1
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Baker KM, Abt M, Doud EH, Oblak AL, Yeh ES. Mapping the Anti-Cancer Activity of α-Connexin Carboxyl-Terminal (aCT1) Peptide in Resistant HER2+ Breast Cancer. Cancers (Basel) 2024; 16:423. [PMID: 38275864 PMCID: PMC10814893 DOI: 10.3390/cancers16020423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Revised: 01/10/2024] [Accepted: 01/17/2024] [Indexed: 01/27/2024] Open
Abstract
Connexin 43 (Cx43) is a protein encoded by the GJA1 gene and is a component of cell membrane structures called gap junctions, which facilitate intercellular communication. Prior evidence indicates that elevated GJA1 expression in the HER2-positive (HER2+) subtype of breast cancer is associated with poor prognosis. Prior evidence also suggests that HER2+ breast cancers that have become refractory to HER2-targeted agents have a loss of Cx43 gap junction intercellular communication (GJIC). In this study, a Cx43-targeted agent called alpha-connexin carboxyl-terminal peptide (aCT1) is examined to determine whether GJIC can be rescued in refractory HER2+ breast cancer cells. A proposed mechanism of action for aCT1 is binding to the tight junction protein Zonal Occludens-1 (ZO-1). However, the true scope of activity for aCT1 has not been explored. In this study, mass spectrometry proteomic analysis is used to determine the breadth of aCT1-interacting proteins. The NanoString nCounter Breast Cancer 360 panel is also used to examine the effect of aCT1 on cancer signaling in HER2+ breast cancer cells. Findings from this study show a dynamic range of binding partners for aCT1, many of which regulate gene expression and RNA biology. nCounter analysis shows that a number of pathways are significantly impacted by aCT1, including upregulation of apoptotic factors, leading to the prediction and demonstration that aCT1 can boost the cell death effects of cisplatin and lapatinib in HER2+ breast cancer cells that have become resistant to HER2-targeted agents.
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Affiliation(s)
- Kimberly M. Baker
- Department of Biology, University of Indianapolis, Indianapolis, IN 46227, USA;
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Melissa Abt
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Emma H. Doud
- Melvin and Bren Simon Comprehensive Cancer Center, Indiana University School of Medicine, Indianapolis, IN 46202, USA;
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Adrian L. Oblak
- Department of Radiology and Imaging Sciences, Indiana University School of Medicine, Indianapolis, IN 46202, USA;
- Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Elizabeth S. Yeh
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
- Melvin and Bren Simon Comprehensive Cancer Center, Indiana University School of Medicine, Indianapolis, IN 46202, USA;
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2
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Segretain D, Di Marco M, Dufeu C, Carette D, Trubuil A, Pointis G. Cooperative cell-cell actin network remodeling to perform Gap junction endocytosis. Basic Clin Androl 2023; 33:20. [PMID: 37533006 PMCID: PMC10399049 DOI: 10.1186/s12610-023-00194-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Accepted: 04/16/2023] [Indexed: 08/04/2023] Open
Abstract
BACKGROUND The endocytosis of Gap junction plaques (GJP) requires cytoskeletal forces to internalize such large membranous structures. Actin, which partners the connexin proteins constituting Gap junctions and is located close to Annular Gap Junctions (AGJ), could be actively involved in this physiological process. RESULTS Electron Microscopy and Light Microscopy images, associated with time-lapse analysis and 3D reconstruction, used at high resolution and enhanced using ImageJ based software analysis, revealed that: i) actin cables, originating from Donor cells, insert on the edge of GJP and contribute to their invagination, giving rise to AGJ, whereas actin cables on the Acceptor cell side of the plaque are not modified; ii) actin cables from the Donor cell are continuous with the actin network present over the entire GJP surface. These actin cables fuse at a single point distant from the plaque, which then detaches itself from the membrane, condensing to form an actin mass during the final internalization process; iii) the Acceptor cell participates in the last step of the endocytic invagination process by forming an annular actin structure known as an actin ring. CONCLUSIONS Together, these data suggest that the endocytosis of GJP is an example of a unique cooperative mechanism between the Donor (the traction of its actin cables) and the Acceptor cells (forming the actin ring).
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Affiliation(s)
- Dominique Segretain
- UMR S1147, Université Paris Descartes, 45 Rue Des Saints-Pères, 75006, Paris, France.
| | - Mathilde Di Marco
- UMR S1147, Université Paris Descartes, 45 Rue Des Saints-Pères, 75006, Paris, France
- Present Address: Institut Curie, PSL Research University, CNRS, UMR144, Structure and Membrane Compartments, 75005, Paris, France
| | - Chloé Dufeu
- Faculté de Pharmacie, Université Paris-Saclay, Saclay, France
| | | | - Alain Trubuil
- MaIAGE, INRAE, Université Paris-Saclay, 78352, Jouy-en-Josas, France
| | - Georges Pointis
- INSERM U 1065, Team 5 Physiopathological Control of Germ Cell Proliferation: Genomic and Non-Genomic Mechanisms, University of Nice Sophia-Antipolis, 151 Route Saint-Antoine de Ginestière BP 2 3194, 06204, Nice Cedex 3, France
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3
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Basu I, Li H, Trease AJ, Sorgen PL. Regulation of Cx43 Gap Junction Intercellular Communication by Bruton's Tyrosine Kinase and Interleukin-2-Inducible T-Cell Kinase. Biomolecules 2023; 13:biom13040660. [PMID: 37189407 DOI: 10.3390/biom13040660] [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: 02/24/2023] [Revised: 03/30/2023] [Accepted: 04/06/2023] [Indexed: 05/17/2023] Open
Abstract
T and B cell receptor signaling involves the activation of Akt, MAPKs, and PKC as well as an increase in intracellular Ca2+ and calmodulin activation. While these coordinate the rapid turnover of gap junctions, also implicated in this process is Src, which is not activated as part of T and B cell receptor signaling. An in vitro kinase screen identified that Bruton's tyrosine kinase (BTK) and interleukin-2-inducible T-cell kinase (ITK) phosphorylate Cx43. Mass spectroscopy revealed that BTK and ITK phosphorylate Cx43 residues Y247, Y265, and Y313, which are identical to the residues phosphorylated by Src. Overexpression of BTK or ITK in the HEK-293T cells led to increased Cx43 tyrosine phosphorylation as well as decreased gap junction intercellular communication (GJIC) and Cx43 membrane localization. In the lymphocytes, activation of the B cell receptor (Daudi cells) or T cell receptor (Jurkat cells) increased the BTK and ITK activity, respectively. While this led to increased tyrosine phosphorylation of Cx43 and decreased GJIC, the cellular localization of Cx43 changed little. We have previously identified that Pyk2 and Tyk2 also phosphorylate Cx43 at residues Y247, Y265, and Y313 with a similar cellular fate to that of Src. With phosphorylation critical to Cx43 assembly and turnover, and kinase expression varying between different cell types, there would be a need for different kinases to achieve the same regulation of Cx43. The work presented herein suggests that in the immune system, ITK and BTK have the capacity for the tyrosine phosphorylation of Cx43 to alter the gap junction function in a similar manner as Pyk2, Tyk2, and Src.
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Affiliation(s)
- Ishika Basu
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Hanjun Li
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Andrew J Trease
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Paul L Sorgen
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE 68198, USA
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4
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Koval M, Cwiek A, Carr T, Good ME, Lohman AW, Isakson BE. Pannexin 1 as a driver of inflammation and ischemia-reperfusion injury. Purinergic Signal 2021; 17:521-531. [PMID: 34251590 PMCID: PMC8273370 DOI: 10.1007/s11302-021-09804-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Accepted: 06/24/2021] [Indexed: 02/06/2023] Open
Abstract
Pannexin 1 (Panx1) is a ubiquitously expressed protein forming large conductance channels that are central to many distinct inflammation and injury responses. There is accumulating evidence showing ATP released from Panx1 channels, as well as metabolites, provide effective paracrine and autocrine signaling molecules that regulate different elements of the injury response. As channels with a broad range of permselectivity, Panx1 channels mediate the secretion and uptake of multiple solutes, ranging from calcium to bacterial derived molecules. In this review, we describe how Panx1 functions in response to different pro-inflammatory stimuli, focusing mainly on signaling coordinated by the vasculature. How Panx1 mediates ATP release by injured cells is also discussed. The ability of Panx1 to serve as a central component of many diverse physiologic responses has proven to be critically dependent on the context of expression, post-translational modification, interacting partners, and the mode of stimulation.
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Affiliation(s)
- Michael Koval
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Medicine, Emory University School of Medicine, 205 Whitehead Building, 615 Michael Street, Atlanta, GA, 30322, USA. .,Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, 30322, USA.
| | - Aleksandra Cwiek
- Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA
| | - Thomas Carr
- Department of Cell Biology and Anatomy, University of Calgary Cumming School of Medicine, Calgary, AB, Canada.,Hotchkiss Brain Institute and Alberta Children's Hospital Research Institute, University of Calgary, Calgary, AB, Canada
| | - Miranda E Good
- Molecular Cardiology Research Institute, Tufts Medical Center, Boston, MA, USA
| | - Alexander W Lohman
- Department of Cell Biology and Anatomy, University of Calgary Cumming School of Medicine, Calgary, AB, Canada.,Hotchkiss Brain Institute and Alberta Children's Hospital Research Institute, University of Calgary, Calgary, AB, Canada
| | - Brant E Isakson
- Robert M. Berne Cardiovascular Research Center, School of Medicine, University of Virginia, PO Box 801394, Charlottesville, VA, 22908, USA. .,Department of Molecular Physiology and Biophysics, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA.
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5
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Lu YZ, Liang LM, Cheng PP, Xiong L, Wang M, Song LJ, Yu F, He XL, Xiong L, Wang XR, Xin JB, Ye H, Ma WL. VEGF/Src signaling mediated pleural barrier damage and increased permeability contributes to subpleural pulmonary fibrosis. Am J Physiol Lung Cell Mol Physiol 2021; 320:L990-L1004. [PMID: 33787325 DOI: 10.1152/ajplung.00436.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The distribution of fibrosis in idiopathic pulmonary fibrosis (IPF) is subpleural with basal predominance. Alveolar epithelial cell was considered as the key cell in the initial phase of IPF. However, the idea of activation and damage of alveolar epithelial cells is very difficult to explain why fibrosis distributes in the subpleural area. In this study, human pleural mesothelial cell (PMC) line and primary rat PMC was used as in vitro model. Intraperitoneal injection of bleomycin was used for making a pulmonary fibrosis model. The integrity of cultured monolayer PMCs was determined by transepithelial electric resistance (TEER). Pleural permeability was estimated by measuring paracellular transport of fluorescein isothiocyanate (FITC)-conjugated dextran. Changes in lung tissue of patients with IPF were analyzed by Masson's and immunofluorescence staining. We found bleomycin induced PMCs damage and increased PMCs permeability; increased PMCs permeability aggravated bleomycin-induced subpleural inflammation and pulmonary fibrosis. Moreover, bleomycin was found to activate VEGF/Src signaling which increased PMCs permeability. In vivo, inhibition of VEGF/Src signaling prevented bleomycin-induced subpleural pulmonary fibrosis. At last, activation of VEGF/Src signaling was confirmed in subpleural area in patients with IPF. Taken together, our findings indicate that VEGF/Src signaling mediated pleural barrier damage and increased permeability which contributes to subpleural pulmonary fibrosis.
