initial, KCl-dependent, peak and stimulated a greater second phase of secretion than at 5 mM. These stimulatory effects of extracellular ATP were almost completely suppressed by 50 μM mefloquine. The magnitude of the second phase of insulin release due to 5 mM extracellular ATP was decreased by addition of 5 mM ADP (extracellular ATP/ADP ratio = 1). ATP acts independently of KATP channels closure and its intracellular concentration and its ATP/ADP ratio seems to regulate the magnitude of both the first (triggering) and second (amplifying) phases of glucose-induced insulin secretion.
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Affiliation(s)
| | - Jude T. Deeney
- Obesity Research Center, Department of Medicine, Boston University School of Medicine, Boston, Massachusetts, United States of America
| | | | - Barbara E. Corkey
- Obesity Research Center, Department of Medicine, Boston University School of Medicine, Boston, Massachusetts, United States of America
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14
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Rubio ME, Nagy JI. Connexin36 expression in major centers of the auditory system in the CNS of mouse and rat: Evidence for neurons forming purely electrical synapses and morphologically mixed synapses. Neuroscience 2015; 303:604-29. [PMID: 26188286 PMCID: PMC4576740 DOI: 10.1016/j.neuroscience.2015.07.026] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Revised: 07/08/2015] [Accepted: 07/09/2015] [Indexed: 10/23/2022]
Abstract
Electrical synapses formed by gap junctions composed of connexin36 (Cx36) are widely distributed in the mammalian central nervous system (CNS). Here, we used immunofluorescence methods to document the expression of Cx36 in the cochlear nucleus and in various structures of the auditory pathway of rat and mouse. Labeling of Cx36 visualized exclusively as Cx36-puncta was densely distributed primarily on the somata and initial dendrites of neuronal populations in the ventral cochlear nucleus, and was abundant in superficial layers of the dorsal cochlear nucleus. Other auditory centers displaying Cx36-puncta included the medial nucleus of the trapezoid body (MNTB), regions surrounding the lateral superior olivary nucleus, the dorsal nucleus of the medial lemniscus, the nucleus sagulum, all subnuclei of the inferior colliculus, and the auditory cerebral cortex. In EGFP-Cx36 transgenic mice, EGFP reporter was detected in neurons located in each of auditory centers that harbored Cx36-puncta. In the ventral cochlear nuclei and the MNTB, many neuronal somata were heavily innervated by nerve terminals containing vesicular glutamate transporter-1 (vglut1) and Cx36 was frequently localized at these terminals. Cochlear ablation caused a near total depletion of vglut1-positive terminals in the ventral cochlear nuclei, with a commensurate loss of labeling for Cx36 around most neuronal somata, but preserved Cx36-puncta at somatic neuronal appositions. The results suggest that electrical synapses formed by Cx36-containing gap junctions occur in most of the widely distributed centers of the auditory system. Further, it appears that morphologically mixed chemical/electrical synapses formed by nerve terminals are abundant in the ventral cochlear nucleus, including those at endbulbs of Held formed by cochlear primary afferent fibers, and those at calyx of Held synapses on MNTB neurons.
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Affiliation(s)
- M E Rubio
- Departments of Otolaryngology and Neurobiology, University of Pittsburgh Medical School, Pittsburgh, USA
| | - J I Nagy
- Department of Physiology and Pathophysiology, Faculty of Medicine, University of Manitoba, Winnipeg, Canada.
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15
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Yesildag B, Bock T, Herrmanns K, Wollscheid B, Stoffel M. Kin of IRRE-like Protein 2 Is a Phosphorylated Glycoprotein That Regulates Basal Insulin Secretion. J Biol Chem 2015; 290:25891-906. [PMID: 26324709 DOI: 10.1074/jbc.m115.684704] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Indexed: 12/17/2022] Open
Abstract
Direct interactions among pancreatic β-cells via cell surface proteins inhibit basal and enhance stimulated insulin secretion. Here, we functionally and biochemically characterized Kirrel2, an immunoglobulin superfamily protein with β-cell-specific expression in the pancreas. Our results show that Kirrel2 is a phosphorylated glycoprotein that co-localizes and interacts with the adherens junction proteins E-cadherin and β-catenin in MIN6 cells. We further demonstrate that the phosphosites Tyr(595-596) are functionally relevant for the regulation of Kirrel2 stability and localization. Analysis of the extracellular and intracellular domains of Kirrel2 revealed that it is cleaved and shed from MIN6 cells and that the remaining membrane spanning cytoplasmic domain is processed by γ-secretase complex. Kirrel2 knockdown with RNA interference in MIN6 cells and ablation of Kirrel2 from mice with genetic deletion resulted in increased basal insulin secretion from β-cells, with no immediate influence on stimulated insulin secretion, total insulin content, or whole body glucose metabolism. Our results show that in pancreatic β-cells Kirrel2 localizes to adherens junctions, is regulated by multiple post-translational events, including glycosylation, extracellular cleavage, and phosphorylation, and engages in the regulation of basal insulin secretion.
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Affiliation(s)
- Burcak Yesildag
- From the Department of Biology, Institute of Molecular Health Sciences, Swiss Federal Institute of Technology (ETH) Zurich, Otto-Stern-Weg 7, 8093 Zurich
| | - Thomas Bock
- the Department of Health Sciences and Technology, Institute of Molecular Systems Biology, Swiss Federal Institute of Technology Zurich, Auguste-Piccard-Hof 1, 8093 Zurich, and
| | - Karolin Herrmanns
- From the Department of Biology, Institute of Molecular Health Sciences, Swiss Federal Institute of Technology (ETH) Zurich, Otto-Stern-Weg 7, 8093 Zurich
| | - Bernd Wollscheid
- the Department of Health Sciences and Technology, Institute of Molecular Systems Biology, Swiss Federal Institute of Technology Zurich, Auguste-Piccard-Hof 1, 8093 Zurich, and
| | - Markus Stoffel
- From the Department of Biology, Institute of Molecular Health Sciences, Swiss Federal Institute of Technology (ETH) Zurich, Otto-Stern-Weg 7, 8093 Zurich, the Department of Health Sciences and Technology, Institute of Molecular Systems Biology, Swiss Federal Institute of Technology Zurich, Auguste-Piccard-Hof 1, 8093 Zurich, and the Faculty of Medicine, University of Zurich, 8091 Zurich, Switzerland
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16
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Voytenko LP, Lushnikova IV, Savotchenko AV, Isaeva EV, Skok MV, Lykhmus OY, Patseva MA, Skibo GG. Hippocampal GABAergic interneurons coexpressing alpha7-nicotinic receptors and connexin-36 are able to improve neuronal viability under oxygen-glucose deprivation. Brain Res 2015; 1616:134-45. [PMID: 25966616 DOI: 10.1016/j.brainres.2015.04.061] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Revised: 02/10/2015] [Accepted: 04/30/2015] [Indexed: 01/09/2023]
Abstract
The hippocampal interneurons are very diverse by chemical profiles and rather inconsistent by sensitivity to CI. Some hippocampal GABAergic interneurons survive certain time after ischemia while ischemia-sensitive interneurons and pyramidal neurons are damaged. GABAergic signaling, nicotinic receptors expressing α7-subunit (α7nAChRs(+)) and connexin-36 (Cx36(+), electrotonic gapjunctions protein) contradictory modulate post-ischemic environment. We hypothesized that hippocampal ischemia-resistant GABAergic interneurons coexpressing glutamate decarboxylase-67 isoform (GAD67(+)), α7nAChRs(+), Cx36(+) are able to enhance neuronal viability. To check this hypothesis the histochemical and electrophysiological investigations have been performed using rat hippocampal organotypic culture in the condition of 30-min oxygen-glucose deprivation (OGD). Post-OGD reoxygenation (4h) revealed in CA1 pyramidal layer numerous damaged cells, decreased population spike amplitude and increased pair-pulse depression. In these conditions GAD67(+) interneurons displayed the OGD-resistance and significant increase of GABA synthesis/metabolism (GAD67-immunofluorescence, mitochondrial activity). The α7nAChRs(+) and Cx36(+) co-localizations were revealed in resistant GAD67(+) interneurons. Under OGD: GABAA-receptors (GABAARs) blockade increased cell damage and exacerbated the pair-pulse depression in CA1 pyramidal layer; α7nAChRs and Cx36-channels separate blockades sufficiently decreased cell damage while interneuronal GAD67-immunofluorescence and mitochondrial activity were similar to the control. Thus, hippocampal GABAergic interneurons co-expressing α7nAChRs and Cx36 remained resistant certain time after OGD and were able to modulate CA1 neuron survival through GABAARs, α7nAChRs and Cx36-channels activity. The enhancements of the neuronal viability together with GABA synthesis/metabolism normalization suggest cooperative neuroprotective mechanism that could be used for increase in efficiency of therapeutic strategies against post-ischemic pathology.
