151
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De Bock M, Wang N, Decrock E, Bol M, Gadicherla AK, Culot M, Cecchelli R, Bultynck G, Leybaert L. Endothelial calcium dynamics, connexin channels and blood-brain barrier function. Prog Neurobiol 2013; 108:1-20. [PMID: 23851106 DOI: 10.1016/j.pneurobio.2013.06.001] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Revised: 06/12/2013] [Accepted: 06/18/2013] [Indexed: 01/11/2023]
Abstract
Situated between the circulation and the brain, the blood-brain barrier (BBB) protects the brain from circulating toxins while securing a specialized environment for neuro-glial signaling. BBB capillary endothelial cells exhibit low transcytotic activity and a tight, junctional network that, aided by the cytoskeleton, restricts paracellular permeability. The latter is subject of extensive research as it relates to neuropathology, edema and inflammation. A key determinant in regulating paracellular permeability is the endothelial cytoplasmic Ca(2+) concentration ([Ca(2+)]i) that affects junctional and cytoskeletal proteins. Ca(2+) signals are not one-time events restricted to a single cell but often appear as oscillatory [Ca(2+)]i changes that may propagate between cells as intercellular Ca(2+) waves. The effect of Ca(2+) oscillations/waves on BBB function is largely unknown and we here review current evidence on how [Ca(2+)]i dynamics influence BBB permeability.
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Affiliation(s)
- Marijke De Bock
- Dept. of Basic Medical Sciences, Ghent University, Ghent, Belgium.
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152
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Chen YS, Toth I, Danesh-Meyer HV, Green CR, Rupenthal ID. Cytotoxicity and vitreous stability of chemically modified connexin43 mimetic peptides for the treatment of optic neuropathy. J Pharm Sci 2013; 102:2322-31. [PMID: 23696181 DOI: 10.1002/jps.23617] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Revised: 04/09/2013] [Accepted: 04/29/2013] [Indexed: 11/07/2022]
Abstract
Optic neuropathy is associated with retinal ganglion cell (RGC) loss leading to optic nerve damage and visual impairment. Unregulated connexin (Cx) hemichannel opening plays a role in RGC loss. Thus, inhibition via Cx43-specific mimetic peptides (MP) may prevent further cell death. However, the highly hydrophilic character and poor stability of native peptides prevent their efficient delivery across biological membranes. The present study aimed to improve the stability of Cx43 MP by conjugation to C12-lipoamino acid (C12-Laa) or sugar groups. Unmodified and modified Cx43 MP were synthesized using solid-phase peptide synthesis. Their functionality was assessed by propidium iodide (PI) uptake into NT2 cells, a human testicular carcinoma progenitor cell line able to differentiate into astrocytes, whereas the stability in ocular vitreous was measured by reversed-phase high-performance liquid chromatography. PI uptake studies showed inhibition of hemichannel opening for unmodified and modified Cx43 MP. Stability measurements revealed improved stability of modified Cx43 MP, with two Laa groups increasing the peptide half-life in bovine vitreous more than twofold. Conjugation to C12 -Laa or sugar did not affect the functionality of Cx43 MP, but addition of two C12-Laa groups significantly improved peptide stability. Laa-modifications may therefore offer improved stability and retinal delivery of peptides in vivo.
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Affiliation(s)
- Ying-Shan Chen
- Department of Ophthalmology, New Zealand National Eye Centre, Faculty of Medical and Health Sciences, The University of Auckland, Auckland 1142, New Zealand
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153
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Iyyathurai J, D'hondt C, Wang N, De Bock M, Himpens B, Retamal MA, Stehberg J, Leybaert L, Bultynck G. Peptides and peptide-derived molecules targeting the intracellular domains of Cx43: gap junctions versus hemichannels. Neuropharmacology 2013; 75:491-505. [PMID: 23664811 DOI: 10.1016/j.neuropharm.2013.04.050] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Revised: 04/17/2013] [Accepted: 04/18/2013] [Indexed: 12/15/2022]
Abstract
About a decade ago, the molecular determinants controlling the opening and closing of Cx43 gap junction channels have been identified. Advanced biophysical approaches revealed a critical role for structural rearrangements in the cytoplasmic loop and dimerization of the C-terminal tail, resulting in binding of the C-terminal tail to the cytoplasmic loop and Cx43 gap junction channel closure during cellular acidosis. This has spurred the development of Cx43-mimetic peptides and peptidomimetics that interfere with these loop/tail interactions, thereby preventing the closure of Cx43 gap junctions, e.g. in the heart upon ischemia. Recently, we found that loop/tail interactions control Cx43-hemichannel activity but with an opposite effect. Binding of the C-terminal tail to the cytoplasmic loop is a requisite for the opening of Cx43 hemichannels in response to different stimuli, like decreased extracellular [Ca2+], increased intracellular [Ca2+], positive membrane potentials or ischemia. Strikingly, peptides that favor the open state of Cx43 gap junctions like the L2 peptide inhibit Cx43-hemichannel opening. These tools now provide unprecedented opportunities to selectively inhibit Cx43 hemichannels while maintaining Cx43 gap junction communication, impossible to achieve with siRNA or knockdown approaches both affecting gap junctions and hemichannels. These tools not only are very helpful to unravel the role of Cx43 hemichannels in complex biological systems, but also hold therapeutic potential to counteract excessive Cx43-hemichannel activity like in ischemia/reperfusion in the brain and the heart or to prevent Cx43 hemichannel-mediated gliotransmitter release in the basal amygdala during memory consolidation in response to emotional events. This article is part of the Special Issue Section entitled 'Current Pharmacology of Gap Junction Channels and Hemichannels'.
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Affiliation(s)
- Jegan Iyyathurai
- KU Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, Campus Gasthuisberg O/N-I Bus 802, Herestraat 49, BE-3000 Leuven, Belgium
| | - Catheleyne D'hondt
- KU Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, Campus Gasthuisberg O/N-I Bus 802, Herestraat 49, BE-3000 Leuven, Belgium
| | - Nan Wang
- Faculty of Medicine and Health Sciences, Physiology Group, Department of Basic Medical Sciences, Ghent University, De Pintelaan 185 (Block B-Rm 310), B-9000 Ghent, Belgium
| | - Marijke De Bock
- Faculty of Medicine and Health Sciences, Physiology Group, Department of Basic Medical Sciences, Ghent University, De Pintelaan 185 (Block B-Rm 310), B-9000 Ghent, Belgium
| | - Bernard Himpens
- KU Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, Campus Gasthuisberg O/N-I Bus 802, Herestraat 49, BE-3000 Leuven, Belgium
| | - Mauricio A Retamal
- Departamento de Fisiología, Facultad de Medicina, Clínica Alemana-Universidad del Desarrollo, Santiago, Chile
| | - Jimmy Stehberg
- Universidad Andres Bello, Laboratorio de Neurobiologia, Departamento de Ciencias Biologicas, Facultad de Ciencias Biologicas & Facultad de Medicina, Santiago, Chile; Universidad Andres Bello, Centro de Investigaciones Biomédicas, Santiago, Chile
| | - Luc Leybaert
- Faculty of Medicine and Health Sciences, Physiology Group, Department of Basic Medical Sciences, Ghent University, De Pintelaan 185 (Block B-Rm 310), B-9000 Ghent, Belgium
| | - Geert Bultynck
- KU Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, Campus Gasthuisberg O/N-I Bus 802, Herestraat 49, BE-3000 Leuven, Belgium.
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154
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Riquelme MA, Kar R, Gu S, Jiang JX. Antibodies targeting extracellular domain of connexins for studies of hemichannels. Neuropharmacology 2013; 75:525-32. [PMID: 23499293 DOI: 10.1016/j.neuropharm.2013.02.021] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2012] [Revised: 02/25/2013] [Accepted: 02/27/2013] [Indexed: 01/11/2023]
Abstract
Hemichannels are transmembrane channels composed of either a connexin or pannexin hexamer. The docking of the extracellular domains of connexin hemichannels contributed by neighboring cells forms a gap junction channel that joins the cytoplasm of adjacent cells. Connexins are expressed ubiquitously in different organs, but some subtypes are expressed exclusively in certain tissues and tumors. Both gap junction channels and hemichannels participate in diverse physiological and pathological responses. However, the lack of specific reagents that inhibit only gap junction channels or hemichannels is a challenge that makes it different to discern the specific roles of either channel. Fortunately, the available information regarding the connexin sequence, secondary and tertiary structure, and their biochemical and physiological properties permits the development of strategies to block exclusively the hemichannel activity exclusively, with no effect on gap junction activity. This task is accomplished through the use of specifics antibodies that target the extracellular sites of desired connexin subtype. However, the underlying mechanism of how antibodies targeting extracellular connexin epitopes actually inhibit hemichannels remains unknown. Although these antibodies are being used for detecting and blocking of hemichannels in normal and tumor cells, they can also be potentially used for tissue-specific treatment and drug delivery in clinical applications. In this article, we will first review the literature concerning the structure of connexins and the unique properties of extracellular loop domains of the connexins. Furthermore, we will discuss briefly the development of connexin (Cx) 43(E2) antibody, a specific antibody which detects the second extracellular loop of Cx43 and specifically prevents the opening of Cx43 hemichannels. We will then summarize the reported studies of specific reagents used for the inhibition of connexin hemichannels including antibodies developed against extracellular loop domains. This article is part of the Special Issue Section entitled 'Current Pharmacology of Gap Junction Channels and Hemichannels'.
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Affiliation(s)
- Manuel A Riquelme
- Department of Biochemistry, University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA
| | - Rekha Kar
- Department of Biochemistry, University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA
| | - Sumin Gu
- Department of Biochemistry, University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA
| | - Jean X Jiang
- Department of Biochemistry, University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA.
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155
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Gap junction channels and hemichannels in the CNS: regulation by signaling molecules. Neuropharmacology 2013; 75:567-82. [PMID: 23499663 DOI: 10.1016/j.neuropharm.2013.02.020] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2012] [Revised: 02/08/2013] [Accepted: 02/26/2013] [Indexed: 11/20/2022]
Abstract
Coordinated interaction among cells is critical to develop the extremely complex and dynamic tasks performed by the central nervous system (CNS). Cell synchronization is in part mediated by connexins and pannexins; two different protein families that form gap junction channels and hemichannels. Whereas gap junction channels connect the cytoplasm of contacting cells and coordinate electric and metabolic activities, hemichannels communicate intra- and extra-cellular compartments and serve as diffusional pathways for ions and small molecules. Cells in the CNS depend on paracrine/autocrine communication via several extracellular signaling molecules, such as, cytokines, growth factors, transmitters and free radical species to sense changes in microenvironment as well as to adapt to them. These signaling molecules modulate crucial processes of the CNS, including, cellular migration and differentiation, synaptic transmission and plasticity, glial activation, cell viability and microvascular blood flow. Gap junction channels and hemichannels are affected by different signaling transduction pathways triggered by these paracrine/autocrine signaling molecules. Most of the modulatory effects induced by these signaling molecules are specific to the cell type and the connexin and pannexin subtype expressed in different brain areas. In this review, we summarized and discussed most of the relevant and recently published information on the effects of signaling molecules on connexin or pannexin based channels and their possible relevance in CNS physiology and pathology. This article is part of the Special Issue Section entitled 'Current Pharmacology of Gap Junction Channels and Hemichannels'.
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156
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Orellana JA, Velasquez S, Williams DW, Sáez JC, Berman JW, Eugenin EA. Pannexin1 hemichannels are critical for HIV infection of human primary CD4+ T lymphocytes. J Leukoc Biol 2013; 94:399-407. [PMID: 23456773 DOI: 10.1189/jlb.0512249] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
HIV is a major public health issue, and infection of CD4(+) T lymphocytes is one of its key features. Whereas several cellular proteins have been identified that facilitate viral infection and replication, the role of hemichannels in these processes has not been fully characterized. We now show that the HIV isolates, R5 and X4, induced a transient-early (5-30 min) and a later, persistent (48-120 h) opening of Panx1 hemichannels, which was dependent on the binding of HIV to CD4 and CCR5/CXCR4 receptors. Blocking Panx1 hemichannels by reducing their opening or protein expression inhibited HIV replication in CD4(+) T lymphocytes. Thus, our findings demonstrate that Panx1 hemichannels play an essential role in HIV infection.
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Affiliation(s)
- J A Orellana
- Departamento de Neurología, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
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157
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Ishihara Y, Sugawara Y, Kamioka H, Kawanabe N, Hayano S, Balam TA, Naruse K, Yamashiro T. Ex vivo real-time observation of Ca(2+) signaling in living bone in response to shear stress applied on the bone surface. Bone 2013; 53:204-15. [PMID: 23246671 DOI: 10.1016/j.bone.2012.12.002] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2012] [Revised: 10/31/2012] [Accepted: 12/03/2012] [Indexed: 12/29/2022]
Abstract
Bone cells respond to mechanical stimuli by producing a variety of biological signals, and one of the earliest events is intracellular calcium ([Ca(2+)](i)) mobilization. Our recently developed ex vivo live [Ca(2+)](i) imaging system revealed that bone cells in intact bone explants showed autonomous [Ca(2+)](i) oscillations, and osteocytes specifically modulated these oscillations through gap junctions. However, the behavior and connectivity of the [Ca(2+)](i) signaling networks in mechanotransduction have not been investigated in intact bone. We herein introduce a novel fluid-flow platform for probing cellular signaling networks in live intact bone, which allows the application of capillary-driven flow just on the bone explant surface while performing real-time fluorogenic monitoring of the [Ca(2+)](i) changes. In response to the flow, the percentage of responsive cells was increased in both osteoblasts and osteocytes, together with upregulation of c-fos expression in the explants. However, enhancement of the peak relative fluorescence intensity was not evident. Treatment with 18 α-GA, a reversible inhibitor of gap junction, significantly blocked the [Ca(2+)](i) responsiveness in osteocytes without exerting any major effect in osteoblasts. On the contrary, such treatment significantly decreased the flow-activated oscillatory response frequency in both osteoblasts and osteocytes. The stretch-activated membrane channel, when blocked by Gd(3+), is less affected in the flow-induced [Ca(2+)](i) response. These findings indicated that flow-induced mechanical stimuli accompanied the activation of the autonomous [Ca(2+)](i) oscillations in both osteoblasts and osteocytes via gap junction-mediated cell-cell communication and hemichannel. Although how the bone sense the mechanical stimuli in vivo still needs to be elucidated, the present study suggests that cell-cell signaling via augmented gap junction and hemichannel-mediated [Ca(2+)](i) mobilization could be involved as an early signaling event in mechanotransduction.
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Affiliation(s)
- Yoshihito Ishihara
- Department of Orthodontics, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, 700-8525, Japan.
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158
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Li K, Chi Y, Gao K, Yan Q, Matsue H, Takeda M, Kitamura M, Yao J. Connexin43 hemichannel-mediated regulation of connexin43. PLoS One 2013; 8:e58057. [PMID: 23460926 PMCID: PMC3584027 DOI: 10.1371/journal.pone.0058057] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Accepted: 01/31/2013] [Indexed: 01/24/2023] Open
Abstract
Background Many signaling molecules and pathways that regulate gap junctions (GJs) protein expression and function are, in fact, also controlled by GJs. We, therefore, speculated an existence of the GJ channel-mediated self-regulation of GJs. Using a cell culture model in which nonjunctional connexin43 (Cx43) hemichannels were activated by cadmium (Cd2+), we tested this hypothesis. Principal Findings Incubation of Cx43-transfected LLC-PK1 cells with Cd2+ led to an increased expression of Cx43. This effect of Cd2+ was tightly associated with JNK activation. Inhibition of JNK abolished the elevation of Cx43. Further analysis revealed that the changes of JNK and Cx43 were controlled by GSH. Supplement of a membrane-permeable GSH analogue GSH ethyl ester or GSH precursor N-acetyl-cystein abrogated the effects of Cd2+ on JNK activation and Cx43 expression. Indeed, Cd2+ induced extracellular release of GSH. Blockade of Cx43 hemichannels with heptanol or Cx43 mimetic peptide Gap26 to prevent the efflux of GSH significantly attenuated the Cx43-elevating effects of Cd2+. Conclusions Collectively, our results thus indicate that Cd2+-induced upregulation of Cx43 is through activation of nonjunctional Cx43 hemichannels. Our findings thus support the existence of a hemichannel-mediated self-regulation of Cx43 and provide novel insights into the molecular mechanisms of Cx43 expression and function.
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Affiliation(s)
- Kai Li
- Department of Molecular Signaling, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Chuo, Yamanashi, Japan
- Department of Urology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Chuo, Yamanashi, Japan
- Department of Surgical Oncology and General Surgery, First Hospital of China Medical University, Shenyang, China
- * E-mail: (JY); (KL)
| | - Yuan Chi
- Department of Molecular Signaling, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Chuo, Yamanashi, Japan
| | - Kun Gao
- Department of Molecular Signaling, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Chuo, Yamanashi, Japan
| | - Qiaojing Yan
- Department of Molecular Signaling, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Chuo, Yamanashi, Japan
| | - Hiroyuki Matsue
- Department of Dermatology, Chiba University School of Medicine, Chiba, Japan
| | - Masayuki Takeda
- Department of Urology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Chuo, Yamanashi, Japan
| | - Masanori Kitamura
- Department of Molecular Signaling, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Chuo, Yamanashi, Japan
| | - Jian Yao
- Department of Molecular Signaling, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Chuo, Yamanashi, Japan
- * E-mail: (JY); (KL)
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159
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Deva NC, Zhang J, Green CR, Danesh-Meyer HV. Connexin43 modulation inhibits scarring in a rabbit eye glaucoma trabeculectomy model. Inflammation 2013; 35:1276-86. [PMID: 22427153 DOI: 10.1007/s10753-012-9439-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We investigated whether one subconjunctival injection of connexin43 antisense oligodeoxynucleotides (Cx43 AsODN) modulates postoperative scarring in a rabbit model of glaucoma trabeculectomy surgery. In a randomised, controlled, masked-observer study, 39 rabbits underwent trabeculectomy surgery with insertion of a 22-gauge cannula in the right eyes and were randomly divided into three treatment groups. Each rabbit received an injection of Cx43 AsODN in Pluronic gel, balanced salt solution or Pluronic gel alone into the formed bled. The animals were euthanized at 8 and 24 h and at 5 and 21 days. Histology and immunohistochemistry results demonstrated that Cx43 AsODN decreased Cx43 upregulation at 8 and 24 h which led to less myofibroblast upregulation at days 5 and 21 and reduced scarring at day 21 compared to controls. We conclude that postoperative use of Cx43 AsODN inhibited subconjunctival scarring and fibrosis. Cx43 AsODN injection may be a safe and effective anti-scarring agent in glaucoma trabeculectomy surgery.
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Affiliation(s)
- Narmadai C Deva
- Department of Ophthalmology, University of Auckland, Private Bag 92019, Auckland Mail Centre, Auckland, 1142, New Zealand
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160
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D'hondt C, Iyyathurai J, Wang N, Gourdie RG, Himpens B, Leybaert L, Bultynck G. Negatively charged residues (Asp378 and Asp379) in the last ten amino acids of the C-terminal tail of Cx43 hemichannels are essential for loop/tail interactions. Biochem Biophys Res Commun 2013; 432:707-12. [PMID: 23376080 DOI: 10.1016/j.bbrc.2013.01.066] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Accepted: 01/17/2013] [Indexed: 01/08/2023]
Abstract
Connexin 43 (Cx43)-hemichannel activity is controlled by intramolecular interactions between cytoplasmic loop and C-terminal tail. We previously identified the last 10 amino acids of the C-terminal tail of Cx43 as essential for Cx43-hemichannel activity. We developed a cell-permeable peptide covering this sequence (TAT-Cx43CT). In this study, we examined the critical molecular determinants in TAT-Cx43CT to restore Cx43-hemichannel activity. Using amino acid substitutions in TAT-Cx43CT, we identified the two aspartate (Asp378 and Asp379) and two proline (Pro375 and Pro377) residues as critical for TAT-Cx43CT activity, since TAT-Cx43CT(DD/AA) and TAT-Cx43CT(PP/GG) did not overcome the inhibition of Cx43-hemichannel activity induced by thrombin, micromolar cytoplasmic Ca(2+) concentration or truncation of Cx43 at M(239). Consistent with this, we found that biotin-Cx43CT(DD/AA) was much less efficient than biotin-Cx43CT to bind the purified CL domain of Cx43 in surface plasmon resonance experiments. In conclusion, we postulate that Asp378 and Asp379 in the C-terminal part of Cx43 are essential for loop/tail interactions in Cx43 hemichannels, while Pro375 and Pro377 may help to properly coordinate the critical Asp residues.
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Affiliation(s)
- Catheleyne D'hondt
- Laboratory of Molecular and Cellular Signalling, Department Cellular and Molecular Medicine, Campus Gasthuisberg O/N-1 Bus 802, Herestraat 49, BE-3000 Leuven, Belgium
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161
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The Role of Connexin 43 and Hemichannels Correlated with the Astrocytic Death Following Ischemia/Reperfusion Insult. Cell Mol Neurobiol 2013; 33:401-10. [DOI: 10.1007/s10571-013-9906-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2012] [Accepted: 01/03/2013] [Indexed: 11/24/2022]
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162
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Ion Channels. Mol Pharmacol 2012. [DOI: 10.1002/9781118451908.ch4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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163
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Wang N, De Vuyst E, Ponsaerts R, Boengler K, Palacios-Prado N, Wauman J, Lai CP, De Bock M, Decrock E, Bol M, Vinken M, Rogiers V, Tavernier J, Evans WH, Naus CC, Bukauskas FF, Sipido KR, Heusch G, Schulz R, Bultynck G, Leybaert L. Selective inhibition of Cx43 hemichannels by Gap19 and its impact on myocardial ischemia/reperfusion injury. Basic Res Cardiol 2012. [PMID: 23184389 DOI: 10.1007/s00395-012-0309-x] [Citation(s) in RCA: 194] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Connexin-43 (Cx43), a predominant cardiac connexin, forms gap junctions (GJs) that facilitate electrical cell-cell coupling and unapposed/nonjunctional hemichannels that provide a pathway for the exchange of ions and metabolites between cytoplasm and extracellular milieu. Uncontrolled opening of hemichannels in the plasma membrane may be deleterious for the myocardium and blocking hemichannels may confer cardioprotection by preventing ionic imbalance, cell swelling and loss of critical metabolites. Currently, all known hemichannel inhibitors also block GJ channels, thereby disturbing electrical cell-cell communication. Here we aimed to characterize a nonapeptide, called Gap19, derived from the cytoplasmic loop (CL) of Cx43 as a hemichannel blocker and examined its effect on hemichannel currents in cardiomyocytes and its influence in cardiac outcome after ischemia/reperfusion. We report that Gap 19 inhibits Cx43 hemichannels without blocking GJ channels or Cx40/pannexin-1 hemichannels. Hemichannel inhibition is due to the binding of Gap19 to the C-terminus (CT) thereby preventing intramolecular CT-CL interactions. The peptide inhibited Cx43 hemichannel unitary currents in both HeLa cells exogenously expressing Cx43 and acutely isolated pig ventricular cardiomyocytes. Treatment with Gap19 prevented metabolic inhibition-enhanced hemichannel openings, protected cardiomyocytes against volume overload and cell death following ischemia/reperfusion in vitro and modestly decreased the infarct size after myocardial ischemia/reperfusion in mice in vivo. We conclude that preventing Cx43 hemichannel opening with Gap19 confers limited protective effects against myocardial ischemia/reperfusion injury.
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Affiliation(s)
- Nan Wang
- Faculty of Medicine and Health Sciences, Physiology group, Department of Basic Medical Sciences, Ghent University, Ghent, Belgium
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164
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Zonta F, Polles G, Zanotti G, Mammano F. Permeation pathway of homomeric connexin 26 and connexin 30 channels investigated by molecular dynamics. J Biomol Struct Dyn 2012; 29:985-98. [PMID: 22292956 DOI: 10.1080/073911012010525027] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Mutations in the genes GJB2 and GJB6 encoding human connnexin26 (hCx26) and connexin30 (hCx30), respectively, are the leading cause of non-syndromic prelingual deafness in several human populations. In this work, we exploited the high degree (77%) of sequence similarity shared by hCx26 and hCx30 to create atomistic models of homomeric hCx26 and hCx30 connexons starting from the X-ray crystallographic structure of an intercellular channel formed by hCx26 protomers at 3.5-å resolution. The equilibrium dynamics of the two protein complexes was followed for 40 ns each by Molecular Dynamics (MD) simulations. Our results indicate that, in hCx26, positively charged Lys41 residues establish a potential barrier within the fully open channel, hindering ion diffusion in the absence of an electrochemical gradient. A similar role is played, in hCx30, by negatively charged Glu49 residues. The different position and charge of these two ion sieves account for the differences in unitary conductance observed experimentally. Our results are discussed in terms of present models of voltage gating in connexin channels.
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Affiliation(s)
- Francesco Zonta
- Department of Physics and Astronomy G.Galilei, University of Padua, 35129 Padua, Italy
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165
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Hawat G, Hélie P, Baroudi G. Single intravenous low-dose injections of connexin 43 mimetic peptides protect ischemic heart in vivo against myocardial infarction. J Mol Cell Cardiol 2012; 53:559-66. [DOI: 10.1016/j.yjmcc.2012.07.008] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/28/2012] [Revised: 07/18/2012] [Accepted: 07/18/2012] [Indexed: 02/05/2023]
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166
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Mammano F. ATP-dependent intercellular Ca2+ signaling in the developing cochlea: facts, fantasies and perspectives. Semin Cell Dev Biol 2012; 24:31-9. [PMID: 23022499 DOI: 10.1016/j.semcdb.2012.09.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2012] [Accepted: 09/14/2012] [Indexed: 10/27/2022]
Abstract
Hearing relies on a sensitive mechanoelectrical transduction process in the cochlea of the inner ear. The cochlea contains sensory, secretory, neural, supporting and epithelial cells which are all essential to the sound transduction process. It is well known that a complex extracellular purinergic signaling system contributes to cochlear homeostasis, altering cochlear sensitivity and neural output via ATP-gated ion channels (P2X receptors) and G protein-coupled P2Y receptors. This review focuses on the emerging roles of ATP that are currently under investigation in the developing sensory epithelium, with particular emphasis on the link between ATP release, Ca(2+) signaling, the expression and function of gap junction proteins connexin26 and connexin30, and the acquisition of hearing.
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Affiliation(s)
- Fabio Mammano
- Dipartimento di Fisica e Astronomia G. Galilei, Università di Padova, 35131 Padova, Italy.
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167
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Abstract
Intercellular calcium (Ca(2+)) waves (ICWs) represent the propagation of increases in intracellular Ca(2+) through a syncytium of cells and appear to be a fundamental mechanism for coordinating multicellular responses. ICWs occur in a wide diversity of cells and have been extensively studied in vitro. More recent studies focus on ICWs in vivo. ICWs are triggered by a variety of stimuli and involve the release of Ca(2+) from internal stores. The propagation of ICWs predominately involves cell communication with internal messengers moving via gap junctions or extracellular messengers mediating paracrine signaling. ICWs appear to be important in both normal physiology as well as pathophysiological processes in a variety of organs and tissues including brain, liver, retina, cochlea, and vascular tissue. We review here the mechanisms of initiation and propagation of ICWs, the key intra- and extracellular messengers (inositol 1,4,5-trisphosphate and ATP) mediating ICWs, and the proposed physiological functions of ICWs.
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Affiliation(s)
- Luc Leybaert
- Department of Basic Medical Sciences, Physiology Group, Faculty of Medicine & Health Sciences, Ghent University, Ghent, Belgium.
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168
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Freitas AS, Xavier ALR, Furtado CM, Hedin-Pereira C, Fróes MM, Menezes JRL. Dye coupling and connexin expression by cortical radial glia in the early postnatal subventricular zone. Dev Neurobiol 2012; 72:1482-97. [PMID: 22234946 DOI: 10.1002/dneu.22005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2011] [Revised: 12/21/2011] [Accepted: 12/29/2011] [Indexed: 11/08/2022]
Abstract
In this study, we have analyzed the specific contribution of the cortical radial glia (RG) for gap junctional communication (GJC) within the postnatal subventricular zone (SVZ). To specifically target RG as source of dye-coupling in situ, we have developed a new technique that involves direct cell loading through the processes that reach the pial surface, with a mix of gap junction permeant (Lucifer yellow, LY) and nonpermeant (rhodamine-conjugated dextran 3 KDa, RD) fluorochromes, the latter used as a marker for direct loaded cells. Tissue sections were analyzed for identification of directly loaded (LY+RD+) and coupled cells (LY+RD-) in the SVZ. Directly loaded cells were restricted to the region underlying the pial loading surface area. Coupled cells were distributed in a bistratified manner, along the outer dorsal surface of the SVZ and aligning the ventricle, leaving the SVZ core relatively free. Blocking GJC prior to pial loading greatly reduced dye coupling. Phenotypic analysis indicated that coupling by RG excludes neuroblasts and is mostly restricted to cells of glial lineage. Notwithstanding, no corresponding restriction to specific cell phenotype was found for two connexin isotypes, Cx43 and Cx45, in the postnatal SVZ. The extensive homocellular cell coupling by RG suggests an important role in the regulation of neurogenesis and functional compartmentalization of the postnatal SVZ.
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Affiliation(s)
- Andressa S Freitas
- Programa de Anatomia and Programa de Ciências Morfológicas, Lab. Neuroanatomia Celular, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Brazil
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169
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Desrochers J, Duncan NA. Intercellular communication via gap junctions affected by mechanical load in the bovine annulus fibrosus. Comput Methods Biomech Biomed Engin 2012; 17:64-71. [DOI: 10.1080/10255842.2012.717268] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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170
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Manipulating Connexin Communication Channels: Use of Peptidomimetics and the Translational Outputs. J Membr Biol 2012; 245:437-49. [PMID: 22886208 PMCID: PMC3456916 DOI: 10.1007/s00232-012-9488-5] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Accepted: 07/07/2012] [Indexed: 12/22/2022]
Abstract
Gap junctions are key components underpinning multicellularity. They provide cell to cell channel pathways that enable direct intercellular communication and cellular coordination in tissues and organs. The channels are constructed of a family of connexin (Cx) membrane proteins. They oligomerize inside the cell, generating hemichannels (connexons) composed of six subunits arranged around a central channel. After transfer to the plasma membrane, arrays of Cx hemichannels (CxHcs) interact and couple with partners in neighboring attached cells to generate gap junctions. Cx channels have been studied using a range of technical approaches. Short peptides corresponding to sequences in the extra- and intracellular regions of Cxs were used first to generate epitope-specific antibodies that helped studies on the organization and functions of gap junctions. Subsequently, the peptides themselves, especially Gap26 and -27, mimetic peptides derived from each of the two extracellular loops of connexin43 (Cx43), a widely distributed Cx, have been extensively applied to block Cx channels and probe the biology of cell communication. The development of a further series of short peptides mimicking sequences in the intracellular loop, especially the extremity of the intracellular carboxyl tail of Cx43, followed. The primary inhibitory action of the peptidomimetics occurs at CxHcs located at unapposed regions of the cell’s plasma membrane, followed by inhibition of cell coupling occurring across gap junctions. CxHcs respond to a range of environmental conditions by increasing their open probability. Peptidomimetics provide a way to block the actions of CxHcs with some selectivity. Furthermore, they are increasingly applied to address the pathological consequences of a range of environmental stresses that are thought to influence Cx channel operation. Cx peptidomimetics show promise as candidates in developing new therapeutic approaches for containing and reversing damage inflicted on CxHcs, especially in hypoxia and ischemia in the heart and in brain functions.
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171
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Kronengold J, Srinivas M, Verselis VK. The N-terminal half of the connexin protein contains the core elements of the pore and voltage gates. J Membr Biol 2012; 245:453-63. [PMID: 22825713 PMCID: PMC3735448 DOI: 10.1007/s00232-012-9457-z] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2012] [Accepted: 06/20/2012] [Indexed: 11/21/2022]
Abstract
Connexins form channels with large aqueous pores that mediate fluxes of inorganic ions and biological signaling molecules. Studies aimed at identifying the connexin pore now include a crystal structure that provides details of putative pore-lining residues that need to be verified using independent biophysical approaches. Here we extended our initial cysteine-scanning studies of the TM1/E1 region of Cx46 hemichannels to include TM2 and TM3 transmembrane segments. No evidence of reactivity was observed in either TM2 or TM3 probed with small or large thiol-modifying reagents. Several identified pore residues in E1 of Cx46 have been verified in different Cx isoforms. Use of variety of thiol reagents indicates that the connexin hemichannel pore is large and flexible enough, at least in the extracellular part of the pore funnel, to accommodate uncommonly large side chains. We also find that that gating characteristics are largely determined by the same domains that constitute the pore. These data indicate that biophysical and structural studies are converging towards a view that the N-terminal half of the Cx protein contains the principal components of the pore and gating elements, with NT, TM1 and E1 forming the pore funnel.
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Affiliation(s)
- Jack Kronengold
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520, USA
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172
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Chen MJ, Kress B, Han X, Moll K, Peng W, Ji RR, Nedergaard M. Astrocytic CX43 hemichannels and gap junctions play a crucial role in development of chronic neuropathic pain following spinal cord injury. Glia 2012; 60:1660-70. [PMID: 22951907 DOI: 10.1002/glia.22384] [Citation(s) in RCA: 146] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Accepted: 06/14/2012] [Indexed: 12/31/2022]
Abstract
Chronic neuropathic pain is a frequent consequence of spinal cord injury (SCI). Yet despite recent advances, upstream releasing mechanisms and effective therapeutic options remain elusive. Previous studies have demonstrated that SCI results in excessive ATP release to the peritraumatic regions and that purinergic signaling, among glial cells, likely plays an essential role in facilitating inflammatory responses and nociceptive sensitization. We sought to assess the role of connexin 43 (Cx43) as a mediator of CNS inflammation and chronic pain. To determine the extent of Cx43 involvement in chronic pain, a weight-drop SCI was performed on transgenic mice with Cx43/Cx30 deletions. SCI induced robust and persistent neuropathic pain including heat hyperalgesia and mechanical allodynia in wild-type control mice, which developed after 4 weeks and was maintained after 8 weeks. Notably, SCI-induced heat hyperalgesia and mechanical allodynia were prevented in transgenic mice with Cx43/Cx30 deletions, but fully developed in transgenic mice with only Cx30 deletion. SCI-induced gliosis, detected as upregulation of glial fibrillary acidic protein in the spinal cord astrocytes at different stages of the injury, was also reduced in the knockout mice with Cx43/Cx30 deletions, when compared with littermate controls. In comparison, a standard regimen of post-SCI treatment of minocycline attenuated neuropathic pain to a significantly lesser degree than Cx43 deletion. These findings suggest Cx43 is critically linked to the development of central neuropathic pain following acute SCI. Since Cx43/Cx30 is expressed by astrocytes, these findings also support an important role of astrocytes in the development of chronic pain.
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Affiliation(s)
- Michael J Chen
- Department of Neurosurgery, Center for Translational Neuromedicine, University of Rochester Medical School, Rochester, New York, USA
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173
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Ceriani F, Mammano F. Calcium signaling in the cochlea - Molecular mechanisms and physiopathological implications. Cell Commun Signal 2012; 10:20. [PMID: 22788415 PMCID: PMC3408374 DOI: 10.1186/1478-811x-10-20] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Accepted: 07/12/2012] [Indexed: 12/20/2022] Open
Abstract
Calcium ions (Ca2+) regulate numerous and diverse aspects of cochlear and vestibular physiology. This review focuses on the Ca2+ control of mechanotransduction and synaptic transmission in sensory hair cells, as well as on Ca2+ signalling in non-sensory cells of the developing cochlea.
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Affiliation(s)
- Federico Ceriani
- Dipartimento di Fisica e Astronomia "G, Galilei", Università di Padova, 35131, Padova, Italy.
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174
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Low extracellular Ca2+ conditions induce an increase in brain endothelial permeability that involves intercellular Ca2+ waves. Brain Res 2012; 1487:78-87. [PMID: 22789903 DOI: 10.1016/j.brainres.2012.06.046] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Revised: 06/19/2012] [Accepted: 06/23/2012] [Indexed: 01/11/2023]
Abstract
The intracellular calcium concentration ([Ca(2+)](i)) is an important factor determining the permeability of endothelial barriers including the blood-brain barrier (BBB). However, nothing is known concerning the effect of spatially propagated intercellular Ca(2+) waves (ICWs). The propagation of ICWs relies in large part on channels formed by connexins that are present in endothelia. We hypothesized that ICWs may result in a strong disturbance of endothelial function, because the [Ca(2+)](i) changes are coordinated and involve multiple cells. