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Sriram S, Carstens K, Dewing W, Fiacco TA. Astrocyte regulation of extracellular space parameters across the sleep-wake cycle. Front Cell Neurosci 2024; 18:1401698. [PMID: 38988660 PMCID: PMC11233815 DOI: 10.3389/fncel.2024.1401698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2024] [Accepted: 06/07/2024] [Indexed: 07/12/2024] Open
Abstract
Multiple subfields of neuroscience research are beginning to incorporate astrocytes into current frameworks of understanding overall brain physiology, neuronal circuitry, and disease etiology that underlie sleep and sleep-related disorders. Astrocytes have emerged as a dynamic regulator of neuronal activity through control of extracellular space (ECS) volume and composition, both of which can vary dramatically during different levels of sleep and arousal. Astrocytes are also an attractive target of sleep research due to their prominent role in the glymphatic system, a method by which toxic metabolites generated during wakefulness are cleared away. In this review we assess the literature surrounding glial influences on fluctuations in ECS volume and composition across the sleep-wake cycle. We also examine mechanisms of astrocyte volume regulation in glymphatic solute clearance and their role in sleep and wake states. Overall, findings highlight the importance of astrocytes in sleep and sleep research.
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Affiliation(s)
- Sandhya Sriram
- Interdepartmental Graduate Program in Neuroscience, University of California, Riverside, Riverside, CA, United States
- Department of Biochemistry and Molecular Biology, University of California, Riverside, Riverside, CA, United States
| | - Kaira Carstens
- Department of Biochemistry and Molecular Biology, University of California, Riverside, Riverside, CA, United States
| | - Wayne Dewing
- Undergraduate Major in Neuroscience, University of California, Riverside, Riverside, CA, United States
| | - Todd A Fiacco
- Interdepartmental Graduate Program in Neuroscience, University of California, Riverside, Riverside, CA, United States
- Department of Biochemistry and Molecular Biology, University of California, Riverside, Riverside, CA, United States
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2
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Pelz L, Dossou L, Kompier N, Jüttner R, Siemonsmeier G, Meyer N, Lowenstein ED, Lahmann I, Kettenmann H, Birchmeier C, Rathjen FG. The IgCAM BT-IgSF (IgSF11) is essential for connexin43-mediated astrocyte-astrocyte coupling in mice. eNeuro 2024; 11:ENEURO.0283-23.2024. [PMID: 38388443 PMCID: PMC10957231 DOI: 10.1523/eneuro.0283-23.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 01/19/2024] [Accepted: 01/24/2024] [Indexed: 02/24/2024] Open
Abstract
The type I transmembrane protein BT-IgSF is predominantly localized in the brain and testes. It belongs to the CAR subgroup of Ig cell adhesion proteins, that are hypothesized to regulate connexin expression or localization. Here, we studied the putative link between BT-IgSF and connexins in astrocytes, ependymal cells and neurons of the mouse. Global knockout of BT-IgSF caused an increase in the clustering of connexin43 (Gja1), but not of connexin30 (Gjb6), on astrocytes and ependymal cells. Additionally, knockout animals displayed reduced expression levels of connexin43 protein in the cortex and hippocampus. Importantly, analysis of biocytin spread in hippocampal or cortical slices from mature mice of either sex revealed a decrease in astrocytic cell-cell coupling in the absence of BT-IgSF. Blocking either protein biosynthesis or proteolysis showed that the lysosomal pathway increased connexin43 degradation in astrocytes. Localization of connexin43 in subcellular compartments was not impaired in astrocytes of BT-IgSF mutants. In contrast to connexin43 the localization and expression of connexin36 (Gjd2) on neurons was not affected by the absence of BT-IgSF. Overall, our data indicate that the IgCAM BT-IgSF is essential for correct gap junction-mediated astrocyte-to-astrocyte cell communication.Significance Statement Astrocytes regulate a variety of physiological processes in the developing and adult brain that are essential for proper brain function. Astrocytes form extensive networks in the brain and communicate via gap junctions. Disruptions of gap junction coupling are found in several diseases such as neurodegeneration or epilepsy. Here, we demonstrate that the cell adhesion protein BT-IgSF is essential for gap junction mediated coupling between astrocytes in the cortex and hippocampus.
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Affiliation(s)
- Laura Pelz
- Max-Delbrück-Center for Molecular Medicine, Berlin DE-13092, Germany
| | - Laura Dossou
- Max-Delbrück-Center for Molecular Medicine, Berlin DE-13092, Germany
| | - Nine Kompier
- Max-Delbrück-Center for Molecular Medicine, Berlin DE-13092, Germany
| | - René Jüttner
- Max-Delbrück-Center for Molecular Medicine, Berlin DE-13092, Germany
| | | | - Niklas Meyer
- Max-Delbrück-Center for Molecular Medicine, Berlin DE-13092, Germany
| | | | - Ines Lahmann
- Max-Delbrück-Center for Molecular Medicine, Berlin DE-13092, Germany
| | - Helmut Kettenmann
- Max-Delbrück-Center for Molecular Medicine, Berlin DE-13092, Germany
- Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Carmen Birchmeier
- Max-Delbrück-Center for Molecular Medicine, Berlin DE-13092, Germany
- NeuroCure Cluster of Excellence, Charité Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin 10117, Germany
| | - Fritz G. Rathjen
- Max-Delbrück-Center for Molecular Medicine, Berlin DE-13092, Germany
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3
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Zhang NN, Zhang Y, Wang ZZ, Chen NH. Connexin 43: insights into candidate pathological mechanisms of depression and its implications in antidepressant therapy. Acta Pharmacol Sin 2022; 43:2448-2461. [PMID: 35145238 PMCID: PMC9525669 DOI: 10.1038/s41401-022-00861-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Accepted: 01/06/2022] [Indexed: 11/09/2022] Open
Abstract
Major depressive disorder (MDD), a chronic and recurrent disease characterized by anhedonia, pessimism or even suicidal thought, remains a major chronic mental concern worldwide. Connexin 43 (Cx43) is the most abundant connexin expressed in astrocytes and forms the gap junction channels (GJCs) between astrocytes, the most abundant and functional glial cells in the brain. Astrocytes regulate neurons' synaptic strength and function by expressing receptors and regulating various neurotransmitters. Astrocyte dysfunction causes synaptic abnormalities, which are related to various mood disorders, e.g., depression. Increasing evidence suggests a crucial role of Cx43 in the pathogenesis of depression. Depression down-regulates Cx43 expression in humans and rats, and dysfunction of Cx43 also induces depressive behaviors in rats and mice. Recently Cx43 has received considerable critical attention and is highly implicated in the onset of depression. However, the pathological mechanisms of depression-like behavior associated with Cx43 still remain ambiguous. In this review we summarize the recent progress regarding the underlying mechanisms of Cx43 in the etiology of depression-like behaviors including gliotransmission, metabolic disorders, and neuroinflammation. We also discuss the effects of antidepressants (monoamine antidepressants and ketamine) on Cx43. The clarity of the candidate pathological mechanisms of depression-like behaviors associated with Cx43 and its potential pharmacological roles for antidepressants will benefit the exploration of a novel antidepressant target.
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Affiliation(s)
- Ning-Ning Zhang
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica & Neuroscience Center, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100050, China
| | - Yi Zhang
- Department of Anatomy, School of Chinese Medicine, Beijing University of Chinese Medicine, Beijing, 102488, China
| | - Zhen-Zhen Wang
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica & Neuroscience Center, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100050, China.
| | - Nai-Hong Chen
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica & Neuroscience Center, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100050, China.
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van der Sande E, Haarman AEG, Quint WH, Tadema KCD, Meester-Smoor MA, Kamermans M, De Zeeuw CI, Klaver CCW, Winkelman BHJ, Iglesias AI. The Role of GJD2(Cx36) in Refractive Error Development. Invest Ophthalmol Vis Sci 2022; 63:5. [PMID: 35262731 PMCID: PMC8934558 DOI: 10.1167/iovs.63.3.5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Accepted: 02/16/2022] [Indexed: 02/06/2023] Open
Abstract
Refractive errors are common eye disorders characterized by a mismatch between the focal power of the eye and its axial length. An increased axial length is a common cause of the refractive error myopia (nearsightedness). The substantial increase in myopia prevalence over the last decades has raised public health concerns because myopia can lead to severe ocular complications later in life. Genomewide association studies (GWAS) have made considerable contributions to the understanding of the genetic architecture of refractive errors. Among the hundreds of genetic variants identified, common variants near the gap junction delta-2 (GJD2) gene have consistently been reported as one of the top hits. GJD2 encodes the connexin 36 (Cx36) protein, which forms gap junction channels and is highly expressed in the neural retina. In this review, we provide current evidence that links GJD2(Cx36) to the development of myopia. We summarize the gap junctional communication in the eye and the specific role of GJD2(Cx36) in retinal processing of visual signals. Finally, we discuss the pathways involving dopamine and gap junction phosphorylation and coupling as potential mechanisms that may explain the role of GJD2(Cx36) in refractive error development.