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Affiliation(s)
- L P Voytenko
- Department of Cytology, Bogomoletz Institute of Physiology, Kiev, Ukraine.
| | - I V Lushnikova
- Department of Cytology, Bogomoletz Institute of Physiology, Kiev, Ukraine
| | - A V Savotchenko
- Department of Cellular Membranology, Bogomoletz Institute of Physiology, Ukraine
| | - E V Isaeva
- Department of Cellular Membranology, Bogomoletz Institute of Physiology, Ukraine
| | - M V Skok
- Palladin Institute of Biochemistry, Kiev, Ukraine
| | - O Yu Lykhmus
- Palladin Institute of Biochemistry, Kiev, Ukraine
| | - M A Patseva
- Department of Cytology, Bogomoletz Institute of Physiology, Kiev, Ukraine
| | - G G Skibo
- Department of Cytology, Bogomoletz Institute of Physiology, Kiev, Ukraine
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17
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Lebreton F, Pirog A, Belouah I, Bosco D, Berney T, Meda P, Bornat Y, Catargi B, Renaud S, Raoux M, Lang J. Slow potentials encode intercellular coupling and insulin demand in pancreatic beta cells. Diabetologia 2015; 58:1291-9. [PMID: 25788295 DOI: 10.1007/s00125-015-3558-z] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Accepted: 02/23/2015] [Indexed: 11/24/2022]
Abstract
AIMS/HYPOTHESIS Ion fluxes constitute a major integrative signal in beta cells that leads to insulin secretion and regulation of gene expression. Understanding these electrical signals is important for deciphering the endogenous algorithms used by islets to attain homeostasis and for the design of new sensors for monitoring beta cell function. METHODS Mouse and human islets were cultured on multielectrode arrays (MEAs) for 3-13 days. Extracellular electrical activities received on each electrode were continuously amplified and recorded for offline characterisation. RESULTS Differential band-pass filtering of MEA recordings of mouse islets showed two extracellular voltage waveforms: action potentials (lasting 40-60 ms) and very robust slow potentials (SPs, lasting 800-1,500 ms), the latter of which have not been described previously. The frequency of SPs directly correlated with glucose concentration, peaked at 10 mmol/l glucose and was further augmented by picomolar concentrations of glucagon-like peptide-1. SPs required the closure of ATP-dependent potassium channels as they were induced by glucose or glibenclamide but were not elicited by KCl-induced depolarisation. Pharmacological tools and the use of beta cell specific knockout mice showed that SPs reflected cell coupling via connexin 36. Moreover, increasing and decreasing glucose ramps showed hysteresis with reduced glucose sensitivity during the decreasing phase. SPs were also observed in human islets and could be continuously recorded over 24 h. CONCLUSIONS/INTERPRETATION This novel electrical signature reflects the syncytial function of the islets and is specific to beta cells. Moreover, the observed hysteresis provides evidence for an endogenous algorithm naturally present in islets to protect against hypoglycaemia.
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Affiliation(s)
- Fanny Lebreton
- CNRS UMR 5248, Chimie et Biologie des Membranes et Nano-objets, Université de Bordeaux, Batiment B14, Allée Geoffroy St Hilaire, CS90063, 33615, Pessac, France
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18
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Marçal-Pessoa AF, Bassi-Branco CL, Salvatierra CDSB, Stoppiglia LF, Ignacio-Souza LM, de Lima Reis SR, Veloso RV, de Barros Reis MA, Carneiro EM, Boschero AC, Arantes VC, Latorraca MQ. A low-protein diet during pregnancy prevents modifications in intercellular communication proteins in rat islets. Biol Res 2015; 48:3. [PMID: 25654754 PMCID: PMC4362834 DOI: 10.1186/0717-6287-48-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Accepted: 01/07/2015] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND Gap junctions between β-cells participate in the precise regulation of insulin secretion. Adherens junctions and their associated proteins are required for the formation, function and structural maintenance of gap junctions. Increases in the number of the gap junctions between β-cells and enhanced glucose-stimulated insulin secretion are observed during pregnancy. In contrast, protein restriction produces structural and functional alterations that result in poor insulin secretion in response to glucose. We investigated whether protein restriction during pregnancy affects the expression of mRNA and proteins involved in gap and adherens junctions in pancreatic islets. An isoenergetic low-protein diet (6% protein) was fed to non-pregnant or pregnant rats from day 1-15 of pregnancy, and rats fed an isocaloric normal-protein diet (17% protein) were used as controls. RESULTS The low-protein diet reduced the levels of connexin 36 and β-catenin protein in pancreatic islets. In rats fed the control diet, pregnancy increased the levels of phospho-[Ser(279/282)]-connexin 43, and it decreased the levels of connexin 36, β-catenin and beta-actin mRNA as well as the levels of connexin 36 and β-catenin protein in islets. The low-protein diet during pregnancy did not alter these mRNA and protein levels, but avoided the increase of levels of phospho-[Ser(279/282)]-connexin 43 in islets. Insulin secretion in response to 8.3 mmol/L glucose was higher in pregnant rats than in non-pregnant rats, independently of the nutritional status. CONCLUSION Short-term protein restriction during pregnancy prevented the Cx43 phosphorylation, but this event did not interfer in the insulin secretion.
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Affiliation(s)
- Ana Flávia Marçal-Pessoa
- Mestrado em Ciências da Saúde, Faculdade de Ciências Médicas, Universidade Federal de Mato Grosso, Cuiabá, Mato Grosso, Brazil.
| | - Carmen Lucia Bassi-Branco
- Departamento de Ciências Básicas em Saúde, Faculdade de Ciências Médicas, Universidade Federal de Mato Grosso, Cuiabá, Mato Grosso, Brazil.
| | | | - Luiz Fabrizio Stoppiglia
- Departamento de Psicologia, Instituto de Educação, Universidade Federal de Mato Grosso, Cuiabá, Mato Grosso, Brazil.
| | - Letícia Martins Ignacio-Souza
- Departamento de Alimentos e Nutrição, Faculdade de Nutrição, Universidade Federal de Mato Grosso, Cuiabá, Mato Grosso, Brazil.
| | - Sílvia Regina de Lima Reis
- Departamento de Alimentos e Nutrição, Faculdade de Nutrição, Universidade Federal de Mato Grosso, Cuiabá, Mato Grosso, Brazil.
| | - Roberto Vilela Veloso
- Departamento de Alimentos e Nutrição, Faculdade de Nutrição, Universidade Federal de Mato Grosso, Cuiabá, Mato Grosso, Brazil.
| | | | - Everardo Magalhães Carneiro
- Departamento de Anatomia, Biologia Celular e Fisiologia e Biofísica, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, SP, Brazil.
| | - Antonio Carlos Boschero
- Departamento de Anatomia, Biologia Celular e Fisiologia e Biofísica, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, SP, Brazil.
| | - Vanessa Cristina Arantes
- Departamento de Alimentos e Nutrição, Faculdade de Nutrição, Universidade Federal de Mato Grosso, Cuiabá, Mato Grosso, Brazil.
| | - Márcia Queiroz Latorraca
- Departamento de Alimentos e Nutrição, Faculdade de Nutrição, Universidade Federal de Mato Grosso, Cuiabá, Mato Grosso, Brazil.
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19
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Pizarro-Delgado J, Fasciani I, Temperan A, Romero M, González-Nieto D, Alonso-Magdalena P, Nualart-Marti A, Estil'les E, Paul DL, Martín-del-Río R, Montanya E, Solsona C, Nadal A, Barrio LC, Tamarit-Rodríguez J. Inhibition of connexin 36 hemichannels by glucose contributes to the stimulation of insulin secretion. Am J Physiol Endocrinol Metab 2014; 306:E1354-66. [PMID: 24735890 DOI: 10.1152/ajpendo.00358.2013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The existence of functional connexin36 (Cx36) hemichannels in β-cells was investigated in pancreatic islets of rat and wild-type (Cx36(+/+)), monoallelic (Cx36(+/-)), and biallelic (Cx36(-/-)) knockout mice. Hemichannel opening by KCl depolarization was studied by measuring ATP release and changes of intracellular ATP (ADP). Cx36(+/+) islets lost ATP after depolarization with 70 mM KCl at 5 mM glucose; ATP loss was prevented by 8 and 20 mM glucose or 50 μM mefloquine (connexin inhibitor). ATP content was higher in Cx36(-/-) than Cx36(+/+) islets and was not decreased by KCl depolarization; Cx36(+/-) islets showed values between that of control and homozygous islets. Five minimolar extracellular ATP increased ATP content and ATP/ADP ratio and induced a biphasic insulin secretion in depolarized Cx36(+/+) and Cx36(+/-) but not Cx36(-/-) islets. Cx36 hemichannels expressed in oocytes opened upon depolarization of membrane potential, and their activation was inhibited by mefloquine and glucose (IC₅₀ ∼8 mM). It is postulated that glucose-induced inhibition of Cx36 hemichannels in islet β-cells might avoid depolarization-induced ATP loss, allowing an optimum increase of the ATP/ADP ratio by sugar metabolism and a biphasic stimulation of insulin secretion. Gradual suppression of glucose-induced insulin release in Cx36(+/-) and Cx36(-/-) islets confirms that Cx36 gap junction channels are necessary for a full secretory stimulation and might account for the glucose intolerance observed in mice with defective Cx36 expression. Mefloquine targeting of Cx36 on both gap junctions and hemichannels also suppresses glucose-stimulated secretion. By contrast, glucose stimulation of insulin secretion requires Cx36 hemichannels' closure but keeping gap junction channels opened.
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Affiliation(s)
| | - Ilaria Fasciani
- Research Department, "Ramón y Cajal" Hospital-IRYCIS, Madrid, Spain
| | - Ana Temperan
- Research Department, "Ramón y Cajal" Hospital-IRYCIS, Madrid, Spain
| | - María Romero
- Research Department, "Ramón y Cajal" Hospital-IRYCIS, Madrid, Spain
| | | | - Paloma Alonso-Magdalena
- Institute of Bioengineering and CIBER de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Miguel Hernández University, Elche, Spain
| | - Anna Nualart-Marti
- Department of Pathology and Experimental Therapeutics, Faculty of Medicine - Campus Bellvitge, University of Barcelona, Hospitalet del Llobregat, Barcelona, Spain; IDIBELL, Institut d'Investigació Biomèdica de Bellvitge, Hospitalet del Llobregat, Barcelona, Spain
| | - Elisabet Estil'les
- CIBERDEM, Barcelona, Spain; Department of Clinical Sciences, University of Barcelona, Feixa Llarga s/n, L'Hospitalet de Llobregat, Barcelona, Spain; and
| | - David L Paul
- Department of Neurobiology, Harvard Medical School, Boston, Massachusetts
| | | | - Eduard Montanya
- CIBERDEM, Barcelona, Spain; Department of Clinical Sciences, University of Barcelona, Feixa Llarga s/n, L'Hospitalet de Llobregat, Barcelona, Spain; and Endocrine Unit, Hospital Universitari Bellvitge-IDIBELL, Barcelona, Spain
| | - Carles Solsona
- Department of Pathology and Experimental Therapeutics, Faculty of Medicine - Campus Bellvitge, University of Barcelona, Hospitalet del Llobregat, Barcelona, Spain; IDIBELL, Institut d'Investigació Biomèdica de Bellvitge, Hospitalet del Llobregat, Barcelona, Spain
| | - Angel Nadal
- Institute of Bioengineering and CIBER de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Miguel Hernández University, Elche, Spain
| | | | - J Tamarit-Rodríguez
- Biochemistry Department, Medical School, Complutense University, Madrid, Spain;
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20
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Chiou SH, Kim-Kiselak C, Risca VI, Heimann MK, Chuang CH, Burds AA, Greenleaf WJ, Jacks TE, Feldser DM, Winslow MM. A conditional system to specifically link disruption of protein-coding function with reporter expression in mice. Cell Rep 2014; 7:2078-86. [PMID: 24931605 DOI: 10.1016/j.celrep.2014.05.031] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Revised: 04/04/2014] [Accepted: 05/15/2014] [Indexed: 10/25/2022] Open
Abstract
Conditional gene deletion in mice has contributed immensely to our understanding of many biological and biomedical processes. Despite an increasing awareness of nonprotein-coding functional elements within protein-coding transcripts, current gene-targeting approaches typically involve simultaneous ablation of noncoding elements within targeted protein-coding genes. The potential for protein-coding genes to have additional noncoding functions necessitates the development of novel genetic tools capable of precisely interrogating individual functional elements. We present a strategy that couples Cre/loxP-mediated conditional gene disruption with faithful GFP reporter expression in mice in which Cre-mediated stable inversion of a splice acceptor-GFP-splice donor cassette concurrently disrupts protein production and creates a GFP fusion product. Importantly, cassette inversion maintains physiologic transcript structure, thereby ensuring proper microRNA-mediated regulation of the GFP reporter, as well as maintaining expression of nonprotein-coding elements. To test this potentially generalizable strategy, we generated and analyzed mice with this conditional knockin reporter targeted to the Hmga2 locus.
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Affiliation(s)
- Shin-Heng Chiou
- Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305-5120, USA
| | - Caroline Kim-Kiselak
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Viviana I Risca
- Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305-5120, USA
| | - Megan K Heimann
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Chen-Hua Chuang
- Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305-5120, USA
| | - Aurora A Burds
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - William J Greenleaf
- Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305-5120, USA
| | - Tyler E Jacks
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - David M Feldser
- Department of Cancer Biology, University of Pennsylvania, Philadelphia, PA 19104-6160, USA; Abramson Family Cancer Research Institute, University of Pennsylvania, Philadelphia, PA 19104-6160, USA
| | - Monte M Winslow
- Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305-5120, USA; Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305-5324, USA; Stanford Cancer Institute, Stanford University School of Medicine, Stanford, CA 94305-5456, USA.
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21
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Bautista W, Nagy JI. Connexin36 in gap junctions forming electrical synapses between motoneurons in sexually dimorphic motor nuclei in spinal cord of rat and mouse. Eur J Neurosci 2014; 39:771-87. [PMID: 24304165 PMCID: PMC3943632 DOI: 10.1111/ejn.12439] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Revised: 10/29/2013] [Accepted: 10/30/2013] [Indexed: 12/01/2022]
Abstract
Pools of motoneurons in the lumbar spinal cord innervate the sexually dimorphic perineal musculature, and are themselves sexually dimorphic, showing differences in number and size between male and female rodents. In two of these pools, the dorsomedial nucleus (DMN) and the dorsolateral nucleus (DLN), dimorphic motoneurons are intermixed with non-dimorphic neurons innervating anal and external urethral sphincter muscles. As motoneurons in these nuclei are reportedly linked by gap junctions, we examined immunofluorescence labeling for the gap junction-forming protein connexin36 (Cx36) in male and female mice and rats. Fluorescent Cx36-labeled puncta occurred in distinctly greater amounts in the DMN and DLN of male rodents than in other spinal cord regions. These puncta were localized to motoneuron somata, proximal dendrites, and neuronal appositions, and were distributed either as isolated or large patches of puncta. In both rats and mice, Cx36-labeled puncta were associated with nearly all (> 94%) DMN and DLN motoneurons. The density of Cx36-labeled puncta increased dramatically from postnatal days 9 to 15, unlike the developmental decreases in these puncta observed in other central nervous system regions. In females, Cx36 labeling of puncta in the DLN was similar to that in males, but was sparse in the DMN. In enhanced green fluorescent protein (EGFP)-Cx36 transgenic mice, motoneurons in the DMN and DLN were intensely labeled for the EGFP reporter in males, but less so in females. The results indicate the presence of Cx36-containing gap junctions in the sexually dimorphic DMN and DLN of both male and female rodents, suggesting coupling of not only sexually dimorphic but also non-dimorphic motoneurons in these nuclei.
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Affiliation(s)
- W. Bautista
- Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Canada
| | - J. I. Nagy
- Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Canada
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22
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Farnsworth NL, Benninger RKP. New insights into the role of connexins in pancreatic islet function and diabetes. FEBS Lett 2014; 588:1278-87. [PMID: 24583073 DOI: 10.1016/j.febslet.2014.02.035] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2013] [Revised: 02/13/2014] [Accepted: 02/19/2014] [Indexed: 12/22/2022]
Abstract
Multi-cellular systems require complex signaling mechanisms for proper tissue function, to mediate signaling between cells in close proximity and at distances. This holds true for the islets of Langerhans, which are multicellular micro-organs located in the pancreas responsible for glycemic control, through secretion of insulin and other hormones. Coupling of electrical and metabolic signaling between islet β-cells is required for proper insulin secretion and effective glycemic control. β-cell specific coupling is established through gap junctions composed of connexin36, which results in coordinated insulin release across the islet. Islet connexins have been implicated in both Type-1 and Type-2 diabetes; however a clear link remains to be determined. The goal of this review is to discuss recent discoveries regarding the role of connexins in regulating insulin secretion, the regulation of connexins within the islet, and recent studies which support a role for connexins in diabetes. Further studies which investigate the regulation of connexins in the islet and their role in diabetes may lead to novel diabetes therapies which regulate islet function and β-cell survival through modulation of gap junction coupling.
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Affiliation(s)
- Nikki L Farnsworth
- Barbara Davis center for childhood diabetes, University of Colorado, Anschutz Medical Campus, Aurora, CO 80045, United States
| | - Richard K P Benninger
- Barbara Davis center for childhood diabetes, University of Colorado, Anschutz Medical Campus, Aurora, CO 80045, United States; Department of Bioengineering, University of Colorado, Anschutz Medical Campus, Aurora, CO 80045, United States.
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23
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Stamper IJ, Jackson E, Wang X. Phase transitions in pancreatic islet cellular networks and implications for type-1 diabetes. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 89:012719. [PMID: 24580269 PMCID: PMC4172977 DOI: 10.1103/physreve.89.012719] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Indexed: 06/03/2023]
Abstract
In many aspects the onset of a chronic disease resembles a phase transition in a complex dynamic system: Quantitative changes accumulate largely unnoticed until a critical threshold is reached, which causes abrupt qualitative changes of the system. In this study we examine a special case, the onset of type-1 diabetes (T1D), a disease that results from loss of the insulin-producing pancreatic islet β cells. Within each islet, the β cells are electrically coupled to each other via gap-junctional channels. This intercellular coupling enables the β cells to synchronize their insulin release, thereby generating the multiscale temporal rhythms in blood insulin that are critical to maintaining blood glucose homeostasis. Using percolation theory we show how normal islet function is intrinsically linked to network connectivity. In particular, the critical amount of β-cell death at which the islet cellular network loses site percolation is consistent with laboratory and clinical observations of the threshold loss of β cells that causes islet functional failure. In addition, numerical simulations confirm that the islet cellular network needs to be percolated for β cells to synchronize. Furthermore, the interplay between site percolation and bond strength predicts the existence of a transient phase of islet functional recovery after onset of T1D and introduction of treatment, potentially explaining the honeymoon phenomenon. Based on these results, we hypothesize that the onset of T1D may be the result of a phase transition of the islet β-cell network.