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Affiliation(s)
- Yu-Zhi Lu
- Department of Respiratory and Critical Care Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People's Republic of China
| | - Li-Mei Liang
- Department of Respiratory and Critical Care Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People's Republic of China
| | - Pei-Pei Cheng
- Department of Pathophysiology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People's Republic of China
| | - Li Xiong
- Department of Respiratory and Critical Care Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People's Republic of China
| | - Meng Wang
- Department of Pathophysiology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People's Republic of China
| | - Lin-Jie Song
- Department of Respiratory and Critical Care Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People's Republic of China.,Key Laboratory of Respiratory Diseases, Ministry of Health of China, Wuhan, People's Republic of China
| | - Fan Yu
- Department of Respiratory and Critical Care Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People's Republic of China.,Key Laboratory of Respiratory Diseases, Ministry of Health of China, Wuhan, People's Republic of China
| | - Xin-Liang He
- Department of Respiratory and Critical Care Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People's Republic of China.,Key Laboratory of Respiratory Diseases, Ministry of Health of China, Wuhan, People's Republic of China
| | - Liang Xiong
- Department of Respiratory and Critical Care Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People's Republic of China.,Key Laboratory of Respiratory Diseases, Ministry of Health of China, Wuhan, People's Republic of China
| | - Xiao-Rong Wang
- Department of Respiratory and Critical Care Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People's Republic of China.,Key Laboratory of Respiratory Diseases, Ministry of Health of China, Wuhan, People's Republic of China
| | - Jian-Bao Xin
- Department of Respiratory and Critical Care Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People's Republic of China.,Key Laboratory of Respiratory Diseases, Ministry of Health of China, Wuhan, People's Republic of China
| | - Hong Ye
- Department of Pathophysiology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People's Republic of China.,Key Laboratory of Respiratory Diseases, Ministry of Health of China, Wuhan, People's Republic of China
| | - Wan-Li Ma
- Department of Respiratory and Critical Care Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People's Republic of China.,Key Laboratory of Respiratory Diseases, Ministry of Health of China, Wuhan, People's Republic of China
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6
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Cao L, Yang T, Huang S, Yun X, Hou H, Wang T, Shi D, Li X. Expression patterns of ZO-1/2 and their effects on porcine oocyte in vitro maturation and early embryonic development. Theriogenology 2020; 161:262-270. [PMID: 33348145 DOI: 10.1016/j.theriogenology.2020.12.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Revised: 12/07/2020] [Accepted: 12/07/2020] [Indexed: 12/30/2022]
Abstract
Zonula occludens (ZO)-1 and ZO-2 are involved in epithelial polarity maintenance, gene transcription, cell proliferation and tumor cell metastasis. Regulating ZO-1/2 expression influences the early embryonic development of mice, but whether they are involved in oocyte maturation is still poorly understood. In the present study, the expression patterns of ZO-1 and ZO-2 in porcine cumulus cells and oocytes matured in vitro and early embryos from parthenogenetic activation were detected by qRT-PCR or Western blot, and then their roles in porcine oocyte maturation and early embryo development were investigated by shRNA technology. ZO-1 and ZO-2 were found to be expressed in cumulus cells, oocytes and early embryos, while ZO-1α+ was expressed only in cumulus cells, morula and blastocysts. During in vitro maturation (IVM), the abundance of ZO-1 and ZO-2 in oocytes was significantly higher than that in cumulus cells at 0 h (P < 0.01), and their mRNA and protein levels displayed relatively higher expression at 0 and 18 h, respectively. Compared with the control groups, cumulus cell expansion, oocyte nucleus maturation, and subsequent cleavage were not influenced by treatment of the cumulus-oocyte complexes (COCs) with ZO-1-shRNA1, ZO-2-shRNA2 or combined ZO-1-shRNA1 and ZO-2-shRNA2 lentivirus (P > 0.05). However, the blastocyst rate was reduced by treatment of COCs with ZO-1-shRNA1 but not ZO-2-shRNA2. The total cell number of blastocysts was decreased by downregulation of ZO-1 and ZO-2 (P < 0.05). Downregulation of ZO-1 and ZO-2 also resulted in a significant decrease (P < 0.05) in the expression of Cx43, Cx45, PTX3 and PTGS2 in cumulus cells, Cx45, BMP15, ZP3 and C-KIT in MII oocytes, and Nanog in blastocysts, with the exception of HAS2 expression in cumulus cells and Oct4 expression in blastocysts (P > 0.05). Altogether, the above results indicate that ZO-1 and ZO-2 display similar expression patterns during porcine oocyte IVM and are critical to porcine oocyte maturation and early embryonic development.
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Affiliation(s)
- Lihua Cao
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangxi University, Nanning, 530005, PR China
| | - Ting Yang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangxi University, Nanning, 530005, PR China
| | - Shihai Huang
- College of Life Science and Technology, Guangxi University, Nanning, 530005, PR China
| | - Xuedan Yun
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangxi University, Nanning, 530005, PR China
| | - Hanqi Hou
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangxi University, Nanning, 530005, PR China
| | - Ting Wang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangxi University, Nanning, 530005, PR China
| | - Deshun Shi
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangxi University, Nanning, 530005, PR China.
| | - Xiangping Li
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangxi University, Nanning, 530005, PR China.
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7
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Solan JL, Lampe PD. Src Regulation of Cx43 Phosphorylation and Gap Junction Turnover. Biomolecules 2020; 10:biom10121596. [PMID: 33255329 PMCID: PMC7759836 DOI: 10.3390/biom10121596] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 11/19/2020] [Accepted: 11/22/2020] [Indexed: 12/18/2022] Open
Abstract
The gap junction protein Connexin43 (Cx43) is highly regulated by phosphorylation at over a dozen sites by probably at least as many kinases. This Cx43 “kinome” plays an important role in gap junction assembly and turnover. We sought to gain a better understanding of the interrelationship of these phosphorylation events particularly related to src activation and Cx43 turnover. Using state-of-the-art live imaging methods, specific inhibitors and many phosphorylation-status specific antibodies, we found phospho-specific domains in gap junction plaques and show evidence that multiple pathways of disassembly exist and can be regulated at the cellular and subcellular level. We found Src activation promotes formation of connexisomes (internalized gap junctions) in a process involving ERK-mediated phosphorylation of S279/282. Proteasome inhibition dramatically and rapidly restored gap junctions in the presence of Src and led to dramatic changes in the Cx43 phospho-profile including to increased Y247, Y265, S279/282, S365, and S373 phosphorylation. Lysosomal inhibition, on the other hand, nearly eliminated phosphorylation on Y247 and Y265 and reduced S368 and S373 while increasing S279/282 phosphorylation levels. We present a model of gap junction disassembly where multiple modes of disassembly are regulated by phosphorylation and can have differential effects on cellular signaling.
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Affiliation(s)
- Joell L. Solan
- Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA;
| | - Paul D. Lampe
- Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA;
- Department of Global Health, Pathobiology Program, University of Washington, Seattle, WA 98109, USA
- Correspondence:
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8
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Abstract
Intercalated discs (ICDs) are highly orchestrated structures that connect neighboring cardiomyocytes in the heart. Three major complexes are distinguished in ICD: desmosome, adherens junction (AJ), and gap junction (GJ). Desmosomes are major cell adhesion junctions that anchor cell membrane to the intermediate filament network; AJs connect the actin cytoskeleton of adjacent cells; and gap junctions metabolically and electrically connect the cytoplasm of adjacent cardiomyocytes. All these complexes work as a single unit, the so-called area composita, interdependently rather than individually. Mutation or altered expression of ICD proteins results in various cardiac diseases, such as ARVC (arrhythmogenic right ventricular cardiomyopathy), dilated cardiomyopathy, and hypotrophy cardiomyopathy, eventually leading to heart failure. In this article, we first review the recent findings on the structural organization of ICD and their functions and then focus on the recent advances in molecular pathogenesis of the ICD-related heart diseases, which include two major areas: i) the ICD gene mutations in cardiac diseases, and ii) the involvement of ICD proteins in signal transduction pathways leading to myocardium remodeling and eventual heart failure. These major ICD-related signaling pathways include Wnt/β-catenin pathway, p38 MAPK cascade, Rho-dependent serum response factor (SRF) signaling, calcineurin/NFAT signaling, Hippo kinase cascade, etc., which are differentially regulated in pathological conditions.
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9
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Eftekhari A, Vahed SZ, Kavetskyy T, Rameshrad M, Jafari S, Chodari L, Hosseiniyan SM, Derakhshankhah H, Ahmadian E, Ardalan M. Cell junction proteins: Crossing the glomerular filtration barrier in diabetic nephropathy. Int J Biol Macromol 2020; 148:475-482. [PMID: 31962072 DOI: 10.1016/j.ijbiomac.2020.01.168] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Revised: 01/17/2020] [Accepted: 01/17/2020] [Indexed: 12/20/2022]
Abstract
Diabetic nephropathy as a deleterious complication of diabetes mellitus and an important cause of end-stage renal failure is characterized by changes in the molecular and cellular levels. Cell-cell communication via the gap and tight junctions are involved in the pathogenesis of diseases such as diabetes and kidney failure. Studying cell junctions including gap junctions, tight junctions, and anchoring junctions within the nephron can be used as an early sign of diabetic nephropathy. Furthermore, cell junctions may be an upcoming target by pharmacological methods to improve treatments of diabetic nephropathy and pave the way to introduce promising therapeutic strategies based on cell-cell communications effects and its translation into clinical studies for the treatment of diabetic nephropathy.
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Affiliation(s)
- Aziz Eftekhari
- Pharmacology and Toxicology Department, Maragheh University of Medical Sciences, Maragheh, Iran
| | | | - Taras Kavetskyy
- Drohobych Ivan Franko State Pedagogical University, Drohobych, Ukraine; The John Paul II Catholic University of Lublin, Lublin, Poland
| | - Maryam Rameshrad
- Natural Products and Medicinal Plants Research Center, North Khorasan University of Medical Sciences, Bojnurd, Iran
| | - Samira Jafari
- Pharmaceutical Sciences Research Center, Health Institute, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Leila Chodari
- Physiology Department, Faculty of Medicine, Urmia University of Medical Sciences, Urmia, Iran
| | | | - Hossein Derakhshankhah
- Pharmaceutical Sciences Research Center, Health Institute, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Elham Ahmadian
- Kidney Research Center, Tabriz University of Medical Sciences, Tabriz, Iran; Students Research Committee, Tabriz University of Medical Sciences, Tabriz, Iran.
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10
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Price GW, Potter JA, Williams BM, Cliff CL, Squires PE, Hills CE. Connexin-mediated cell communication in the kidney: A potential therapeutic target for future intervention of diabetic kidney disease?: Joan Mott Prize Lecture. Exp Physiol 2020; 105:219-229. [PMID: 31785013 DOI: 10.1113/ep087770] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Accepted: 11/19/2019] [Indexed: 12/21/2022]
Abstract
The ability of cells to communicate and synchronise their activity is essential for the maintenance of tissue structure, integrity and function. A family of membrane-bound proteins called connexins are largely responsible for mediating the local transfer of information between cells. Assembled in the cell membrane as a hexameric connexon, they either function as a conduit for paracrine signalling, forming a transmembrane hemi-channel, or, if aligned with connexons on neighbouring cells, form a continuous aqueous pore or gap junction, which allows for the direct transmission of metabolic and electrical signals. Regulation of connexin synthesis and activity is critical to cellular function, and a number of diseases are attributed to changes in the expression and/or function of these important proteins. A link between hyperglycaemia, connexin expression, altered nucleotide concentrations and impaired function highlights a potential role for connexin-mediated cell communication in complications of diabetes. In the diabetic kidney, glycaemic injury is the leading cause of end-stage renal failure, reflecting multiple aetiologies including glomerular hyperfiltration, albuminuria, increased deposition of extracellular matrix and tubulointerstitial fibrosis. Loss of connexin-mediated cell-to-cell communication in diabetic nephropathy may represent an early sign of disease progression, but our understanding of the process remains severely limited. This review focuses on recent evidence demonstrating that glucose-evoked changes in connexin-mediated cell communication and associated purinergic signalling may contribute to the pathogenesis of kidney disease in diabetes, highlighting the tantalising potential of targeting these proteins as a novel therapeutic intervention.
