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Jung SE, Choi JW, Moon H, Oh S, Lim S, Lee S, Kim SW, Hwang KC. Small G protein signaling modulator 3 (SGSM3) knockdown attenuates apoptosis and cardiogenic differentiation in rat mesenchymal stem cells exposed to hypoxia. PLoS One 2020; 15:e0231272. [PMID: 32271805 PMCID: PMC7145021 DOI: 10.1371/journal.pone.0231272] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Accepted: 03/19/2020] [Indexed: 12/15/2022] Open
Abstract
Connexin 43 (Cx43) may be important in cell death and survival due to cell-to-cell communication-independent mechanisms. In our previous study, we found that small G protein signaling modulator 3 (SGSM3), a partner of Cx43, contributes to myocardial infarction (MI) in rat hearts. Based on these previous results, we hypothesized that SGSM3 could also play a role in bone marrow-derived rat mesenchymal stem cells (MSCs), which differentiate into cardiomyocytes and/or cells with comparable phenotypes under low oxygen conditions. Cx43 and Cx43-related factor expression profiles were compared between normoxic and hypoxic conditions according to exposure time, and Sgsm3 gene knockdown (KD) using siRNA transfection was performed to validate the interaction between SGSM3 and Cx43 and to determine the roles of SGSM3 in rat MSCs. We identified that SGSM3 interacts with Cx43 in MSCs under different oxygen conditions and that Sgsm3 knockdown inhibits apoptosis and cardiomyocyte differentiation under hypoxic stress. SGSM3/Sgsm3 probably has an effect on MSC survival and thus therapeutic potential in diseased hearts, but SGSM3 may worsen the development of MSC-based therapeutic approaches in regenerative medicine. This study was performed to help us better understand the mechanisms involved in the therapeutic efficacy of MSCs, as well as provide data that could be used pharmacologically.
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Affiliation(s)
- Seung Eun Jung
- Institute for Bio-Medical Convergence, College of Medicine, Catholic Kwandong University, Gangneung-si, Gangwon-do, Republic of Korea
| | - Jung-Won Choi
- Institute for Bio-Medical Convergence, College of Medicine, Catholic Kwandong University, Gangneung-si, Gangwon-do, Republic of Korea
| | - Hanbyeol Moon
- Department of Integrated Omics for Biomedical Sciences, Graduate School, Yonsei University, Seoul, Republic of Korea
| | - Sena Oh
- Institute for Bio-Medical Convergence, College of Medicine, Catholic Kwandong University, Gangneung-si, Gangwon-do, Republic of Korea
| | - Soyeon Lim
- Institute for Bio-Medical Convergence, College of Medicine, Catholic Kwandong University, Gangneung-si, Gangwon-do, Republic of Korea
- International St. Mary’s Hospital, Catholic Kwandong University, Incheon Metropolitan City, Republic of Korea
| | - Seahyoung Lee
- Institute for Bio-Medical Convergence, College of Medicine, Catholic Kwandong University, Gangneung-si, Gangwon-do, Republic of Korea
- International St. Mary’s Hospital, Catholic Kwandong University, Incheon Metropolitan City, Republic of Korea
| | - Sang Woo Kim
- Institute for Bio-Medical Convergence, College of Medicine, Catholic Kwandong University, Gangneung-si, Gangwon-do, Republic of Korea
- International St. Mary’s Hospital, Catholic Kwandong University, Incheon Metropolitan City, Republic of Korea
| | - Ki-Chul Hwang
- Institute for Bio-Medical Convergence, College of Medicine, Catholic Kwandong University, Gangneung-si, Gangwon-do, Republic of Korea
- International St. Mary’s Hospital, Catholic Kwandong University, Incheon Metropolitan City, Republic of Korea
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2
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Long non-coding RNA CCRR controls cardiac conduction via regulating intercellular coupling. Nat Commun 2018; 9:4176. [PMID: 30301979 PMCID: PMC6177441 DOI: 10.1038/s41467-018-06637-9] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Accepted: 09/10/2018] [Indexed: 12/31/2022] Open
Abstract
Long non-coding RNAs (lncRNAs) have emerged as a new class of gene expression regulators playing key roles in many biological and pathophysiological processes. Here, we identify cardiac conduction regulatory RNA (CCRR) as an antiarrhythmic lncRNA. CCRR is downregulated in a mouse model of heart failure (HF) and in patients with HF, and this downregulation slows cardiac conduction and enhances arrhythmogenicity. Moreover, CCRR silencing induces arrhythmias in healthy mice. CCRR overexpression eliminates these detrimental alterations. HF or CCRR knockdown causes destruction of intercalated discs and gap junctions to slow longitudinal cardiac conduction. CCRR overexpression improves cardiac conduction by blocking endocytic trafficking of connexin43 (Cx43) to prevent its degradation via binding to Cx43-interacting protein CIP85, whereas CCRR silence does the opposite. We identified the functional domain of CCRR, which can reproduce the functional roles and pertinent molecular events of full-length CCRR. Our study suggests CCRR replacement a potential therapeutic approach for pathological arrhythmias.
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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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Majoul IV, Ernesti JS, Butkevich EV, Duden R. Drebrins and Connexins: A Biomedical Perspective. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1006:225-247. [DOI: 10.1007/978-4-431-56550-5_13] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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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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6
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Iyyathurai J, Decuypere JP, Leybaert L, D'hondt C, Bultynck G. Connexins: substrates and regulators of autophagy. BMC Cell Biol 2016; 17 Suppl 1:20. [PMID: 27229147 PMCID: PMC4896244 DOI: 10.1186/s12860-016-0093-9] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Connexins mediate intercellular communication by assembling into hexameric channel complexes that act as hemichannels and gap junction channels. Most connexins are characterized by a very rapid turn-over in a variety of cell systems. The regulation of connexin turn-over by phosphorylation and ubiquitination events has been well documented. Moreover, different pathways have been implicated in connexin degradation, including proteasomal and lysosomal-based pathways. Only recently, autophagy emerged as an important connexin-degradation pathway for different connexin isoforms. As such, conditions well known to induce autophagy have an immediate impact on the connexin-expression levels. This is not only limited to experimental conditions but also several pathophysiological conditions associated with autophagy (dys)function affect connexin levels and their presence at the cell surface as gap junctions. Finally, connexins are not only substrates of autophagy but also emerge as regulators of the autophagy process. In particular, several connexin isoforms appear to recruit pre-autophagosomal autophagy-related proteins, including Atg16 and PI3K-complex components, to the plasma membrane, thereby limiting their availability and capacity for regulating autophagy.
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Affiliation(s)
- Jegan Iyyathurai
- KU Leuven, Laboratory of Molecular and Cellular Signaling, Department Cellular and Molecular Medicine, Campus Gasthuisberg O/N-I bus 802, Herestraat 49, B-3000, Leuven, Belgium
| | - Jean-Paul Decuypere
- KU Leuven, Laboratory for Membrane Trafficking, Department of Human Genetics, and VIB-Center for the Biology of Disease, Campus Gasthuisberg, O/N-IV, 7.159, Herestraat 49, 3000, Leuven, Belgium
| | - Luc Leybaert
- Ghent University, Physiology Group, Department of Basic Medical Sciences, 9000, Ghent, Belgium
| | - Catheleyne D'hondt
- KU Leuven, Laboratory of Molecular and Cellular Signaling, Department Cellular and Molecular Medicine, Campus Gasthuisberg O/N-I bus 802, Herestraat 49, B-3000, Leuven, Belgium
| | - Geert Bultynck
- KU Leuven, Laboratory of Molecular and Cellular Signaling, Department Cellular and Molecular Medicine, Campus Gasthuisberg O/N-I bus 802, Herestraat 49, B-3000, Leuven, Belgium.
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7
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Leithe E. Regulation of connexins by the ubiquitin system: Implications for intercellular communication and cancer. Biochim Biophys Acta Rev Cancer 2016; 1865:133-46. [DOI: 10.1016/j.bbcan.2016.02.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Revised: 01/15/2016] [Accepted: 02/04/2016] [Indexed: 12/31/2022]
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8
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Intracellular Cleavage of the Cx43 C-Terminal Domain by Matrix-Metalloproteases: A Novel Contributor to Inflammation? Mediators Inflamm 2015; 2015:257471. [PMID: 26424967 PMCID: PMC4573893 DOI: 10.1155/2015/257471] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2015] [Accepted: 08/13/2015] [Indexed: 01/11/2023] Open
Abstract
The coordination of tissue function is mediated by gap junctions (GJs) that enable direct cell-cell transfer of metabolic and electric signals. GJs are formed by connexin (Cx) proteins of which Cx43 is most widespread in the human body. Beyond its role in direct intercellular communication, Cx43 also forms nonjunctional hemichannels (HCs) in the plasma membrane that mediate the release of paracrine signaling molecules in the extracellular environment. Both HC and GJ channel function are regulated by protein-protein interactions and posttranslational modifications that predominantly take place in the C-terminal domain of Cx43. Matrix metalloproteases (MMPs) are a major group of zinc-dependent proteases, known to regulate not only extracellular matrix remodeling, but also processing of intracellular proteins. Together with Cx43 channels, both GJs and HCs, MMPs contribute to acute inflammation and a small number of studies reports on an MMP-Cx43 link. Here, we build further on these reports and present a novel hypothesis that describes proteolytic cleavage of the Cx43 C-terminal domain by MMPs and explores possibilities of how such cleavage events may affect Cx43 channel function. Finally, we set out how aberrant channel function resulting from cleavage can contribute to the acute inflammatory response during tissue injury.
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9
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Kelly JJ, Simek J, Laird DW. Mechanisms linking connexin mutations to human diseases. Cell Tissue Res 2014; 360:701-21. [DOI: 10.1007/s00441-014-2024-4] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Accepted: 09/26/2014] [Indexed: 11/30/2022]
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10
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Ailion M, Hannemann M, Dalton S, Pappas A, Watanabe S, Hegermann J, Liu Q, Han HF, Gu M, Goulding MQ, Sasidharan N, Schuske K, Hullett P, Eimer S, Jorgensen EM. Two Rab2 interactors regulate dense-core vesicle maturation. Neuron 2014; 82:167-80. [PMID: 24698274 DOI: 10.1016/j.neuron.2014.02.017] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/23/2014] [Indexed: 12/14/2022]
Abstract
Peptide neuromodulators are released from a unique organelle: the dense-core vesicle. Dense-core vesicles are generated at the trans-Golgi and then sort cargo during maturation before being secreted. To identify proteins that act in this pathway, we performed a genetic screen in Caenorhabditis elegans for mutants defective in dense-core vesicle function. We identified two conserved Rab2-binding proteins: RUND-1, a RUN domain protein, and CCCP-1, a coiled-coil protein. RUND-1 and CCCP-1 colocalize with RAB-2 at the Golgi, and rab-2, rund-1, and cccp-1 mutants have similar defects in sorting soluble and transmembrane dense-core vesicle cargos. RUND-1 also interacts with the Rab2 GAP protein TBC-8 and the BAR domain protein RIC-19, a RAB-2 effector. In summary, a pathway of conserved proteins controls the maturation of dense-core vesicles at the trans-Golgi network.
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Affiliation(s)
- Michael Ailion
- Howard Hughes Medical Institute, Department of Biology, University of Utah, Salt Lake City, UT 84112, USA; Department of Biochemistry, University of Washington, Seattle WA, 98195, USA.
| | - Mandy Hannemann
- European Neuroscience Institute, 37077 Göttingen, Germany; International Max Planck Research School Molecular Biology, 37077 Göttingen, Germany
| | - Susan Dalton
- Howard Hughes Medical Institute, Department of Biology, University of Utah, Salt Lake City, UT 84112, USA
| | - Andrea Pappas
- Howard Hughes Medical Institute, Department of Biology, University of Utah, Salt Lake City, UT 84112, USA
| | - Shigeki Watanabe
- Howard Hughes Medical Institute, Department of Biology, University of Utah, Salt Lake City, UT 84112, USA
| | - Jan Hegermann
- European Neuroscience Institute, 37077 Göttingen, Germany; DFG research Center for Molecular Physiology of the Brain (CMPB), 37077 Göttingen, Germany
| | - Qiang Liu
- Howard Hughes Medical Institute, Department of Biology, University of Utah, Salt Lake City, UT 84112, USA
| | - Hsiao-Fen Han
- Howard Hughes Medical Institute, Department of Biology, University of Utah, Salt Lake City, UT 84112, USA
| | - Mingyu Gu
- Howard Hughes Medical Institute, Department of Biology, University of Utah, Salt Lake City, UT 84112, USA
| | - Morgan Q Goulding
- Department of Biochemistry, University of Washington, Seattle WA, 98195, USA
| | | | - Kim Schuske
- Howard Hughes Medical Institute, Department of Biology, University of Utah, Salt Lake City, UT 84112, USA
| | - Patrick Hullett
- Howard Hughes Medical Institute, Department of Biology, University of Utah, Salt Lake City, UT 84112, USA
| | - Stefan Eimer
- European Neuroscience Institute, 37077 Göttingen, Germany; DFG research Center for Molecular Physiology of the Brain (CMPB), 37077 Göttingen, Germany
| | - Erik M Jorgensen
- Howard Hughes Medical Institute, Department of Biology, University of Utah, Salt Lake City, UT 84112, USA.
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11
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Cone AC, Cavin G, Ambrosi C, Hakozaki H, Wu-Zhang AX, Kunkel MT, Newton AC, Sosinsky GE. Protein kinase Cδ-mediated phosphorylation of Connexin43 gap junction channels causes movement within gap junctions followed by vesicle internalization and protein degradation. J Biol Chem 2014; 289:8781-98. [PMID: 24500718 PMCID: PMC3979370 DOI: 10.1074/jbc.m113.533265] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2013] [Revised: 01/29/2014] [Indexed: 01/14/2023] Open
Abstract
Phosphorylation of gap junction proteins, connexins, plays a role in global signaling events involving kinases. Connexin43 (Cx43), a ubiquitous and important connexin, has several phosphorylation sites for specific kinases. We appended an imaging reporter tag for the activity of the δ isoform of protein kinase C (PKCδ) to the carboxyl terminus of Cx43. The FRET signal of this reporter is inversely related to the phosphorylation of serine 368 of Cx43. By activating PKC with the phorbol ester phorbol 12,13-dibutyrate (PDBu) or a natural stimulant, UTP, time lapse live cell imaging movies indicated phosphorylated Ser-368 Cx43 separated into discrete domains within gap junctions and was internalized in small vesicles, after which it was degraded by lysosomes and proteasomes. Mutation of Ser-368 to an Ala eliminated the response to PDBu and changes in phosphorylation of the reporter. A phosphatase inhibitor, calyculin A, does not change this pattern, indicating PKC phosphorylation causes degradation of Cx43 without dephosphorylation, which is in accordance with current hypotheses that cells control their intercellular communication by a fast and constant turnover of connexins, using phosphorylation as part of this mechanism.
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Affiliation(s)
- Angela C. Cone
- From the National Center for Microscopy and Imaging Research
| | - Gabriel Cavin
- From the National Center for Microscopy and Imaging Research
| | - Cinzia Ambrosi
- From the National Center for Microscopy and Imaging Research
| | | | | | | | | | - Gina E. Sosinsky
- From the National Center for Microscopy and Imaging Research
- the Department of Neurosciences, University of California, San Diego, California 92093
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12
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Kurtenbach S, Kurtenbach S, Zoidl G. Gap junction modulation and its implications for heart function. Front Physiol 2014; 5:82. [PMID: 24578694 PMCID: PMC3936571 DOI: 10.3389/fphys.2014.00082] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Accepted: 02/10/2014] [Indexed: 01/04/2023] Open
Abstract
Gap junction communication (GJC) mediated by connexins is critical for heart function. To gain insight into the causal relationship of molecular mechanisms of disease pathology, it is important to understand which mechanisms contribute to impairment of gap junctional communication. Here, we present an update on the known modulators of connexins, including various interaction partners, kinases, and signaling cascades. This gap junction network (GJN) can serve as a blueprint for data mining approaches exploring the growing number of publicly available data sets from experimental and clinical studies.
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Affiliation(s)
- Stefan Kurtenbach
- Department of Psychology, Faculty of Health, York University Toronto, ON, Canada
| | - Sarah Kurtenbach
- Department of Psychology, Faculty of Health, York University Toronto, ON, Canada
| | - Georg Zoidl
- Department of Psychology, Faculty of Health, York University Toronto, ON, Canada ; Department of Biology, Faculty of Science, York University Toronto, ON, Canada ; Center for Vision Research, York University Toronto, ON, Canada
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13
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CIP75 (connexin43-interacting protein of 75 kDa) mediates the endoplasmic reticulum dislocation of connexin43. Biochem J 2014; 458:57-67. [DOI: 10.1042/bj20131247] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The proteasomal degradation of the gap junction protein connexin43 is facilitated by its interaction with the connexin43-interacting protein of 75 kDa at the endoplasmic reticulum membrane.
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14
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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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15
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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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16
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Chen VC, Kristensen AR, Foster LJ, Naus CC. Association of Connexin43 with E3 Ubiquitin Ligase TRIM21 Reveals a Mechanism for Gap Junction Phosphodegron Control. J Proteome Res 2012; 11:6134-46. [DOI: 10.1021/pr300790h] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Vincent C. Chen
- Department
of Biochemistry and Molecular Biology, Centre for High-Throughput
Biology, ‡Department
of Cellular and Physiological Sciences, Life Sciences
Institute, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia, V6T 1Z3,
Canada
| | - Anders R. Kristensen
- Department
of Biochemistry and Molecular Biology, Centre for High-Throughput
Biology, ‡Department
of Cellular and Physiological Sciences, Life Sciences
Institute, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia, V6T 1Z3,
Canada
| | - Leonard J. Foster
- Department
of Biochemistry and Molecular Biology, Centre for High-Throughput
Biology, ‡Department
of Cellular and Physiological Sciences, Life Sciences
Institute, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia, V6T 1Z3,
Canada
| | - Christian C. Naus
- Department
of Biochemistry and Molecular Biology, Centre for High-Throughput
Biology, ‡Department
of Cellular and Physiological Sciences, Life Sciences
Institute, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia, V6T 1Z3,
Canada
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17
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The role of the C-terminus in functional expression and internalization of rat connexin46 (rCx46). J Bioenerg Biomembr 2012; 45:59-70. [PMID: 23065326 DOI: 10.1007/s10863-012-9480-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Accepted: 10/01/2012] [Indexed: 12/17/2022]
Abstract
The C-terminus (CT) of rCx46 consists of 186 residues (H230-I416). Recent studies showed that rCx46(28.2), truncated after H243, altered the formation of functional hemichannels when expressed in Xenopus oocytes, while rCx46(37.7), truncated after A333 formed gap junction hemichannels similarly to rCx46(wt). To analyze the role of the CT up to A333 in functional expression with cell imaging and dye-transfer techniques, different mutants were generated by C-terminal truncation between H243-A333, labeled with EGFP and expressed in HeLa cells. These rCx46 variants were characterized according to their compartmentalization in organelles, their presence in microscopic detectable vesicles and their ability to form gap junction plaques. rCx46 truncated after A311 (rCx46(35.3)) was compartmentalized, was found in vesicles and formed functional gap junction plaques similarly to rCx46(wt). With a truncation after P284 (rCx46(32.6)), the protein was not compartmentalized and the amount of vesicles containing the protein were reduced; however, functional gap junction plaque formation was not affected as compared to rCx46(35.3). rCx46(28.2) did not form functional gap junction plaques; it was not found in vesicles or in cellular compartments. Live-cell imaging and detection of annular junctions for rCx46(32.6) and rCx46(35.3) revealed that the truncation after P284 reduced the frequency of vesicle budding from gap junction plaques and the formation of annular junctions. These results suggest that the C-terminal region of rCx46 up to A311 (rCx46(35.3)) is necessary for its correct compartmentalization and internalization in the form of annular junctions, while the H230-P284 C-terminal region (rCx46(32.6)) is sufficient for the formation of dye coupled gap junction channels.
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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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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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20
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Suh HN, Kim MO, Han HJ. Laminin-111 stimulates proliferation of mouse embryonic stem cells through a reduction of gap junctional intercellular communication via RhoA-mediated Cx43 phosphorylation and dissociation of Cx43/ZO-1/drebrin complex. Stem Cells Dev 2012; 21:2058-70. [PMID: 22150760 DOI: 10.1089/scd.2011.0505] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Gap junctions within extracellular matrix (ECM)-defined boundaries ensure synchronous activity between cells destined to become functional mediators that regulate cell behavior. However, the role of ECM in connexin (Cx) function in mouse embryonic stem cells (mESCs) has not been elucidated. Therefore, we examined the role of laminin-111 in the control of Cx43 functions and related signal pathways in mESCs. ECM components (laminin-111, fibronectin, and collagen I) increased Cx43 phosphorylation and decreased Lucifer yellow (Ly) diffusion. In addition, laminin-111 increased the proliferation index through reduction of gap junctional intercellular communication (GJIC), which was confirmed by 18α-glycyrrhetinic acid (18α-GA). Laminin-111 increased phosphorylation of focal adhesion kinase (FAK)/Src and protein kinase C (PKC), which were inhibited by integrin β1 antibody (Ab) and laminin receptor-1 (LR-1) Ab, respectively. In addition, inhibition of both FAK/Src and PKC blocked Cx43 phosphorylation. Laminin-111 increased the Ras homolog gene family, member A (RhoA) activation, which was blocked by FAK/Src and PKC inhibitors, suggesting the existence of parallel pathways that merge at RhoA. Inhibition of RhoA reversed the laminin-111-induced increase of Cx43 phosphorylation and reduction of GJIC. Laminin-111 also stimulated the dissociation of Cx43/ZO-1 complex followed by disruption of Cx43/drebrin and Cx43/F-actin complexes, which were reversed by C3 (RhoA inhibitor). ZO-1 small interfering (si) RNA significantly decreased Ly diffusion. Moreover, laminin-111 decreased Cx43 labeling at the intercellular junction, whereas pretreatment with degradation inhibitors (lysosomal protease inhibitor, chloroquine; proteasome inhibitor, lactacystin) increased Cx43 expression, reversely. In conclusion, laminin-111 stimulated mESC proliferation through a reduction of GJIC via RhoA-mediated Cx43 phosphorylation and Cx43/ZO-1/drebrin complex instability-mediated Cx43 degradation.
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Affiliation(s)
- Han Na Suh
- Department of Veterinary Physiology, College of Veterinary Medicine, Chonnam National University, Gwangju, South Korea
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21
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Hervé JC, Derangeon M, Sarrouilhe D, Giepmans BNG, Bourmeyster N. Gap junctional channels are parts of multiprotein complexes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:1844-65. [PMID: 22197781 DOI: 10.1016/j.bbamem.2011.12.009] [Citation(s) in RCA: 110] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2011] [Revised: 11/28/2011] [Accepted: 12/06/2011] [Indexed: 12/16/2022]
Abstract
Gap junctional channels are a class of membrane channels composed of transmembrane channel-forming integral membrane proteins termed connexins, innexins or pannexins that mediate direct cell-to-cell or cell-to extracellular medium communication in almost all animal tissues. The activity of these channels is tightly regulated, particularly by intramolecular modifications as phosphorylations of proteins and via the formation of multiprotein complexes where pore-forming subunits bind to auxiliary channel subunits and associate with scaffolding proteins that play essential roles in channel localization and activity. Scaffolding proteins link signaling enzymes, substrates, and potential effectors (such as channels) into multiprotein signaling complexes that may be anchored to the cytoskeleton. Protein-protein interactions play essential roles in channel localization and activity and, besides their cell-to-cell channel-forming functions, gap junctional proteins now appear involved in different cellular functions (e.g. transcriptional and cytoskeletal regulations). The present review summarizes the recent progress regarding the proteins capable of interacting with junctional proteins and highlights the function of these protein-protein interactions in cell physiology and aberrant function in diseases. This article is part of a Special Issue entitled: The Communicating junctions, composition, structure and functions.