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Affiliation(s)
- I. J. Stamper
- Department of Physics, the University of Alabama at Birmingham, Birmingham, Alabama, USA
- The Comprehensive Diabetes Center, the University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Elais Jackson
- Department of Computer and Information Sciences, the University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Xujing Wang
- Department of Physics, the University of Alabama at Birmingham, Birmingham, Alabama, USA
- The Comprehensive Diabetes Center, the University of Alabama at Birmingham, Birmingham, Alabama, USA
- Systems Biology Center, the National Heart, Lung, and Blood Institute, the National Institutes of Health, Bethesda, Maryland, USA
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24
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Pérez-Armendariz EM. Connexin 36, a key element in pancreatic beta cell function. Neuropharmacology 2013; 75:557-66. [PMID: 23973309 DOI: 10.1016/j.neuropharm.2013.08.015] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Revised: 08/05/2013] [Accepted: 08/07/2013] [Indexed: 12/01/2022]
Abstract
The prevalence of diabetes at a global scale has markedly increased during the last three decades. Diabetes is a chronic disease that includes a group of metabolic disorders, in which high serum glucose levels is a common factor. Insulin is the only hormone that decreases serum glucose levels. Therefore, it is relevant to deepen our understanding of cell mechanisms that regulate insulin production and release. Insulin is produced in pancreatic islet beta cells. They are excitable cells and most of them are electrically coupled through gap junction channels. Connexin 36 (Cx36) has been identified at junctional membranes of islet beta cells in both rodents and humans. Co-localization of Cx36 with Cx30.2 has been recently identified. Functional studies in Cx36 deficient mice have provided direct evidence that Cx36 gap junction channels are necessary for the synchronization of [Ca(2+)]i oscillations in islet beta cells. The latter allows for the generation of insulin pulses in a single perfused islet. Moreover, Cx36 deficient mice were found to have altered serum insulin pulse dynamics and to be glucose intolerant. In addition, Cx36 has been recently identified as an early gene that is specifically expressed in embryonic beta cells, whose transcript and protein are upregulated in unison with the main wave of beta cell differentiation. In conclusion, Cx36 is critical for endocrine pancreatic function and may represent a molecular target for future prevention and treatment of diabetes. This article is part of the Special Issue Section entitled 'Current Pharmacology of Gap Junction Channels and Hemichannels'.
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Affiliation(s)
- E Martha Pérez-Armendariz
- Unidad de Medicina Experimental, Facultad de Medicina, Universidad Nacional Autónoma de México, Torre de Investigación 5to piso, Avenida Universidad 3000, Circuito Interior, Ciudad Universitaria, UNAM, México D.F. 04510, Mexico; Hospital General de México, Hospital General de México/Unidad de Medicina Experimental, Facultad de Medicina, UNAM, Dr Balmis 148, Colonia Doctores, Delegación Cuahutémoc, CP 06726 Ciudad de México, Mexico; Departamento of Biología Celular yTisular, Universidad Nacional Autónoma de México, Avenida Universidad 3000, Circuito Interior, Ciudad Universitaria, UNAM, Mexico D.F. 04510, Mexico.
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25
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Hanstein R, Negoro H, Patel NK, Charollais A, Meda P, Spray DC, Suadicani SO, Scemes E. Promises and pitfalls of a Pannexin1 transgenic mouse line. Front Pharmacol 2013; 4:61. [PMID: 23675350 PMCID: PMC3648696 DOI: 10.3389/fphar.2013.00061] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2013] [Accepted: 04/20/2013] [Indexed: 12/26/2022] Open
Abstract
Gene targeting strategies have become a powerful technology for elucidating mammalian gene function. The recently generated knockout (KO)-first strategy produces a KO at the RNA processing level and also allows for the generation of conditional KO alleles by combining FLP/FRT and Cre/loxP systems, thereby providing high flexibility in gene manipulation. However, this multipurpose KO-first cassette might produce hypomorphic rather than complete KOs if the RNA processing module is bypassed. Moreover, the generation of a conditional phenotype is also dependent on specific activity of Cre recombinase. Here, we report the use of an efficient molecular biological approach to test pannexin1 (Panx1) mRNA expression in global and conditional Panx1 KO mice derived from the KO-first mouse line, Panx1tm1a(KOMP)Wtsi. Using qRT-PCR, we demonstrate that tissues from wild-type (WT) mice show a range of Panx1 mRNA expression levels, with highest expression in trigeminal ganglia, bladder and spleen. Unexpectedly, we found that in mice homozygous for the KO-first allele, Panx1 mRNA expression is not abolished but reduced by 70% compared to that of WT tissues. Thus, Panx1 KO-first mice present a hypomorphic phenotype. Crosses of Panx1 KO-first with FLP deleter mice generated Panx1f/f mice. Further crosses of the latter mice with mGFAP-Cre or NFH-Cre mice were used to generate astrocyte- and neuron-specific Panx1 deletions, respectively. A high incidence of ectopic Cre expression was found in offspring of both types of conditional Panx1 KO mice. Our study demonstrates that Panx1 expression levels in the global and conditional Panx1 KO mice derived from KO-first mouse lines must be carefully characterized to ensure modulation of Panx1 gene expression. The precise quantitation of Panx1 expression and its relation to function is expected to provide a foundation for future efforts aimed at deciphering the role of Panx1 under physiological and pathological conditions.
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Affiliation(s)
- Regina Hanstein
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Yeshiva University New York, NY, USA
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26
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Marandykina A, Palacios-Prado N, Rimkutė L, Skeberdis VA, Bukauskas FF. Regulation of connexin36 gap junction channels by n-alkanols and arachidonic acid. J Physiol 2013; 591:2087-101. [PMID: 23420660 PMCID: PMC3634521 DOI: 10.1113/jphysiol.2013.250910] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Accepted: 02/13/2013] [Indexed: 12/18/2022] Open
Abstract
We examined junctional conductance (gj) and its dependence on transjunctional voltage in gap junction (GJ) channels formed of wild-type connexin36 (Cx36) or its fusion form with green fluorescent protein (Cx36-EGFP) transfected in HeLa cells or endogenously expressed in primary culture of pancreatic β-cells. Only a very small fraction (∼0.8%) of Cx36-EGFP channels assembled into junctional plaques of GJs were open under control conditions. We found that short carbon chain n-alkanols (SCCAs) increased gj, while long carbon chain n-alkanols resulted in full uncoupling; cutoff is between heptanol and octanol. The fraction of functional channels and gj increased several fold under an exposure to SCCAs, or during reduction of endogenous levels of arachidonic acid (AA) by exposure to fatty acid-free BSA or cytosolic phospholipase A2 inhibitors. Moreover, uncoupling caused by exogenously applied AA can be rescued by BSA, which binds AA and other polyunsaturated fatty acids (PUFAs), but not by BSA modified with 1,2-cyclohexanedione, which does not bind AA and other PUFAs. We propose that under control conditions, Cx36 GJ channels in HeLa transfectants and β-cells are inhibited by endogenous AA, which stabilizes a closed conformational state of the channel that leads to extremely low fraction of functional channels. In addition, SCCAs increase gj by interfering with endogenous AA-dependent inhibition, increasing open probability and the fraction of functional channels.
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Affiliation(s)
- Alina Marandykina
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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27
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Frinchi M, Di Liberto V, Turimella S, D'Antoni F, Theis M, Belluardo N, Mudò G. Connexin36 (Cx36) expression and protein detection in the mouse carotid body and myenteric plexus. Acta Histochem 2013; 115:252-6. [PMID: 22897942 DOI: 10.1016/j.acthis.2012.07.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2012] [Revised: 07/17/2012] [Accepted: 07/18/2012] [Indexed: 11/29/2022]
Abstract
Although connexin36 (Cx36) has been studied in several tissues, it is notable that no data are available on Cx36 expression in the carotid body and the intestine. The present study was undertaken to evaluate using immunohistochemistry, PCR and Western blotting procedures, whether Cx36 was expressed in the mouse carotid body and in the intestine at ileum and colon level. In the carotid body, Cx36 was detected as diffuse punctate immunostaining and as protein by Western blotting and mRNA by RT-PCR. Cx36 punctate immunostaining was also evident in the intestine with localization restricted to the myenteric plexus of both the ileum and the colon, and this detection was also confirmed by Western blotting and RT-PCR. All the data obtained were validated using Cx36 knockout mice. Taken together the present data on localization of Cx36 gap-junctions in two tissues of neural crest-derived neuroendocrine organs may provide an anatomical basis for future functional investigations.
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Affiliation(s)
- Monica Frinchi
- Department of Experimental Biomedicine and Clinical Neuroscience, University of Palermo, Palermo, Italy
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28
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Cigliola V, Chellakudam V, Arabieter W, Meda P. Connexins and β-cell functions. Diabetes Res Clin Pract 2013; 99:250-9. [PMID: 23176806 DOI: 10.1016/j.diabres.2012.10.016] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Accepted: 10/15/2012] [Indexed: 11/20/2022]
Abstract
Proper functioning of pancreatic islets requires that numerous β-cells are properly coordinated. With evolution, many mechanisms have converged, which now allow individual β-cells to sense the state of activity of their neighbors as well as the changes taking place in the extracellular medium, and to regulate accordingly their own function. Here, we review one such mechanism for intercellular coordination, which depends on connexins. These integral membrane proteins accumulate at sites of close apposition between adjacent islet cell membranes, referred to as gap junctions. Recent evidence demonstrates that connexin-dependent signaling is relevant for the in vivo control of insulin biosynthesis and release, as well as for the survival of β-cells under stressing conditions. The data suggest that alterations of this signaling may be implicated in the β-cell alterations which characterize most forms of diabetes, raising the tantalizing possibility that targeting of the direct intercellular communications β-cells establish within each pancreatic islet may provide a novel, therapeutically useful strategy.
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Affiliation(s)
- Valentina Cigliola
- Department of Cell Physiology and Metabolism, University of Geneva School of Medicine, 1 rue Michel-Servet, Geneva, Switzerland
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29
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Tang MCW, Jacobs SA, Wong LH, Mann JR. Conditional allelic replacement applied to genes encoding the histone variant H3.3 in the mouse. Genesis 2013; 51:142-6. [PMID: 23315948 DOI: 10.1002/dvg.22366] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Revised: 01/03/2012] [Indexed: 11/09/2022]
Abstract
Post-translational modifications to residues in core histones convey epigenetic information. Their function can be evaluated in amino acid substitution mutants, although to date this method has not been used in mice. To this end, we have evaluated gene targeting vectors designed for Cre recombinase-mediated conditional allelic replacement at the two unlinked genes encoding the histone variant H3.3. The conditional alleles consist of an uninterrupted wild-type H3.3 coding sequence upstream of a desired alternative or proxy coding sequence. The arrangement of two loxP sites allows Cre-mediated replacement of the wild-type coding sequence with the proxy. To demonstrate proof of principle, at each locus we replaced the wild-type coding sequence with a fluorescent reporter. This produced null alleles that will be useful to analyse the effects of H3.3 deficiency in development. Each targeting vector can readily be retrofitted with a proxy coding sequence encoding a modified H3.3 protein. Such vectors will allow for the conditional substitution of specific residues in order to dissect the roles of H3.3 post-translational modifications in development and disease.
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Affiliation(s)
- Michelle C W Tang
- Theme of Genetic Disorders, Murdoch Childrens Research Institute, The Royal Children's Hospital, Victoria, 3052, Australia
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30
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Meda P. Protein-mediated interactions of pancreatic islet cells. SCIENTIFICA 2013; 2013:621249. [PMID: 24278783 PMCID: PMC3820362 DOI: 10.1155/2013/621249] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Accepted: 12/10/2012] [Indexed: 05/29/2023]
Abstract
The islets of Langerhans collectively form the endocrine pancreas, the organ that is soley responsible for insulin secretion in mammals, and which plays a prominent role in the control of circulating glucose and metabolism. Normal function of these islets implies the coordination of different types of endocrine cells, noticeably of the beta cells which produce insulin. Given that an appropriate secretion of this hormone is vital to the organism, a number of mechanisms have been selected during evolution, which now converge to coordinate beta cell functions. Among these, several mechanisms depend on different families of integral membrane proteins, which ensure direct (cadherins, N-CAM, occludin, and claudins) and paracrine communications (pannexins) between beta cells, and between these cells and the other islet cell types. Also, other proteins (integrins) provide communication of the different islet cell types with the materials that form the islet basal laminae and extracellular matrix. Here, we review what is known about these proteins and their signaling in pancreatic β -cells, with particular emphasis on the signaling provided by Cx36, given that this is the integral membrane protein involved in cell-to-cell communication, which has so far been mostly investigated for effects on beta cell functions.
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Affiliation(s)
- Paolo Meda
- Department of Cell Physiology and Metabolism, University of Geneva School of Medicine, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland
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31
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Affiliation(s)
- Paolo Meda
- Department of Cell Physiology and Metabolism, University of Geneva, Geneva, Switzerland.
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32
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Carvalho CPF, Oliveira RB, Britan A, Santos-Silva JC, Boschero AC, Meda P, Collares-Buzato CB. Impaired β-cell-β-cell coupling mediated by Cx36 gap junctions in prediabetic mice. Am J Physiol Endocrinol Metab 2012; 303:E144-51. [PMID: 22569071 DOI: 10.1152/ajpendo.00489.2011] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Gap junctional intercellular communication between β-cells is crucial for proper insulin biosynthesis and secretion. The aim of this work was to investigate the expression of connexin (Cx)36 at the protein level as well as the function and structure of gap junctions (GJ) made by this protein in the endocrine pancreas of prediabetic mice. C57BL/6 mice were fed a high-fat (HF) or regular chow diet for 60 days. HF-fed mice became obese and prediabetic, as shown by peripheral insulin resistance, moderate hyperglycemia, hyperinsulinemia, and compensatory increase in endocrine pancreas mass. Compared with control mice, prediabetic animals showed a significant decrease in insulin-secretory response to glucose and displayed a significant reduction in islet Cx36 protein. Ultrastructural analysis further showed that prediabetic mice had GJ plaques about one-half the size of those of the control group. Microinjection of isolated pancreatic islets with ethidium bromide revealed that prediabetic mice featured a β-cell-β-cell coupling 30% lower than that of control animals. We conclude that β-cell-β-cell coupling mediated by Cx36 made-channels is impaired in prediabetic mice, suggesting a role of Cx36-dependent cell-to-cell communication in the pathogenesis of the early β-cell dysfunctions that lead to type 2-diabetes.
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Affiliation(s)
- C P F Carvalho
- Department of Histology and Embryology, Institute of Biology, University of Campinas, Campinas, São Paulo, Brazil
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33
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Abstract
The pancreatic beta cell is responsible for maintaining normoglycaemia by secreting an appropriate amount of insulin according to blood glucose levels. The accurate sensing of the beta cell extracellular environment is therefore crucial to this endocrine function and is transmitted via its cell surface proteome. Various surface proteins that mediate or affect beta cell endocrine function have been identified, including growth factor and cytokine receptors, transporters, ion channels and proteases, attributing important roles to surface proteins in the adaptive behaviour of beta cells in response to acute and chronic environmental changes. However, the largely unknown composition of the beta cell surface proteome is likely to harbour yet more information about these mechanisms and provide novel points of therapeutic intervention and diagnostic tools. This article will provide an overview of the functional complexity of the beta cell surface proteome and selected surface proteins, outline the mechanisms by which their activity may be modulated, discuss the methods and challenges of comprehensively mapping and studying the beta cell surface proteome, and address the potential of this interesting subproteome for diagnostic and therapeutic applications in human disease.
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Affiliation(s)
- I. Stützer
- Institute of Molecular Systems Biology, HPT E73, ETH Zurich, Wolfgang-Pauli-Str. 16, 8093 Zurich, Switzerland
- Competence Center for Systems Physiology and Metabolic Diseases, ETH Zurich, Zurich, Switzerland
| | - D. Esterházy
- Institute of Molecular Systems Biology, HPT E73, ETH Zurich, Wolfgang-Pauli-Str. 16, 8093 Zurich, Switzerland
- Competence Center for Systems Physiology and Metabolic Diseases, ETH Zurich, Zurich, Switzerland
| | - M. Stoffel
- Institute of Molecular Systems Biology, HPT E73, ETH Zurich, Wolfgang-Pauli-Str. 16, 8093 Zurich, Switzerland
- Competence Center for Systems Physiology and Metabolic Diseases, ETH Zurich, Zurich, Switzerland
- Faculty of Medicine, University of Zurich, Zurich, Switzerland
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Matsumoto T, Sakurai K, Tanaka A, Ishibashi T, Tachibana K, Ishikawa K, Yokote K. The anti-ulcer agent, irsogladine, increases insulin secretion by MIN6 cells. Eur J Pharmacol 2012; 685:213-7. [PMID: 22542662 DOI: 10.1016/j.ejphar.2012.04.005] [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] [Received: 10/28/2011] [Revised: 03/28/2012] [Accepted: 04/05/2012] [Indexed: 10/28/2022]
Abstract
Insulin secretion by pancreatic islets is a multicellular process. In addition to other essential systems, gap junctions are an important component of cell-to-cell communication in pancreatic islets. It is well known that dysfunction of gap junctions causes inappropriate insulin secretion. The anti-ulcer agent, irsogladine, increases gap junctions in some cell types. To examine the effect of irsogladine on insulin secretion, we investigated insulin secretion by MIN6 cells treated with or without irsogladine. The expression of connexin 36 proteins and intracellular cAMP levels were also determined using immunoblotting and ELISA assays, respectively. Irsogladine had no effect on insulin secretion under 5.6mM glucose conditions. However, under 16.7 mM glucose conditions, irsogladine (1.0 × 10(-5)M) induced a 1.7 ± 0.20 fold increase in insulin secretion compared to the control (P<0.05). This effect of irsogladine on insulin secretion was inhibited by the addition of the gap junction inhibitor 18-beta-glycyrrhetinic acid. Irsogladine treatment increased the protein level of connexin 36 in the plasma membrane fraction. The intracellular cAMP level in MIN6 cells was significantly, but mildly, increased by irsogladine treatment. Furthermore, Rp-cAMP and H89 inhibited the effects of irsogladine on insulin secretion under high glucose conditions. Irsogladine increases insulin secretion under high glucose conditions. The up-regulation of gap junction channels and the increased level of intracellular cAMP induced by irsogladine treatment suggest that these phenomena are involved in irsogladine-induced increased insulin secretion.
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Affiliation(s)
- Tsuyoshi Matsumoto
- Department of Clinical Cell Biology and Medicine, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8670, Japan.