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Affiliation(s)
- Gareth W Price
- Joseph Banks Laboratories, School of Life Sciences, University of Lincoln, Brayford Pool, Lincoln, LN6 7TS, UK
| | - Joe A Potter
- Joseph Banks Laboratories, School of Life Sciences, University of Lincoln, Brayford Pool, Lincoln, LN6 7TS, UK
| | - Bethany M Williams
- Joseph Banks Laboratories, School of Life Sciences, University of Lincoln, Brayford Pool, Lincoln, LN6 7TS, UK
| | - Chelsy L Cliff
- Joseph Banks Laboratories, School of Life Sciences, University of Lincoln, Brayford Pool, Lincoln, LN6 7TS, UK
| | - Paul E Squires
- Joseph Banks Laboratories, School of Life Sciences, University of Lincoln, Brayford Pool, Lincoln, LN6 7TS, UK
| | - Claire E Hills
- Joseph Banks Laboratories, School of Life Sciences, University of Lincoln, Brayford Pool, Lincoln, LN6 7TS, UK
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11
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Ghasemi Tahrir F, Gupta M, Myers V, Gordon J, Cheung JY, Feldman AM, Khalili K. Role of Bcl2-associated Athanogene 3 in Turnover of Gap Junction Protein, Connexin 43, in Neonatal Cardiomyocytes. Sci Rep 2019; 9:7658. [PMID: 31114002 PMCID: PMC6529437 DOI: 10.1038/s41598-019-44139-w] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Accepted: 12/10/2018] [Indexed: 12/20/2022] Open
Abstract
Any pathological stress that impairs expression, turnover and phosphorylation of connexin 43 (Cx43), one of the major proteins of gap junctions, can adversely impact myocardial cell behavior, thus leading to the development of cardiac arrhythmias and heart failure. Our results in primary neonatal rat ventricular cardiomyocytes (NRVCs) show that impairment of the autophagy-lysosome pathway dysregulates degradation of Cx43, either by inhibiting lysosomal activity or suppressing the level of Bcl2-associated athanogene 3 (BAG3), a stress-induced pleiotropic protein that is involved in protein quality control (PQC) via the autophagy pathway. Inhibition of lysosomal activity leads to the accumulation of Cx43 aggregates and suppression of BAG3 significantly diminished turnover of Cx43. In addition, knock-down of BAG3 reduced the levels of Cx43 by dysregulating Cx43 protein stability. Under stress conditions, expression of BAG3 affected the state of Cx43 phosphorylation and its degradation. Furthermore, we found that BAG3 co-localized with the cytoskeleton protein, α-Tubulin, and depolymerization of α-Tubulin led to the intracellular accumulation of Cx43. These observations ascribe a novel function for BAG3 that involves control of Cx43 turnover under normal and stress conditions and potentially for optimizing communication of cardiac muscle cells through gap junctions.
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Affiliation(s)
- Farzaneh Ghasemi Tahrir
- Department of Neuroscience, Center for Neurovirology, Lewis Katz School of Medicine at Temple University, Philadelphia, Pennsylvania, USA
| | - Manish Gupta
- Department of Neuroscience, Center for Neurovirology, Lewis Katz School of Medicine at Temple University, Philadelphia, Pennsylvania, USA
| | - Valerie Myers
- Department of Medicine, Lewis Katz School of Medicine at Temple University, Philadelphia, Pennsylvania, USA.,Cardiovascular Research Center, Lewis Katz School of Medicine at Temple University, Philadelphia, Pennsylvania, USA
| | - Jennifer Gordon
- Department of Neuroscience, Center for Neurovirology, Lewis Katz School of Medicine at Temple University, Philadelphia, Pennsylvania, USA
| | - Joseph Y Cheung
- Department of Medicine, Lewis Katz School of Medicine at Temple University, Philadelphia, Pennsylvania, USA.,Center for Translational Medicine, Lewis Katz School of Medicine at Temple University, Philadelphia, Pennsylvania, USA
| | - Arthur M Feldman
- Department of Medicine, Lewis Katz School of Medicine at Temple University, Philadelphia, Pennsylvania, USA.,Cardiovascular Research Center, Lewis Katz School of Medicine at Temple University, Philadelphia, Pennsylvania, USA
| | - Kamel Khalili
- Department of Neuroscience, Center for Neurovirology, Lewis Katz School of Medicine at Temple University, Philadelphia, Pennsylvania, USA.
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12
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Xiao X, Yang Y, Mao B, Cheng CY, Ni Y. Emerging role for SRC family kinases in junction dynamics during spermatogenesis. Reproduction 2019; 157:R85-R94. [PMID: 30608903 PMCID: PMC6602873 DOI: 10.1530/rep-18-0440] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Accepted: 01/03/2019] [Indexed: 12/22/2022]
Abstract
SRC family kinases (SFKs) are known regulators of multiple cellular events, including cell movement, differentiation, proliferation, survival and apoptosis. SFKs are expressed virtually by all mammalian cells. They are non-receptor protein kinases that phosphorylate a variety of cellular proteins on tyrosine, leading to the activation of protein targets in response to environmental stimuli. Among SFKs, SRC, YES and FYN are the ubiquitously expressed and best studied members. In fact, SRC, the prototypical SFK, was the first tyrosine kinase identified in mammalian cells. Studies have shown that SFKs are regulators of cell junctions, and function in endocytosis and membrane trafficking to regulate junction restructuring events. Herein, we briefly summarize the recent findings in the field regarding the role of SFKs in the testis in regulating spermatogenesis, particularly in Sertoli-Sertoli and Sertoli-germ cell adhesion. While it is almost 50 years since the identification of the oncogene v-Src encoded by Rous sarcoma transforming virus, the understanding of SFK involvement during spermatogenesis in the testis remains far behind that in other epithelia and tissues. The goal of this review is to bridge this gap.
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Affiliation(s)
- Xiang Xiao
- Department of Reproductive Physiology, Zhejiang Academy of Medical Sciences, Hangzhou 310013, Zhejiang, China
| | - Yue Yang
- Department of Reproductive Physiology, Zhejiang Academy of Medical Sciences, Hangzhou 310013, Zhejiang, China
| | - Baiping Mao
- The Mary M. Woldford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council, 1230 York Ave, New York, NY 10065, United States
| | - C. Yan Cheng
- The Mary M. Woldford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council, 1230 York Ave, New York, NY 10065, United States
| | - Ya Ni
- Department of Reproductive Physiology, Zhejiang Academy of Medical Sciences, Hangzhou 310013, Zhejiang, China
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13
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Bell CL, Shakespeare TI, Smith AR, Murray SA. Visualization of Annular Gap Junction Vesicle Processing: The Interplay Between Annular Gap Junctions and Mitochondria. Int J Mol Sci 2018; 20:ijms20010044. [PMID: 30583492 PMCID: PMC6337258 DOI: 10.3390/ijms20010044] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Revised: 12/15/2018] [Accepted: 12/20/2018] [Indexed: 11/16/2022] Open
Abstract
It is becoming clear that in addition to gap junctions playing a role in cell⁻cell communication, gap junction proteins (connexins) located in cytoplasmic compartments may have other important functions. Mitochondrial connexin 43 (Cx43) is increased after ischemic preconditioning and has been suggested to play a protective role in the heart. How Cx43 traffics to the mitochondria and the interactions of mitochondria with other Cx43-containing structures are unclear. In this study, immunocytochemical, super-resolution, and transmission electron microscopy were used to detect cytoplasmic Cx43-containing structures and to demonstrate their interactions with other cytoplasmic organelles. The most prominent cytoplasmic Cx43-containing structures-annular gap junctions-were demonstrated to form intimate associations with lysosomes as well as with mitochondria. Surprisingly, the frequency of associations between mitochondria and annular gap junctions was greater than that between lysosomes and annular gap junctions. The benefits of annular gap junction/mitochondrial associations are not known. However, it is tempting to suggest, among other possibilities, that the contact between annular gap junction vesicles and mitochondria facilitates Cx43 delivery to the mitochondria. Furthermore, it points to the need for investigating annular gap junctions as more than only vesicles destined for degradation.
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Affiliation(s)
- Cheryl L Bell
- Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA.
| | | | - Amber R Smith
- Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA.
| | - Sandra A Murray
- Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA.
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14
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Sorgen PL, Trease AJ, Spagnol G, Delmar M, Nielsen MS. Protein⁻Protein Interactions with Connexin 43: Regulation and Function. Int J Mol Sci 2018; 19:E1428. [PMID: 29748463 PMCID: PMC5983787 DOI: 10.3390/ijms19051428] [Citation(s) in RCA: 66] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Revised: 05/07/2018] [Accepted: 05/08/2018] [Indexed: 12/11/2022] Open
Abstract
Connexins are integral membrane building blocks that form gap junctions, enabling direct cytoplasmic exchange of ions and low-molecular-mass metabolites between adjacent cells. In the heart, gap junctions mediate the propagation of cardiac action potentials and the maintenance of a regular beating rhythm. A number of connexin interacting proteins have been described and are known gap junction regulators either through direct effects (e.g., kinases) or the formation of larger multifunctional complexes (e.g., cytoskeleton scaffold proteins). Most connexin partners can be categorized as either proteins promoting coupling by stimulating forward trafficking and channel opening or inhibiting coupling by inducing channel closure, internalization, and degradation. While some interactions have only been implied through co-localization using immunohistochemistry, others have been confirmed by biophysical methods that allow detection of a direct interaction. Our understanding of these interactions is, by far, most well developed for connexin 43 (Cx43) and the scope of this review is to summarize our current knowledge of their functional and regulatory roles. The significance of these interactions is further exemplified by demonstrating their importance at the intercalated disc, a major hub for Cx43 regulation and Cx43 mediated effects.
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Affiliation(s)
- Paul L Sorgen
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE 68198, USA.
| | - Andrew J Trease
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE 68198, USA.
| | - Gaelle Spagnol
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE 68198, USA.
| | - Mario Delmar
- Leon H Charney Division of Cardiology, NYU School of Medicine, New York, NY 10016, USA.
| | - Morten S Nielsen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen, Denmark.
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15
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Bachelot A, Gilleron J, Meduri G, Guberto M, Dulon J, Boucherie S, Touraine P, Misrahi M. A common African variant of human connexin 37 is associated with Caucasian primary ovarian insufficiency and has a deleterious effect in vitro. Int J Mol Med 2018; 41:640-648. [PMID: 29207017 PMCID: PMC5752242 DOI: 10.3892/ijmm.2017.3257] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Accepted: 10/20/2017] [Indexed: 11/06/2022] Open
Abstract
Folliculogenesis requires communication between granulosa cells and oocytes, mediated by connexin-based gap junctions. Connexin 37 (Cx37)-deficient female mice are infertile. The present study assessed Cx37 deficiency in patients with primary ovarian insufficiency (POI). A candidate gene study was performed in patients and controls from the National Genotyping Center (Evry, France) including 58 Caucasian patients with idiopathic isolated POI and 142 Caucasian controls. Direct genomic sequencing of the coding regions of the GJA4 gene (encoding Cx37) was performed with the aim to identify a deleterious variant associated with POI and absent in ethnically matched controls. A single Cx37 variant absent in the control population was identified, namely a c.946G>A heterozygous substitution leading to a p.Gly316Ser variant that was present in two POI patients. This variant was absent in all Caucasian controls from various databases, and has been observed exclusively in African populations. This variant was identified to have a dominant negative effect in HeLa cells in vitro to alter connexon function (by 67.2±7.17%), as determined by Gap-fluorescence recovery after photobleaching. The alteration principally resulted from a decrease of cell surface connexons due to altered trafficking (by 47.73±8.59%). In marked contrast to this observation, a p.Pro258Ser variant frequent in all ethnic populations in databases had no functional effect in vitro. In conclusion, the present study reported on a Cx37 variant in two Caucasian POI patients, which was absent in control Caucasian populations, and which had a deleterious effect in vitro. It is therefore suggested that in the genetic context of the Caucasian population, this variant may contribute to POI.
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Affiliation(s)
- Anne Bachelot
- AP-HP, Department of Endocrinology and Reproductive Medicine, Pitié-Salpêtrière Hospital, Reference Center for Rare Endocrine Diseases of Growth, Reference Center for Rare Gynecological Pathologies
- University Pierre and Marie Curie, University Paris 6, F-75013 Paris
| | - Jerome Gilleron
- National Institute of Health and Medical Research INSERM U1065 - University of Nice-Sophia Antipolis, Mediterranean Center for Molecular Medicine C3M, F-06000 Nice
| | - Geri Meduri
- National Institute of Health and Medical Research INSERM U1195
| | - Mihelai Guberto
- University Paris-Sud, University Paris Saclay, Medical Faculty Paris-Sud, Bicêtre Hospital, F-94275 Le Kremlin Bicêtre
| | - Jerome Dulon
- AP-HP, Department of Endocrinology and Reproductive Medicine, Pitié-Salpêtrière Hospital, Reference Center for Rare Endocrine Diseases of Growth, Reference Center for Rare Gynecological Pathologies
| | - Sylviane Boucherie
- National Institute of Health and Medical Research UMR-S 757 INSERM, University Paris-Sud, F-91400 Orsay, France
| | - Philippe Touraine
- AP-HP, Department of Endocrinology and Reproductive Medicine, Pitié-Salpêtrière Hospital, Reference Center for Rare Endocrine Diseases of Growth, Reference Center for Rare Gynecological Pathologies
- University Pierre and Marie Curie, University Paris 6, F-75013 Paris
| | - Micheline Misrahi
- University Paris-Sud, University Paris Saclay, Medical Faculty Paris-Sud, Bicêtre Hospital, F-94275 Le Kremlin Bicêtre
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16
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Thévenin AF, Margraf RA, Fisher CG, Kells-Andrews RM, Falk MM. Phosphorylation regulates connexin43/ZO-1 binding and release, an important step in gap junction turnover. Mol Biol Cell 2017; 28:3595-3608. [PMID: 29021339 PMCID: PMC5706988 DOI: 10.1091/mbc.e16-07-0496] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Revised: 10/02/2017] [Accepted: 10/03/2017] [Indexed: 12/11/2022] Open
Abstract
To investigate whether connexin phosphorylation regulates the known role of zonula occludens-1 protein (ZO-1) in gap junction (GJ) function, we generated and analyzed a series of phosphomimetic and phosphorylation-dead mutants by mutating known conserved regulatory serine (S) residues 255, 279/282, 365, 368, and 373 located in the C-terminal domain of connexin43 (Cx43) into glutamic acid (E) or alanine (A) residues. All connexin mutants were translated into stable, full-length proteins and assembled into GJs when expressed in HeLa or Madin-Darby canine kidney epithelial cells. However, mutants with S residues exchanged at positions 365, 368, and 373 exhibited a significantly altered ZO-1 interaction profile, while mutants with S residues exchanged at 255 and 279/282 did not. Unlike wild-type Cx43, in which ZO-1 binding is restricted to the periphery of GJ plaques, S365A, S365E, S368A, S368E, and S373A mutants bound ZO-1 throughout the GJ plaques, while the S373E mutant did not bind ZO-1 at all. Inability to disengage from ZO-1 correlated with increased GJ plaque size and increased connexin protein half-life, while maintaining GJ channels in an open, functional state. Quantitative clathrin-binding analyses revealed no significant alterations in clathrin-binding efficiency, suggesting that the inability to disengage from ZO-1 prevented maturation of functional into nonfunctional/endocytic channels, rather than ZO-1 interfering with GJ endocytosis directly. Collectively, our results indicate that ZO-1 binding regulates channel accrual, while disengagement from ZO-1 is critical for GJ channel closure and transitioning GJ channels for endocytosis. Intriguingly, these transitional ZO-1 binding/release and channel-aging steps are mediated by a series of hierarchical phosphorylation/dephosphorylation events at S373, S365, and S368, well-known Cx43 Akt, protein kinase A, and protein kinase C phosphorylation sites located in the vicinity of the ZO-1 binding site.
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Affiliation(s)
| | - Rachel A Margraf
- Department of Biological Sciences, Lehigh University, Bethlehem, PA 18015
| | - Charles G Fisher
- Department of Biological Sciences, Lehigh University, Bethlehem, PA 18015
| | | | - Matthias M Falk
- Department of Biological Sciences, Lehigh University, Bethlehem, PA 18015
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17
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Leybaert L, Lampe PD, Dhein S, Kwak BR, Ferdinandy P, Beyer EC, Laird DW, Naus CC, Green CR, Schulz R. Connexins in Cardiovascular and Neurovascular Health and Disease: Pharmacological Implications. Pharmacol Rev 2017; 69:396-478. [PMID: 28931622 PMCID: PMC5612248 DOI: 10.1124/pr.115.012062] [Citation(s) in RCA: 164] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Connexins are ubiquitous channel forming proteins that assemble as plasma membrane hemichannels and as intercellular gap junction channels that directly connect cells. In the heart, gap junction channels electrically connect myocytes and specialized conductive tissues to coordinate the atrial and ventricular contraction/relaxation cycles and pump function. In blood vessels, these channels facilitate long-distance endothelial cell communication, synchronize smooth muscle cell contraction, and support endothelial-smooth muscle cell communication. In the central nervous system they form cellular syncytia and coordinate neural function. Gap junction channels are normally open and hemichannels are normally closed, but pathologic conditions may restrict gap junction communication and promote hemichannel opening, thereby disturbing a delicate cellular communication balance. Until recently, most connexin-targeting agents exhibited little specificity and several off-target effects. Recent work with peptide-based approaches has demonstrated improved specificity and opened avenues for a more rational approach toward independently modulating the function of gap junctions and hemichannels. We here review the role of connexins and their channels in cardiovascular and neurovascular health and disease, focusing on crucial regulatory aspects and identification of potential targets to modify their function. We conclude that peptide-based investigations have raised several new opportunities for interfering with connexins and their channels that may soon allow preservation of gap junction communication, inhibition of hemichannel opening, and mitigation of inflammatory signaling.
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Affiliation(s)
- Luc Leybaert
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Paul D Lampe
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Stefan Dhein
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Brenda R Kwak
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Peter Ferdinandy
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Eric C Beyer
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Dale W Laird
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Christian C Naus
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Colin R Green
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Rainer Schulz
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
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18
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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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19
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Leithe E, Mesnil M, Aasen T. The connexin 43 C-terminus: A tail of many tales. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1860:48-64. [PMID: 28526583 DOI: 10.1016/j.bbamem.2017.05.008] [Citation(s) in RCA: 137] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Revised: 05/10/2017] [Accepted: 05/12/2017] [Indexed: 10/19/2022]
Abstract
Connexins are chordate gap junction channel proteins that, by enabling direct communication between the cytosols of adjacent cells, create a unique cell signalling network. Gap junctional intercellular communication (GJIC) has important roles in controlling cell growth and differentiation and in tissue development and homeostasis. Moreover, several non-canonical connexin functions unrelated to GJIC have been discovered. Of the 21 members of the human connexin family, connexin 43 (Cx43) is the most widely expressed and studied. The long cytosolic C-terminus (CT) of Cx43 is subject to extensive post-translational modifications that modulate its intracellular trafficking and gap junction channel gating. Moreover, the Cx43 CT contains multiple domains involved in protein interactions that permit crosstalk between Cx43 and cytoskeletal and regulatory proteins. These domains endow Cx43 with the capacity to affect cell growth and differentiation independently of GJIC. Here, we review the current understanding of the regulation and unique functions of the Cx43 CT, both as an essential component of full-length Cx43 and as an independent signalling hub. We highlight the complex regulatory and signalling networks controlled by the Cx43 CT, including the extensive protein interactome that underlies both gap junction channel-dependent and -independent functions. We discuss these data in relation to the recent discovery of the direct translation of specific truncated forms of Cx43. This article is part of a Special Issue entitled: Gap Junction Proteins edited by Jean Claude Herve.
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Affiliation(s)
- Edward Leithe
- Department of Molecular Oncology, Institute for Cancer Research, University of Oslo, NO-0424 Oslo, Norway; Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, NO-0424 Oslo, Norway
| | - Marc Mesnil
- STIM Laboratory ERL 7368 CNRS - Faculté des Sciences Fondamentales et Appliquées, Université de Poitiers, Poitiers 86073, France
| | - Trond Aasen
- Translational Molecular Pathology, Vall d'Hebron Institute of Research (VHIR), Autonomous University of Barcelona, CIBERONC, 08035 Barcelona, Spain.
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Shimizu H, Wilkin MB, Woodcock SA, Bonfini A, Hung Y, Mazaleyrat S, Baron M. The Drosophila ZO-1 protein Polychaetoid suppresses Deltex-regulated Notch activity to modulate germline stem cell niche formation. Open Biol 2017; 7:rsob.160322. [PMID: 28424321 PMCID: PMC5413905 DOI: 10.1098/rsob.160322] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Accepted: 03/13/2017] [Indexed: 11/24/2022] Open
Abstract
The developmental signalling protein Notch can be proteolytically activated following ligand-interaction at the cell surface, or can be activated independently of its ligands, following Deltex (Dx)-induced Notch endocytosis and trafficking to the lysosomal membrane. The means by which different pools of Notch are directed towards these alternative outcomes remains poorly understood. We found that the Drosophila ZO-1 protein Polychaetoid (Pyd) suppresses specifically the Dx-induced form of Notch activation both in vivo and in cell culture assays. In vivo we confirmed the physiological relevance and direction of the Pyd/Dx interaction by showing that the expanded ovary stem cell niche phenotypes of pyd mutants require the presence of functional Dx and other components that are specific to the Dx-induced Notch activation mechanism. In S2 cells we found that Pyd can form a complex with Dx and Notch at the cell surface and reduce Dx-induced Notch endocytosis. Similar to other known activities of ZO-1 family proteins, the action of Pyd on Dx-induced endocytosis and signalling was found to be cell density dependent. Thus, together, our results suggest an alternative means by which external cues can tune Notch signalling through Pyd regulation of Dx-induced Notch trafficking.
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Affiliation(s)
- Hideyuki Shimizu
- University of Manchester, School of Biological Sciences, Manchester Academic Health Science Centre, Michael Smith Building, Oxford Road, Manchester M13 9PL, UK
| | - Marian B Wilkin
- University of Manchester, School of Biological Sciences, Manchester Academic Health Science Centre, Michael Smith Building, Oxford Road, Manchester M13 9PL, UK
| | - Simon A Woodcock
- University of Manchester, School of Biological Sciences, Manchester Academic Health Science Centre, Michael Smith Building, Oxford Road, Manchester M13 9PL, UK
| | - Alessandro Bonfini
- University of Manchester, School of Biological Sciences, Manchester Academic Health Science Centre, Michael Smith Building, Oxford Road, Manchester M13 9PL, UK
| | - Yvonne Hung
- University of Manchester, School of Biological Sciences, Manchester Academic Health Science Centre, Michael Smith Building, Oxford Road, Manchester M13 9PL, UK
| | - Sabine Mazaleyrat
- University of Manchester, School of Biological Sciences, Manchester Academic Health Science Centre, Michael Smith Building, Oxford Road, Manchester M13 9PL, UK
| | - Martin Baron
- University of Manchester, School of Biological Sciences, Manchester Academic Health Science Centre, Michael Smith Building, Oxford Road, Manchester M13 9PL, UK
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Falk MM, Bell CL, Kells Andrews RM, Murray SA. Molecular mechanisms regulating formation, trafficking and processing of annular gap junctions. BMC Cell Biol 2016; 17 Suppl 1:22. [PMID: 27230503 PMCID: PMC4896261 DOI: 10.1186/s12860-016-0087-7] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Internalization of gap junction plaques results in the formation of annular gap junction vesicles. The factors that regulate the coordinated internalization of the gap junction plaques to form annular gap junction vesicles, and the subsequent events involved in annular gap junction processing have only relatively recently been investigated in detail. However it is becoming clear that while annular gap junction vesicles have been demonstrated to be degraded by autophagosomal and endo-lysosomal pathways, they undergo a number of additional processing events. Here, we characterize the morphology of the annular gap junction vesicle and review the current knowledge of the processes involved in their formation, fission, fusion, and degradation. In addition, we address the possibility for connexin protein recycling back to the plasma membrane to contribute to gap junction formation and intercellular communication. Information on gap junction plaque removal from the plasma membrane and the subsequent processing of annular gap junction vesicles is critical to our understanding of cell-cell communication as it relates to events regulating development, cell homeostasis, unstable proliferation of cancer cells, wound healing, changes in the ischemic heart, and many other physiological and pathological cellular phenomena.
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Affiliation(s)
- Matthias M Falk
- Department of Biological Sciences, Lehigh University, Bethlehem, PA, 18049, USA.
| | - Cheryl L Bell
- Department of Cell Biology and Physiology, University of Pittsburgh, School of Medicine, Pittsburgh, PA, l5261, USA
| | | | - Sandra A Murray
- Department of Cell Biology and Physiology, University of Pittsburgh, School of Medicine, Pittsburgh, PA, l5261, USA.