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Affiliation(s)
- Jean-Claude Hervé
- Institut de Physiologie et Biologie Cellulaires, Université de Poitiers, CNRS, Poitiers, France.
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22
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Leithe E, Sirnes S, Fykerud T, Kjenseth A, Rivedal E. Endocytosis and post-endocytic sorting of connexins. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:1870-9. [PMID: 21996040 DOI: 10.1016/j.bbamem.2011.09.029] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2011] [Revised: 09/19/2011] [Accepted: 09/28/2011] [Indexed: 12/15/2022]
Abstract
The connexins constitute a family of integral membrane proteins that form intercellular channels, enabling adjacent cells in solid tissues to directly exchange ions and small molecules. These channels assemble into distinct plasma membrane domains known as gap junctions. Gap junction intercellular communication plays critical roles in numerous cellular processes, including control of cell growth and differentiation, maintenance of tissue homeostasis and embryonic development. Gap junctions are dynamic plasma membrane domains, and there is increasing evidence that modulation of endocytosis and post-endocytic trafficking of connexins are important mechanisms for regulating the level of functional gap junctions at the plasma membrane. The emerging picture is that multiple pathways exist for endocytosis and sorting of connexins to lysosomes, and that these pathways are differentially regulated in response to physiological and pathophysiological stimuli. Recent studies suggest that endocytosis and lysosomal degradation of connexins is controlled by a complex interplay between phosphorylation and ubiquitination. This review summarizes recent progress in understanding the molecular mechanisms involved in endocytosis and post-endocytic sorting of connexins, and the relevance of these processes to the regulation of gap junction intercellular communication under normal and pathophysiological conditions. This article is part of a Special Issue entitled: The Communicating junctions, composition, structure and characteristics.
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Affiliation(s)
- Edward Leithe
- Department of Cancer Prevention, Oslo University Hospital, Oslo, Norway
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Palatinus JA, Rhett JM, Gourdie RG. The connexin43 carboxyl terminus and cardiac gap junction organization. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:1831-43. [PMID: 21856279 DOI: 10.1016/j.bbamem.2011.08.006] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2011] [Revised: 07/25/2011] [Accepted: 08/03/2011] [Indexed: 12/09/2022]
Abstract
The precise spatial order of gap junctions at intercalated disks in adult ventricular myocardium is thought vital for maintaining cardiac synchrony. Breakdown or remodeling of this order is a hallmark of arrhythmic disease of the heart. The principal component of gap junction channels between ventricular cardiomyocytes is connexin43 (Cx43). Protein-protein interactions and modifications of the carboxyl-terminus of Cx43 are key determinants of gap junction function, size, distribution and organization during normal development and in disease processes. Here, we review data on the role of proteins interacting with the Cx43 carboxyl-terminus in the regulation of cardiac gap junction organization, with particular emphasis on Zonula Occludens-1. The rapid progress in this area suggests that in coming years we are likely to develop a fuller understanding of the molecular mechanisms causing pathologic remodeling of gap junctions. With these advances come the promise of novel approach to the treatment of arrhythmia and the prevention of sudden cardiac death. This article is part of a Special Issue entitled: The Communicating junctions, composition, structure and characteristics.
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Affiliation(s)
- Joseph A Palatinus
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC, USA
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Yoshida H, Kitagishi Y, Okumura N, Murakami M, Nishimura Y, Matsuda S. How do you RUN on? FEBS Lett 2011; 585:1707-10. [PMID: 21570977 DOI: 10.1016/j.febslet.2011.05.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2011] [Revised: 05/03/2011] [Accepted: 05/03/2011] [Indexed: 10/18/2022]
Abstract
RUN domain is present in several proteins related to the functions of Rap and Rab family GTPases. Accumulating evidence supports the hypothesis that RUN domain-containing proteins act as a component of vesicle traffic and might be responsible for an interaction with a filamentous network linked to actin cytoskeleton or microtubules. That is to say, on one hand, RUN domains associate with Rab or Rap family proteins, on the other hand, they also might interact with motor proteins such as kinesin or myosin via intervention molecules. In this review, we summarize the background and current status of RUN domain research with an emphasis on the interaction between RUN domain and motor proteins with respect to the vesicle traffic on filamentous network.
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Affiliation(s)
- Hitomi Yoshida
- Department of Environmental Health Science, Nara Women's University, Kita-Uoya Nishimachi, Nara, Japan
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25
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Abstract
The TBC (Tre-2/Bub2/Cdc16) domain was originally identified as a conserved domain among the tre-2 oncogene product and the yeast cell cycle regulators Bub2 and Cdc16, and it is now widely recognized as a conserved protein motif that consists of approx. 200 amino acids in all eukaryotes. Since the TBC domain of yeast Gyps [GAP (GTPase-activating protein) for Ypt proteins] has been shown to function as a GAP domain for small GTPase Ypt/Rab, TBC domain-containing proteins (TBC proteins) in other species are also expected to function as a certain Rab-GAP. More than 40 different TBC proteins are present in humans and mice, and recent accumulating evidence has indicated that certain mammalian TBC proteins actually function as a specific Rab-GAP. Some mammalian TBC proteins {e.g. TBC1D1 [TBC (Tre-2/Bub2/Cdc16) domain family, member 1] and TBC1D4/AS160 (Akt substrate of 160 kDa)} play an important role in homoeostasis in mammals, and defects in them are directly associated with mouse and human diseases (e.g. leanness in mice and insulin resistance in humans). The present study reviews the structure and function of mammalian TBC proteins, especially in relation to Rab small GTPases.
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Su V, Nakagawa R, Koval M, Lau AF. Ubiquitin-independent proteasomal degradation of endoplasmic reticulum-localized connexin43 mediated by CIP75. J Biol Chem 2010; 285:40979-90. [PMID: 20940304 DOI: 10.1074/jbc.m110.170753] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Connexin43 (Cx43) is a transmembrane protein that forms gap junction channels. Regulation of Cx43 turnover is one mechanism to control the level of intercellular communication that occurs through gap junction channels. Proteasomal degradation of Cx43 is regulated in part through CIP75, a ubiquitin-like and ubiquitin-associated domain containing protein. CIP75 interacts with endoplasmic reticulum-localized Cx43, as demonstrated through co-immunoprecipitation and immunofluorescence microscopy experiments. CIP75 also binds to free monoubiquitin and lysine 48-linked tetraubiquitin chains in vitro and binds to ubiquitinated proteins in cellular lysates. However, analysis of Cx43 that immunoprecipitated with CIP75 demonstrated that the Cx43 associated with CIP75 was not ubiquitinated, and a mutant form of Cx43 that lacked lysines capable of ubiquitination retained the capacity to interact with CIP75. These results suggest that although CIP75 can interact with ubiquitinated cellular proteins, its interaction with Cx43 and stimulation of Cx43 proteasomal degradation does not require the ubiquitination of Cx43.
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Affiliation(s)
- Vivian Su
- Natural Products and Cancer Biology Program, Cancer Research Center of Hawaii, Honolulu, Hawaii 96813, USA
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27
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Abstract
Gap junctions are aggregates of intercellular channels that permit direct cell-cell transfer of ions and small molecules. Initially described as low-resistance ion pathways joining excitable cells (nerve and muscle), gap junctions are found joining virtually all cells in solid tissues. Their long evolutionary history has permitted adaptation of gap-junctional intercellular communication to a variety of functions, with multiple regulatory mechanisms. Gap-junctional channels are composed of hexamers of medium-sized families of integral proteins: connexins in chordates and innexins in precordates. The functions of gap junctions have been explored by studying mutations in flies, worms, and humans, and targeted gene disruption in mice. These studies have revealed a wide diversity of function in tissue and organ biology.