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Affiliation(s)
- Emilie van der Sande
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
- Netherlands Institute for Neuroscience (NIN), Royal Dutch Academy of Art & Science (KNAW), Amsterdam, The Netherlands
| | - Annechien E. G. Haarman
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Wim H. Quint
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Kirke C. D. Tadema
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Magda A. Meester-Smoor
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Maarten Kamermans
- Netherlands Institute for Neuroscience (NIN), Royal Dutch Academy of Art & Science (KNAW), Amsterdam, The Netherlands
- Department of Biomedical Physics and Biomedical Photonics, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Chris I. De Zeeuw
- Netherlands Institute for Neuroscience (NIN), Royal Dutch Academy of Art & Science (KNAW), Amsterdam, The Netherlands
- Department of Neuroscience, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Caroline C. W. Klaver
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Ophthalmology, Radboud University Medical Center, Nijmegen, The Netherlands
- Institute of Molecular and Clinical Ophthalmology, Basel, Switzerland
| | - Beerend H. J. Winkelman
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
- Netherlands Institute for Neuroscience (NIN), Royal Dutch Academy of Art & Science (KNAW), Amsterdam, The Netherlands
- Department of Neuroscience, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Adriana I. Iglesias
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, The Netherlands
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Sun XH, Xiao HM, Zhang M, Lin ZY, Yang Y, Chen R, Liu PQ, Huang KP, Huang HQ. USP9X deubiquitinates connexin43 to prevent high glucose-induced epithelial-to-mesenchymal transition in NRK-52E cells. Biochem Pharmacol 2021; 188:114562. [PMID: 33857489 DOI: 10.1016/j.bcp.2021.114562] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 04/08/2021] [Accepted: 04/08/2021] [Indexed: 01/24/2023]
Abstract
Epithelial-to-mesenchymal transition (EMT) plays an important role in diabetic nephropathy (DN). Ubiquitin-specific protease 9X (USP9X/FAM) is closely linked to TGF-β and fibrosis signaling pathway. However, it remains unknown whether USP9X is involved in the process of EMT in DN. Our previous study has shown that connexin 43 (Cx43) activation attenuated the development of diabetic renal tubulointerstitial fibrosis (RIF). Here, we showed that USP9X is a novel negative regulator of EMT and the potential mechanism is related to the deubiquitination and degradation of Cx43. To explore the potential regulatory mechanism of USP9X, the expression and activity of USP9X were studied by CRISPR/Cas9-based synergistic activation mediator (SAM) system, short hairpin RNAs, and selective inhibitor. The following findings were observed: (1) Expression of USP9X was down-regulated in the kidney tissue of db/db diabetic mice; (2) overexpression of USP9X suppressed high glucose (HG)-induced expressions of EMT markers and extra cellular matrix (ECM) in NRK-52E cells; (3) depletion of USP9X further aggravated EMT process and ECM production in NRK-52E cells; (4) USP9X deubiquitinated Cx43 and suppressed its degradation to regulate EMT process; (5) USP9X deubiquitinated Cx43 by directly binding to the C-terminal Tyr286 of Cx43. The current study determined the protective role of USP9X in the process of EMT and the molecular mechanism clarified that the protective effects of USP9X on DN were associated with the deubiquitination of Cx43.
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Affiliation(s)
- Xiao-Hong Sun
- Laboratory of Pharmacology & Toxicology, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Hai-Ming Xiao
- Laboratory of Pharmacology & Toxicology, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Meng Zhang
- Laboratory of Pharmacology & Toxicology, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Ze-Yuan Lin
- Laboratory of Pharmacology & Toxicology, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Yan Yang
- Laboratory of Pharmacology & Toxicology, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Rui Chen
- Laboratory of Pharmacology & Toxicology, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Pei-Qing Liu
- Laboratory of Pharmacology & Toxicology, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Kai-Peng Huang
- Phase I Clinical Trial Center, Guangzhou Eighth People's Hospital, Guangzhou Medical University, Guangzhou 510060, China.
| | - He-Qing Huang
- Laboratory of Pharmacology & Toxicology, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China; Guangdong Provincial Key Laboratory of New Drug Design and Evaluation, Sun Yat-sen University, Guangzhou 510006, China.
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6
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Connexins-Therapeutic Targets in Cancers. Int J Mol Sci 2020; 21:ijms21239119. [PMID: 33266154 PMCID: PMC7730856 DOI: 10.3390/ijms21239119] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 11/24/2020] [Accepted: 11/26/2020] [Indexed: 12/11/2022] Open
Abstract
Connexins (Cx) are members of a protein family that forms intercellular channels localised in gap junction (GJ) plaques and single transmembrane channels called hemichannels. They participate in intercellular communication or communication between the intracellular and extracellular environments. Connexins affect cell homeostasis, growth and differentiation by enabling the exchange of metabolites or by interfering with various signalling pathways. Alterations in the functionality and the expression of connexins have been linked to the occurrence of many diseases. Connexins have been already linked to cancers, cardiac and brain disorders, chronic lung and kidney conditions and wound healing processes. Connexins have been shown either to suppress cancer tumour growth or to increase tumorigenicity by promoting cancer cell growth, migration and invasiveness. A better understanding of the complexity of cancer biology related to connexins and intercellular communication could result in the design of novel therapeutic strategies. The modulation of connexin expression may be an effective therapeutic approach in some types of cancers. Therefore, one important challenge is the search for mechanisms and new drugs, selectively modulating the expression of various connexin isoforms. We performed a systematic literature search up to February 2020 in the electronic databases PubMed and EMBASE. Our search terms were as follows: connexins, hemichannels, cancer and cancer treatment. This review aims to provide information about the role of connexins and gap junctions in cancer, as well as to discuss possible therapeutic options that are currently being studied.
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7
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Gap Junctions between Endothelial Cells Are Disrupted by Circulating Extracellular Vesicles from Sickle Cell Patients with Acute Chest Syndrome. Int J Mol Sci 2020; 21:ijms21238884. [PMID: 33255173 PMCID: PMC7727676 DOI: 10.3390/ijms21238884] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Revised: 11/13/2020] [Accepted: 11/20/2020] [Indexed: 12/21/2022] Open
Abstract
Intercellular junctions maintain the integrity of the endothelium. We previously found that the adherens and tight junctions between endothelial cells are disrupted by plasma extracellular vesicles from patients with sickle cell disease (especially those with Acute Chest Syndrome). In the current study, we evaluated the effects of these vesicles on endothelial gap junctions. The vesicles from sickle cell patients (isolated during episodes of Acute Chest Syndrome) disrupted gap junction structures earlier and more severely than the other classes of intercellular junctions (as detected by immunofluorescence). These vesicles were much more potent than those isolated at baseline from the same subject. The treatment of endothelial cells with these vesicles led to reduced levels of connexin43 mRNA and protein. These vesicles severely reduced intercellular communication (transfer of microinjected Neurobiotin). Our data suggest a hierarchy of progressive disruption of different intercellular connections between endothelial cells by circulating extracellular vesicles that may contribute to the pathophysiology of the endothelial disturbances in sickle cell disease.
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8
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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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9
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McCutcheon S, Stout RF, Spray DC. The dynamic Nexus: gap junctions control protein localization and mobility in distinct and surprising ways. Sci Rep 2020; 10:17011. [PMID: 33046777 PMCID: PMC7550573 DOI: 10.1038/s41598-020-73892-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Accepted: 09/23/2020] [Indexed: 12/24/2022] Open
Abstract
Gap junction (GJ) channels permit molecules, such as ions, metabolites and second messengers, to transfer between cells. Their function is critical for numerous cellular interactions, providing exchange of metabolites, signaling molecules, and ionic currents. GJ channels are composed of Connexin (Cx) hexamers paired across extracellular space and typically form large rafts of clustered channels, called plaques, at cell appositions. Cxs together with molecules that interact with GJ channels make up a supramolecular structure known as the GJ Nexus. While the stability of connexin localization in GJ plaques has been studied, mobility of other Nexus components has yet to be addressed. Colocalization analysis of several nexus components and other membrane proteins reveal that certain molecules are excluded from the GJ plaque (Aquaporin 4, EAAT2b), while others are quite penetrant (lipophilic molecules, Cx30, ZO-1, Occludin). Fluorescence recovery after photobleaching of tagged Nexus-associated proteins showed that mobility in plaque domains is affected by mobility of the Cx proteins. These novel findings indicate that the GJ Nexus is a dynamic membrane organelle, with cytoplasmic and membrane-embedded proteins binding and diffusing according to distinct parameters.
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Affiliation(s)
- Sean McCutcheon
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, 1410 Pelham Parkway South, Bronx, NY, 10461, USA.
| | - Randy F Stout
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, 1410 Pelham Parkway South, Bronx, NY, 10461, USA.,Department of Biomedical Sciences, The New York Institute of Technology College of Osteopathic Medicine, 101 Northern Blvd., Old Westbury, NY, 11586, USA
| | - David C Spray
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, 1410 Pelham Parkway South, Bronx, NY, 10461, USA
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Liang Z, Wang X, Hao Y, Qiu L, Lou Y, Zhang Y, Ma D, Feng J. The Multifaceted Role of Astrocyte Connexin 43 in Ischemic Stroke Through Forming Hemichannels and Gap Junctions. Front Neurol 2020; 11:703. [PMID: 32849190 PMCID: PMC7411525 DOI: 10.3389/fneur.2020.00703] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Accepted: 06/09/2020] [Indexed: 12/13/2022] Open
Abstract
Ischemic stroke is a multi-factorial cerebrovascular disease with high worldwide morbidity and mortality. In the past few years, multiple studies have revealed the underlying mechanism of ischemia/reperfusion injury, including calcium overload, amino acid toxicity, oxidative stress, and inflammation. Connexin 43 (Cx43), the predominant connexin protein in astrocytes, has been recently proven to display non-substitutable roles in the pathology of ischemic stroke development and progression through forming gap junctions and hemichannels. Under normal conditions, astrocytic Cx43 could be found in hemichannels or in the coupling with other hemichannels on astrocytes, neurons, or oligodendrocytes to form the neuro-glial syncytium, which is involved in metabolites exchange between communicated cells, thus maintaining the homeostasis of the CNS environment. In ischemic stroke, the phosphorylation of Cx43 might cause the degradation of gap junctions and the opening of hemichannels, contributing to the release of inflammatory mediators. However, the remaining gap junctions could facilitate the exchange of protective and harmful metabolites between healthy and injured cells, protecting the injured cells to some extent or damaging the healthy cells depending on the balance of the exchange of protective and harmful metabolites. In this study, we review the changes in astrocytic Cx43 expression and distribution as well as the influence of these changes on the function of astrocytes and other cells in the CNS, providing new insight into the pathology of ischemic stroke injury; we also discuss the potential of astrocytic Cx43 as a target for the treatment of ischemic stroke.
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Affiliation(s)
- Zhen Liang
- Department of Neurology and Neuroscience Center, The First Hospital of Jilin University, Changchun, China
| | - Xu Wang
- Department of Neurology and Neuroscience Center, The First Hospital of Jilin University, Changchun, China
| | - Yulei Hao
- Department of Neurology and Neuroscience Center, The First Hospital of Jilin University, Changchun, China
| | - Lin Qiu
- Department of Neurology and Neuroscience Center, The First Hospital of Jilin University, Changchun, China
| | - Yingyue Lou
- Department of Plastic and Reconstructive Surgery, The First Hospital of Jilin University, Changchun, China
| | - Yaoting Zhang
- Department of Cardiology, The First Hospital of Jilin University, Changchun, China
| | - Di Ma
- Department of Neurology and Neuroscience Center, The First Hospital of Jilin University, Changchun, China
| | - Jiachun Feng
- Department of Neurology and Neuroscience Center, The First Hospital of Jilin University, Changchun, China
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Evidence of decreased gap junction coupling between astrocytes and oligodendrocytes in the anterior cingulate cortex of depressed suicides. Neuropsychopharmacology 2019; 44:2099-2111. [PMID: 31374562 PMCID: PMC6897926 DOI: 10.1038/s41386-019-0471-z] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Revised: 07/23/2019] [Accepted: 07/26/2019] [Indexed: 12/13/2022]
Abstract
Glial dysfunction is a major pathophysiological feature of mood disorders. While altered astrocyte (AS) and oligodendrocyte-lineage (OL) functions have been associated with depression, the crosstalk between these glial cell types has never been assessed in that context. AS are potent regulators of myelination, in part through gap junction (GJ) channels formed by the heterotypic coupling of AS-specific (Cx30 and Cx43) and OL-specific (Cx32 and Cx47) connexins. This study therefore aimed at addressing the integrity of AS/OL coupling in the anterior cingulate cortex (ACC) of depressed suicides. Using immunofluorescence and confocal imaging, we characterized the distribution of Cx30 and mapped its expression onto OL somas, myelinated axons, and brain vasculature in postmortem brain samples from depressed suicides (N = 48) and matched controls (N = 23). Differential gene expression of key components of the GJ nexus was also screened through RNA-sequencing previously generated by our group, and validated by quantitative real-time PCR. We show that Cx30 expression localized onto OL cells and myelinated fibers is decreased in deep cortical layers of the ACC in male-depressed suicides. This effect was associated with decreased expression of OL-specific connexins, as well as the downregulation of major connexin-interacting proteins essential for the scaffolding, trafficking, and function of GJs. These results provide a first evidence of impaired AS/OL GJ-mediated communication in the ACC of individuals with mood disorders. These changes in glial coupling are likely to have significant impact on brain function, and may contribute to the altered OL function previously reported in this brain region.
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12
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Dispelling myths about connexins, pannexins and P2X7 in hypoxic-ischemic central nervous system. Neurosci Lett 2019; 695:76-85. [PMID: 29195910 DOI: 10.1016/j.neulet.2017.11.044] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Revised: 10/07/2017] [Accepted: 11/21/2017] [Indexed: 01/17/2023]
Abstract
In membrane physiology, as in other fields, myths or speculations may be repeated so often and so widely that they are perceived as facts. To some extent, this has occurred with regard to gap junctions, hemichannels, pannexin channels and P2X7 (ionotropic receptors), especially concerning the interpretation of the individual role of these channels in hypoxic-ischemic CNS since these channels may be closed by the same pharmacological blockers. Significance of existing controversial data are highlighted and contradictory views from different groups are critically discussed herein.
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13
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The Role of Connexin-43 in the Inflammatory Process: A New Potential Therapy to Influence Keratitis. J Ophthalmol 2019; 2019:9312827. [PMID: 30805212 PMCID: PMC6360563 DOI: 10.1155/2019/9312827] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Revised: 11/12/2018] [Accepted: 11/19/2018] [Indexed: 12/22/2022] Open
Abstract
The studies outlined in this review highlight the relationship between inflammatory signaling molecules and connexin-43 (Cx43). Gap junction (GJ) channels and hemichannels (HCs) participate in the metabolic activity between intra- and extracellular space. Some ions and small molecules are exchanged from cell to cell or cell to extracellular space to affect the process of inflammation via GJ. We analyzed the effects of signaling molecules, such as innate immunity messengers, transcription factors, LPS, cytokine, inflammatory chemokines, and MMPs, on Cx43 expression during the inflammatory process. At the same time, we found that these signaling molecules play a critical role in the pathogenesis of keratitis. Thus, we assessed the function of Cx43 during inflammatory corneal disease. Corneal healing plays an essential role in the late stage of keratitis. We found that Cx43 is involved in wound healing. Studies have shown that the decrease of Cx43 can decrease the time of healing. We also report several Cx43 mimic peptides which can inhibit the activity of Cx43 Hc to mediate the releasing of adenosine triphosphate (ATP), which may in turn influence the inflammatory process.
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14
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Farnsworth NL, Walter R, Piscopio RA, Schleicher WE, Benninger RKP. Exendin-4 overcomes cytokine-induced decreases in gap junction coupling via protein kinase A and Epac2 in mouse and human islets. J Physiol 2019; 597:431-447. [PMID: 30412665 PMCID: PMC6332825 DOI: 10.1113/jp276106] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Accepted: 11/07/2018] [Indexed: 12/21/2022] Open
Abstract
KEY POINTS The pancreatic islets of Langerhans maintain glucose homeostasis through insulin secretion, where insulin secretion dynamics are regulated by intracellular Ca2+ signalling and electrical coupling of the insulin producing β-cells in the islet. We have previously shown that cytokines decrease β-cell coupling and that compounds which increase cAMP can increase coupling. In both mouse and human islets exendin-4, which increases cAMP, protected against cytokine-induced decreases in coupling and in mouse islets preserved glucose-stimulated calcium signalling by increasing connexin36 gap junction levels on the plasma membrane. Our data indicate that protein kinase A regulates β-cell coupling through a fast mechanism, such as channel gating or membrane organization, while Epac2 regulates slower mechanisms of regulation, such as gap junction turnover. Increases in β-cell coupling with exendin-4 may protect against cytokine-mediated β-cell death as well as preserve insulin secretion dynamics during the development of diabetes. ABSTRACT The pancreatic islets of Langerhans maintain glucose homeostasis. Insulin secretion from islet β-cells is driven by glucose metabolism, depolarization of the cell membrane and an influx of calcium, which initiates the release of insulin. Gap junctions composed of connexin36 (Cx36) electrically couple β-cells, regulating calcium signalling and insulin secretion dynamics. Cx36 coupling is decreased in pre-diabetic mice, suggesting a role for altered coupling in diabetes. Our previous work has shown that pro-inflammatory cytokines decrease Cx36 coupling and that compounds which increase cAMP can increase Cx36 coupling. The goal of this study was to determine if exendin-4, which increases cAMP, can protect against cytokine-induced decreases in Cx36 coupling and altered islet function. In both mouse and human islets, exendin-4 protected against cytokine-induced decreases in coupling and preserved glucose-stimulated calcium signalling. Exendin-4 also protected against protein kinase Cδ-mediated decreases in Cx36 coupling. Exendin-4 preserved coupling in mouse islets by preserving Cx36 levels on the plasma membrane. Exendin-4 regulated Cx36 coupling via both protein kinase A (PKA)- and Epac2-mediated mechanisms in cytokine-treated islets. In mouse islets, modulating Epac2 had a greater impact in mediating Cx36 coupling, while in human islets modulating PKA had a greater impact on Cx36 coupling. Our data indicate that PKA regulates Cx36 coupling through a fast mechanism, such as channel gating, while Epac2 regulates slower mechanisms of regulation, such as Cx36 turnover in the membrane. Increases in Cx36 coupling with exendin-4 may protect against cytokine-mediated β-cell dysfunction to insulin secretion dynamics during the development of diabetes.
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Affiliation(s)
- Nikki L. Farnsworth
- Barbara Davis Center for Childhood DiabetesUniversity of Colorado Anschutz Medical CampusAuroraCO80045USA
| | - Rachelle Walter
- Department of BioengineeringUniversity of Colorado Anschutz Medical CampusAuroraCO80045USA
| | - Robert A. Piscopio
- Department of BioengineeringUniversity of Colorado Anschutz Medical CampusAuroraCO80045USA
| | - Wolfgang E. Schleicher
- Department of BioengineeringUniversity of Colorado Anschutz Medical CampusAuroraCO80045USA
| | - Richard K. P. Benninger
- Barbara Davis Center for Childhood DiabetesUniversity of Colorado Anschutz Medical CampusAuroraCO80045USA
- Department of BioengineeringUniversity of Colorado Anschutz Medical CampusAuroraCO80045USA
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15
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Pelz L, Purfürst B, Rathjen FG. The cell adhesion molecule BT-IgSF is essential for a functional blood-testis barrier and male fertility in mice. J Biol Chem 2017; 292:21490-21503. [PMID: 29123028 DOI: 10.1074/jbc.ra117.000113] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Revised: 11/07/2017] [Indexed: 12/14/2022] Open
Abstract
The Ig-like cell adhesion molecule (IgCAM) BT-IgSF (brain- and testis-specific Ig superfamily protein) plays a major role in male fertility in mice. However, the molecular mechanism by which BT-IgSF supports fertility is unclear. Here, we found that it is localized in Sertoli cells at the blood-testis barrier (BTB) and at the apical ectoplasmic specialization. The absence of BT-IgSF in Sertoli cells in both global and conditional mouse mutants (i.e. AMHCre and Rosa26CreERT2 lines) resulted in male infertility, atrophic testes with vacuolation, azoospermia, and spermatogenesis arrest. Although transcripts of junctional proteins such as connexin43, ZO-1, occludin, and claudin11 were up-regulated in the absence of BT-IgSF, the functional integrity of the BTB was impaired, as revealed by injection of a BTB-impermeable component into the testes under in vivo conditions. Disruption of the BTB coincided with mislocalization of connexin43, which was present throughout the seminiferous epithelium and not restricted to the BTB as in wild-type tissues, suggesting impaired cell-cell communication in the BT-IgSF-KO mice. Because EM images revealed a normal BTB structure between Sertoli cells in the BT-IgSF-KO mice, we conclude that infertility in these mice is most likely caused by a functionally impaired BTB. In summary, our results indicate that BT-IgSF is expressed at the BTB and is required for male fertility by supporting the functional integrity of the BTB.
