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Van Campenhout R, Leroy K, Cooreman A, Tabernilla A, Cogliati B, Kadam P, Vinken M. Connexin-Based Channels in the Liver. Compr Physiol 2022; 12:4147-4163. [PMID: 35950654 DOI: 10.1002/cphy.c220007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Connexin proteins oligomerize in hexameric structures called connexin hemichannels, which then dock to form gap junctions. Gap junctions direct cell-cell communication by allowing the exchange of small molecules and ions between neighboring cells. In this way, hepatic gap junctions support liver homeostasis. Besides serving as building blocks for gap junctions, connexin hemichannels provide a pathway between the intracellular and the extracellular environment. The activation of connexin hemichannels is associated with acute and chronic liver pathologies. This article discusses the role of gap junctions and connexin hemichannels in the liver. © 2022 American Physiological Society. Compr Physiol 12:1-17, 2022.
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Affiliation(s)
- Raf Van Campenhout
- Entity of In Vitro Toxicology and Dermato-Cosmetology, Department of Pharmaceutical and Pharmacological Sciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Kaat Leroy
- Entity of In Vitro Toxicology and Dermato-Cosmetology, Department of Pharmaceutical and Pharmacological Sciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Axelle Cooreman
- Entity of In Vitro Toxicology and Dermato-Cosmetology, Department of Pharmaceutical and Pharmacological Sciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Andrés Tabernilla
- Entity of In Vitro Toxicology and Dermato-Cosmetology, Department of Pharmaceutical and Pharmacological Sciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Bruno Cogliati
- School of Veterinary Medicine and Animal Science, Department of Pathology, University of São Paulo, São Paulo, Brazil
| | - Prashant Kadam
- Entity of In Vitro Toxicology and Dermato-Cosmetology, Department of Pharmaceutical and Pharmacological Sciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Mathieu Vinken
- Entity of In Vitro Toxicology and Dermato-Cosmetology, Department of Pharmaceutical and Pharmacological Sciences, Vrije Universiteit Brussel, Brussels, Belgium
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Applicability of Scrape Loading-Dye Transfer Assay for Non-Genotoxic Carcinogen Testing. Int J Mol Sci 2021; 22:ijms22168977. [PMID: 34445682 PMCID: PMC8396440 DOI: 10.3390/ijms22168977] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 07/30/2021] [Accepted: 07/31/2021] [Indexed: 12/27/2022] Open
Abstract
Dysregulation of gap junction intercellular communication (GJIC) is recognized as one of the key hallmarks for identifying non-genotoxic carcinogens (NGTxC). Currently, there is a demand for in vitro assays addressing the gap junction hallmark, which would have the potential to eventually become an integral part of an integrated approach to the testing and assessment (IATA) of NGTxC. The scrape loading-dye transfer (SL-DT) technique is a simple assay for the functional evaluation of GJIC in various in vitro cultured mammalian cells and represents an interesting candidate assay. Out of the various techniques for evaluating GJIC, the SL-DT assay has been used frequently to assess the effects of various chemicals on GJIC in toxicological and tumor promotion research. In this review, we systematically searched the existing literature to gather papers assessing GJIC using the SL-DT assay in a rat liver epithelial cell line, WB-F344, after treating with chemicals, especially environmental and food toxicants, drugs, reproductive-, cardio- and neuro-toxicants and chemical tumor promoters. We discuss findings derived from the SL-DT assay with the known knowledge about the tumor-promoting activity and carcinogenicity of the assessed chemicals to evaluate the predictive capacity of the SL-DT assay in terms of its sensitivity, specificity and accuracy for identifying carcinogens. These data represent important information with respect to the applicability of the SL-DT assay for the testing of NGTxC within the IATA framework.
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Willebrords J, Crespo Yanguas S, Maes M, Decrock E, Wang N, Leybaert L, da Silva TC, Veloso Alves Pereira I, Jaeschke H, Cogliati B, Vinken M. Structure, Regulation and Function of Gap Junctions in Liver. ACTA ACUST UNITED AC 2016; 22:29-37. [PMID: 27001459 DOI: 10.3109/15419061.2016.1151875] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Gap junctions are a specialized group of cell-to-cell junctions that mediate direct intercellular communication between cells. They arise from the interaction of two hemichannels of adjacent cells, which in turn are composed of six connexin proteins. In liver, gap junctions are predominantly found in hepatocytes and play critical roles in virtually all phases of the hepatic life cycle, including cell growth, differentiation, liver-specific functionality and cell death. Liver gap junctions are directed through a broad variety of mechanisms ranging from epigenetic control of connexin expression to post-translational regulation of gap junction activity. This paper reviews established and novel aspects regarding the architecture, control and functional relevance of liver gap junctions.
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Affiliation(s)
- Joost Willebrords
- Department of In Vitro Toxicology and Dermato-Cosmetology, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Brussels, Belgium
| | - Sara Crespo Yanguas
- Department of In Vitro Toxicology and Dermato-Cosmetology, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Brussels, Belgium
| | - Michaël Maes
- Department of In Vitro Toxicology and Dermato-Cosmetology, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Brussels, Belgium
| | - Elke Decrock
- Department of Basic Medical Sciences, Physiology Group, Ghent University, Ghent, Belgium
| | - Nan Wang
- Department of Basic Medical Sciences, Physiology Group, Ghent University, Ghent, Belgium
| | - Luc Leybaert
- Department of Basic Medical Sciences, Physiology Group, Ghent University, Ghent, Belgium
| | - Tereza Cristina da Silva
- Department of Pathology, School of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, Brazil
| | - Isabel Veloso Alves Pereira
- Department of Pathology, School of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, Brazil
| | - Hartmut Jaeschke
- Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City, Kansas, United States of America
| | - Bruno Cogliati
- Department of Pathology, School of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, Brazil
| | - Mathieu Vinken
- Department of In Vitro Toxicology and Dermato-Cosmetology, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Brussels, Belgium
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Joshi CN, Martin DN, Shaver P, Madamanchi C, Muller-Borer BJ, Tulis DA. Control of vascular smooth muscle cell growth by connexin 43. Front Physiol 2012; 3:220. [PMID: 22737133 PMCID: PMC3380337 DOI: 10.3389/fphys.2012.00220] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Accepted: 06/01/2012] [Indexed: 12/04/2022] Open
Abstract
Connexin 43 (Cx43), the principal gap junction protein in vascular smooth muscle cells (VSMCs), regulates movement of ions and other signaling molecules through gap junction intercellular communication (GJIC) and plays important roles in maintaining normal vessel function; however, many of the signaling mechanisms controlling Cx43 in VSMCs are not clearly described. The goal of this study was to investigate mechanisms of Cx43 regulation with respect to VSMC proliferation. Treatment of rat primary VSMCs with the cAMP analog 8Br-cAMP, the soluble guanylate cyclase (sGC) stimulator BAY 41-2272 (BAY), or the Cx inducer diallyl disulfide (DADS) significantly reduced proliferation after 72 h compared with vehicle controls. Bromodeoxyuridine uptake revealed reduction (p < 0.05) in DNA synthesis after 6 h and flow cytometry showed reduced (40%) S-phase cell numbers after 16 h in DADS-treated cells compared with vehicle controls. Cx43 expression significantly increased after 270 min treatment with 8Br-cAMP, 8Br-cGMP, BAY or DADS. Inhibition of PKA, PKG or PKC reversed 8Br-cAMP-stimulated increases in Cx43 expression, whereas only PKG or PKC inhibition reversed 8Br-cGMP- and BAY-stimulated increases in total Cx43. Interestingly, stimulation of Cx43 expression by DADS was not dependent on PKA, PKG or PKC. Using fluorescence recovery after photobleaching, only 8Br-cAMP or DADS increased GJIC with 8Br-cAMP mediated by PKC and DADS mediated by PKG. Further, DADS significantly increased phosphorylation at MAPK-sensitive Serine (Ser)255 and Ser279, the cell cycle regulatory kinase-sensitive Ser262 and PKC-sensitive Ser368 after 30 min while 8Br-cAMP significantly increased phosphorylation only at Ser279 compared with controls. This study demonstrates that 8Br-cAMP- and DADS-enhanced GJIC rather than Cx43 expression and/or phosphorylation plays important roles in the regulation of VSMC proliferation and provides new insights into the growth-regulatory capacities of Cx43 in VSM.