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Ponsaerts R, De Vuyst E, Retamal M, D'hondt C, Vermeire D, Wang N, De Smedt H, Zimmermann P, Himpens B, Vereecke J, Leybaert L, Bultynck G. Intramolecular loop/tail interactions are essential for connexin 43-hemichannel activity. FASEB J 2010; 24:4378-95. [PMID: 20634352 DOI: 10.1096/fj.09-153007] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Connexin-assembled gap junctions (GJs) and hemichannels coordinate intercellular signaling processes. Although the regulation of connexins in GJs has been well characterized, the molecular determinants controlling connexin-hemichannel activity are unresolved. Here we investigated the regulation of Cx43-hemichannel activity by actomyosin contractility and intracellular [Ca(2+)] ([Ca(2+)](i)) using plasma membrane-permeable TAT peptides (100 μM) designed to interfere with interactions between the cytoplasmic loop (CL) and carboxy-terminal (CT) in primary bovine corneal endothelial cells and HeLa, C6 glioma, and Xenopus oocytes ectopically expressing Cx43. Peptides corresponding to the last 10 CT aa (TAT-Cx43CT) prevented the inhibition of Cx43-hemichannel activity by contractility/high [Ca(2+)](i), whereas a reverse peptide (TAT-Cx43CTrev) did not. These effects were independent of zonula occludens-1, a cytoskeletal-associated Cx43-binding protein. In contrast, peptides corresponding to CL (TAT-L2) inhibited Cx43-hemichannel responses, whereas a mutant peptide (TAT-L2(H126K/I130N)) did not inhibit. In these assays, TAT-Cx43CT acted as a scaffold for TAT-L2 and vice versa, a finding supported by surface plasmon resonance measurements. Loop/tail interactions appeared essential for Cx43-hemichannel activity, because TAT-Cx43CT restored the activity of nonfunctional hemichannels, consisting of either Cx43 lacking the C-terminal tail (Cx43(M239)) or intact Cx43 ectopically expressed in Xenopus oocytes. We conclude that intramolecular loop/tail interactions control Cx43-hemichannel activity, laying the basis for developing hemichannel-specific blockers.
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Affiliation(s)
- Raf Ponsaerts
- Department Molecular Cell Biology, KU Leuven, Leuven, Belgium
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29
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Abstract
Gap junctions (GJs) allow direct communication between cells. In the heart, GJs mediate the electrical coupling of cardiomyocytes and as such dictate the speed and direction of cardiac conduction. A prominent feature of acquired structural heart disease is remodeling of GJ protein expression and localization concomitant with increased susceptibility to lethal arrhythmias, leading many to hypothesize that the two are causally linked. Detailed understanding of the cellular mechanisms that regulate GJ localization and function within cardiomyocytes may therefore uncover potential therapeutic strategies for a significant clinical problem. This review will outline our current understanding of GJ cell biology with the intent of highlighting cellular mechanisms responsible for GJ remodeling associated with cardiac disease.
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Cochrane K, Berestecky JM, Kitamura C, Lau AF. Monoclonal antibodies against the connexin43-interacting protein CIP85. Hybridoma (Larchmt) 2010; 28:355-61. [PMID: 19857117 DOI: 10.1089/hyb.2009.0033] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The connexin43 (Cx43)-interacting protein of 85 kDa CIP85 has been identified as an interacting partner for the cytoplasmically located, carboxyl-terminal tail of Cx43. Further characterization has shown that the interaction between Cx43 and CIP85 is associated with increased turnover of Cx43 that may be lysosome-mediated. This suggests that CIP85 may regulate the endocytic trafficking of Cx43 from the plasma membrane and its degradation, and thus, indirectly influence gap junction function. This study reports the first successful production of monoclonal antibodies (MAbs) against CIP85. These antibodies are useful in detecting CIP85 expressed in several species in immunoblotting, immunoprecipitation, and immunofluorescence microscopy experiments. These MAbs will assist in defining the functional roles of CIP85, including its influence on Cx43 trafficking and intercellular communication through Cx43-containing gap junctions.
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Affiliation(s)
- Kimberly Cochrane
- Natural Products and Cancer Biology Program, Cancer Research Center of Hawaii, Honolulu, Hawaii, USA
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31
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Laird DW. The gap junction proteome and its relationship to disease. Trends Cell Biol 2010; 20:92-101. [DOI: 10.1016/j.tcb.2009.11.001] [Citation(s) in RCA: 217] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2009] [Revised: 10/30/2009] [Accepted: 11/02/2009] [Indexed: 02/07/2023]
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del Castillo FJ, Cohen-Salmon M, Charollais A, Caille D, Lampe PD, Chavrier P, Meda P, Petit C. Consortin, a trans-Golgi network cargo receptor for the plasma membrane targeting and recycling of connexins. Hum Mol Genet 2009; 19:262-75. [PMID: 19864490 DOI: 10.1093/hmg/ddp490] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Targeting of numerous transmembrane proteins to the cell surface is thought to depend on their recognition by cargo receptors that interact with the adaptor machinery for anterograde traffic at the distal end of the Golgi complex. We report here on consortin, a novel integral membrane protein that is predicted to be intrinsically disordered, i.e. that contains large segments whose native state is unstructured. We identified consortin as a binding partner of connexins, the building blocks of gap junctions. Consortin is located at the trans-Golgi network (TGN), in tubulovesicular transport organelles, and at the plasma membrane. It directly interacts with the TGN clathrin adaptors GGA1 and GGA2, and disruption of this interaction by expression of a consortin mutant lacking the acidic cluster-dileucine (DXXLL) GGA interaction motif causes an intracellular accumulation of several connexins. RNA interference-mediated silencing of consortin expression in HeLa cells blocks the cell surface targeting of these connexins, which accumulate intracellularly, whereas partial depletion and redistribution of the consortin pool slows down the intracellular degradation of gap junction plaques. Altogether, our results show that, by studying connexin trafficking, we have identified the first TGN cargo receptor for the targeting of transmembrane proteins to the plasma membrane. The identification of consortin provides in addition a potential target for therapies aimed at diseases in which connexin traffic is altered, including cardiac ischemia, peripheral neuropathies, cataracts and hearing impairment. Sequence accession numbers. GenBank: Human CNST cDNA, NM_152609; mouse Cnst cDNA, NM_146105.
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MAbs D11, G10, E1, and F6 Recognizing the Mouse Connexin43-interacting Protein CIP85. Hybridoma (Larchmt) 2009. [DOI: 10.1089/hyb.2009.0046.mab] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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34
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Abstract
Vertebrate gap junctions, composed of proteins from the connexin gene family, play critical roles in embryonic development, co-ordinated contraction of excitable cells, tissue homoeostasis, normal cell growth and differentiation. Phosphorylation of connexin43, the most abundant and ubiquitously expressed connexin, has been implicated in the regulation of gap junctional communication at several stages of the connexin 'life cycle', including hemichannel oligomerization, export of the protein to the plasma membrane, hemichannel activity, gap junction assembly, gap junction channel gating and connexin degradation. Consistent with a short (1-5 h) protein half-life, connexin43 phosphorylation is dynamic and changes in response to activation of many different kinases. The present review assesses our current understanding of the effects of phosphorylation on connexin43 structure and function that in turn regulate gap junction biology, with an emphasis on events occurring in heart and skin.