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Affiliation(s)
| | - Bettina Purfürst
- the Core Facility for Electron Microscopy, Max Delbrück Center for Molecular Medicine, Helmholtz Association, D-13092 Berlin, Germany
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16
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Majoul IV, Ernesti JS, Butkevich EV, Duden R. Drebrins and Connexins: A Biomedical Perspective. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1006:225-247. [DOI: 10.1007/978-4-431-56550-5_13] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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17
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Stout RF, Spray DC. Cysteine residues in the cytoplasmic carboxy terminus of connexins dictate gap junction plaque stability. Mol Biol Cell 2017; 28:2757-2764. [PMID: 28835376 PMCID: PMC5638580 DOI: 10.1091/mbc.e17-03-0206] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Revised: 07/21/2017] [Accepted: 08/14/2017] [Indexed: 01/01/2023] Open
Abstract
Cysteine residues within the cytoplasmic carboxyl-terminus of gap junction–forming proteins are required to stabilize gap junction plaque organization. The stability of gap junction plaque organization can be modified. Gap junction stability may provide a stable supramolecular platform for modulation of gap junction functions. Gap junctions are cellular contact sites composed of clustered connexin transmembrane proteins that act in dual capacities as channels for direct intercellular exchange of small molecules and as structural adhesion complexes known as gap junction nexuses. Depending on the connexin isoform, the cluster of channels (the gap junction plaque) can be stably or fluidly arranged. Here we used confocal microscopy and mutational analysis to identify the residues within the connexin proteins that determine gap junction plaque stability. We found that stability is altered by changing redox balance using a reducing agent—indicating gap junction nexus stability is modifiable. Stability of the arrangement of connexins is thought to regulate intercellular communication by establishing an ordered supramolecular platform. By identifying the residues that establish plaque stability, these studies lay the groundwork for exploration of mechanisms by which gap junction nexus stability modulates intercellular communication.
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Affiliation(s)
- Randy F Stout
- Department of Biomedical Sciences, New York Institute of Technology College of Osteopathic Medicine, Old Westbury, NY 11568-8000 .,Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461
| | - David C Spray
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461
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18
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Miller AC, Pereda AE. The electrical synapse: Molecular complexities at the gap and beyond. Dev Neurobiol 2017; 77:562-574. [PMID: 28170151 DOI: 10.1002/dneu.22484] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Revised: 01/04/2017] [Accepted: 01/04/2017] [Indexed: 12/21/2022]
Abstract
Gap junctions underlie electrical synaptic transmission between neurons. Generally perceived as simple intercellular channels, "electrical synapses" have demonstrated to be more functionally sophisticated and structurally complex than initially anticipated. Electrical synapses represent an assembly of multiple molecules, consisting of channels, adhesion complexes, scaffolds, regulatory machinery, and trafficking proteins, all required for their proper function and plasticity. Additionally, while electrical synapses are often viewed as strictly symmetric structures, emerging evidence has shown that some components forming electrical synapses can be differentially distributed at each side of the junction. We propose that the molecular complexity and asymmetric distribution of proteins at the electrical synapse provides rich potential for functional diversity. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 562-574, 2017.
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Affiliation(s)
- Adam C Miller
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon
| | - Alberto E Pereda
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York
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19
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Wong P, Tan T, Chan C, Laxton V, Chan YWF, Liu T, Wong WT, Tse G. The Role of Connexins in Wound Healing and Repair: Novel Therapeutic Approaches. Front Physiol 2016; 7:596. [PMID: 27999549 PMCID: PMC5138227 DOI: 10.3389/fphys.2016.00596] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Accepted: 11/16/2016] [Indexed: 12/26/2022] Open
Abstract
Gap junctions are intercellular proteins responsible for mediating both electrical and biochemical coupling through the exchange of ions, second messengers and small metabolites. They consist of two connexons, with (one) connexon supplied by each cell. A connexon is a hexamer of connexins and currently more than 20 connexin isoforms have been described in the literature thus far. Connexins have a short half-life, and therefore gap junction remodeling constantly occurs with a high turnover rate. Post-translational modification, such as phosphorylation, can modify their channel activities. In this article, the roles of connexins in wound healing and repair are reviewed. Novel strategies for modulating the function or expression of connexins, such as the use of antisense technology, synthetic mimetic peptides and bioactive materials for the treatment of skin wounds, diabetic and pressure ulcers as well as cornea wounds, are considered.
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Affiliation(s)
- Pui Wong
- Li Ka Shing Faculty of Medicine, School of Biomedical Sciences, University of Hong Kong Hong Kong, Hong Kong
| | - Teresa Tan
- Department of Surgery, Faculty of Medicine, Chinese University of Hong Kong Hong Kong, Hong Kong
| | - Catherine Chan
- Department of Surgery, Faculty of Medicine, Chinese University of Hong Kong Hong Kong, Hong Kong
| | - Victoria Laxton
- Intensive Care Department, Royal Brompton and Harefield NHS Foundation Trust London, UK
| | - Yin Wah Fiona Chan
- Department of Psychology, School of Biological Sciences, University of Cambridge Cambridge, UK
| | - Tong Liu
- Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular Disease, Department of Cardiology, Tianjin Institute of Cardiology, Second Hospital of Tianjin Medical University Tianjin, China
| | - Wing Tak Wong
- School of Life Sciences, Chinese University of Hong Kong Hong Kong, Hong Kong
| | - Gary Tse
- Department of Medicine and Therapeutics, Faculty of Medicine, Chinese University of Hong KongHong Kong, Hong Kong; Faculty of Medicine, Li Ka Shing Institute of Health Sciences, Chinese University of Hong KongHong Kong, Hong Kong
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Connexin43 Forms Supramolecular Complexes through Non-Overlapping Binding Sites for Drebrin, Tubulin, and ZO-1. PLoS One 2016; 11:e0157073. [PMID: 27280719 PMCID: PMC4900556 DOI: 10.1371/journal.pone.0157073] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2016] [Accepted: 05/24/2016] [Indexed: 02/06/2023] Open
Abstract
Gap junctions are membrane specialization domains identified in most tissue types where cells abut each other. The connexin channels found in these membrane domains are conduits for direct cell-to-cell transfer of ions and molecules. Connexin43 (Cx43) is the most ubiquitous connexin, with critical roles in heart, skin, and brain. Several studies described the interaction between Cx43 and the cytoskeleton involving the actin binding proteins Zonula occludens (ZO-1) and drebrin, as well as with tubulin. However, a direct interaction has not been identified between drebrin and Cx43. In this study, co-IP and NMR experiments were used to demonstrate that the Cx43-CT directly interacts with the highly conserved N-terminus region of drebrin. Three Cx43-CT areas were found to be involved in drebrin binding, with residues 264–275 being critical for the interaction. Mimicking Src phosphorylation within this region (Y265) significantly disrupted the interaction between the Cx43-CT and drebrin. Immunofluorescence showed colocalization of Cx43, drebrin, and F-actin in astrocytes and Vero cells membrane, indicating that Cx43 forms a submembrane protein complex with cytoskeletal and scaffolding proteins. The co-IP data suggest that Cx43 indirectly interacts with F-actin through drebrin. Along with the known interaction of the Cx43-CT with ZO-1 and tubulin, the data presented here for drebrin indicate non-overlapping and separated binding sites for all three proteins for which simultaneous binding could be important in regulating cytoskeleton rearrangements, especially for neuronal migration during brain development.
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21
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Connexins, E-cadherin, Claudin-7 and β-catenin transiently form junctional nexuses during the post-natal mammary gland development. Dev Biol 2016; 416:52-68. [PMID: 27291930 DOI: 10.1016/j.ydbio.2016.06.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2016] [Revised: 05/15/2016] [Accepted: 06/03/2016] [Indexed: 12/21/2022]
Abstract
Gap junctions are intercellular channels made of connexins (Cxs) that allow direct communication between adjacent cells. Modulation of Cxs has been associated with abnormal development and function of the mammary gland and breast cancer. However, the mechanisms underlying their expression during normal mammary gland are not yet known. Cxs interact with components of tight and adherens junctions. Thus, we hypothesized that the expression levels of Cxs vary during mammary gland development and are regulated through stage-dependent interactions with members of the tight and adherens junctions. Our specific objectives were to: 1) determine the expression of Cxs and tight and adherens junction proteins throughout development and 2) characterize Cxs interactions with components of tight and adherens junctions. Murine mammary glands were sampled at various developmental stages (pre-pubescent to post-weaning). RT-qPCR and western-blot analyses demonstrated differential expression patterns for all gap (Cx43, Cx32, Cx26, Cx30), tight (Claudin-1, -3, -4, -7) and adherens (β-catenin, E- and P-cadherins) junctions throughout development. Interestingly, co-immunoprecipitation demonstrated interactions between these different types of junctions. Cx30 interacted with Cx26 just at the late pregnancy stage. While Cx43 showed a persistent interaction with β-catenin from virginity to post-weaning, its interactions with E-cadherin and Claudin-7 were transient. Cx32 interacted with Cx26, E-cadherin and β-catenin during lactation. Immunofluorescence results confirmed the existence of a junctional nexus that remodeled during mammary gland development. Together, our results confirm that the expression levels of Cxs vary concomitantly and that Cxs form junctional nexuses with tight and adherens junctions, suggesting the existence of common regulatory pathways.
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Kinase programs spatiotemporally regulate gap junction assembly and disassembly: Effects on wound repair. Semin Cell Dev Biol 2015; 50:40-8. [PMID: 26706150 DOI: 10.1016/j.semcdb.2015.12.010] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 12/08/2015] [Indexed: 01/05/2023]
Abstract
Gap junctions are highly ordered plasma membrane domains that are constantly assembled, remodeled and turned over due to the short half-life of connexins, the integral membrane proteins that form gap junctions. Connexin 43 (Cx43), by far the most widely expressed connexin, is phosphorylated at multiple serine residues in the cytoplasmic, C-terminal region allowing for exquisite cellular control over gap junctional communication. This is evident during epidermal wounding where spatiotemporal changes in connexin expression occur as cells are instructed whether to die, proliferate or migrate to promote repair. Early gap junctional communication is required for initiation of keratinocyte migration, but accelerated Cx43 turnover is also critical for proper wound healing at later stages. These events are controlled via a "kinase program" where sequential phosphorylation of Cx43 leads to reductions in Cx43's half-life and significant depletion of gap junctions from the plasma membrane within several hours. The complex regulation of gap junction assembly and turnover affords several steps where intervention might speed wound healing.
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23
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Gago-Fuentes R, Fernández-Puente P, Megias D, Carpintero-Fernández P, Mateos J, Acea B, Fonseca E, Blanco FJ, Mayan MD. Proteomic Analysis of Connexin 43 Reveals Novel Interactors Related to Osteoarthritis. Mol Cell Proteomics 2015; 14:1831-45. [PMID: 25903580 DOI: 10.1074/mcp.m115.050211] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Indexed: 11/06/2022] Open
Abstract
We have previously reported that articular chondrocytes in tissue contain long cytoplasmic arms that physically connect two distant cells. Cell-to-cell communication occurs through connexin channels termed Gap Junction (GJ) channels, which achieve direct cellular communication by allowing the intercellular exchange of ions, small RNAs, nutrients, and second messengers. The Cx43 protein is overexpressed in several human diseases and inflammation processes and in articular cartilage from patients with osteoarthritis (OA). An increase in the level of Cx43 is known to alter gene expression, cell signaling, growth, and cell proliferation. The interaction of proteins with the C-terminal tail of connexin 43 (Cx43) directly modulates GJ-dependent and -independent functions. Here, we describe the isolation of Cx43 complexes using mild extraction conditions and immunoaffinity purification. Cx43 complexes were extracted from human primary articular chondrocytes isolated from healthy donors and patients with OA. The proteomic content of the native complexes was determined using LC-MS/MS, and protein associations with Cx43 were validated using Western blot and immunolocalization experiments. We identified >100 Cx43-associated proteins including previously uncharacterized proteins related to nucleolar functions, RNA transport, and translation. We also identified several proteins involved in human diseases, cartilage structure, and OA as novel functional Cx43 interactors, which emphasized the importance of Cx43 in the normal physiology and structural and functional integrity of chondrocytes and articular cartilage. Gene Ontology (GO) terms of the proteins identified in the OA samples showed an enrichment of Cx43-interactors related to cell adhesion, calmodulin binding, the nucleolus, and the cytoskeleton in OA samples compared with healthy samples. However, the mitochondrial proteins SOD2 and ATP5J2 were identified only in samples from healthy donors. The identification of Cx43 interactors will provide clues to the functions of Cx43 in human cells and its roles in the development of several diseases, including OA.
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Affiliation(s)
- Raquel Gago-Fuentes
- From the ‡CellCOM Research Group. Instituto de Investigación Biomédica A Coruña (INIBIC), XXIAC, University of A Coruña. Xubias de Arriba 84, 15006 A Coruña, Spain
| | - Patricia Fernández-Puente
- §Rheumatology Division, ProteoRed/ISCIII, Proteomics Group, Instituto de Investigación Biomédica A Coruña (INIBIC), XXIAC. University of A Coruña. Xubias de Arriba 84, 15006 A Coruña, Spain; ¶Rheumatology Division, CIBER-BBN/ISCIII, Instituto de Investigación Biomédica A Coruña (INIBIC), XXIAC. University of A Coruña. Xubias de Arriba 84, 15006 A Coruña, Spain
| | - Diego Megias
- ‖Confocal Microscopy Core Unit. Centro Nacional de Investigaciones Oncológicas (CNIO), 28029, Madrid, Spain
| | - Paula Carpintero-Fernández
- From the ‡CellCOM Research Group. Instituto de Investigación Biomédica A Coruña (INIBIC), XXIAC, University of A Coruña. Xubias de Arriba 84, 15006 A Coruña, Spain
| | - Jesus Mateos
- §Rheumatology Division, ProteoRed/ISCIII, Proteomics Group, Instituto de Investigación Biomédica A Coruña (INIBIC), XXIAC. University of A Coruña. Xubias de Arriba 84, 15006 A Coruña, Spain; ¶Rheumatology Division, CIBER-BBN/ISCIII, Instituto de Investigación Biomédica A Coruña (INIBIC), XXIAC. University of A Coruña. Xubias de Arriba 84, 15006 A Coruña, Spain
| | - Benigno Acea
- From the ‡CellCOM Research Group. Instituto de Investigación Biomédica A Coruña (INIBIC), XXIAC, University of A Coruña. Xubias de Arriba 84, 15006 A Coruña, Spain
| | - Eduardo Fonseca
- From the ‡CellCOM Research Group. Instituto de Investigación Biomédica A Coruña (INIBIC), XXIAC, University of A Coruña. Xubias de Arriba 84, 15006 A Coruña, Spain
| | - Francisco Javier Blanco
- §Rheumatology Division, ProteoRed/ISCIII, Proteomics Group, Instituto de Investigación Biomédica A Coruña (INIBIC), XXIAC. University of A Coruña. Xubias de Arriba 84, 15006 A Coruña, Spain; ¶Rheumatology Division, CIBER-BBN/ISCIII, Instituto de Investigación Biomédica A Coruña (INIBIC), XXIAC. University of A Coruña. Xubias de Arriba 84, 15006 A Coruña, Spain
| | - Maria Dolores Mayan
- From the ‡CellCOM Research Group. Instituto de Investigación Biomédica A Coruña (INIBIC), XXIAC, University of A Coruña. Xubias de Arriba 84, 15006 A Coruña, Spain;
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Molica F, Meens MJP, Morel S, Kwak BR. Mutations in cardiovascular connexin genes. Biol Cell 2014; 106:269-93. [PMID: 24966059 DOI: 10.1111/boc.201400038] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Accepted: 06/20/2014] [Indexed: 12/25/2022]
Abstract
Connexins (Cxs) form a family of transmembrane proteins comprising 21 members in humans. Cxs differ in their expression patterns, biophysical properties and ability to combine into homomeric or heteromeric gap junction channels between neighbouring cells. The permeation of ions and small metabolites through gap junction channels or hemichannels confers a crucial role to these proteins in intercellular communication and in maintaining tissue homeostasis. Among others, Cx37, Cx40, Cx43, Cx45 and Cx47 are found in heart, blood and lymphatic vessels. Mutations or polymorphisms in the genes coding for these Cxs have not only been implicated in cardiovascular pathologies but also in a variety of other disorders. While mutations in Cx43 are mostly linked to oculodentodigital dysplasia, Cx47 mutations are associated with Pelizaeus-Merzbacher-like disease and lymphoedema. Cx40 mutations are principally linked to atrial fibrillation. Mutations in Cx37 have not yet been described, but polymorphisms in the Cx37 gene have been implicated in the development of arterial disease. This review addresses current knowledge on gene mutations in cardiovascular Cxs systematically and links them to alterations in channel properties and disease.
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Affiliation(s)
- Filippo Molica
- Department of Pathology and Immunology, Faculty of Medicine, University of Geneva, Geneva, Switzerland; Department of Medical Specializations - Cardiology, Faculty of Medicine, University of Geneva, Geneva, Switzerland
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25
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O'Carroll SJ, Becker DL, Davidson JO, Gunn AJ, Nicholson LFB, Green CR. The use of connexin-based therapeutic approaches to target inflammatory diseases. Methods Mol Biol 2014; 1037:519-46. [PMID: 24029957 DOI: 10.1007/978-1-62703-505-7_31] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Alterations in Connexin43 (Cx43) expression levels have been shown to play a role in inflammatory processes including skin wounding and neuroinflammation. Cx43 protein levels increase following a skin wound and can inhibit wound healing. Increased Cx43 has been observed following stroke, epilepsy, ischemia, optic nerve damage, and spinal cord injury with gap junctional communication and hemichannel opening leading to increased secondary damage via the inflammatory response. Connexin43 modulation has been identified as a potential target for protection and repair in neuroinflammation and skin wound repair. This review describes the use of a Cx43 specific antisense oligonucleotide (Cx43 AsODN) and peptide mimetics of the connexin extracellular loop domain to modulate Cx43 expression and/or function in inflammatory disorders of the skin and central nervous system. An overview of the role of connexin43 in inflammatory conditions, how antisense and peptide have allowed us to elucidate the role of Cx43 in these diseases, create models of diseases to test interventions and their potential for use clinically or in current clinical trials is presented. Antisense oligonucleotides are applied topically and have been used to improve wound healing following skin injury. They have also been used to develop ex vivo models of neuroinflammatory diseases that will allow testing of intervention strategies. The connexin mimetic peptides have shown potential in a number of neuroinflammatory disorders in ex vivo models as well as in vivo when delivered directly to the injury site or when delivered systemically.
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Affiliation(s)
- Simon J O'Carroll
- Department of Anatomy with Radiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
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26
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Morel S. Multiple roles of connexins in atherosclerosis- and restenosis-induced vascular remodelling. J Vasc Res 2014; 51:149-61. [PMID: 24853725 DOI: 10.1159/000362122] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Accepted: 03/01/2014] [Indexed: 12/19/2022] Open
Abstract
Endothelial dysfunction is the initial step in atherosclerotic plaque development in large- and medium-sized arteries. This progressive disease, which starts during childhood, is characterized by the accumulation of lipids, macrophages, neutrophils, T lymphocytes and smooth muscle cells in the intima of the vessels. Erosion and rupture of the atherosclerotic plaque may induce myocardial infarction and cerebrovascular accidents, which are responsible for a large percentage of sudden deaths. The most common treatment for atherosclerosis is angioplasty and stent implantation, but these surgical interventions favour a vascular reaction called restenosis and the associated de-endothelialization increases the risk of thrombosis. This review provides an overview of the role of connexins, a large family of transmembrane proteins, in vascular remodelling associated with atherosclerosis and restenosis. The connexins expressed in the vascular wall are Cx37, Cx40, Cx43 and Cx45; their expressions vary with vascular territory and species. Connexins form hemichannels or gap junction channels, allowing the exchange of ions and small metabolites between the cytosol and extracellular space or between neighbouring cells, respectively. Connexins have important roles in vascular physiology; they support radial and longitudinal cell-to-cell communication in the vascular wall, and significant changes in their expression patterns have been described during atherosclerosis and restenosis.
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Affiliation(s)
- Sandrine Morel
- Department of Pathology and Immunology, Faculty of Medicine, University of Geneva, Geneva, Switzerland
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27
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A new angle on blood-CNS interfaces: A role for connexins? FEBS Lett 2014; 588:1259-70. [DOI: 10.1016/j.febslet.2014.02.060] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Revised: 02/27/2014] [Accepted: 02/28/2014] [Indexed: 12/12/2022]
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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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29
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Solan JL, Lampe PD. Specific Cx43 phosphorylation events regulate gap junction turnover in vivo. FEBS Lett 2014; 588:1423-9. [PMID: 24508467 DOI: 10.1016/j.febslet.2014.01.049] [Citation(s) in RCA: 188] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Revised: 01/28/2014] [Accepted: 01/28/2014] [Indexed: 10/25/2022]
Abstract
Gap junctions, composed of proteins from the connexin gene family, are highly dynamic structures that are regulated by kinase-mediated signaling pathways and interactions with other proteins. Phosphorylation of Connexin43 (Cx43) at different sites controls gap junction assembly, gap junction size and gap junction turnover. Here we present a model describing how Akt, mitogen activated protein kinase (MAPK) and src kinase coordinate to regulate rapid turnover of gap junctions. Specifically, Akt phosphorylates Cx43 at S373 eliminating interaction with zona occludens-1 (ZO-1) allowing gap junctions to enlarge. Then MAPK and src phosphorylate Cx43 to initiate turnover. We integrate published data with new data to test and refine this model. Finally, we propose that differential coordination of kinase activation and Cx43 phosphorylation controls the specific routes of disassembly, e.g., annular junction formation or gap junctions can potentially "unzip" and be internalized/endocytosed into the cell that produced each connexin.
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Affiliation(s)
- Joell L Solan
- Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, United States
| | - Paul D Lampe
- Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, United States.
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30
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Moore K, Ghatnekar G, Gourdie RG, Potts JD. Impact of the controlled release of a connexin 43 peptide on corneal wound closure in an STZ model of type I diabetes. PLoS One 2014; 9:e86570. [PMID: 24466155 PMCID: PMC3900565 DOI: 10.1371/journal.pone.0086570] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Accepted: 12/12/2013] [Indexed: 12/20/2022] Open
Abstract
The alpha-carboxy terminus 1 (αCT1) peptide is a synthetically produced mimetic modified from the DDLEI C-terminus sequence of connexin 43 (Cx43). Previous research using various wound healing models have found promising therapeutic effects when applying the drug, resulting in increased wound healing rates and reduced scarring. Previous data suggested a rapid metabolism rate in vitro, creating an interest in long term release. Using a streptozotocin (STZ) type I diabetic rat model with a surgically induced corneal injury, we delivered αCT1 both directly, in a pluronic gel solution, and in a sustained system, using polymeric alginate-poly-l-ornithine (A-PLO) microcapsules (MC). Fluorescent staining of wound area over a 5 day period indicated a significant increase in wound closure rates for both αCT1 and αCT1 MC treated groups, withαCT1 MC groups showing the most rapid wound closure overall. Analysis of inflammatory reaction to the treatment groups indicated significantly lower levels of both Interferon Inducible T-Cell Alpha Chemoattractant (ITAC) and Tumor Necrosis Factor Alpha (TNFα) markers using confocal quantification and ELISA assays. Additional analysis examining genes selected from the EMT pathway using RT-PCR and Western blotting suggested αCT1 modification of Transforming Growth Factor Beta 2 (TGFβ2), Keratin 8 (Krt8), Estrogen Receptor 1 (Esr1), and Glucose Transporter 4 (Glut4) over a 14 day period. Combined, this data indicated a possible suppression of the inflammatory response by αCT1, leading to increased wound healing rates.
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Affiliation(s)
- Keith Moore
- University of South Carolina School of Medicine, Columbia, South Carolina, United States of America
- * E-mail:
| | - Gautam Ghatnekar
- FirstString Research Inc., Mount Pleasant, South Carolina, United States of America
- Medical University of South Carolina, Charleston, South Carolina, United States of America
| | - Robert G. Gourdie
- Virginia Polytechnic and State University Carilion, Roanoke, Virginia, United States of America
| | - Jay D. Potts
- University of South Carolina School of Medicine, Columbia, South Carolina, United States of America
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31
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Nielsen MS, Axelsen LN, Sorgen PL, Verma V, Delmar M, Holstein-Rathlou NH. Gap junctions. Compr Physiol 2013; 2:1981-2035. [PMID: 23723031 DOI: 10.1002/cphy.c110051] [Citation(s) in RCA: 298] [Impact Index Per Article: 27.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Gap junctions are essential to the function of multicellular animals, which require a high degree of coordination between cells. In vertebrates, gap junctions comprise connexins and currently 21 connexins are known in humans. The functions of gap junctions are highly diverse and include exchange of metabolites and electrical signals between cells, as well as functions, which are apparently unrelated to intercellular communication. Given the diversity of gap junction physiology, regulation of gap junction activity is complex. The structure of the various connexins is known to some extent; and structural rearrangements and intramolecular interactions are important for regulation of channel function. Intercellular coupling is further regulated by the number and activity of channels present in gap junctional plaques. The number of connexins in cell-cell channels is regulated by controlling transcription, translation, trafficking, and degradation; and all of these processes are under strict control. Once in the membrane, channel activity is determined by the conductive properties of the connexin involved, which can be regulated by voltage and chemical gating, as well as a large number of posttranslational modifications. The aim of the present article is to review our current knowledge on the structure, regulation, function, and pharmacology of gap junctions. This will be supported by examples of how different connexins and their regulation act in concert to achieve appropriate physiological control, and how disturbances of connexin function can lead to disease.
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Affiliation(s)
- Morten Schak Nielsen
- Department of Biomedical Sciences and The Danish National Research Foundation Centre for Cardiac Arrhythmia, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
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32
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Hsiao PJ, Jao JC, Tsai JL, Chang WT, Jeng KS, Kuo KK. Inorganic arsenic trioxide induces gap junction loss in association with the downregulation of connexin43 and E-cadherin in rat hepatic "stem-like" cells. Kaohsiung J Med Sci 2013; 30:57-67. [PMID: 24444534 DOI: 10.1016/j.kjms.2013.10.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Accepted: 07/01/2013] [Indexed: 11/26/2022] Open
Abstract
Chronic exposure to inorganic arsenic trioxide causes tumors of the skin, urinary bladder, lung, and liver. Several cancer initiators and promoters have been shown to alter cell-cell signaling by interference with gap junction intercellular communication (GJIC) and/or modulation of cell adhesion molecules, such as connexin43 (Cx43), E-cadherin, and β-catenin. The aim of this study was to determine whether the disruption of cell-cell interactions occurs in liver epithelial cells after exposure to arsenic trioxide. WB-F344 cells were treated with arsenic trioxide (6.25-50 μM) for up to 8 hours, and gap junction function was analyzed using the scrape-load/dye transfer assay. In addition, the changes in mRNA and protein levels of Cx43, E-cadherin, and β-catenin were determined. A significant dose- and time-dependent decrease in GJIC was observed when WB-F344 cells were exposed to arsenic trioxide (p < 0.05). Consistent with the inhibition of GJIC, cells' exposure to arsenic trioxide resulted in dose- and time-dependent decreases in Cx43 and E-cadherin mRNA expression and protein levels. However, arsenic trioxide did not alter the mRNA or protein levels of β-catenin. In an immunofluorescence study, nuclei were heavily stained with anti-β-catenin antibody, indicating significant nuclear translocation. In this study, we also demonstrated that arsenic trioxide-induced GJIC loss was a reversible process. Taken together, these data support the hypothesis that disruption of cell-cell communication may contribute to the tumor-promoting effect of inorganic arsenic trioxide.
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Affiliation(s)
- Pi-Jung Hsiao
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan
| | - Jo-Chi Jao
- College of Health Science, Kaohsiung Medical University, Department of Medical Imaging and Radiological Sciences, Kaohsiung, Taiwan
| | - Jin-Lian Tsai
- Graduate Institute of Occupational Safety, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Wen-Tsan Chang
- Division of Hepatobiliopancreatic Surgery, Department of Surgery, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan
| | - Kuo-Shyang Jeng
- Department of Surgery, Far Eastern Memorial Hospital, Taipei, Taiwan
| | - Kung-Kai Kuo
- Division of Hepatobiliopancreatic Surgery, Department of Surgery, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.
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33
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Boucherie S, Decaens C, Verbavatz JM, Grosse B, Erard M, Merola F, Cassio D, Combettes L. Cadmium disorganises the scaffolding of gap and tight junction proteins in the hepatic cell line WIF B9. Biol Cell 2013; 105:561-75. [DOI: 10.1111/boc.201200092] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Accepted: 10/01/2013] [Indexed: 01/05/2023]
Affiliation(s)
- Sylviane Boucherie
- INSERM U 757; Orsay F-91405 France
- Université Paris-sud; Orsay F-91405 France
| | - Catherine Decaens
- INSERM U 757; Orsay F-91405 France
- Université Paris-sud; Orsay F-91405 France
| | - Jean-Marc Verbavatz
- CEA Saclay, Laboratoire du trafic membranaire; Gif-sur-Yvette F-91191 France
| | - Brigitte Grosse
- INSERM U 757; Orsay F-91405 France
- Université Paris-sud; Orsay F-91405 France
| | - Marie Erard
- Laboratoire de Chimie Physique; Université Paris-sud; Orsay F-91405 France
- CNRS UMR 8000; Orsay F-91405 France
| | - Fabienne Merola
- Laboratoire de Chimie Physique; Université Paris-sud; Orsay F-91405 France
- CNRS UMR 8000; Orsay F-91405 France
| | - Doris Cassio
- INSERM U 757; Orsay F-91405 France
- Université Paris-sud; Orsay F-91405 France
| | - Laurent Combettes
- INSERM U 757; Orsay F-91405 France
- Université Paris-sud; Orsay F-91405 France
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34
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A synthetic connexin 43 mimetic peptide augments corneal wound healing. Exp Eye Res 2013; 115:178-88. [PMID: 23876491 DOI: 10.1016/j.exer.2013.07.001] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Revised: 06/24/2013] [Accepted: 07/01/2013] [Indexed: 01/23/2023]
Abstract
The ability to safely and quickly close wounds and lacerations is an area of need in regenerative medicine, with implications toward healing a wide range of tissues and wounds. Using an in vivo corneal injury model, our study applied a newly developed peptide capable of promotion of wound healing and epithelial regeneration. The alpha-carboxy terminus 1 (αCT1) peptide is a 25 amino acid peptide from the C-terminus of connexin 43 (Cx43), modified to promote cellular uptake. Previous studies applying αCT1 to excisional skin wounds in porcine models produced tissues having an overall reduced level of scar tissue and decreased healing time. Rapid metabolism of αCT1 in previous work led to the investigation of extended release on wound healing rate used in this study. Here we delivered αCT1 both directly, in a concentrated pluronic solution, and in a sustained system, using polymeric alginate-poly-l-ornithine (A-PLO) microcapsules. Cell toxicity analysis showed minimal cell-loss with microcapsule treatment. Measurement of wound healing using histology and fluorescence microscopy indicated significant reduction in healing time of αCT1 microcapsule treated rat corneas compared with controls (88% vs. 38%). RT-PCR analysis showed an initial up regulation followed by down regulation of the gene keratin-19 (Krt19). Zonula occludens 1 (ZO-1) showed an opposite down regulation followed by an up regulation whereas Cx43 showed a biphasic response. Inflammatory indexes demonstrated a reduction in the inflammation of corneas treated with αCT1 microcapsules when compared with pluronic gel vehicle. These results suggest αCT1, when applied in a sustained release system, acts as a beneficial wound healing treatment.