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22
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Shishido SN, Nguyen TA. Induction of Apoptosis by PQ1, a Gap Junction Enhancer that Upregulates Connexin 43 and Activates the MAPK Signaling Pathway in Mammary Carcinoma Cells. Int J Mol Sci 2016; 17:ijms17020178. [PMID: 26840298 PMCID: PMC4783912 DOI: 10.3390/ijms17020178] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Revised: 12/07/2015] [Accepted: 01/22/2016] [Indexed: 11/24/2022] Open
Abstract
The mechanism of gap junction enhancer (PQ1) induced cytotoxicity is thought to be attributed to the change in connexin 43 (Cx43) expression; therefore, the effects of Cx43 modulation in cell survival were investigated in mammary carcinoma cells (FMC2u) derived from a malignant neoplasm of a female FVB/N-Tg(MMTV-PyVT)634Mul/J (PyVT) transgenic mouse. PQ1 was determined to have an IC50 of 6.5 µM in FMC2u cells, while inducing an upregulation in Cx43 expression. The effects of Cx43 modulation in FMC2u cell survival was determined through transfection experiments with Cx43 cDNA, which induced an elevated level of protein expression similar to that seen with PQ1 exposure, or siRNA to silence Cx43 protein expression. Overexpression or silencing of Cx43 led to a reduction or an increase in cell viability, respectively. The mitogen-activated protein kinase (MAPK) family has been implicated in the regulation of cell survival and cell death; therefore, the gap junctional intercellular communication (GJIC)-independent function of PQ1 and Cx43 in the Raf/Mitogen-activated protein kinase/ERK kinase/extracellular-signal-regulated kinase (Raf-MEK-ERK) cascade of cellular survival and p38 MAPK-dependent pathway of apoptosis were explored. PQ1 treatment activated p44/42 MAPK, while the overexpression of Cx43 resulted in a reduced expression. This suggests that PQ1 affects the Raf-MEK-ERK cascade independent of Cx43 upregulation. Both overexpression of Cx43 and PQ1 treatment stimulated an increase in the phosphorylated form of p38-MAPK, reduced levels of the anti-apoptotic protein Bcl-2, and increased the cleavage of pro-caspase-3. Silencing of Cx43 protein expression led to a reduction in the phosphorylation of p38-MAPK and an increase in Bcl-2 expression. The mechanism behind PQ1-induced cytotoxicity in FMC2u mammary carcinoma cells is thought to be attributed to the change in Cx43 expression. Furthermore, PQ1-induced apoptosis through the upregulation of Cx43 may depend on p38 MAPK, highlighting that the effect of PQ1 on gap junctions as well as cellular survival via a MAPK-dependent pathway.
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Affiliation(s)
- Stephanie N Shishido
- Department of Diagnostic Medicine/Pathobiology, Kansas State University, Manhattan, KS 66506, USA.
| | - Thu A Nguyen
- Department of Diagnostic Medicine/Pathobiology, Kansas State University, Manhattan, KS 66506, USA.
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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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Chojnacka K, Mruk DD. The Src non-receptor tyrosine kinase paradigm: New insights into mammalian Sertoli cell biology. Mol Cell Endocrinol 2015; 415:133-42. [PMID: 26296907 DOI: 10.1016/j.mce.2015.08.012] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Revised: 07/27/2015] [Accepted: 08/09/2015] [Indexed: 11/23/2022]
Abstract
Src kinases are non-receptor tyrosine kinases that phosphorylate diverse substrates, which control processes such as cell proliferation, differentiation and survival; cell adhesion; and cell motility. c-Src, the prototypical member of this protein family, is widely expressed by several organs that include the testis. In the seminiferous epithelium of the adult rat testis, c-Src is highest at the tubule lumen during the release of mature spermatids. Other studies show that testosterone regulates spermatid adhesion to Sertoli cells via c-Src, indicating Src phosphorylates key substrates that prompt the disassembly of Sertoli cell-spermatid junctions. A more recent in vitro study reveals that c-Src participates in the internalization of proteins that constitute the blood-testis barrier, which is present between Sertoli cells, suggesting a similar mechanism of junction disassembly is at play during spermiation. In this review, we discuss recent findings on c-Src, with an emphasis on its role in spermatogenesis in the mammalian testis.
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Affiliation(s)
| | - Dolores D Mruk
- Center for Biomedical Research, Population Council, New York, USA.
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25
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Connexin 43 stabilizes astrocytes in a stroke-like milieu to facilitate neuronal recovery. Acta Pharmacol Sin 2015; 36:928-38. [PMID: 26095039 DOI: 10.1038/aps.2015.39] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 04/02/2015] [Indexed: 01/26/2023] Open
Abstract
AIM Connexin 43 (Cx43) is a member of connexin family mainly expressed in astrocytes, which forms gap junctions and hemichannels and maintains the normal shape and function of astrocytes. In this study we investigated the role of Cx43 in astrocytes in facilitating neuronal recovery during ischemic stroke. METHODS Primary culture of astrocytes or a mixed culture of astrocytes and cortical neurons was subjected to oxygen glucose deprivation and reperfusion (OGD/R). The expression of Cx43 and Ephrin-A4 in astrocytes was detected using immunocytochemical staining and Western blot assays. Intercellular Ca(2+) concentration was determined with Fluo-4 AM fluorescent staining. Middle cerebral artery occlusion (MCAO) model rats were used for in vivo studies. RESULTS OGD/R treatment of cultured astrocytes caused a decrement of Cx43 expression and translocation of Cx43 from cell membrane to cytoplasm, accompanied by cell retraction. Furthermore, OGD/R increased intracellular Ca(2+) concentration, activated CaMKII/CREB pathways and upregulated expression of Ephrin-A4 in the astrocytes. All these changes in OGD/R-treated astrocytes were alleviated by overexpression of Cx43. In the cortical neurons cultured with astrocytes, OGD/R inhibited the neurite growth, whereas overexpression of Cx43 or knockdown of Ephrin-A4 in astrocytes restored the neurite growth. In MCAO model rats, neuronal recovery was found to be correlated with the recuperation of Cx43 and Ephrin-A4 in astrocytes. CONCLUSION Cx43 can stabilize astrocytes and facilitate the resistance to the deleterious effects of a stroke-like milieu and promote neuronal recovery.
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Schulz R, Görge PM, Görbe A, Ferdinandy P, Lampe PD, Leybaert L. Connexin 43 is an emerging therapeutic target in ischemia/reperfusion injury, cardioprotection and neuroprotection. Pharmacol Ther 2015; 153:90-106. [PMID: 26073311 DOI: 10.1016/j.pharmthera.2015.06.005] [Citation(s) in RCA: 163] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Accepted: 05/29/2015] [Indexed: 12/22/2022]
Abstract
Connexins are widely distributed proteins in the body that are crucially important for heart and brain functions. Six connexin subunits form a connexon or hemichannel in the plasma membrane. Interactions between two hemichannels in a head-to-head arrangement result in the formation of a gap junction channel. Gap junctions are necessary to coordinate cell function by passing electrical current flow between heart and nerve cells or by allowing exchange of chemical signals and energy substrates. Apart from its localization at the sarcolemma of cardiomyocytes and brain cells, connexins are also found in the mitochondria where they are involved in the regulation of mitochondrial matrix ion fluxes and respiration. Connexin expression is affected by age and gender as well as several pathophysiological alterations such as hypertension, hypertrophy, diabetes, hypercholesterolemia, ischemia, post-myocardial infarction remodeling or heart failure, and post-translationally connexins are modified by phosphorylation/de-phosphorylation and nitros(yl)ation which can modulate channel activity. Using knockout/knockin technology as well as pharmacological approaches, one of the connexins, namely connexin 43, has been identified to be important for cardiac and brain ischemia/reperfusion injuries as well as protection from it. Therefore, the current review will focus on the importance of connexin 43 for irreversible injury of heart and brain tissues following ischemia/reperfusion and will highlight the importance of connexin 43 as an emerging therapeutic target in cardio- and neuroprotection.
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Affiliation(s)
- Rainer Schulz
- Institut für Physiologie, JustusLiebig Universität Giessen, Gießen, Germany.
| | | | - Anikó Görbe
- Cardiovascular Research Group, Department of Biochemistry, Faculty of Medicine, University of Szeged, Hungary; Pharmahungary Group, Szeged, Hungary
| | - Péter Ferdinandy
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary; Pharmahungary Group, Szeged, Hungary
| | - Paul D Lampe
- Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Luc Leybaert
- Physiology Group, Department Basic Medical Sciences, Ghent University, Belgium
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27
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Carette D, Gilleron J, Denizot JP, Grant K, Pointis G, Segretain D. New cellular mechanisms of gap junction degradation and recycling. Biol Cell 2015; 107:218-31. [PMID: 25818265 DOI: 10.1111/boc.201400048] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Accepted: 03/23/2015] [Indexed: 11/29/2022]
Abstract
BACKGROUND INFORMATION Connexins (Cxs), the constitutive proteins of gap junctions, are key actors of many physiological processes. Therefore, alterations of Cx expression and degradation lead to the development of physiopathological disorders. Because of the formation of a double membrane vesicle termed annular gap junction (AGJ), gap junction degradation is a unique physiological process for which many cellular aspects remain unclear. RESULTS By using a combination of time-lapse fluorescence microscopy and high-resolution transmission electron microscopy, we evidenced new specific cellular events concerning gap junction degradation and recycling. Indeed, by time lapse video microscopy we demonstrated, for the first time to our knowledge, that an entire AGJ can be fully recycled back to the plasma membrane. Moreover, we dissected the degradative processes of gap junction by electron microscopy approaches. Interestingly, in addition to canonical autophagy and heterophagy pathways, previously described, we discovered that both pathways could sometimes intermingle. Strikingly, our results also highlighted a new lysosome-based autophagy pathway that could play a pivotal role in common autophagy degradation. CONCLUSIONS The present investigation reveals that AGJ degradation is a more complex process that it was previously thought. First, a complete recycling of the gap junction plaque after its internalisation could occur. Second, the degradation of this peculiar double membrane structure is possible through autophagy, heterophagy, hetero-autophagy or by lysosomal-based autophagy. Altogether, this work underlines novel aspects of gap junction degradation that could be extended to other cell biology processes.
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Affiliation(s)
- Diane Carette
- INSERM U 1065, Team 5 «Physiopathological control of germ cell proliferation: genomic and non-genomic mechanisms», University of Nice Sophia-Antipolis, Nice cedex 3, 06204, France.,UMR S1147, University Paris Descartes, Paris, 75006, France.,University of Versailles, Saint Quentin, 78035, France
| | - Jérôme Gilleron
- INSERM U 1065, Team 5 «Physiopathological control of germ cell proliferation: genomic and non-genomic mechanisms», University of Nice Sophia-Antipolis, Nice cedex 3, 06204, France
| | - Jean-Pierre Denizot
- Unité de Neurosciences, Information et Complexité, CNRS UPR3293, Gif-sur-Yvette, 91190, France
| | - Kirsty Grant
- Unité de Neurosciences, Information et Complexité, CNRS UPR3293, Gif-sur-Yvette, 91190, France
| | - Georges Pointis
- INSERM U 1065, Team 5 «Physiopathological control of germ cell proliferation: genomic and non-genomic mechanisms», University of Nice Sophia-Antipolis, Nice cedex 3, 06204, France
| | - Dominique Segretain
- UMR S1147, University Paris Descartes, Paris, 75006, France.,University of Versailles, Saint Quentin, 78035, France
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Hills CE, Price GW, Squires PE. Mind the gap: connexins and cell-cell communication in the diabetic kidney. Diabetologia 2015; 58:233-41. [PMID: 25358446 DOI: 10.1007/s00125-014-3427-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Accepted: 09/25/2014] [Indexed: 10/24/2022]
Abstract
Connexins, assembled as a hexameric connexon, form a transmembrane hemichannel that provides a conduit for paracrine signalling of small molecules and ions to regulate the activity and function of adjacent cells. When hemichannels align and associate with similar channels on opposing cells, they form a continuous aqueous pore or gap junction, allowing the direct transmission of metabolic and electrical signals between coupled cells. Regulation of gap junction synthesis and channel activity is critical for cell function, and a number of diseases can be attributed to changes in the expression/function of these important proteins. Diabetic nephropathy is associated with several complex metabolic and inflammatory responses characterised by defects at the molecular, cellular and tissue level. In both type 1 and type 2 diabetes, glycaemic injury of the kidney is the leading cause of end-stage renal failure, a consequence of multiple aetiologies, including increased deposition of extracellular matrix, glomerular hyperfiltration, albuminuria and tubulointerstitial fibrosis. In diabetic nephropathy, loss of connexin mediated cell-cell communication within the nephron may represent an early sign of disease; however, our current knowledge of the role of connexins in the diabetic kidney is sparse. This review highlights recent evidence demonstrating that maintenance of connexin-mediated cell-cell communication could benefit region-specific renal function in diabetic nephropathy and suggests that these proteins should be viewed as a tantalising novel target for therapeutic intervention.
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Affiliation(s)
- Claire E Hills
- School of Life Sciences, University of Lincoln, Brayford Pool, Lincoln, LN6 7TS, UK,
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29
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Zhang Z, Huang Y, Xie H, Pan J, Liu F, Li X, Chen W, Hu J, Liu Z. Benzalkonium chloride suppresses rabbit corneal endothelium intercellular gap junction communication. PLoS One 2014; 9:e109708. [PMID: 25299343 PMCID: PMC4192355 DOI: 10.1371/journal.pone.0109708] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2014] [Accepted: 09/12/2014] [Indexed: 01/12/2023] Open
Abstract
Purpose Gap junction intercellular communication (GJIC) plays a critical role in the maintenance of corneal endothelium homeostasis. We determined if benzalkonium chloride (BAK) alters GJIC activity in the rabbit corneal endothelium since it is commonly used as a drug preservative in ocular eyedrop preparations even though it can have cytotoxic effects. Methods Thirty-six adult New Zealand albino rabbits were randomly divided into three groups. BAK at 0.01%, 0.05%, and 0.1% was applied twice daily to one eye of each of the rabbits in one of the three groups for seven days. The contralateral untreated eyes were used as controls. Corneal endothelial morphological features were observed by in vivo confocal microscopy (IVCM). Immunofluorescent staining resolved changes in gap junction integrity and localization. Western blot analysis and RT-PCR evaluated changes in levels of connexin43 (Cx43) and tight junction zonula occludens-1 (ZO-1) gene and protein expression, respectively. Cx43 and ZO-1 physical interaction was detected by immunoprecipitation (IP). Primary rabbit corneal endothelial cells were cultured in Dulbecco's Modified Eagle Medium (DMEM) containing BAK for 24 hours. The scrape-loading dye transfer technique (SLDT) was used to assess GJIC activity. Results Topical administration of BAK (0.05%, 0.1%) dose dependently disrupted corneal endothelial cell morphology, altered Cx43 and ZO-1 distribution and reduced Cx43 expression. BAK also markedly induced increases in Cx43 phosphorylation status concomitant with decreases in the Cx43-ZO-1 protein-protein interaction. These changes were associated with marked declines in GJIC activity. Conclusions The dose dependent declines in rabbit corneal endothelial GJIC activity induced by BAK are associated with less Cx43-ZO-1 interaction possibly arising from increases in Cx43 phosphorylation and declines in its protein expression. These novel changes provide additional evidence that BAK containing eyedrop preparations should be used with caution to avoid declines in corneal transparency resulting from losses in GJIC activity and endothelial function.
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Affiliation(s)
- Zhenhao Zhang
- Eye Institute and affiliated Xiamen Eye Center of Xiamen University; Fujian Provincial Key Laboratory of Ophthalmology and Vision Science, Xiamen, Fujian, China
| | - Yue Huang
- Institute of Stem Cell and Regenerative Medicine, Medical College, Xiamen University, Xiamen, Fujian, China
| | - Hui Xie
- Eye Institute and affiliated Xiamen Eye Center of Xiamen University; Fujian Provincial Key Laboratory of Ophthalmology and Vision Science, Xiamen, Fujian, China
| | - Juxin Pan
- Eye Institute and affiliated Xiamen Eye Center of Xiamen University; Fujian Provincial Key Laboratory of Ophthalmology and Vision Science, Xiamen, Fujian, China
| | - Fanfei Liu
- Eye Institute and affiliated Xiamen Eye Center of Xiamen University; Fujian Provincial Key Laboratory of Ophthalmology and Vision Science, Xiamen, Fujian, China
| | - Xuezhi Li
- Eye Institute and affiliated Xiamen Eye Center of Xiamen University; Fujian Provincial Key Laboratory of Ophthalmology and Vision Science, Xiamen, Fujian, China
| | - Wensheng Chen
- Eye Institute and affiliated Xiamen Eye Center of Xiamen University; Fujian Provincial Key Laboratory of Ophthalmology and Vision Science, Xiamen, Fujian, China
| | - Jiaoyue Hu
- Eye Institute and affiliated Xiamen Eye Center of Xiamen University; Fujian Provincial Key Laboratory of Ophthalmology and Vision Science, Xiamen, Fujian, China
- * E-mail: (ZL); (JH)
| | - Zuguo Liu
- Eye Institute and affiliated Xiamen Eye Center of Xiamen University; Fujian Provincial Key Laboratory of Ophthalmology and Vision Science, Xiamen, Fujian, China
- * E-mail: (ZL); (JH)
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Deficiency of transcription factor Brn4 disrupts cochlear gap junction plaques in a model of DFN3 non-syndromic deafness. PLoS One 2014; 9:e108216. [PMID: 25259580 PMCID: PMC4178122 DOI: 10.1371/journal.pone.0108216] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2014] [Accepted: 08/26/2014] [Indexed: 11/19/2022] Open
Abstract
Brn4, which encodes a POU transcription factor, is the gene responsible for DFN3, an X chromosome-linked, non-syndromic type of hearing loss. Brn4-deficient mice have a low endocochlear potential (EP), hearing loss, and ultrastructural alterations in spiral ligament fibrocytes, however the molecular pathology through which Brn4 deficiency causes low EP is still unclear. Mutations in the Gjb2 and Gjb6 genes encoding the gap junction proteins connexin26 (Cx26) and connexin30 (Cx30) genes, respectively, which encode gap junction proteins and are expressed in cochlear fibrocytes and non-sensory epithelial cells (i.e., cochlear supporting cells) to maintain the proper EP, are responsible for hereditary sensorineural deafness. It has been hypothesized that the gap junction in the cochlea provides an intercellular passage by which K+ is transported to maintain the EP at the high level necessary for sensory hair cell excitation. Here we analyzed the formation of gap junction plaques in cochlear supporting cells of Brn4-deficient mice at different stages by confocal microscopy and three-dimensional graphic reconstructions. Gap junctions from control mice, which are composed mainly of Cx26 and Cx30, formed linear plaques along the cell-cell junction sites with adjacent cells. These plaques formed pentagonal or hexagonal outlines of the normal inner sulcus cells and border cells. Gap junction plaques in Brn4-deficient mice did not, however, show the normal linear structure but instead formed small spots around the cell-cell junction sites. Gap junction lengths were significantly shorter, and the level of Cx26 and Cx30 was significantly reduced in Brn4-deficient mice compared with littermate controls. Thus the Brn4 mutation affected the assembly and localization of gap junction proteins at the cell borders of cochlear supporting cells, suggesting that Brn4 substantially contributes to cochlear gap junction properties to maintain the proper EP in cochleae, similar to connexin-related deafness.
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31
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Wen B, Combes V, Bonhoure A, Weksler BB, Couraud PO, Grau GER. Endotoxin-induced monocytic microparticles have contrasting effects on endothelial inflammatory responses. PLoS One 2014; 9:e91597. [PMID: 24646764 PMCID: PMC3960107 DOI: 10.1371/journal.pone.0091597] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Accepted: 02/11/2014] [Indexed: 12/31/2022] Open
Abstract
Septic shock is a severe disease state characterised by the body's life threatening response to infection. Complex interactions between endothelial cells and circulating monocytes are responsible for microvasculature dysfunction contributing to the pathogenesis of this syndrome. Here, we intended to determine whether microparticles derived from activated monocytes contribute towards inflammatory processes and notably vascular permeability. We found that endotoxin stimulation of human monocytes enhances the release of microparticles of varying phenotypes and mRNA contents. Elevated numbers of LPS-induced monocytic microparticles (mMP) expressed CD54 and contained higher levels of transcripts for pro-inflammatory cytokines such as TNF, IL-6 and IL-8. Using a prothrombin time assay, a greater reduction in plasma coagulation time was observed with LPS-induced mMP than with non-stimulated mMP. Co-incubation of mMP with the human brain endothelial cell line hCMEC/D3 triggered their time-dependent uptake and significantly enhanced endothelial microparticle release. Unexpectedly, mMP also modified signalling pathways by diminishing pSrc (tyr416) expression and promoted endothelial monolayer tightness, as demonstrated by endothelial impedance and permeability assays. Altogether, these data strongly suggest that LPS-induced mMP have contrasting effects on the intercellular communication network and display a dual potential: enhanced pro-inflammatory and procoagulant properties, together with protective function of the endothelium.
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Affiliation(s)
- Beryl Wen
- Vascular Immunology Unit, Sydney Medical School & Bosch Institute, University of Sydney, Camperdown, Australia
| | - Valery Combes
- Vascular Immunology Unit, Sydney Medical School & Bosch Institute, University of Sydney, Camperdown, Australia
| | - Amandine Bonhoure
- Vascular Immunology Unit, Sydney Medical School & Bosch Institute, University of Sydney, Camperdown, Australia
| | - Babette B Weksler
- Weill Medical College, Cornell University, New York, New York, United States of America
| | - Pierre-Olivier Couraud
- Institut Cochin, INSERM U1016, Paris, France; CNRS, UMR 8104, Paris, France; Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Georges E R Grau
- Vascular Immunology Unit, Sydney Medical School & Bosch Institute, University of Sydney, Camperdown, Australia
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Rutledge CA, Ng FS, Sulkin MS, Greener ID, Sergeyenko AM, Liu H, Gemel J, Beyer EC, Sovari AA, Efimov IR, Dudley SC. c-Src kinase inhibition reduces arrhythmia inducibility and connexin43 dysregulation after myocardial infarction. J Am Coll Cardiol 2014; 63:928-34. [PMID: 24361364 PMCID: PMC3963804 DOI: 10.1016/j.jacc.2013.10.081] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2013] [Revised: 10/20/2013] [Accepted: 10/28/2013] [Indexed: 10/25/2022]
Abstract
OBJECTIVES The aim of this study was to evaluate the role of tyrosine kinase cellular-Src (c-Src) inhibition on connexin43 (Cx43) regulation in a mouse model of myocardial infarction (MI). BACKGROUND MI is associated with decreased expression of Cx43, the principal gap junction protein responsible for propagating current in ventricles. Activated c-Src has been linked to Cx43 dysregulation. METHODS MI was induced in 12-week-old mice by coronary artery occlusion. MI mice were treated with c-Src inhibitors (PP1 or AZD0530), PP3 (an inactive analogue of PP1), or saline. Treated hearts were compared to sham mice by echocardiography, optical mapping, telemetry electrocardiographic monitoring, and inducibility studies. Tissues were collected for immunoblotting, quantitative polymerase chain reaction, and immunohistochemistry. RESULTS Active c-Src was elevated in PP3-treated MI mice compared to sham at the scar border (280%, p = 0.003) and distal ventricle (346%, p = 0.013). PP1 treatment restored active c-Src to sham levels at the scar border (86%, p = 0.95) and distal ventricle (94%, p = 1.0). PP1 raised Cx43 expression by 69% in the scar border (p = 0.048) and by 73% in the distal ventricle (p = 0.043) compared with PP3 mice. PP1-treated mice had restored conduction velocity at the scar border (PP3: 32 cm/s, PP1: 41 cm/s, p < 0.05) and lower arrhythmic inducibility (PP3: 71%, PP1: 35%, p < 0.05) than PP3 mice. PP1 did not change infarct size, electrocardiographic pattern, or cardiac function. AZD0530 treatment demonstrated restoration of Cx43 comparable to PP1. CONCLUSIONS c-Src inhibition improved Cx43 levels and conduction velocity and lowered arrhythmia inducibility after MI, suggesting a new approach for arrhythmia reduction following MI.
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Affiliation(s)
- Cody A Rutledge
- Department of Physiology, University of Illinois at Chicago, Chicago, Illinois; Lifespan Cardiovascular Institute, the Warren Alpert School of Medicine of Brown University, and the Providence Veterans Administration Medical Center, Providence. Rhode Island
| | - Fu Siong Ng
- Department of Biomedical Engineering, Washington University, St. Louis, Missouri
| | - Matthew S Sulkin
- Department of Biomedical Engineering, Washington University, St. Louis, Missouri
| | - Ian D Greener
- Lifespan Cardiovascular Institute, the Warren Alpert School of Medicine of Brown University, and the Providence Veterans Administration Medical Center, Providence. Rhode Island
| | - Artem M Sergeyenko
- Lifespan Cardiovascular Institute, the Warren Alpert School of Medicine of Brown University, and the Providence Veterans Administration Medical Center, Providence. Rhode Island
| | - Hong Liu
- Lifespan Cardiovascular Institute, the Warren Alpert School of Medicine of Brown University, and the Providence Veterans Administration Medical Center, Providence. Rhode Island
| | - Joanna Gemel
- Department of Pediatrics, University of Chicago, Chicago, Illinois
| | - Eric C Beyer
- Department of Pediatrics, University of Chicago, Chicago, Illinois
| | - Ali A Sovari
- Lifespan Cardiovascular Institute, the Warren Alpert School of Medicine of Brown University, and the Providence Veterans Administration Medical Center, Providence. Rhode Island
| | - Igor R Efimov
- Department of Biomedical Engineering, Washington University, St. Louis, Missouri
| | - Samuel C Dudley
- Lifespan Cardiovascular Institute, the Warren Alpert School of Medicine of Brown University, and the Providence Veterans Administration Medical Center, Providence. Rhode Island.
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Hervé JC, Derangeon M, Sarrouilhe D, Bourmeyster N. Influence of the scaffolding protein Zonula Occludens (ZOs) on membrane channels. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:595-604. [DOI: 10.1016/j.bbamem.2013.07.006] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Revised: 07/02/2013] [Accepted: 07/04/2013] [Indexed: 01/20/2023]
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Fong JT, Nimlamool W, Falk MM. EGF induces efficient Cx43 gap junction endocytosis in mouse embryonic stem cell colonies via phosphorylation of Ser262, Ser279/282, and Ser368. FEBS Lett 2014; 588:836-44. [PMID: 24492000 DOI: 10.1016/j.febslet.2014.01.048] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Revised: 01/15/2014] [Accepted: 01/16/2014] [Indexed: 11/28/2022]
Abstract
Gap junctions (GJs) traverse apposing membranes of neighboring cells to mediate intercellular communication by passive diffusion of signaling molecules. We have shown previously that cells endocytose GJs utilizing the clathrin machinery. Endocytosis generates cytoplasmic double-membrane vesicles termed annular gap junctions or connexosomes. However, the signaling pathways and protein modifications that trigger GJ endocytosis are largely unknown. Treating mouse embryonic stem cell colonies - endogenously expressing the GJ protein connexin43 (Cx43) - with epidermal growth factor (EGF) inhibited intercellular communication by 64% and activated both, MAPK and PKC signaling cascades to phosphorylate Cx43 on serines 262, 279/282, and 368. Upon EGF treatment Cx43 phosphorylation transiently increased up to 4-fold and induced efficient (66.4%) GJ endocytosis as evidenced by a 5.9-fold increase in Cx43/clathrin co-precipitation.
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Affiliation(s)
- John T Fong
- Department of Biological Sciences, Lehigh University, 111 Research Drive, Iacocca Hall, Bethlehem, PA 18015, USA
| | - Wutigri Nimlamool
- Department of Biological Sciences, Lehigh University, 111 Research Drive, Iacocca Hall, Bethlehem, PA 18015, USA
| | - Matthias M Falk
- Department of Biological Sciences, Lehigh University, 111 Research Drive, Iacocca Hall, Bethlehem, PA 18015, USA.
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Falk MM, Kells RM, Berthoud VM. Degradation of connexins and gap junctions. FEBS Lett 2014; 588:1221-9. [PMID: 24486527 DOI: 10.1016/j.febslet.2014.01.031] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2013] [Revised: 01/21/2014] [Accepted: 01/22/2014] [Indexed: 12/21/2022]
Abstract
Connexin proteins are short-lived within the cell, whether present in the secretory pathway or in gap junction plaques. Their levels can be modulated by their rate of degradation. Connexins, at different stages of assembly, are degraded through the proteasomal, endo-/lysosomal, and phago-/lysosomal pathways. In this review, we summarize the current knowledge about connexin and gap junction degradation including the signals and protein-protein interactions that participate in their targeting for degradation.
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Affiliation(s)
- Matthias M Falk
- Department of Biological Sciences, Lehigh University, 111 Research Drive, Iacocca Hall, D-218, Bethlehem, PA 18015, USA.
| | - Rachael M Kells
- Department of Biological Sciences, Lehigh University, 111 Research Drive, Iacocca Hall, D-218, Bethlehem, PA 18015, USA
| | - Viviana M Berthoud
- Department of Pediatrics, University of Chicago, 900 East 57th St., KCBD, Room 5150, Chicago, IL 60637, USA.
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Connexins: mechanisms regulating protein levels and intercellular communication. FEBS Lett 2014; 588:1212-20. [PMID: 24457202 DOI: 10.1016/j.febslet.2014.01.013] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Revised: 01/10/2014] [Accepted: 01/13/2014] [Indexed: 11/21/2022]
Abstract
Intercellular communication can occur through gap junction channels, which are comprised of connexin proteins. Therefore, levels of connexins can directly correlate with gap junctional intercellular communication. Because gap junctions have a critical role in maintaining cellular homeostasis, the regulation of connexin protein levels is important. In the connexin life cycle, connexin protein levels can be modified through differential gene transcription or altered through trafficking and degradation mechanisms. More recently, significant attention has been directed to the pathways that cells utilize to increase or decrease connexin levels and thus indirectly, gap junctional communication. Here, we review the studies revealing the mechanisms that affect connexin protein levels and gap junctional intercellular communication.
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Thévenin AF, Kowal TJ, Fong JT, Kells RM, Fisher CG, Falk MM. Proteins and mechanisms regulating gap-junction assembly, internalization, and degradation. Physiology (Bethesda) 2014; 28:93-116. [PMID: 23455769 DOI: 10.1152/physiol.00038.2012] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Gap junctions (GJs) are the only known cellular structures that allow a direct cell-to-cell transfer of signaling molecules by forming densely packed arrays or "plaques" of hydrophilic channels that bridge the apposing membranes of neighboring cells. The crucial role of GJ-mediated intercellular communication (GJIC) for all aspects of multicellular life, including coordination of development, tissue function, and cell homeostasis, has been well documented. Assembly and degradation of these membrane channels is a complex process that includes biosynthesis of the connexin (Cx) subunit proteins (innexins in invertebrates) on endoplasmic reticulum (ER) membranes, oligomerization of compatible subunits into hexameric hemichannels (connexons), delivery of the connexons to the plasma membrane (PM), head-on docking of compatible connexons in the extracellular space at distinct locations, arrangement of channels into dynamic spatially and temporally organized GJ channel plaques, as well as internalization of GJs into the cytoplasm followed by their degradation. Clearly, precise modulation of GJIC, biosynthesis, and degradation are crucial for accurate function, and much research currently addresses how these fundamental processes are regulated. Here, we review posttranslational protein modifications (e.g., phosphorylation and ubiquitination) and the binding of protein partners (e.g., the scaffolding protein ZO-1) known to regulate GJ biosynthesis, internalization, and degradation. We also look closely at the atomic resolution structure of a GJ channel, since the structure harbors vital cues relevant to GJ biosynthesis and turnover.
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Affiliation(s)
- Anastasia F Thévenin
- Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania, USA
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Fong JT, Kells RM, Falk MM. Two tyrosine-based sorting signals in the Cx43 C-terminus cooperate to mediate gap junction endocytosis. Mol Biol Cell 2013; 24:2834-48. [PMID: 23885125 PMCID: PMC3771946 DOI: 10.1091/mbc.e13-02-0111] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Three tyrosine-based sorting signals in the gap junction protein connexin 43 were identified, two of which function cooperatively as adaptor protein complex-2 binding sites. The analyses provide a molecular model for clathrin to efficiently internalize large plasma membrane structures and suggest a mechanism for regulating constitutive versus acute gap junction internalization. Gap junction (GJ) channels that electrically and chemically couple neighboring cells are formed when two hemichannels (connexons) of apposed cells dock head-on in the extracellular space. Remarkably, docked connexons are inseparable under physiological conditions, and we and others have shown that GJs are internalized in whole, utilizing the endocytic clathrin machinery. Endocytosis generates double-membrane vesicles (annular GJs or connexosomes) in the cytoplasm of one of the apposed cells that are degraded by autophagosomal and, potentially, endo/lysosomal pathways. In this study, we investigated the structural motifs that mediate Cx43 GJ endocytosis. We identified three canonical tyrosine-based sorting signals of the type “YXXΦ” in the Cx43 C-terminus, two of which function cooperatively as AP-2 binding sites. We generated a set of green fluorescent protein–tagged and untagged Cx43 mutants that targeted these two sites either individually or together. Mutating both sites completely abolished Cx43-AP-2/Dab2/clathrin interaction and resulted in increased GJ plaque size, longer Cx43 protein half-lives, and impaired GJ internalization. Interestingly, Dab2, an accessory clathrin adaptor found earlier to be important for GJ endocytosis, interacts indirectly with Cx43 via AP-2, permitting the recruitment of up to four clathrin complexes per Cx43 protein. Our analyses provide a mechanistic model for clathrin's efficient internalization of large plasma membrane structures, such as GJs.
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Affiliation(s)
- John T Fong
- Department of Biological Sciences, Lehigh University, Bethlehem, PA 18015
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Xie X, Lan T, Chang X, Huang K, Huang J, Wang S, Chen C, Shen X, Liu P, Huang H. Connexin43 mediates NF-κB signalling activation induced by high glucose in GMCs: involvement of c-Src. Cell Commun Signal 2013; 11:38. [PMID: 23718910 PMCID: PMC3699363 DOI: 10.1186/1478-811x-11-38] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Accepted: 05/10/2013] [Indexed: 12/23/2022] Open
Abstract
Background Nuclear factor kappa-B (NF-κB) signalling plays an important role in diabetic nephropathy. Altered expression of connexin43 (Cx43) has been found in kidneys of diabetic animals. The aim of the current study was to investigate the role of Cx43 in the activation of NF-κB induced by high glucose in glomerular mesangial cells (GMCs) and to determine whether c-Src is involved in this process. Results We found that downregulation of Cx43 expression induced by high glucose activated NF-κB in GMCs. Orverexpression of Cx43 attenuated NF-κB p65 nuclear translocation induced by high glucose. High glucose inhibited the interaction between Cx43 and c-Src, and enhanced the interaction between c-Src and IκB-α. PP2, a c-Src inhibitor, also inhibited the tyrosine phosphorylation of IκB-α and NF-κB p65 nuclear translocation induced by high glucose. Furthermore, overexpression of Cx43 or inhibition of c-Src attenuated the upregulation of intercellular adhesion molecule-1 (ICAM-1), transforming growth factor-beta 1 (TGF-β1) and fibronectin (FN) expression induced by high glucose. Conclusions In conclusion, downregulation of Cx43 in GMCs induced by high glucose activates c-Src, which in turn promotes interaction between c-Src and IκB-α and contributes to NF-κB activation in GMCs, leading to renal inflammation.
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Affiliation(s)
- Xi Xie
- Laboratory of Pharmacology & Toxicology, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, 510006, China.
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Cochrane K, Su V, Lau AF. The connexin43-interacting protein, CIP85, mediates the internalization of connexin43 from the plasma membrane. ACTA ACUST UNITED AC 2013; 20:53-66. [PMID: 23586710 DOI: 10.3109/15419061.2013.784745] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
CIP85 was previously identified as a connexin43 (Cx43)-interacting protein that is ubiquitously expressed in multiple mammalian tissues and cell types. The interaction between the SH3 domain of CIP85 and a proline-rich region of Cx43 has previously been associated with an increased rate of Cx43 turnover through lysosomal mechanisms. This report presents biochemical and immunofluorescence evidence that overexpression of CIP85 reduced the presence of Cx43 in gap junction plaques at the plasma membrane. Furthermore, this effect was dependent upon the interaction of CIP85 with Cx43 at the plasma membrane. These results indicate that CIP85 increases Cx43 turnover by accelerating the internalization of Cx43 from the plasma membrane. CIP85 was also observed to interact with clathrin, which suggested a role for CIP85 in the clathrin-mediated internalization of Cx43.
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Affiliation(s)
- Kimberly Cochrane
- Cancer Biology Program, University of Hawaii Cancer Center, Honolulu, HI, USA
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Gap junctions and blood-tissue barriers. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 763:260-80. [PMID: 23397629 DOI: 10.1007/978-1-4614-4711-5_13] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Gap junction is a cell-cell communication junction type found in virtually all mammalian epithelia and endothelia and provides the necessary "signals" to coordinate physiological events to maintain the homeostasis of an epithelium and/or endothelium under normal physiological condition and following changes in the cellular environment (e.g., stimuli from stress, growth, development, inflammation, infection). Recent studies have illustrated the significance of this junction type in the maintenance of different blood-tissue barriers, most notably the blood-brain barrier and blood-testis barrier, which are dynamic ultrastructures, undergoing restructuring in response to stimuli from the environment. In this chapter, we highlight and summarize the latest findings in the field regarding how changes at the gap junction, such as the result of a knock-out, knock-down, knock-in, or gap junction inhibition and/or its activation via the use of inhibitors and/or activators, would affect the integrity or permeability of the blood-tissue barriers. These findings illustrate that much research is needed to delineate the role of gap junction in the blood-tissue barriers, most notably its likely physiological role in mediating or regulating the transport of therapeutic drugs across the blood-tissue barriers.
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Mauro V, Carette D, Pontier-Bres R, Dompierre J, Czerucka D, Segretain D, Gilleron J, Pointis G. The anti-mitotic drug griseofulvin induces apoptosis of human germ cell tumor cells through a connexin 43-dependent molecular mechanism. Apoptosis 2013; 18:480-91. [DOI: 10.1007/s10495-012-0800-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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A functional interaction between the MAGUK protein hDlg and the gap junction protein connexin 43 in cervical tumour cells. Biochem J 2012; 446:9-21. [PMID: 22657348 DOI: 10.1042/bj20111144] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Gap junctions, composed of Cxs (connexins), allow direct intercellular communication. Gap junctions are often lost during the development of malignancy, although the processes behind this are not fully understood. Cx43 is a widely expressed Cx with a long cytoplasmic C-terminal tail that contains several potential protein-interaction domains. Previously, in a model of cervical carcinogenesis, we showed that the loss of gap junctional communication correlated with relocalization of Cx43 to the cytoplasm late in tumorigenesis. In the present study, we demonstrate a similar pattern of altered expression for the hDlg (human discs large) MAGUK (membrane-associated guanylate kinase) family tumour suppressor protein in cervical tumour cells, with partial co-localization of Cx43 and hDlg in an endosomal/lysosomal compartment. Relocalization of these proteins is not due to a general disruption of cell membrane integrity or Cx targeting. Cx43 (via its C-terminus) and hDlg interact directly in vitro and can form a complex in cells. This novel interaction requires the N- and C-termini of hDlg. hDlg is not required for Cx43 internalization in W12GPXY cells. Instead, hDlg appears to have a role in maintaining a cytoplasmic pool of Cx43. These results demonstrate that hDlg is a physiologically relevant regulator of Cx43 in transformed epithelial cells.
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Falk MM, Fong JT, Kells RM, O'Laughlin MC, Kowal TJ, Thévenin AF. Degradation of endocytosed gap junctions by autophagosomal and endo-/lysosomal pathways: a perspective. J Membr Biol 2012; 245:465-76. [PMID: 22825714 DOI: 10.1007/s00232-012-9464-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Accepted: 06/13/2012] [Indexed: 12/24/2022]
Abstract
Gap junctions (GJs) are composed of tens to many thousands of double-membrane spanning GJ channels that cluster together to form densely packed channel arrays (termed GJ plaques) in apposing plasma membranes of neighboring cells. In addition to providing direct intercellular communication (GJIC, their hallmark function), GJs, based on their characteristic double-membrane-spanning configuration, likely also significantly contribute to physical cell-to-cell adhesion. Clearly, modulation (up-/down-regulation) of GJIC and of physical cell-to-cell adhesion is as vitally important as the basic ability of GJ formation itself. Others and we have previously described that GJs can be removed from the plasma membrane via the internalization of entire GJ plaques (or portions thereof) in a cellular process that resembles clathrin-mediated endocytosis. GJ endocytosis results in the formation of double-membrane vesicles [termed annular gap junctions (AGJs) or connexosomes] in the cytoplasm of one of the coupled cells. Four recent independent studies, consistent with earlier ultrastructural analyses, demonstrate the degradation of endocytosed AGJ vesicles via autophagy. However, in TPA-treated cells others report degradation of AGJs via the endo-/lysosomal degradation pathway. Here we summarize evidence that supports the concept that autophagy serves as the cellular default pathway for the degradation of internalized GJs. Furthermore, we highlight and discuss structural criteria that seem required for an alternate degradation via the endo-/lysosomal pathway.
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Affiliation(s)
- Matthias M Falk
- Department of Biological Sciences, Lehigh University, 111 Research Drive, Iacocca Hall, D-218, Bethlehem, PA 18015, USA.
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Degradation of connexins through the proteasomal, endolysosomal and phagolysosomal pathways. J Membr Biol 2012; 245:389-400. [PMID: 22772442 DOI: 10.1007/s00232-012-9461-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Accepted: 06/20/2012] [Indexed: 01/23/2023]
Abstract
Connexins comprise gap junction channels, which create a direct conduit between the cytoplasms of adjacent cells and provide for intercellular communication. Therefore, the level of total cellular connexin protein can have a direct influence on the level of intercellular communication. Control of connexin protein levels can occur through different mechanisms during the connexin life cycle, such as by regulation of connexin gene expression and turnover of existing protein. The degradation of connexins has been extensively studied, revealing proteasomal, endolysosomal and more recently autophagosomal degradation mechanisms that modulate connexin turnover and, subsequently, affect intercellular communication. Here, we review the current knowledge of connexin degradation pathways.
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Tarulli GA, Stanton PG, Meachem SJ. Is the adult Sertoli cell terminally differentiated? Biol Reprod 2012; 87:13, 1-11. [PMID: 22492971 DOI: 10.1095/biolreprod.111.095091] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
New data have challenged the convention that the adult Sertoli cell population is fixed and unmodifiable. The Sertoli cell has two distinct functions: 1) formation of the seminiferous cords and 2) provision of nutritional and structural support to developing germ cells. For these to occur successfully, Sertoli cells must undergo many maturational changes between fetal and adult life, the main switches occurring around puberty, including the loss of proliferative activity and the formation of the blood-testis barrier. Follicle-stimulating hormone plays a key role in promoting Sertoli cell proliferation, while thyroid hormone inhibits proliferative activity in early postnatal life. Together these regulate the Sertoli-germ cell complement and sperm output in adulthood. By puberty, the Sertoli cell population is considered to be stable and unmodifiable by hormones. But there is mounting evidence that the size of the adult Sertoli cell population and its maturational status is modifiable by hormones and that Sertoli cells can gain proliferative ability in the spermatogenically disrupted hamster and human model. This new information demonstrates that the adult Sertoli cell population, at least in the settings of testicular regression in the hamster and impaired fertility in humans in vivo and from mice and men in vitro, is not a terminally differentiated population. Data from the hamster now show that the adult Sertoli cell population size is regulated by hormones. This creates exciting prospects for basic and clinical research in testis biology. The potential to replenish an adult Sertoli-germ cell complement to normal in a setting of infertility may now be realized.
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Affiliation(s)
- Gerard A Tarulli
- Prince Henry's Institute of Medical Research, Clayton, Victoria, Australia
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Connexin43 cardiac gap junction remodeling: lessons from genetically engineered murine models. J Membr Biol 2012; 245:275-81. [PMID: 22722763 DOI: 10.1007/s00232-012-9448-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2012] [Accepted: 06/01/2012] [Indexed: 10/28/2022]
Abstract
Sudden cardiac death is responsible for several hundred thousand deaths each year in the United States. Multiple lines of evidence suggest that perturbation of gap junction expression and function in the heart, or what has come to be known as cardiac gap junction remodeling, plays a key mechanistic role in the pathophysiology of clinically significant cardiac arrhythmias. Here we review recent studies from our laboratory using genetically engineered murine models to explore mechanisms implicated in pathologic gap junction remodeling and their proarrhythmic consequences, with a particular focus on aberrant posttranslational phosphorylation of connexin43.
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48
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Gilleron J, Carette D, Chevallier D, Segretain D, Pointis G. Molecular connexin partner remodeling orchestrates connexin traffic: from physiology to pathophysiology. Crit Rev Biochem Mol Biol 2012; 47:407-23. [PMID: 22551357 DOI: 10.3109/10409238.2012.683482] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Connexins, through gap junctional intercellular communication, are known to regulate many physiological functions involved in developmental processes such as cell proliferation, differentiation, migration and apoptosis. Strikingly, alterations of connexin expression and trafficking are often, if not always, associated with human developmental diseases and carcinogenesis. In this respect, disrupted trafficking dynamics and aberrant intracytoplasmic localization of connexins are considered as typical features of functionality failure leading to the pathological state. Recent findings demonstrate that interactions of connexins with numerous protein partners, which take place throughout connexin trafficking, are essential for gap junction formation, membranous stabilization and degradation. In the present study, we give an overview of the physiological molecular machinery and of the specific interactions between connexins and their partners, which are involved in connexin trafficking, and we highlight their changes in pathological situations.
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Affiliation(s)
- Jérôme Gilleron
- INSERM U 1065, University Nice Sophia Antipolis, Team 5, C3M, 151 route Saint-Antoine de Ginestière, France
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Fong JT, Kells RM, Gumpert AM, Marzillier JY, Davidson MW, Falk MM. Internalized gap junctions are degraded by autophagy. Autophagy 2012; 8:794-811. [PMID: 22635056 PMCID: PMC3378421 DOI: 10.4161/auto.19390] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Direct intercellular communication mediated by gap junctions (GJs) is a hallmark of normal cell and tissue physiology. In addition, GJs significantly contribute to physical cell-cell adhesion. Clearly, these cellular functions require precise modulation. Typically, GJs represent arrays of hundreds to thousands of densely packed channels, each one assembled from two half-channels (connexons), that dock head-on in the extracellular space to form the channel arrays that link neighboring cells together. Interestingly, docked GJ channels cannot be separated into connexons under physiological conditions, posing potential challenges to GJ channel renewal and physical cell-cell separation. We described previously that cells continuously—and effectively after treatment with natural inflammatory mediators—internalize their GJs in an endo-/exocytosis process that utilizes clathrin-mediated endocytosis components, thus enabling these critical cellular functions. GJ internalization generates characteristic cytoplasmic double-membrane vesicles, described and termed earlier annular GJs (AGJs) or connexosomes. Here, using expression of the major fluorescent-tagged GJ protein, connexin 43 (Cx43-GFP/YFP/mApple) in HeLa cells, analysis of endogenously expressed Cx43, ultrastructural analyses, confocal colocalization microscopy, pharmacological and molecular biological RNAi approaches depleting cells of key-autophagic proteins, we provide compelling evidence that GJs, following internalization, are degraded by autophagy. The ubiquitin-binding protein p62/sequestosome 1 was identified in targeting internalized GJs to autophagic degradation. While previous studies identified proteasomal and endo-/lysosomal pathways in Cx43 and GJ degradation, our study provides novel molecular and mechanistic insights into an alternative GJ degradation pathway. Its recent link to health and disease lends additional importance to this GJ degradation mechanism and to autophagy in general.
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Affiliation(s)
- John T Fong
- Department of Biological Sciences, Lehigh University, Bethlehem, PA, USA
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Lazarowski ER. Vesicular and conductive mechanisms of nucleotide release. Purinergic Signal 2012; 8:359-73. [PMID: 22528679 DOI: 10.1007/s11302-012-9304-9] [Citation(s) in RCA: 228] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Accepted: 01/21/2012] [Indexed: 12/22/2022] Open
Abstract
Extracellular nucleotides and nucleosides promote a vast range of physiological responses, via activation of cell surface purinergic receptors. Virtually all tissues and cell types exhibit regulated release of ATP, which, in many cases, is accompanied by the release of uridine nucleotides. Given the relevance of extracellular nucleotide/nucleoside-evoked responses, understanding how ATP and other nucleotides are released from cells is an important physiological question. By facilitating the entry of cytosolic nucleotides into the secretory pathway, recently identified vesicular nucleotide and nucleotide-sugar transporters contribute to the exocytotic release of ATP and UDP-sugars not only from endocrine/exocrine tissues, but also from cell types in which secretory granules have not been biochemically characterized. In addition, plasma membrane connexin hemichannels, pannexin channels, and less-well molecularly defined ATP conducting anion channels have been shown to contribute to the release of ATP (and UTP) under a variety of conditions.
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Affiliation(s)
- Eduardo R Lazarowski
- School of Medicine, University of North Carolina, Chapel Hill, NC 27599-7248, USA.
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