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Nlend RN, Aït-Lounis A, Allagnat F, Cigliola V, Charollais A, Reith W, Haefliger JA, Meda P. Cx36 is a target of Beta2/NeuroD1, which associates with prenatal differentiation of insulin-producing β cells. J Membr Biol 2012; 245:263-73. [PMID: 22729650 DOI: 10.1007/s00232-012-9447-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2012] [Accepted: 06/01/2012] [Indexed: 10/28/2022]
Abstract
The insulin-producing β cells of pancreatic islets are coupled by connexin36 (Cx36) channels. To investigate what controls the expression of this connexin, we have investigated its pattern during mouse pancreas development, and the influence of three transcription factors that are critical for β-cell development and differentiation. We show that (1) the Cx36 gene (Gjd2) is activated early in pancreas development and is markedly induced at the time of the surge of the transcription factors that determine β-cell differentiation; (2) the cognate protein is detected about a week later and is selectively expressed by β cells throughout the prenatal development of mouse pancreas; (3) a 2-kbp fragment of the Gjd2 promoter, which contains three E boxes for the binding of the bHLH factor Beta2/NeuroD1, ensures the expression of Cx36 by β cells; and (4) Beta2/NeuroD1 binds to these E boxes and, in the presence of the E47 ubiquitous cofactor, transactivates the Gjd2 promoter. The data identify Cx36 as a novel early marker of β cells and as a target of Beta2/NeuroD1, which is essential for β-cell development and differentiation.
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Affiliation(s)
- Rachel Nlend Nlend
- Department of Cell Physiology and Metabolism, University of Geneva, CMU, 1 Rue Michel Servet CH- 1211, Geneva 4, Switzerland
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36
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Voytenko LP, Lushnikova IV, Skok MV, Lykhmus OY, Deuchars J, Skibo GG. Co-Expression of Glutamic Acid Decarboxylase Isoform 67, Membrane Nicotinic Acetylcholine Receptors, and Connexin 36 in Ischemia-Resistant Hippocampal Interneurons. NEUROPHYSIOLOGY+ 2012. [DOI: 10.1007/s11062-012-9239-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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Hodson DJ, Romanò N, Schaeffer M, Fontanaud P, Lafont C, Fiordelisio T, Mollard P. Coordination of calcium signals by pituitary endocrine cells in situ. Cell Calcium 2011; 51:222-30. [PMID: 22172406 DOI: 10.1016/j.ceca.2011.11.007] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2011] [Revised: 11/08/2011] [Accepted: 11/17/2011] [Indexed: 12/20/2022]
Abstract
The pulsatile secretion of hormones from the mammalian pituitary gland drives a wide range of homeostatic responses by dynamically altering the functional set-point of effector tissues. To accomplish this, endocrine cell populations residing within the intact pituitary display large-scale changes in coordinated calcium-spiking activity in response to various hypothalamic and peripheral inputs. Although the pituitary gland is structurally compartmentalized into specific and intermingled endocrine cell networks, providing a clear morphological basis for such coordinated activity, the mechanisms which facilitate the timely propagation of information between cells in situ remain largely unexplored. Therefore, the aim of the current review is to highlight the range of signalling modalities known to be employed by endocrine cells to coordinate intracellular calcium rises, and discuss how these mechanisms are integrated at the population level to orchestrate cell function and tissue output.
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Affiliation(s)
- David J Hodson
- CNRS, UMR-5203, Institut de Génomique Fonctionnelle, F-34000 Montpellier, France.
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Klee P, Allagnat F, Pontes H, Cederroth M, Charollais A, Caille D, Britan A, Haefliger JA, Meda P. Connexins protect mouse pancreatic β cells against apoptosis. J Clin Invest 2011; 121:4870-9. [PMID: 22056383 PMCID: PMC3225984 DOI: 10.1172/jci40509] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2011] [Accepted: 09/28/2011] [Indexed: 12/18/2022] Open
Abstract
Type 1 diabetes develops when most insulin-producing β cells of the pancreas are killed by an autoimmune attack. The in vivo conditions modulating the sensitivity and resistance of β cells to this attack remain largely obscure. Here, we show that connexin 36 (Cx36), a trans-membrane protein that forms gap junctions between β cells in the pancreatic islets, protects mouse β cells against both cytotoxic drugs and cytokines that prevail in the islet environment at the onset of type 1 diabetes. We documented that this protection was at least partially dependent on intercellular communication, which Cx36 and other types of connexin channels establish within pancreatic islets. We further found that proinflammatory cytokines decreased expression of Cx36 and that experimental reduction or augmentation of Cx36 levels increased or decreased β cell apoptosis, respectively. Thus, we conclude that Cx36 is central to β cell protection from toxic insults.
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Affiliation(s)
- Philippe Klee
- Department of Cell Physiology and Metabolism, University of Geneva, Medical School, Geneva, Switzerland.
Service of Internal Medicine, University Hospital of Lausanne (CHUV), Lausanne, Switzerland
| | - Florent Allagnat
- Department of Cell Physiology and Metabolism, University of Geneva, Medical School, Geneva, Switzerland.
Service of Internal Medicine, University Hospital of Lausanne (CHUV), Lausanne, Switzerland
| | - Helena Pontes
- Department of Cell Physiology and Metabolism, University of Geneva, Medical School, Geneva, Switzerland.
Service of Internal Medicine, University Hospital of Lausanne (CHUV), Lausanne, Switzerland
| | - Manon Cederroth
- Department of Cell Physiology and Metabolism, University of Geneva, Medical School, Geneva, Switzerland.
Service of Internal Medicine, University Hospital of Lausanne (CHUV), Lausanne, Switzerland
| | - Anne Charollais
- Department of Cell Physiology and Metabolism, University of Geneva, Medical School, Geneva, Switzerland.
Service of Internal Medicine, University Hospital of Lausanne (CHUV), Lausanne, Switzerland
| | - Dorothée Caille
- Department of Cell Physiology and Metabolism, University of Geneva, Medical School, Geneva, Switzerland.
Service of Internal Medicine, University Hospital of Lausanne (CHUV), Lausanne, Switzerland
| | - Aurore Britan
- Department of Cell Physiology and Metabolism, University of Geneva, Medical School, Geneva, Switzerland.
Service of Internal Medicine, University Hospital of Lausanne (CHUV), Lausanne, Switzerland
| | - Jacques-Antoine Haefliger
- Department of Cell Physiology and Metabolism, University of Geneva, Medical School, Geneva, Switzerland.
Service of Internal Medicine, University Hospital of Lausanne (CHUV), Lausanne, Switzerland
| | - Paolo Meda
- Department of Cell Physiology and Metabolism, University of Geneva, Medical School, Geneva, Switzerland.
Service of Internal Medicine, University Hospital of Lausanne (CHUV), Lausanne, Switzerland
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Bedner P, Steinhäuser C, Theis M. Functional redundancy and compensation among members of gap junction protein families? BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:1971-84. [PMID: 22044799 DOI: 10.1016/j.bbamem.2011.10.016] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2011] [Revised: 10/08/2011] [Accepted: 10/17/2011] [Indexed: 12/15/2022]
Abstract
Gap junctions are intercellular conduits for small molecules made up by protein subunits called connexins. A large number of connexin genes were found in mouse and man, and most cell types express several connexins, lending support to the view that redundancy and compensation among family members exist. This review gives an overview of the current knowledge on redundancy and functional compensation - or lack thereof. It takes into account the different properties of connexin subunits which comprise gap junctional intercellular channels, but also the compatibility of connexins in gap junctions. Most insight has been gained by the investigation of mice deficient for one or more connexins and transgenic mice with functional replacement of one connexin gene by another. Most single deficient mice show phenotypical alterations limited to critical developmental time points or to specific organs and tissues, while mice doubly deficient for connexins expressed in the same cell type usually show more severe phenotypical alterations. Replacement of a connexin by another connexin in some cases gave rise to rescue of phenotypical alterations of connexin deficiencies, which were restricted to specific tissues. In many tissues, connexin substitution did not restore phenotypical alterations of connexin deficiencies, indicating that connexins are specialized in function. In some cases, fatal consequences arose from the replacement. The current consensus gained from such studies is that redundancy and compensation among connexins exists at least to a limited extent. This article is part of a Special Issue entitled: The Communicating junctions, composition, structure and characteristics.
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Potolicchio I, Cigliola V, Velazquez-Garcia S, Klee P, Valjevac A, Kapic D, Cosovic E, Lepara O, Hadzovic-Dzuvo A, Mornjacovic Z, Meda P. Connexin-dependent signaling in neuro-hormonal systems. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:1919-36. [PMID: 22001400 DOI: 10.1016/j.bbamem.2011.09.022] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Revised: 09/14/2011] [Accepted: 09/23/2011] [Indexed: 01/04/2023]
Abstract
The advent of multicellular organisms was accompanied by the development of short- and long-range chemical signalling systems, including those provided by the nervous and endocrine systems. In turn, the cells of these two systems have developed mechanisms for interacting with both adjacent and distant cells. With evolution, such mechanisms have diversified to become integrated in a complex regulatory network, whereby individual endocrine and neuro-endocrine cells sense the state of activity of their neighbors and, accordingly, regulate their own level of functioning. A consistent feature of this network is the expression of connexin-made channels between the (neuro)hormone-producing cells of all endocrine glands and secretory regions of the central nervous system so far investigated in vertebrates. This review summarizes the distribution of connexins in the mammalian (neuro)endocrine systems, and what we know about the participation of these proteins on hormone secretion, the life of the producing cells, and the action of (neuro)hormones on specific targets. The data gathered since the last reviews on the topic are summarized, with particular emphasis on the roles of Cx36 in the function of the insulin-producing beta cells of the endocrine pancreas, and of Cx40 in that of the renin-producing juxta-glomerular epithelioid cells of the kidney cortex. This article is part of a Special Issue entitled: The Communicating junctions, composition, structure and characteristics.
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Affiliation(s)
- Ilaria Potolicchio
- Department of Cell Physiology and Metabolism, University of Geneva Medical School, Switzerland
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41
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Abstract
The appearance of multicellular organisms imposed the development of several mechanisms for cell-to-cell communication, whereby different types of cells coordinate their function. Some of these mechanisms depend on the intercellular diffusion of signal molecules in the extracellular spaces, whereas others require cell-to-cell contact. Among the latter mechanisms, those provided by the proteins of the connexin family are widespread in most tissues. Connexin signaling is achieved via direct exchanges of cytosolic molecules between adjacent cells at gap junctions, for cell-to-cell coupling, and possibly also involves the formation of membrane "hemi-channels," for the extracellular release of cytosolic signals, direct interactions between connexins and other cell proteins, and coordinated influence on the expression of multiple genes. Connexin signaling appears to be an obligatory attribute of all multicellular exocrine and endocrine glands. Specifically, the experimental evidence we review here points to a direct participation of the Cx36 isoform in the function of the insulin-producing β-cells of the endocrine pancreas, and of the Cx40 isoform in the function of the renin-producing juxtaglomerular epithelioid cells of the kidney cortex.
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Affiliation(s)
- Domenico Bosco
- Department of Surgery, University of Geneva Medical School, Geneva, Switzerland
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42
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Yang KC, Qi Z, Yanai G, Shirouza Y, Lu DH, Lee HS, Sumi S. Cell coupling regulates Ins1, Pdx-1 and MafA to promote insulin secretion in mouse pancreatic beta cells. Process Biochem 2011. [DOI: 10.1016/j.procbio.2011.06.018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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43
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Klee P, Lamprianou S, Charollais A, Caille D, Sarro R, Cederroth M, Haefliger JA, Meda P. Connexin implication in the control of the murine beta-cell mass. Pediatr Res 2011; 70:142-7. [PMID: 21527868 DOI: 10.1203/pdr.0b013e318220f106] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Diabetes develops when the insulin needs of peripheral cells exceed the availability or action of the hormone. This situation results from the death of most beta-cells in type 1 diabetes, and from an inability of the beta-cell mass to adapt to increasing insulin needs in type 2 and gestational diabetes. We analyzed several lines of transgenic mice and showed that connexins (Cxs), the transmembrane proteins that form gap junctions, are implicated in the modulation of the beta-cell mass. Specifically, we found that the native Cx36 does not alter islet size or insulin content, whereas the Cx43 isoform increases both parameters, and Cx32 has a similar effect only when combined with GH. These findings open interesting perspectives for the in vitro and in vivo regulation of the beta-cell mass.
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Affiliation(s)
- Philippe Klee
- Department of Pediatrics, University Hospital of Geneva, Geneva 1211, Switzerland.
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44
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Campbell RE, Ducret E, Porteous R, Liu X, Herde MK, Wellerhaus K, Sonntag S, Willecke K, Herbison AE. Gap junctions between neuronal inputs but not gonadotropin-releasing hormone neurons control estrous cycles in the mouse. Endocrinology 2011; 152:2290-301. [PMID: 21447638 DOI: 10.1210/en.2010-1311] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The role of gap junctions in the neural control of fertility remains poorly understood. Using acute brain slices from adult GnRH-green fluorescent protein transgenic mice, individual GnRH neurons were filled with a mixture of fluorescent dextran and neurobiotin. No dye transfer was found between any GnRH neurons, although approximately 30% of GnRH neurons exchanged neurobiotin with closely apposed cells. Dual electrophysiological recordings from pairs of GnRH neurons revealed an absence of electrical coupling. Using adult connexin 36 (Cx36)-cyan fluorescent protein transgenic mice, Cx36 was identified in cells within several hypothalamic brain regions, including 64% of preoptic area kisspeptin neurons but not in GnRH neurons. To assess the potential role of Cx36 in non-GnRH neurons within the GnRH neuronal network (i.e. neurons providing afferent inputs to GnRH neurons), a calmodulin kinase IIα-Cre (CKC)-LoxP strategy was used to generate mice with a neuron-specific deletion of Cx36 beginning in the first postnatal week. Mutant female mice exhibited normal puberty onset but disordered estrous cyclicity, although their fecundity was normal as was their estrogen-negative and -positive feedback mechanisms. The effects of adult deletion of Cx36 from neurons were assessed using a tamoxifen-dependent inducible CKC-Cx36 transgenic strategy. Mutant mice exhibited the same reproductive phenotype as the CKC-Cx36 animals. Together these observations demonstrate that there is no gap junctional coupling between GnRH neurons. However, it is apparent that other neurons within the GnRH neuronal network, potentially the preoptic kisspeptin neurons, are dependent on Cx36 gap junctions and that this is critical for normal estrous cyclicity.
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Affiliation(s)
- Rebecca E Campbell
- Centre for Neuroendocrinology, Department of Physiology, University of Otago School of Medical Sciences, Dunedin, New Zealand
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45
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Abstract
The mechanisms involved in Alzheimer's disease are not completely understood and how glial cells contribute to this neurodegenerative disease remains to be elucidated. Because inflammatory treatments and products released from activated microglia increase glial hemichannel activity, we investigated whether amyloid-β peptide (Aβ) could regulate these channels in glial cells and affect neuronal viability. Microglia, astrocytes, or neuronal cultures as well as acute hippocampal slices made from GFAP-eGFP transgenic mice were treated with the active fragment of Aβ. Hemichannel activity was monitored by single-channel recordings and by time-lapse ethidium uptake, whereas neuronal death was assessed by Fluoro-Jade C staining. We report that low concentrations of Aβ(25-35) increased hemichannel activity in all three cell types and microglia initiate these effects triggered by Aβ. Finally, neuronal damage occurs by activation of neuronal hemichannels induced by ATP and glutamate released from Aβ(25-35)-activated glia. These responses were observed in the presence of external calcium and were differently inhibited by hemichannel blockers, whereas the Aβ(25-35)-induced neuronal damage was importantly reduced in acute slices made from Cx43 knock-out mice. Thus, Aβ leads to a cascade of hemichannel activation in which microglia promote the release of glutamate and ATP through glial (microglia and astrocytes) hemichannels that induces neuronal death by triggering hemichannels in neurons. Consequently, this work opens novel avenues for alternative treatments that target glial cells and neurons to maintain neuronal survival in the presence of Aβ.
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46
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Helbig I, Sammler E, Eliava M, Bolshakov AP, Rozov A, Bruzzone R, Monyer H, Hormuzdi SG. In vivo evidence for the involvement of the carboxy terminal domain in assembling connexin 36 at the electrical synapse. Mol Cell Neurosci 2010; 45:47-58. [PMID: 20510366 PMCID: PMC3025355 DOI: 10.1016/j.mcn.2010.05.008] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2010] [Revised: 05/03/2010] [Accepted: 05/15/2010] [Indexed: 12/03/2022] Open
Abstract
Connexin 36 (Cx36)-containing electrical synapses contribute to the timing and amplitude of neural responses in many brain regions. A Cx36-EGFP transgenic was previously generated to facilitate their identification and study. In this study we demonstrate that electrical coupling is normal in transgenic mice expressing Cx36 from the genomic locus and suggest that fluorescent puncta present in brain tissue represent distributed electrical synapses. These qualities emphasize the usefulness of the Cx36-EGFP reporter as a tool for the detailed anatomical characterization of electrical synapses in fixed and living tissue. However, though the fusion protein is able to form gap junctions between Xenopus laevis oocytes it is unable to restore electrical coupling to interneurons in the Cx36-deficient mouse. Further experiments in transgenic tissue and non-neural cell lines reveal impaired transport to the plasma membrane as the possible cause. By analyzing the functional deficits exhibited by the fusion protein in vivo and in vitro, we identify a motif within Cx36 that may interact with other trafficking or scaffold proteins and thereby be responsible for its incorporation into electrical synapses.
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Affiliation(s)
- Ingo Helbig
- Department of Neuropediatrics, University Medical Center Schleswig-Holstein (UKSH), Schwanenweg 20, 24105 Kiel, Germany
| | - Esther Sammler
- Centre for Neuroscience, Ninewells Hospital and Medical School, University of Dundee, Dundee, DD1 9SY, UK
| | - Marina Eliava
- Department of Clinical Neurobiology, University of Heidelberg, Im Neuenheimer Feld 364, 69120 Heidelberg, Germany
| | - Alexey P. Bolshakov
- Centre for Neuroscience, Ninewells Hospital and Medical School, University of Dundee, Dundee, DD1 9SY, UK
| | - Andrei Rozov
- Centre for Neuroscience, Ninewells Hospital and Medical School, University of Dundee, Dundee, DD1 9SY, UK
| | - Roberto Bruzzone
- HKU-Pasteur Research Centre, 1/F, Dexter HC Man Building, Pokfulam, Hong Kong
| | - Hannah Monyer
- Department of Clinical Neurobiology, University of Heidelberg, Im Neuenheimer Feld 364, 69120 Heidelberg, Germany
| | - Sheriar Gustad Hormuzdi
- Centre for Neuroscience, Ninewells Hospital and Medical School, University of Dundee, Dundee, DD1 9SY, UK
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Carvalho CPF, Barbosa HCL, Britan A, Santos-Silva JCR, Boschero AC, Meda P, Collares-Buzato CB. Beta cell coupling and connexin expression change during the functional maturation of rat pancreatic islets. Diabetologia 2010; 53:1428-37. [PMID: 20361177 DOI: 10.1007/s00125-010-1726-8] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2009] [Accepted: 01/22/2010] [Indexed: 12/01/2022]
Abstract
AIMS/HYPOTHESIS Cell-cell coupling mediated by gap junctions formed from connexin (CX) contributes to the control of insulin secretion in the endocrine pancreas. We investigated the cellular production and localisation of CX36 and CX43, and gap junction-mediated beta cell coupling in pancreatic islets from rats of different ages, displaying different degrees of maturation of insulin secretion. METHODS The presence and distribution of islet connexins were assessed by immunoblotting and immunofluorescence. The expression of connexin genes was evaluated by RT-PCR and quantitative real-time PCR. The ultrastructure of gap junctions and the function of connexin channels were assessed by freeze-fracture electron microscopy and tracer microinjection, respectively. RESULTS Young and adult beta cells, which respond to glucose, expressed significantly higher levels of Cx36 (also known as Gjd2) than fetal and newborn beta cells, which respond poorly to the sugar. Accordingly, adult beta cells also showed a significantly higher membrane density of gap junctions and greater intercellular exchange of ethidium bromide than newborn beta cells. Cx43 (also known as Gja1) was not expressed by beta cells, but was located in various cell types at the periphery of fetal and newborn islets. CONCLUSIONS/INTERPRETATION These findings show that the pattern of connexins, gap junction membrane density and coupling changes in islets during the functional maturation of beta cells.
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Affiliation(s)
- C P F Carvalho
- Department of Histology and Embryology, Institute of Biology, University of Campinas (UNICAMP), Campinas, São Paulo, CEP 13083-970, Brazil
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48
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Hettiarachchi NT, Dallas ML, Pearson HA, Bruce G, Deuchars S, Boyle JP, Peers C. Gap junction-mediated spontaneous Ca(2+) waves in differentiated cholinergic SN56 cells. Biochem Biophys Res Commun 2010; 397:564-8. [PMID: 20573603 DOI: 10.1016/j.bbrc.2010.05.159] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2010] [Accepted: 05/31/2010] [Indexed: 11/27/2022]
Abstract
Neuronal gap junctions are receiving increasing attention as a physiological means of intercellular communication, yet our understanding of them is poorly developed when compared to synaptic communication. Using microfluorimetry, we demonstrate that differentiation of SN56 cells (hybridoma cells derived from murine septal neurones) leads to the spontaneous generation of Ca(2+) waves. These waves were unaffected by tetrodotoxin (1microM), but blocked by removal of extracellular Ca(2+), or addition of non-specific Ca(2+) channel inhibitors (Cd(2+) (0.1mM) or Ni(2+) (1mM)). Combined application of antagonists of NMDA receptors (AP5; 100microM), AMPA/kainate receptors (NBQX; 20microM), nicotinic AChR receptors (hexamethonium; 100microM) or inotropic purinoceptors (brilliant blue; 100nM) was also without effect. However, Ca(2+) waves were fully prevented by carbenoxolone (200microM), halothane (3mM) or niflumic acid (100microM), three structurally diverse inhibitors of gap junctions, and mRNA for connexin 36 was detected by PCR. Whole-cell patch-clamp recordings revealed spontaneous inward currents in voltage-clamped cells which we inhibited by Cd(2+), Ni(2+) or niflumic acid. Our data suggest that differentiated SN56 cells generated spontaneous Ca(2+) waves which are propagated by intercellular gap junctions. We propose that this system can be exploited conveniently for the development of neuronal gap junction modulators.
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49
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Ro S, Park C, Jin J, Zheng H, Blair PJ, Redelman D, Ward SM, Yan W, Sanders KM. A model to study the phenotypic changes of interstitial cells of Cajal in gastrointestinal diseases. Gastroenterology 2010; 138:1068-78.e1-2. [PMID: 19917283 PMCID: PMC4793910 DOI: 10.1053/j.gastro.2009.11.007] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2009] [Revised: 10/27/2009] [Accepted: 11/05/2009] [Indexed: 12/11/2022]
Abstract
BACKGROUND & AIMS Interstitial cells of Cajal (ICC) express the receptor tyrosine kinase, KIT, the receptor for stem cell factor. In the gastrointestinal (GI) tract, ICC are pacemaker cells that generate spontaneous electrical slow waves, and mediate inputs from motor neurons. Absence or loss of ICC are associated with GI motility disorders, including those consequent of diabetes. Studies of ICC have been hampered by the low density of these cells and difficulties in recognizing these cells in cell dispersions. METHODS Kit(+/copGFP) mice harboring a copepod super green fluorescent protein (copGFP) complementary DNA, inserted at the Kit locus, were generated. copGFP(+) ICC from GI muscles were analyzed using confocal microscopy and flow cytometry. copGFP(+) ICC from the jejunum were purified by a fluorescence-activated cell sorter and validated by cell-specific markers. Kit(+/copGFP) mice were crossbred with diabetic Lep(+/ob) mice to generate compound Kit(+/copGFP);Lep(ob/ob) mutant mice. copGFP(+) ICC from compound transgenic mice were analyzed by confocal microscopy. RESULTS copGFP in Kit(+/copGFP) mice colocalized with KIT immunofluorescence and thus was predominantly found in ICC. In other smooth muscles, mast cells were also labeled, but these cells were relatively rare in the murine GI tract. copGFP(+) cells from jejunal muscles were Kit(+) and free of contaminating cell-specific markers. Kit(+/copGFP);Lep(ob/ob) mice displayed ICC networks that were dramatically disrupted during the development of diabetes. CONCLUSIONS Kit(+/copGFP) mice offer a powerful new model to study the function and genetic regulation of ICC phenotypes. Isolation of ICC from animal models will help determine the causes and responses of ICC to therapeutic agents.
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Affiliation(s)
- Seungil Ro
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
| | - Chanjae Park
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
| | - Jingling Jin
- Huffington Center on Aging and Department of Pathology, Baylor College of Medicine, One Baylor Plaza, Houston, Texas
| | - Huili Zheng
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
| | - Peter J. Blair
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
| | - Doug Redelman
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
| | - Sean M. Ward
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
| | - Wei Yan
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
| | - Kenton M. Sanders
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
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Borinstein SC, Conerly M, Dzieciatkowski S, Biswas S, Washington MK, Trobridge P, Henikoff S, Grady WM. Aberrant DNA methylation occurs in colon neoplasms arising in the azoxymethane colon cancer model. Mol Carcinog 2010; 49:94-103. [PMID: 19777566 PMCID: PMC2875385 DOI: 10.1002/mc.20581] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Mouse models of intestinal tumors have advanced our understanding of the role of gene mutations in colorectal malignancy. However, the utility of these systems for studying the role of epigenetic alterations in intestinal neoplasms remains to be defined. Consequently, we assessed the role of aberrant DNA methylation in the azoxymethane (AOM) rodent model of colon cancer. AOM induced tumors display global DNA hypomethylation, which is similar to human colorectal cancer. We next assessed the methylation status of a panel of candidate genes previously shown to be aberrantly methylated in human cancer or in mouse models of malignant neoplasms. This analysis revealed different patterns of DNA methylation that were gene specific. Zik1 and Gja9 demonstrated cancer-specific aberrant DNA methylation, whereas, Cdkn2a/p16, Igfbp3, Mgmt, Id4, and Cxcr4 were methylated in both the AOM tumors and normal colon mucosa. No aberrant methylation of Dapk1 or Mlt1 was detected in the neoplasms, but normal colon mucosa samples displayed methylation of these genes. Finally, p19(Arf), Tslc1, Hltf, and Mlh1 were unmethylated in both the AOM tumors and normal colon mucosa. Thus, aberrant DNA methylation does occur in AOM tumors, although the frequency of aberrantly methylated genes appears to be less common than in human colorectal cancer. Additional studies are necessary to further characterize the patterns of aberrantly methylated genes in AOM tumors.
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Affiliation(s)
- Scott C. Borinstein
- Fred Hutchinson Cancer Research Center, Clinical Research Division
- Seattle Childrens Hospital, Seattle, WA
- University of Washington, Department of Pediatrics, Division of Pediatric Hematology/Oncology, Seattle, WA
| | - Melissa Conerly
- Fred Hutchinson Cancer Research Center, Basic Science Division
| | | | - Swati Biswas
- Vanderbilt University Medical School, Nashville, TN
| | | | - Patty Trobridge
- Fred Hutchinson Cancer Research Center, Clinical Research Division
| | - Steve Henikoff
- Fred Hutchinson Cancer Research Center, Basic Science Division
| | - William M. Grady
- Fred Hutchinson Cancer Research Center, Clinical Research Division
- University of Washington, Department of Medicine, Division of Gastroenterology
- R&D Service, VA Puget Sound Health Care System, Seattle, WA
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