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35
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Rehm K, Panzer L, van Vliet V, Genot E, Linder S. Drebrin preserves endothelial integrity by stabilizing nectin at adherens junctions. J Cell Sci 2013; 126:3756-69. [DOI: 10.1242/jcs.129437] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Regulation of cell-cell contacts is essential for integrity of the vascular endothelium. Here, a critical role of the F-actin binding protein drebrin in maintaining endothelial integrity is revealed under conditions mimicking vascular flow. Drebrin knockdown leads to weakening of cell-cell contacts, characterized by loss of nectin from adherens junctions and its subsequent lysosomal degradation. Immunoprecipitation, FRAP and mitochondrial retargeting experiments show that nectin stabilization occurs through a chain of interactions: drebrin binding to F-actin, interaction of drebrin and afadin through their polyproline and PR1-2 regions, and recruitment of nectin through afadin's PDZ region. Key elements are drebrin's modules that confer binding to afadin and F-actin. Evidence is provided by constructs containing afadin's PDZ region coupled to drebrin's F-actin binding region or to lifeact, which restore junctional nectin under knockdown of drebrin or of both drebrin and afadin. Drebrin, containing binding sites for both afadin and F-actin, is thus uniquely equipped to stabilize nectin at endothelial junctions and to preserve endothelial integrity under vascular flow.
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36
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Kronengold J, Srinivas M, Verselis VK. The N-terminal half of the connexin protein contains the core elements of the pore and voltage gates. J Membr Biol 2012; 245:453-63. [PMID: 22825713 PMCID: PMC3735448 DOI: 10.1007/s00232-012-9457-z] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2012] [Accepted: 06/20/2012] [Indexed: 11/21/2022]
Abstract
Connexins form channels with large aqueous pores that mediate fluxes of inorganic ions and biological signaling molecules. Studies aimed at identifying the connexin pore now include a crystal structure that provides details of putative pore-lining residues that need to be verified using independent biophysical approaches. Here we extended our initial cysteine-scanning studies of the TM1/E1 region of Cx46 hemichannels to include TM2 and TM3 transmembrane segments. No evidence of reactivity was observed in either TM2 or TM3 probed with small or large thiol-modifying reagents. Several identified pore residues in E1 of Cx46 have been verified in different Cx isoforms. Use of variety of thiol reagents indicates that the connexin hemichannel pore is large and flexible enough, at least in the extracellular part of the pore funnel, to accommodate uncommonly large side chains. We also find that that gating characteristics are largely determined by the same domains that constitute the pore. These data indicate that biophysical and structural studies are converging towards a view that the N-terminal half of the Cx protein contains the principal components of the pore and gating elements, with NT, TM1 and E1 forming the pore funnel.
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Affiliation(s)
- Jack Kronengold
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520, USA
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37
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Gap junction proteins on the move: connexins, the cytoskeleton and migration. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1828:94-108. [PMID: 22613178 DOI: 10.1016/j.bbamem.2012.05.014] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Revised: 04/25/2012] [Accepted: 05/04/2012] [Indexed: 01/08/2023]
Abstract
Connexin43 (Cx43) has roles in cell-cell communication as well as channel independent roles in regulating motility and migration. Loss of function approaches to decrease Cx43 protein levels in neural cells result in reduced migration of neurons during cortical development in mice and impaired glioma tumor cell migration. In other cell types, correlations between Cx43 expression and cell morphology, adhesion, motility and migration have been noted. In this review we will discuss the common themes that have been revealed by a detailed comparison of the published results of neuronal cells with that of other cell types. In brief, these comparisons clearly show differences in the stability and directionality of protrusions, polarity of movement, and migration, depending on whether a) residual Cx43 levels remain after siRNA or shRNA knockdown, b) Cx43 protein levels are not detectable as in cells from Cx43(-/-) knockout mice or in cells that normally have no endogenous Cx43 expression, c) gain-of-function approaches are used to express Cx43 in cells that have no endogenous Cx43 and, d) Cx43 is over-expressed in cells that already have low endogenous Cx43 protein levels. What is clear from our comparisons is that Cx43 expression influences the adhesiveness of cells and the directionality of cellular processes. These observations are discussed in light of the ability of cells to rearrange their cytoskeleton and move in an organized manner. This article is part of a Special Issue entitled: The Communicating junctions, roles and dysfunctions.
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38
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Kaufmann S, Weiss IM, Eckstein V, Tanaka M. Functional expression of Ca²⁺ dependent mammalian transmembrane gap junction protein Cx43 in slime mold Dictyostelium discoideum. Biochem Biophys Res Commun 2012; 419:165-9. [PMID: 22330805 DOI: 10.1016/j.bbrc.2012.01.126] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Accepted: 01/26/2012] [Indexed: 11/16/2022]
Abstract
In this paper, we expressed murine gap junction protein Cx43 in Dictyostelium discoideum by introducing the specific vector pDXA. In the first step, the successful expression of Cx43 and Cx43-eGFP was verified by (a) Western blot (anti-Cx43, anti-GFP), (b) fluorescence microscopy (eGFP-Cx43 co-expression, Cx43 immunostaining), and (c) flow cytometry analysis (eGFP-Cx43 co-expression). Although the fluorescence signals from cells expressing Cx43-eGFP detected by fluorescence microscopy seem relatively low, analysis by flow cytometry demonstrated that more than 60% of cells expressed Cx43-eGFP. In order to evaluate the function of expressed Cx43 in D. discoideum, we examined the hemi-channel function of Cx43. In this series of experiments, the passive uptake of carboxyfluorescein was monitored using flow cytometric analysis. A significant number of the transfected cells showed a prominent dye uptake in the absence of Ca(2+). The dye uptake by transfected cells in the presence of Ca(2+) was even lower than the non-specific dye uptake by non-transformed Ax3 orf+ cells, confirming that Cx43 expressed in D. discoideum retains its Ca(2+)-dependent, specific gating function. The expression of gap junction proteins expressed in slime molds opens a possibility to the biological significance of intercellular communications in development and maintenance of multicellular organisms.
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Affiliation(s)
- Stefan Kaufmann
- Physical Chemistry of Biosystems, Institute of Physical Chemistry, University of Heidelberg, D69120 Heidelberg, Germany.
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Abstract
Cell-to-cell interactions via gap junctional communication and connexon hemichannels are involved in the pathogenesis of diabetes. Gap junctions are highly specialized transmembrane structures that are formed by connexon hemichannels, which are further assembled from proteins called “connexins.” In this paper, we discuss current knowledge about connexins in diabetes. We also discuss mechanisms of connexin influence and the role of individual connexins in various tissues and how these are affected in diabetes. Connexins may be a future target by both genetic and pharmacological approaches to develop treatments for the treatment of diabetes and its complications.
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40
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Talhouk RS, Khalil AA, Bajjani R, Rahme GJ, El-Sabban ME. Gap junctions mediate STAT5-independent β-casein expression in CID-9 mammary epithelial cells. ACTA ACUST UNITED AC 2011; 18:104-16. [DOI: 10.3109/15419061.2011.639468] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- Rabih S. Talhouk
- Department of Biology, American University of Beirut, Beirut, Lebanon
| | - Antoine A. Khalil
- Department of Biology, American University of Beirut, Beirut, Lebanon
| | - Rachid Bajjani
- Department of Biology, American University of Beirut, Beirut, Lebanon
| | - Gilbert J. Rahme
- Department of Biology, American University of Beirut, Beirut, Lebanon
| | - Marwan E. El-Sabban
- Department of Human Morphology, American University of Beirut, Beirut, Lebanon
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Becker DL, Thrasivoulou C, Phillips ARJ. Connexins in wound healing; perspectives in diabetic patients. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:2068-75. [PMID: 22155211 DOI: 10.1016/j.bbamem.2011.11.017] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Revised: 11/07/2011] [Accepted: 11/18/2011] [Indexed: 11/19/2022]
Abstract
Skin lesions are common events and we have evolved to rapidly heal them in order to maintain homeostasis and prevent infection and sepsis. Most acute wounds heal without issue, but as we get older our bodies become compromised by poor blood circulation and conditions such as diabetes, leading to slower healing. This can result in stalled or hard-to-heal chronic wounds. Currently about 2% of the Western population develop a chronic wound and this figure will rise as the population ages and diabetes becomes more prevalent [1]. Patient morbidity and quality of life are profoundly altered by chronic wounds [2]. Unfortunately a significant proportion of these chronic wounds fail to respond to conventional treatment and can result in amputation of the lower limb. Life quality and expectancy following amputation is severely reduced. These hard to heal wounds also represent a growing economic burden on Western society with published estimates of costs to healthcare services in the region of $25B annually [3]. There exists a growing need for specific and effective therapeutic agents to improve healing in these wounds. In recent years the gap junction protein Cx43 has been shown to play a pivotal role early on in the acute wound healing process at a number of different levels [4-7]. Conversely, abnormal expression of Cx43 in wound edge keratinocytes was shown to underlie the poor rate of healing in diabetic rats, and targeting its expression with an antisense gel restored normal healing rates [8]. The presence of Cx43 in the wound edge keratinocytes of human chronic wounds has also been reported [9]. Abnormal Cx43 biology may underlie the poor healing of human chronic wounds and be amenable therapeutic intervention [7]. This article is part of a Special Issue entitled: The Communicating junctions, composition, structure and characteristics.