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Das Sarma J, Kaplan BE, Willemsen D, Koval M. Identification of rab20 as a potential regulator of connexin 43 trafficking. ACTA ACUST UNITED AC 2008; 15:65-74. [PMID: 18649179 DOI: 10.1080/15419060802014305] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Connexin oligomerization and trafficking are regulated processes. To identify proteins that control connexin 43 (Cx43), a screen was designed using HeLa cells expressing a Cx43 construct with di-lysine endoplasmic reticulum (ER)-retention/retrieval motif, Cx43-HKKSL. At moderate levels of expression, Cx43-HKKSL is retained in the ER as monomers; however, Cx43-HKKSL stably overexpressed by HeLa cells localizes to the perinuclear region and oligomerizes. HeLa/Cx43-HKKSL overexpressors were transiently transfected with pooled clones from a human kidney cDNA library and used immunofluorescence microscopy to identify cDNAs that enabled overexpressed Cx43-HKKSL to convert from a perinuclear to ER localization pattern. Using this approach, a small molecular weight GTPase, rab20, was identified as a candidate protein with the ability to regulate Cx43 trafficking. Enhanced green fluorescent protein (EGFP)-tagged rab20 showed a predominantly perinuclear and ER localization pattern and caused wild-type Cx43 to be retained inside the cell. By contrast, mutant EGFP-rab20T19N, which lacks the ability to bind GTP, had no effect on Cx43. These results suggest Cx43 is transported through an intracellular compartment regulated by rab20 along the secretory pathway.
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Affiliation(s)
- Jayasri Das Sarma
- Department of Neurology, Jefferson Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
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36
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Park DJ, Wallick CJ, Martyn KD, Lau AF, Jin C, Warn-Cramer BJ. Akt phosphorylates Connexin43 on Ser373, a "mode-1" binding site for 14-3-3. ACTA ACUST UNITED AC 2008; 14:211-26. [PMID: 18163231 DOI: 10.1080/15419060701755958] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Connexin43 (Cx43) is a membrane-spanning protein that forms channels that bridge the gap between adjacent cells and this allows for the intercellular exchange of information. Cx43 is regulated by phosphorylation and by interacting proteins. "Mode-1" interaction with 14-3-3 requires phosphorylation of Ser373 on Cx43 (Park et al. 2006). Akt phosphorylates and targets a number of proteins to interactions with 14-3-3. Here we demonstrate that Akt phosphorylates Cx43 on Ser373 and Ser369; antibodies recognizing Akt-phosphorylated sites or phospho-Ser "mode-1" 14-3-3-binding sites recognize a protein from EGF-treated cells that migrates as Cx43, and GST-14-3-3 binds to Cx43 phosphorylated endogenously in EGF-treated cells. Confocal microscopy supports the co-localization of Cx43 with Akt and with 14-3-3 at the outer edges of gap junctional plaques. These data suggest that Akt could target Cx43 to an interaction with 14-3-3 that may play a role in the forward trafficking of Cx43 multimers and/or their incorporation into existing gap junctional plaques.
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Affiliation(s)
- Darren J Park
- Natural Products & Cancer Biology Program, Cancer Research Center, University of Hawaii at Manoa, Honolulu, Hawaii 96813, USA
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37
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Li X, Su V, Kurata WE, Jin C, Lau AF. A novel connexin43-interacting protein, CIP75, which belongs to the UbL-UBA protein family, regulates the turnover of connexin43. J Biol Chem 2007; 283:5748-59. [PMID: 18079109 DOI: 10.1074/jbc.m709288200] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The degradation of connexin43 (Cx43) has been reported to involve both lysosomal and proteasomal degradation pathways; however, very little is known about the mechanisms regulating these Cx43 degradation pathways. Using yeast two-hybrid, glutathione S-transferase pull-down, and co-immunoprecipitation approaches, we have identified a novel Cx43-interacting protein of approximately 75 kDa, CIP75. Laser confocal microscopy showed that CIP75 is located primarily at the endoplasmic reticulum, as indicated by the calnexin marker, with Cx43 co-localization in this perinuclear region. CIP75 belongs to the UbL (ubiquitin-like)-UBA (ubiquitin-associated) domain-containing protein family with a N-terminal UbL domain and a C-terminal UBA domain. The UBA domain of CIP75 is the main element mediating the interaction with Cx43, whereas the CIP75-interacting region in Cx43 resides in the PY motif and multiphosphorylation sites located between Lys 264 and Asn 302. Interestingly, the UbL domain interacts with the S2/RPN1 and S5a/RPN10 protein subunits of the regulatory 19 S proteasome cap subunit of the 26 S proteasome complex. Overexpression experiments suggested that CIP75 is involved in the turnover of Cx43 as measured by a significant stimulation of Cx43 degradation and reduction in its half-life with the opposite effects on Cx43 degradation observed in small interference RNA knockdown experiments.
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Affiliation(s)
- Xinli Li
- Natural Products and Cancer Biology Program, Cancer Research Center of Hawaii, Honolulu, Hawaii 96813, USA
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38
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Sharrow AC, Li Y, Micsenyi A, Griswold RD, Wells A, Monga SSP, Blair HC. Modulation of osteoblast gap junction connectivity by serum, TNFalpha, and TRAIL. Exp Cell Res 2007; 314:297-308. [PMID: 18022159 DOI: 10.1016/j.yexcr.2007.10.010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2007] [Revised: 09/14/2007] [Accepted: 10/09/2007] [Indexed: 10/22/2022]
Abstract
We studied the effects of serum growth factors and of TNF family proteins on osteoblast gap junction connectivity. Serum starvation of human MG63 osteosarcoma cells or nontransformed osteoblasts decreased connexin43 protein. TNFalpha or TRAIL reduced connexin43 further. Serum starvation redistributed gap junctions but did not reduce intercellular diffusion. In contrast, TNFalpha or TRAIL reduced gap junctions on cell processes and decreased intercellular diffusion. Effects of TNFs on connexin43 were mediated by lysosomal proteolysis. Activating analogs of cAMP increased connexin43 protein, but did not block effects of serum starvation, TNFalpha, or TRAIL on connexin43 protein. Connexin43 and connectivity recovered overnight if stimuli were withdrawn. Surprisingly, connexin43 mRNA increased in serum starvation and with TNFalpha or TRAIL. Since beta-catenin is a binding partner of connexin43, when connexin43 is degraded, beta-catenin activation may contribute to a reflexive increase in connexin43 transcription. We conclude that osteoblast connectivity is regulated by a multifactorial system that maintains intercellular connections. Serum starvation, TNFalpha and TRAIL augmented connexin43 degradation and connexin43 transcription. Cell-cell communication was maintained in serum starvation, which may model response to acute injury, but was sensitive to TNFs. These inflammatory agents mediated selective, reversible removal of connexin43 from cell processes.
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Affiliation(s)
- Allison C Sharrow
- Department of Pathology, University of Pittsburgh, Pittsburgh, PA 15243, USA
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Miserey-Lenkei S, Waharte F, Boulet A, Cuif MH, Tenza D, El Marjou A, Raposo G, Salamero J, Héliot L, Goud B, Monier S. Rab6-interacting protein 1 links Rab6 and Rab11 function. Traffic 2007; 8:1385-403. [PMID: 17725553 DOI: 10.1111/j.1600-0854.2007.00612.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Rab11 and Rab6 guanosine triphosphatases are associated with membranes of the recycling endosomes (REs) and Golgi complex, respectively. Evidence indicates that they sequentially regulate a retrograde transport pathway between these two compartments, suggesting the existence of proteins that must co-ordinate their functions. Here, we report the characterization of two isoforms of a protein, Rab6-interacting protein 1 (R6IP1), originally identified as a Rab6-binding protein. R6IP1 also binds to Rab11A in its GTP-bound conformation. In interphase cells, R6IP1 is targeted to the Golgi in a Rab6-dependent manner but can associate with Rab11-positive compartments when the level of Rab11A is increased within the cells. Fluorescence resonance energy transfer analysis using fluorescence lifetime imaging shows that the overexpression of R6IP1 promotes an interaction between Rab11A and Rab6 in living cells. Accordingly, the REs marked by Rab11 and transferrin receptor are depleted from the cell periphery and accumulate in the pericentriolar area. However, endosomal and Golgi membranes do not appear to fuse with each other. We also show that R6IP1 function is required during metaphase and cytokinesis, two mitotic steps in which a role of Rab6 and Rab11 has been previously documented. We propose that R6IP1 may couple Rab6 and Rab11 function throughout the cell cycle.