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Affiliation(s)
- Chintamani N Joshi
- Department of Physiology, Brody School of Medicine, East Carolina University Greenville, NC, USA
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5
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Chloral hydrate decreases gap junction communication in rat liver epithelial cells. Cell Biol Toxicol 2011; 27:207-16. [PMID: 21243523 DOI: 10.1007/s10565-011-9182-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2009] [Accepted: 01/06/2011] [Indexed: 12/16/2022]
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Vinken M, Decrock E, De Vuyst E, Ponsaerts R, D'hondt C, Bultynck G, Ceelen L, Vanhaecke T, Leybaert L, Rogiers V. Connexins: sensors and regulators of cell cycling. Biochim Biophys Acta Rev Cancer 2010; 1815:13-25. [PMID: 20801193 DOI: 10.1016/j.bbcan.2010.08.004] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Revised: 08/18/2010] [Accepted: 08/20/2010] [Indexed: 12/13/2022]
Abstract
It is nowadays well established that gap junctions are critical gatekeepers of cell proliferation, by controlling the intercellular exchange of essential growth regulators. In recent years, however, it has become clear that the picture is not as simple as originally anticipated, as structural precursors of gap junctions can affect cell cycling by performing actions not related to gap junctional intercellular communication. Indeed, connexin hemichannels also foresee a pathway for cell growth communication, albeit between the intracellular compartment and the extracellular environment, while connexin proteins as such can directly or indirectly influence the production of cell cycle regulators independently of their channel activities. Furthermore, a novel set of connexin-like proteins, the pannexins, have lately joined in as regulators of the cell proliferation process, which they can affect as either single units or as channel entities. In the current paper, these multifaceted aspects of connexin-related signalling in cell cycling are reviewed.
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Affiliation(s)
- Mathieu Vinken
- Department of Toxicology, Vrije Universiteit Brussel, Laarbeeklaan 103, B-1090 Brussels, Belgium.
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Establishment of human corneal epithelial cells stably expressing human connexin43. Exp Eye Res 2009; 90:4-9. [PMID: 19799899 DOI: 10.1016/j.exer.2009.09.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2009] [Revised: 08/12/2009] [Accepted: 09/03/2009] [Indexed: 01/22/2023]
Abstract
Corneal epithelial cells communicate with each other through gap junctions. Whereas this property is retained in corneal epithelial cells in primary culture, it is often lost in immortalized epithelial cells. However, the life span of primary cultured corneal epithelial cells is short and the availability of human tissue for their preparation is limited. To examine the role of the gap-junction protein connexin43 (Cx43) in human corneal epithelial cells, we set out to establish an immortal human corneal epithelial cell line that stably expresses this protein. An expression vector encoding human Cx43 fused to enhanced green fluorescent protein (EGFP) was constructed and introduced by transfection into SV40-immortalized human corneal epithelial (HCE) cells. Stable transfectants were isolated by selection with the antibiotic G418. The expression and localization of the Cx43-EGFP fusion protein were examined by immunoblot analysis and fluorescence microscopy, respectively, and gap-junctional intercellular communication was monitored on the basis of dye coupling. HCE cells stably expressing Cx43-EGFP manifested intercellular dye transfer, whereas those stably expressing EGFP alone did not. Cx43-EGFP localized to the interfaces of neighboring cells. Stable expression of Cx43-EGFP in HCE cells did not affect the expression of keratins 3 and 12, which is a characteristic of corneal epithelial cells, but it did inhibit cell proliferation. We have established an HCE cell line that stably expresses human Cx43 and forms functional gap junctions. These cells may prove useful for studies of the role of gap junctions in the human corneal epithelium.
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Vinken M, Doktorova T, Decrock E, Leybaert L, Vanhaecke T, Rogiers V. Gap junctional intercellular communication as a target for liver toxicity and carcinogenicity. Crit Rev Biochem Mol Biol 2009; 44:201-22. [PMID: 19635038 DOI: 10.1080/10409230903061215] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Direct communication between hepatocytes, mediated by gap junctions, constitutes a major regulatory platform in the control of liver homeostasis, ranging from hepatocellular proliferation to hepatocyte cell death. Inherent to this pivotal task, gap junction functionality is frequently disrupted upon impairment of the homeostatic balance, as occurs during liver toxicity and carcinogenicity. In the present paper, the deleterious effects of a number of chemical and biological toxic compounds on hepatic gap junctions are discussed, including environmental pollutants, biological toxins, organic solvents, pesticides, pharmaceuticals, peroxides, metals and phthalates. Particular attention is paid to the molecular mechanisms that underlie the abrogation of gap junction functionality. Since hepatic gap junctions are specifically targeted by tumor promoters and epigenetic carcinogens, both in vivo and in vitro, inhibition of gap junction functionality is considered as a suitable indicator for the detection of nongenotoxic hepatocarcinogenicity.
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Affiliation(s)
- Mathieu Vinken
- Department of Toxicology, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Brussels, Belgium.
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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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Vinken M, Henkens T, De Rop E, Fraczek J, Vanhaecke T, Rogiers V. Biology and pathobiology of gap junctional channels in hepatocytes. Hepatology 2008; 47:1077-88. [PMID: 18058951 DOI: 10.1002/hep.22049] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The present review provides the state of the art of the current knowledge concerning gap junctional channels and their roles in liver functioning. In the first part, we summarize some relevant biochemical properties of hepatic gap junctional channels, including their structure and regulation. In the second part, we discuss the involvement of gap junctional channels in the occurrence of liver cell growth, liver cell differentiation, and liver cell death. We further exemplify their relevance in hepatic pathophysiology. Finally, a number of directions for future liver gap junctional channel research are proposed, and the up-regulation of gap junctional channel activity as a novel strategy in (liver) cancer therapy is illustrated.
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Affiliation(s)
- Mathieu Vinken
- Department of Toxicology, Vrije Universiteit Brussel, Laarbeeklaan 103, B-1090 Brussels, Belgium.
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Melchheier I, von Montfort C, Stuhlmann D, Sies H, Klotz LO. Quinone-induced Cdc25A inhibition causes ERK-dependent connexin phosphorylation. Biochem Biophys Res Commun 2005; 327:1016-23. [PMID: 15652497 DOI: 10.1016/j.bbrc.2004.12.107] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2004] [Indexed: 01/08/2023]
Abstract
Gap junctional intercellular communication (GJC) varies during progression of the cell cycle. We propose here that Cdc25A, a dual specificity phosphatase crucial for cell cycle progression, is linked to connexin (Cx) phosphorylation and the modulation of GJC. Inhibition of Cdc25 phosphatases in rat liver epithelial cells employing a 1,4-naphthoquinone-based inhibitor, NSC95397, induced cell cycle arrest, tyrosine phosphorylation of the epidermal growth factor receptor (EGFR), and activation of extracellular signal-regulated kinases ERK-1 and -2. ERK activation was blocked by specific inhibitors of MAPK/ERK kinases 1/2 or of the EGFR tyrosine kinase. An EGFR-dephosphorylation assay suggested that Cdc25A interacts with the EGFR, with inhibition by NSC95397 resulting in activation of the receptor. As a consequence of ERK activation, Cx43 was phosphorylated, resulting in a downregulation of GJC. Loss of GJC was prevented by inhibition of ERK activation. In summary, cell cycle and GJC are connected via Cdc25A and the EGFR-ERK pathway.
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Affiliation(s)
- Ira Melchheier
- Institut für Biochemie und Molekularbiologie I, Heinrich-Heine-Universität Düsseldorf, D-40225 Düsseldorf, Germany
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12
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Lampe PD, Lau AF. The effects of connexin phosphorylation on gap junctional communication. Int J Biochem Cell Biol 2004; 36:1171-86. [PMID: 15109565 PMCID: PMC2878204 DOI: 10.1016/s1357-2725(03)00264-4] [Citation(s) in RCA: 457] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2003] [Accepted: 07/10/2003] [Indexed: 11/25/2022]
Abstract
Gap junctions are specialized membrane domains composed of collections of channels that directly connect neighboring cells providing for the cell-to-cell diffusion of small molecules, including ions, amino acids, nucleotides, and second messengers. Vertebrate gap junctions are composed of proteins encoded by the "connexin" gene family. In most cases examined, connexins are modified post-translationally by phosphorylation. Phosphorylation has been implicated in the regulation of gap junctional communication at several stages of the connexin "lifecycle", such as the trafficking, assembly/disassembly, degradation, as well as, the gating of gap junction channels. Since connexin43 (Cx43) is widely expressed in tissues and cell lines, we understand the most about how it is regulated, and thus, connexin43 phosphorylation is a major focus of this review. Recent reports utilizing new methodologies combined with the latest genome information have shown that activation of several kinases including protein kinase A, protein kinase C, p34(cdc2)/cyclin B kinase, casein kinase 1, mitogen-activated protein (MAP) kinase and pp60(src) kinase can lead to phosphorylation at 12 of the 21 serine and two of the six tyrosine residues in the C-terminal region of connexin43. In several cases, use of site-directed mutants of these sites have shown that these specific phosphorylation events can be linked to changes in gap junctional communication.
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Affiliation(s)
- Paul D Lampe
- Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North DE-320, Box 19024, Seattle, WA 98109, USA.
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Solan JL, Lampe PD. Connexin phosphorylation as a regulatory event linked to gap junction channel assembly. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2004; 1711:154-63. [PMID: 15955300 DOI: 10.1016/j.bbamem.2004.09.013] [Citation(s) in RCA: 234] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2004] [Revised: 09/29/2004] [Accepted: 09/30/2004] [Indexed: 12/15/2022]
Abstract
Gap junctions, composed of proteins from the connexin family, allow for intercellular communication between cells and are important in development and maintenance of cell homeostasis. Phosphorylation has been implicated in the regulation of gap junctional communication at several stages of the cell cycle and the connexin "lifecycle", such as trafficking, assembly/disassembly, degradation, as well as in the gating of "hemi" channels or intact gap junction channels. This review focuses on how phosphorylation can regulate the early stages of the connexin life cycle through assembly of functional gap junctional channels. The availability of sequences from the human genome databases has indicated that the number of connexins in the gene family is approximately 20, but we know mostly about how connexin43 (Cx43) is regulated. Recent technologies and investigations of interacting proteins have shown that activation of several kinases including protein kinase A, protein kinase C (PKC), p34(cdc2)/cyclin B kinase, casein kinase 1 (CK1), mitogen-activated protein kinase (MAPK) and pp60(src) kinase can lead to phosphorylation of the majority of the 21 serine and two of the tyrosine residues in the C-terminal region of Cx43. While many studies have correlated changes in kinase activity with changes in gap junctional communication, further research is needed to directly link specific phosphorylation events with changes in connexin oligomerization and gap junction assembly.
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Affiliation(s)
- Joell L Solan
- Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, M5C800, Box 19024, Seattle, Washington 98109, United States
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Hockett ME, Rohrbach NR, Schrick FN. Alterations in embryo development in progestogen-supplemented cows administered prostaglandin F2α. Prostaglandins Other Lipid Mediat 2004; 73:227-36. [PMID: 15287154 DOI: 10.1016/j.prostaglandins.2004.02.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The objective was to examine effects of elevated prostaglandin F2alpha (PGF) on embryo development in cows supplemented with exogenous progestogen. Cows were artificially inseminated at estrus (Day 0) and a synthetic progestogen supplemented in the feed from Days 3 to 8. Cows were allotted randomly to receive either 15 mg PGF (TRT) or saline (CON) at 06:00, 14:00 and 22:00 h from Days 5 to 8. Blood samples were collected at 06:00 and 22:00 h from Days 5 to 8 for determination of progesterone and 13,14-dihydro-15-keto-PGF2alpha (PGFM). Single embryos were recovered on Day 8, assigned a quality score, and stage of development recorded. Progesterone was lower from Days 5 to 8 in TRT versus CON cows (P = 0.0001). Concentrations of PGFM from Days 5 to 8 were elevated in TRT compared to CON cows (P = 0.0001). Embryo quality was reduced in TRT cows compared to CON cows (P = 0.059). Percentage of embryos considered transferable was decreased by administration of PGF (P = 0.003). Sixty-four percent of TRT embryos were retarded in development at Day 8, whereas 80% of CON embryos had developed to expanded blastocysts (P = 0.003). In conclusion, treatment of progestogen-supplemented cows with PGF reduced quality and retarded development of embryos. Decreased fertility in conditions causing elevated concentrations of PGF may result from altered embryo development and quality.
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Affiliation(s)
- M E Hockett
- Department of Animal Science, University of Tennessee, 205 C Brehm Animal Science Building, Knoxville, TN 37996-4574, USA
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15
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Nishida M, Futami S, Morita I, Maekawa K, Murota SI. Hypoxia-reoxygenation inhibits gap junctional communication in cultured human umbilical vein endothelial cells. ENDOTHELIUM : JOURNAL OF ENDOTHELIAL CELL RESEARCH 2001; 7:279-86. [PMID: 11201525 DOI: 10.3109/10623320009072214] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
We studied the change in gap junctional intercellular communication (GJIC) on human umbilical vein endothelial cells (HUVEC) under hypoxia-reoxygenation (H-R) conditions by the fluorescence redistribution after photobleaching (FRAP) method. Confluent HUVEC monolayers were exposed to hypoxia (pO2<0.1%) for 12 hours, and then were returned to normal atmospheric conditions for reoxygenation. Contrast microscopic observation showed no significant changes in the morphology of the HUVEC at any times after H-R. Reoxygenation following hypoxia caused time-dependent decrease in GJIC, that is, GJIC reduction was induced after 2 hours and reached maximum at 4-6 hours which recovered to normal levels after 18 hours. Oxidant sensitive fluorescence dye assay revealed that the generation of intracellular free radicals increased during the first 2 hours after reoxygenation. Hydroxyl radical scavengers (MCI-186, DMSO) and an iron chelator (deferoxamine) abolished the reduction of GJIC due to H-R. However, SOD, catalase and probucol were essentially inactive on this reduction. These data suggest that ischemia-reperfusion injury may be caused by a functional defect of GJIC induced by reactive oxygen radicals.
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Affiliation(s)
- M Nishida
- Department of Cellular Physiological Chemistry, Graduate School, Tokyo Medical and Dental University, Japan
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16
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Koffler L, Roshong S, Kyu Park I, Cesen-Cummings K, Thompson DC, Dwyer-Nield LD, Rice P, Mamay C, Malkinson AM, Ruch RJ. Growth inhibition in G(1) and altered expression of cyclin D1 and p27(kip-1 )after forced connexin expression in lung and liver carcinoma cells. J Cell Biochem 2000; 79:347-54. [PMID: 10972973 DOI: 10.1002/1097-4644(20001201)79:3<347::aid-jcb10>3.0.co;2-2] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Gap junctional intercellular communication (GJIC) and connexin expression are frequently decreased in neoplasia and may contribute to defective growth control and loss of differentiated functions. GJIC, in E9 mouse lung carcinoma cells and WB-aB1 neoplastic rat liver epithelial cells, was elevated by forced expression of the gap junction proteins, connexin43 (Cx43) and connexin32 (Cx32), respectively. Transfection of Cx43 into E9 cells increased fluorescent dye-coupling in the transfected clones, E9-2 and E9-3, to levels comparable to the nontransformed sibling cell line, E10, from which E9 cells originated. Transduction of Cx32 into WB-aB1 cells also increased dye-coupling in the clone, WB-a/32-10, to a level that was comparable to the nontransformed sibling cell line, WB-F344. The cell cycle distribution was also affected as a result of forced connexin expression. The percentage of cells in G(1)-phase increased and the percentage in S-phase decreased in E9-2 and WB-a/32-10 cells as compared to E9 and WB-aB1 cells. Concomitantly, these cells exhibited changes in G(1)-phase cell cycle regulators. E9-2 and WB-a/32-10 cells expressed significantly less cyclin D1 and more p27(kip-1) protein than E9 and WB-aB1 cells. Other growth-related properties (expression of platelet-derived growth factor receptor-beta, epidermal growth factor receptor, protein kinase C-alpha, protein kinase A regulatory subunit-Ialpha, and production of nitric oxide in response to a cocktail of pro-inflammatory cytokines) were minimally altered or unaffected. Thus, enhancement of connexin expression and GJIC in neoplastic mouse lung and rat liver epithelial cells restored G(1) growth control. This was associated with decreased expression of cyclin D1 and increased expression of p27(kip-1), but not with changes in other growth-related functions.
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Affiliation(s)
- L Koffler
- Department of Pathology, Medical College of Ohio, Toledo, Ohio 43699, USA
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Zhang YW, Morita I, Nishida M, Murota SI. Involvement of tyrosine kinase in the hypoxia/reoxygenation-induced gap junctional intercellular communication abnormality in cultured human umbilical vein endothelial cells. J Cell Physiol 1999; 180:305-13. [PMID: 10430170 DOI: 10.1002/(sici)1097-4652(199909)180:3<305::aid-jcp1>3.0.co;2-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Vascular endothelial cells (EC), communicating with one another across gap junctions, are usually made dysfunctional by hypoxia and reoxygenation (H/R); however, very limited information exists regarding the effects of H/R on the endothelial gap junctions. We investigated whether H/R interferes with endothelial gap junctional intercellular communication (GJIC). After human umbilical vein EC had grown to confluence, they were exposed to hypoxia (pO2 < 0.1%) for 12-16 h and then returned to normal atmospheric conditions for reoxygenation. At 0-, 2-, 4-, 6-h reoxygenation, GJIC was detected by means of a fluorescence recovery after a photobleaching technique. The results demonstrated that a GJIC reduction (about 20% less than that under normoxia) was induced after 2 h of reoxygenation; after 4 h of reoxygenation, it began to recover (to about 10% less than that under normoxia); and after 6 h of reoxygenation, GJIC was restored to the normal level. Calphostin C (1 x 10(-7) mol/l), a specific protein kinase C inhibitor, partially inhibited the reduction in GJIC (resulting in a level about 10% less than that under normoxia), whereas the tyrosine kinase inhibitor genistein (10 micromol/L) completely blocked the reduction in GJIC. Vanadate (1.5 mmol/l), a tyrosine phosphatase inhibitor, amplified the inhibitory effect of H/R on GJIC (to about 40% less than that under normoxia). Immunofluorescence and immunoprecipitation showed that 2-h reoxygenation significantly stimulated tyrosine protein phosphorylation, and this phosphorylation event was obviously enhanced by vanadate. The results of Western blotting showed that the gap junctional protein connexin 43 (Cx43) was phosphorylated by H/R; moreover, immunoprecipitation demonstrated that 2-h reoxygenation induced a prominent increase of tyrosine phosphorylation of Cx43 compared with that under normoxia. These data indicate that H/R induces a transient endothelial GJIC dysfunction through the activation of tyrosine kinase and phosphorylation of tyrosine residues of Cx43.
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Affiliation(s)
- Y W Zhang
- Department of Physiological Chemistry, Graduate School, Tokyo Medical and Dental University, Japan
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Kim DY, Kam Y, Koo SK, Joe CO. Gating connexin 43 channels reconstituted in lipid vesicles by mitogen-activated protein kinase phosphorylation. J Biol Chem 1999; 274:5581-7. [PMID: 10026174 DOI: 10.1074/jbc.274.9.5581] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The regulation of gap junctional permeability by phosphorylation was examined in a model system in which connexin 43 (Cx43) gap junction hemichannels were reconstituted in lipid vesicles. Cx43 was immunoaffinity-purified from rat brain, and Cx43 channels were reconstituted into unilamellar phospholipid liposomes. The activities of the reconstituted channels were measured by monitoring liposome permeability. Liposomes containing the Cx43 protein were fractionated on the basis of permeability to sucrose using sedimentation in an iso-osmolar density gradient. The gradient allowed separation of the sucrose-permeable and -impermeable liposomes. Liposomes that were permeable to sucrose were also permeable to the communicating dye molecule lucifer yellow. Permeability, and therefore activity of the reconstituted Cx43 channels, were directly dependent on the state of Cx43 phosphorylation. The permeability of liposomes containing Cx43 channels was increased by treatment of liposomes with calf intestinal phosphatase. Moreover, liposomes formed with Cx43 that had been dephosphorylated by calf intestinal phosphatase treatment showed increased permeability to sucrose. The role of phosphorylation in the gating mechanism of Cx43 channels was supported further by the observation that phosphorylation of Cx43 by mitogen-activated protein kinase reversibly reduced the permeability of liposomes containing dephosphorylated Cx43. Our results show a direct correlation between gap junctional permeability and the phosphorylation state of Cx43.
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Affiliation(s)
- D Y Kim
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Taejon 305-701, Republic of Korea
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Chapter 24: Role of Gap Junctions in Cellular Growth Control and Neoplasia: Evidence and Mechanisms. CURRENT TOPICS IN MEMBRANES 1999. [DOI: 10.1016/s0070-2161(08)61028-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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Ward KW, Rogers EH, Hunter ES. Dysmorphogenic effects of a specific protein kinase C inhibitor during neurulation. Reprod Toxicol 1998; 12:525-34. [PMID: 9763244 DOI: 10.1016/s0890-6238(98)00032-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Protein kinase C (PKC) plays a key role in signal transduction and is an important mediator of events throughout development. However, no information exists regarding the effect of a specific PKC inhibitor on mammalian embryogenesis during neurulation. This investigation was undertaken to examine the effects of a specific inhibitor of PKC, as well as inhibitors of other important kinases, on cultured mouse embryos. CD-1 mouse embryos (3 to 6 somite stage) were exposed to bisindolylmaleimide I (a specific PKC inhibitor) as well as specific inhibitors of PKA, PKG, and MAP kinase kinase for 24 h. The PKC inhibitor was a potent embryotoxicant and elicited malformations at concentrations as low as 0.01 microM. Inhibitors of other kinases also produced malformations but at much higher concentrations than those required to produce similar defects with the PKC inhibitor. These data suggest that PKC plays an important role in mammalian neurulation. Further research is required to clarify the mechanism by which PKC inhibition at this developmental stage produces malformations and the potential effects of environmental toxicants with PKC inhibitory properties on this signal transduction pathway.
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Affiliation(s)
- K W Ward
- Curriculum in Toxicology, University of North Carolina at Chapel Hill, USA
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