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Affiliation(s)
- David L Becker
- Department of Cell and Developmental Biology, University College, London, WC1E 6BT, UK.
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Abstract
Cx (connexin) proteins are components of gap junctions which are aqueous pores that allow intercellular exchange of ions and small molecules. Mutations in Cx genes are linked to a range of human disorders. In the present review we discuss mutations in β-Cx genes encoding Cx26, Cx30, Cx30.3 and Cx31 which lead to skin disease and deafness. Functional studies with Cx proteins have given insights into disease-associated mechanisms and non-gap junctional roles for Cx proteins.
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43
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Non-channel functions of connexins in cell growth and cell death. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:2002-8. [PMID: 21718687 DOI: 10.1016/j.bbamem.2011.06.011] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Revised: 06/08/2011] [Accepted: 06/15/2011] [Indexed: 12/12/2022]
Abstract
Cellular communication mediated by gap junction channels and hemichannels, both composed of connexin proteins, constitutes two acknowledged regulatory platforms in the accomplishment of tissue homeostasis. In recent years, an abundance of reports has been published indicating functions for connexin proteins in the control of the cellular life cycle that occur independently of their channel activities. This has yet been most exemplified in the context of cell growth and cell death, and is therefore as such addressed in the current paper. Specific attention is hereby paid to the molecular mechanisms that underpin the cellular non-channel roles of connexin proteins, namely the alteration of the expression of tissue homeostasis determinants and the physical interaction with cell growth and cell death regulators. This article is part of a Special Issue entitled: The Communicating junctions, composition, structure and characteristics.
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Vinken M, Decrock E, De Vuyst E, Ponsaerts R, D'hondt C, Bultynck G, Ceelen L, Vanhaecke T, Leybaert L, Rogiers V. Connexins: sensors and regulators of cell cycling. Biochim Biophys Acta Rev Cancer 2010; 1815:13-25. [PMID: 20801193 DOI: 10.1016/j.bbcan.2010.08.004] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Revised: 08/18/2010] [Accepted: 08/20/2010] [Indexed: 12/13/2022]
Abstract
It is nowadays well established that gap junctions are critical gatekeepers of cell proliferation, by controlling the intercellular exchange of essential growth regulators. In recent years, however, it has become clear that the picture is not as simple as originally anticipated, as structural precursors of gap junctions can affect cell cycling by performing actions not related to gap junctional intercellular communication. Indeed, connexin hemichannels also foresee a pathway for cell growth communication, albeit between the intracellular compartment and the extracellular environment, while connexin proteins as such can directly or indirectly influence the production of cell cycle regulators independently of their channel activities. Furthermore, a novel set of connexin-like proteins, the pannexins, have lately joined in as regulators of the cell proliferation process, which they can affect as either single units or as channel entities. In the current paper, these multifaceted aspects of connexin-related signalling in cell cycling are reviewed.
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Affiliation(s)
- Mathieu Vinken
- Department of Toxicology, Vrije Universiteit Brussel, Laarbeeklaan 103, B-1090 Brussels, Belgium.
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Plante I, Wallis A, Shao Q, Laird DW. Milk Secretion and Ejection Are Impaired in the Mammary Gland of Mice Harboring a Cx43 Mutant While Expression and Localization of Tight and Adherens Junction Proteins Remain Unchanged1. Biol Reprod 2010; 82:837-47. [DOI: 10.1095/biolreprod.109.081406] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
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Olk S, Zoidl G, Dermietzel R. Connexins, cell motility, and the cytoskeleton. ACTA ACUST UNITED AC 2010; 66:1000-16. [PMID: 19544403 DOI: 10.1002/cm.20404] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Connexins (Cx) comprise a family of transmembrane proteins, which form intercellular channels between plasma membranes of two adjoining cells, commonly known as gap junctions. Recent reports revealed that Cx proteins interact with diverse cellular components to form a multiprotein complex, which has been termed "Nexus". Potential interaction partners include proteins such as cytoskeletal proteins, scaffolding proteins, protein kinases and phosphatases. These interactions allow correct subcellular localization of Cxs and functional regulation of gap junction-mediated intercellular communication. Evidence is accruing that Cxs might have channel-independent functions, which potentially include regulation of cell migration, cell polarization and growth control. In the current review, we summarize recent knowledge on Cx interactions with cytoskeletal proteins and highlight some aspects of their role in cellular motility.
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Affiliation(s)
- Stephan Olk
- Department of Neuroanatomy and Molecular Brain Research, Ruhr-University Bochum, Bochum, Germany
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Rhee DY, Zhao XQ, Francis RJB, Huang GY, Mably JD, Lo CW. Connexin 43 regulates epicardial cell polarity and migration in coronary vascular development. Development 2009; 136:3185-93. [PMID: 19700622 DOI: 10.1242/dev.032334] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Connexin 43 knockout (Cx43 KO) mice exhibit conotruncal malformations and coronary artery defects. We observed epicardial blisters in the Cx43 KO hearts that suggest defects in epicardial epithelial-mesenchymal transformation (EMT), a process that generates coronary vascular progenitors. Analysis using a three-dimensional collagen gel invasion assay showed that Cx43 KO epicardial cells are less invasive and that, unlike wild-type epicardial cells, they fail to organize into thin vessel-like projections. Examination of Cx43 KO hearts using Wt1 as an epicardial marker revealed a disorganized pattern of epicardial cell infiltration. Time-lapse imaging and motion analysis using epicardial explants showed a defect in directional cell migration. This was associated with changes in the actin/tubulin cytoskeleton. A defect in cell polarity was indicated by a failure of the microtubule-organizing center to align with the direction of cell migration. Forced expression of Cx43 constructs in epicardial explants showed the Cx43 tubulin-binding domain is required for Cx43 modulation of cell polarity and cell motility. Pecam staining revealed early defects in remodeling of the primitive coronary vascular plexuses in the Cx43 KO heart. Together, these findings suggest an early defect in coronary vascular development arising from a global perturbation of the cytoarchitecture of the cell. Consistent with this, we found aberrant myocardialization of the outflow tract, a process also known to be EMT dependent. Together, these findings suggest cardiac defects in the Cx43 KO mice arise from the disruption of cell polarity, a process that may be dependent on Cx43-tubulin interactions.
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Affiliation(s)
- David Y Rhee
- Laboratory of Developmental Biology, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
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Bekheet SHM, Stahlmann R. Disruption of gap junctional intercellular communication by antibiotic gentamicin is associated with aberrant localization of occludin, N-cadherin, connexin 43, and vimentin in SerW3 Sertoli cells in vitro. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2009; 28:155-160. [PMID: 21783997 DOI: 10.1016/j.etap.2009.03.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2008] [Revised: 02/12/2009] [Accepted: 03/03/2009] [Indexed: 05/31/2023]
Abstract
Spermatogenesis is a very complex process by which male germ cells differentiate into mature spermatozoa. The sophisticated communication network that controls spermatogenesis can be derailed so that dysfunction of one cell type propagates to all types as a cascade. This accounts for the particular vulnerability of the testis to environmental factors such as drugs and xenobiotics. Sertoli cells play an important role in protecting developing germ cells by forming a physiological barrier, limiting exposure to potentially toxic substrates, or conversely, facilitating uptake of xenobiotics within the testis. In this study, cells from the rat Sertoli line (SerW3) were incubated for 3, 6 and 9 subsequent days in serum free DMEM (SFDM) composed of DMEM supplemented with three different concentrations of antibiotic gentamicin (10, 30, and 100 μg). The effect of the three different concentrations of this antibiotic was determined on Sertoli cell-cell interaction through impaired expression of their constitutive tight junction proteins as early targets for different toxicants in vitro by immunochemistry analysis. The Sertoli SerW3 cell line illustrated the cytotoxicity of GS, as the intercellular junction proteins such as occludin, N-cadherin, connexin 43, and vimentin were delocalized from the membrane to the cytoplasmic compartment during exposure to the antibiotic. This study underlines the potential deleterious effects of the routine use of antibiotics during continuous cell culture.
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Affiliation(s)
- Souad H M Bekheet
- Zoology Department, Faculty of Science, South Valley University, Aswan, Egypt.
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Duffy HS, O'Donnell P, Coombs W, Taffet SM, Delmar M, Spray DC. Kinetics of Protein-Protein Interactions of Connexins: Use of Enzyme Linked Sorbent Assays. ACTA ACUST UNITED AC 2009; 10:207-10. [PMID: 14681017 DOI: 10.1080/cac.10.4-6.207.210] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Determination of the protein-protein interactions of connexins has become a rapidly expanding field of research. While there are multiple methods of determining the identity of binding partners, determination of the strengths of interactions is not as simple. Here we describe the use of the in vitro method Enzyme Linked Sorbent Assay (ELSA) to compare binding affinities of known protein partners for Connexin43. We used the binding of Cx43 Carboxyl Terminal domain to the PDZ-2 domain of Zonula Occludens-1 and to the SH3 domain of c-Src. In the ELSA assay we found that while the binding of the SH3 domain of c-Src is pH-dependent, the interaction of the PDZ domain of ZO-1 is not. These data confirm findings using Surface Plasmon Resonance (1) and indicate that ELSA can be a useful tool in determining the kinetics of protein-protein interactions.
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Affiliation(s)
- Heather S Duffy
- Albert Einstein College of Medicine, Bronx, New York 10461, USA.
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50
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Morel S, Burnier L, Kwak BR. Connexins participate in the initiation and progression of atherosclerosis. Semin Immunopathol 2009; 31:49-61. [DOI: 10.1007/s00281-009-0147-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2009] [Accepted: 04/07/2009] [Indexed: 01/20/2023]
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