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Iacobas DA, Suadicani SO, Iacobas S, Chrisman C, Cohen MA, Spray DC, Scemes E. Gap junction and purinergic P2 receptor proteins as a functional unit: insights from transcriptomics. J Membr Biol 2007; 217:83-91. [PMID: 17665085 DOI: 10.1007/s00232-007-9039-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2007] [Accepted: 05/14/2007] [Indexed: 10/23/2022]
Abstract
Gap junctions and purinergic P2 receptors (P2Rs) can be regarded as belonging to a common functional unit, given that they are involved in the transmission of calcium signals between cells. We have previously shown that deletion of the Gja1 gene alters expression levels of numerous genes encoding proteins with diverse functions, including purinergic receptors (P2Rs), and have found that genes synergistically or antagonistically expressed in wild-type tissues are more prone to be similarly or oppositely regulated in Cx43-nulls. We have now explored the use of coordination analysis of gene expression as a strategy to identify interlinked genes encoding functionally related proteins and pull-downs to evaluate their interlinkage. Our findings indicate that, in brain and in cultured astrocytes, several of these coexpressed genes encode proteins that are components of P2R signal-transduction pathways and/or directly interact with these receptors, including the gap junction protein connexin43 (Cx43) and Cx45 as well as pannexins. It is proposed that coordination analysis of gene expression may provide a novel unbiased strategy for the identification of proteins belonging to supramolecular complexes.
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Affiliation(s)
- Dumitru A Iacobas
- Dominick P Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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41
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Leithe E, Rivedal E. Ubiquitination of gap junction proteins. J Membr Biol 2007; 217:43-51. [PMID: 17657522 DOI: 10.1007/s00232-007-9050-z] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2007] [Accepted: 05/14/2007] [Indexed: 12/01/2022]
Abstract
Gap junctions are plasma membrane domains containing arrays of channels that exchange ions and small molecules between neighboring cells. Gap junctional intercellular communication enables cells to directly cooperate both electrically and metabolically. Several lines of evidence indicate that gap junctions are important in regulating cell growth and differentiation and for maintaining tissue homeostasis. Gap junction channels consist of a family of transmembrane proteins called connexins. Gap junctions are dynamic structures, and connexins have a high turnover rate in most tissues. Connexin43 (Cx43), the best-studied connexin isoform, has a half-life of 1.5-5 h; and its degradation involves both the lysosomal and proteasomal systems. Increasing evidence suggests that ubiquitin is important in the regulation of Cx43 endocytosis. Ubiquitination of Cx43 is thought to occur at the plasma membrane and has been shown to be regulated by protein kinase C and the mitogen-activated protein kinase pathway. Cx43 binds to the E3 ubiquitin ligase Nedd4, in a process modulated by Cx43 phosphorylation. The interaction between Nedd4 and Cx43 is mediated by the WW domains of Nedd4 and involves a proline-rich sequence conforming to a PY (XPPXY) consensus motif in the C terminus of Cx43. In addition to the PY motif, an overlapping tyrosine-based sorting signal conforming to the consensus of an YXXphi motif is involved in Cx43 endocytosis, indicating that endocytosis of gap junctions involves both ubiquitin-dependent and -independent pathways. Here, we discuss current knowledge on the ubiquitination of connexins.
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Affiliation(s)
- Edward Leithe
- Department of Cancer Prevention, Institute for Cancer Research, Rikshospitalet-Radiumhospitalet Medical Center, 0310, Oslo, Norway.
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Hervé JC, Bourmeyster N, Sarrouilhe D, Duffy HS. Gap junctional complexes: From partners to functions. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2007; 94:29-65. [PMID: 17507078 DOI: 10.1016/j.pbiomolbio.2007.03.010] [Citation(s) in RCA: 173] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Gap junctions (GJ), specialised membrane structures that mediate cell-to-cell communication in almost all animal tissues, are composed of intercellular channel-forming integral membrane proteins termed connexins (Cxs), innexins or pannexins. The activity of these channels is closely regulated, particularly by intramolecular modifications as phosphorylation of proteins, via the formation of multiprotein complexes where pore-forming subunits bind to auxiliary channel subunits and associate with scaffolding proteins that play essential roles in channel localization and activity. Scaffolding proteins link signalling enzymes, substrates, and potential effectors (such as channels) into multiprotein signalling complexes that may be anchored to the cytoskeleton. Protein-protein interactions play essential roles in channel localization and activity and, besides their cell-to-cell channel-forming functions, gap junctional proteins now appear involved in different cellular functions (e.g. transcriptional and cytoskeletal regulation). The present review summarizes the recent progress regarding the proteins capable of interacting with junctional proteins and their functional importance.
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Affiliation(s)
- Jean-Claude Hervé
- Interactions et Communications Cellulaires, Université de Poitiers, Poitiers, France.
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43
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Park DJ, Freitas TA, Wallick CJ, Guyette CV, Warn-Cramer BJ. Molecular dynamics and in vitro analysis of Connexin43: A new 14-3-3 mode-1 interacting protein. Protein Sci 2007; 15:2344-55. [PMID: 17008717 PMCID: PMC2242386 DOI: 10.1110/ps.062172506] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The interaction of cellular proteins with the gap junction protein Connexin43 (Cx43) is thought to form a dynamic scaffolding complex that functions as a platform for the assembly of signaling, structural, and cytoskeletal proteins. A high stringency Scansite search of rat Cx43 identified the motif containing Ser373 (S373) as a 14-3-3 binding site. The S373 motif and the second best mode-1 motif, containing Ser244 (S244), are conserved in rat, mouse, human, chicken, and bovine, but not in Xenopus or zebrafish Cx43. Docking studies of a mouse/rat 14-3-3 homology model with the modeled phosphorylated S373 or S244 peptide ligands or their serine-to-alanine mutants, S373A or S244A, revealed that the pS373 motif facilitated a greater number of intermolecular contacts than the pS244 motif, thus supporting a stronger 14-3-3 binding interaction with the pS373 motif. The alanine substitution also reduced more than half the number of intermolecular contacts between 14-3-3 and the S373 motif, emphasizing the phosphorylation dependence of this interaction. Furthermore, the ability of the wild-type or the S244A GST-Cx43 C-terminal fusion protein, but not the S373A fusion protein, to interact with either 14-3-3 or 14-3-3zeta in GST pull-down experiments clearly demonstrated that the S373 motif mediates the direct interaction between Cx43 and 14-3-3 proteins. Blocking growth factor-induced Akt activation and presumably any Akt-mediated phosphorylation of the S373 motif in ROSE 199 cells did not prevent the down-regulation of Cx43-mediated cell-cell communication, suggesting that an Akt-mediated interaction with 14-3-3 was not involved in the disruption of Cx43 function.
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Affiliation(s)
- Darren J Park
- Natural Products and Cancer Biology Program, Cancer Research Center of Hawaii, University of Hawaii at Manoa, Honolulu, Hawaii 96813, USA
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McLachlan E, Shao Q, Wang HL, Langlois S, Laird DW. Connexins act as tumor suppressors in three-dimensional mammary cell organoids by regulating differentiation and angiogenesis. Cancer Res 2006; 66:9886-94. [PMID: 17047050 DOI: 10.1158/0008-5472.can-05-4302] [Citation(s) in RCA: 162] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Connexins are tumor suppressors, and human breast connexin 26 (Cx26) and connexin 43 (Cx43) gap junctions are often down-regulated in breast cancer. We previously showed that Cx26 and Cx43 overexpressed in MDA-MB-231 breast cancer cells inhibited tumor growth in vivo but not in two-dimensional cultures. In the current study, we show that overexpression of Cx26 or Cx43 has tumor-suppressive properties in a three-dimensional environment such that they reduced anchorage-independent cell growth and induced partial redifferentiation of three-dimensional organoids of MDA-MB-231 cells. Importantly, the majority of exogenous connexins did not localize to the cell-cell interface or rescue gap junctional intercellular communication (GJIC) as assessed by dye transfer, providing evidence of a GJIC-independent mechanism of mammary tumor suppression. To further elucidate the mechanisms involved in connexin-induced three-dimensional redifferentiation of tumor cells, we examined whether connexin expression has a role in epithelial to mesenchymal transition (EMT). Cx26 and Cx43 reduced cell migration, increased cytokeratin 18 expression, and decreased vimentin levels, indicating a shift from a mesenchymal towards an epithelial phenotype. In addition, we examined the role of connexins in angiogenesis by probing an angiogenesis antibody array with conditioned media from three-dimensional MDA-MB-231 cultures. This revealed that connexin overexpression regulated various angiogenesis-linked proteins. Furthermore, secreted factors from connexin overexpressing cells inhibited endothelial cell tubulogenesis and migration, and xenografts of Cx43 overexpressing MDA-MB-231 cells showed reduced tumor angiogenesis. In summary, Cx26 and Cx43 inhibit the malignant properties of MDA-MB-231 cells via GJIC-independent mechanisms, including regulation of EMT and angiogenesis.
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Affiliation(s)
- Elizabeth McLachlan
- Departments of Anatomy and Cell Biology and Physiology and Pharmacology, The University of Western Ontario, London, Ontario, Canada
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Lin R, Martyn KD, Guyette CV, Lau AF, Warn-Cramer BJ. v-Src tyrosine phosphorylation of connexin43: regulation of gap junction communication and effects on cell transformation. ACTA ACUST UNITED AC 2006; 13:199-216. [PMID: 16916748 PMCID: PMC2712291 DOI: 10.1080/15419060600848516] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The oncogenic tyrosine kinase, v-Src, phosphorylates connexin43 (Cx43) on Y247 and Y265 and inhibits Cx43 gap junctional communication (GJC), the process of intercellular exchange of ions and metabolites. To test the role of a negative charge on Cx43 induced by tyrosine phosphorylation, we expressed Cx43 with glutamic acid substitutions at Y247 or Y265. The Cx43Y247E or Cx43Y265E channels were functional in Cx43 knockout fibroblasts, indicating that introducing a negative charge on Cx43 was not likely the mechanism for v-Src disruption of GJC. Cells coexpressing v-Src and the triple serine to alanine mutant, Cx43S255/279/282A, confirmed that mitogen-activated protein (MAP) kinase phosphorylation of Cx43 was not required for v-Src-induced disruption of GJC and that tyrosine phosphorylation was sufficient. In addition, v-Src cells containing v-Src-resistant gap junctions, Cx43Y247/265F, displayed properties of cell migration, adhesion, and proliferation similar to Cx43wt/v-Src cells, suggesting that Cx43 tyrosine phosphorylation and disruption of GJC are not involved in these transformed cell properties.
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Affiliation(s)
- Rui Lin
- Department of Immunology, The Scripps Research Institute, La Jolla, California, USA
| | - Kendra D. Martyn
- Natural Products and Cancer Biology Program, Cancer Research Center of Hawaii, Honolulu, Hawaii, USA
| | - Carrie V. Guyette
- Natural Products and Cancer Biology Program, Cancer Research Center of Hawaii, Honolulu, Hawaii, USA
| | - Alan F. Lau
- Natural Products and Cancer Biology Program, Cancer Research Center of Hawaii, Honolulu, Hawaii, USA
- Department of Cell and Molecular Biology, University of Hawaii at Manoa, Honolulu, HI, USA
| | - Bonnie J. Warn-Cramer
- Natural Products and Cancer Biology Program, Cancer Research Center of Hawaii, Honolulu, Hawaii, USA
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Functional Characterization of a GJA1 Frameshift Mutation Causing Oculodentodigital Dysplasia and Palmoplantar Keratoderma. J Biol Chem 2006. [DOI: 10.1016/s0021-9258(19)84095-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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47
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Gong XQ, Shao Q, Lounsbury CS, Bai D, Laird DW. Functional Characterization of aGJA1Frameshift Mutation Causing Oculodentodigital Dysplasia and Palmoplantar Keratoderma. J Biol Chem 2006; 281:31801-11. [PMID: 16891658 DOI: 10.1074/jbc.m605961200] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A frameshift mutation generated from a dinucleotide deletion (780-781del) in the GJA1 gene encoding Cx43 results in a frameshift yielding 46 aberrant amino acids after residue 259 and a shortened protein of 305 residues compared with the 382 in wild-type Cx43. This frameshift mutant (fs260) causes oculodentodigital dysplasia (ODDD) that includes the added condition of palmoplantar keratoderma. When expressed in a variety of cell lines, the fs260 mutant was typically localized to the endoplasmic reticulum and other intracellular compartments. The fs260 mutant, but not the G138R ODDD-linked Cx43 mutant or a Cx43 mutant truncated at residue 259 (T259), reduced the number of apparent gap junction plaques formed from endogenous Cx43 in normal rat kidney cells or keratinocytes. Interestingly, mutation of a putative FF endoplasmic reticulum retention motif encoded within the 46 aberrant amino acid domain failed to restore efficient assembly of the fs260 mutant into gap junctions. Dual whole cell patch-clamp recording revealed that fs260-expressing N2A cells exerted severely reduced electrical coupling in comparison to wild-type Cx43 or the T259 mutant, whereas single patch capacitance recordings showed that fs260 could also dominantly inhibit the function of wild-type Cx43. Co-expression studies further revealed that the dominant negative effect of fs260 on wild-type Cx43 was dose-dependent, and at a predicted 1:1 expression ratio the fs260 mutant reduced wild-type Cx43-mediated gap junctional conductance by over 60%. These results suggest that the 46 aberrant amino acid residues associated with the frameshift mutant are, at least in part, responsible for the manifestation of palmoplantar keratoderma symptoms.
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Affiliation(s)
- Xiang-Qun Gong
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario N6A 5C1, Canada
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Abstract
Evaluation of the human genome suggests that all members of the connexin family of gap-junction proteins have now been successfully identified. This large and diverse family of proteins facilitates a number of vital cellular functions coupled with their roles, which range from the intercellular propagation of electrical signals to the selective intercellular passage of small regulatory molecules. Importantly, the extent of gap-junctional intercellular communication is under the direct control of regulatory events associated with channel assembly and turnover, as the vast majority of connexins have remarkably short half-lives of only a few hours. Since most cell types express multiple members of the connexin family, compensatory mechanisms exist to salvage tissue function in cases when one connexin is mutated or lost. However, numerous studies of the last decade have revealed that mutations in connexin genes can also lead to severe and debilitating diseases. In many cases, single point mutations lead to dramatic effects on connexin trafficking, assembly and channel function. This review will assess the current understanding of wild-type and selected disease-linked mutant connexin transport through the secretory pathway, gap-junction assembly at the cell surface, internalization and degradation.
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Affiliation(s)
- Dale W Laird
- Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario, Canada N6A 5C1.
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Akiyama M, Ishida N, Ogawa T, Yogo K, Takeya T. Molecular cloning and functional analysis of a novel Cx43 partner protein CIP150. Biochem Biophys Res Commun 2005; 335:1264-71. [PMID: 16112082 DOI: 10.1016/j.bbrc.2005.08.019] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2005] [Accepted: 08/03/2005] [Indexed: 11/25/2022]
Abstract
We identified and cloned a novel gene encoding a partner protein, CIP150, of connexin 43 (Cx43). CIP150 associates with Cx43 through its carboxyl terminal domain. Conversely, a region consisting of 16 amino acids in the juxtamembrane region (amino acids 227-242) in the carboxyl terminal tail of Cx43 was identified to be responsible for the association. A variant of Cx43 lacking this region was expressed only in a nonphosphorylated form and appeared to lose the capacity to localize to the region of cell-cell contact and dye transfer activity. When the expression of CIP150 was suppressed using small interfering RNA, the localization to the plasma membrane as well as dye transfer activity of Cx43 was significantly reduced. These results suggest that the newly identified domain is essential for the proper phosphorylation and localization of Cx43, and CIP150 is a novel partner protein targeting this domain.
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Affiliation(s)
- Motofusa Akiyama
- Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0129, Japan
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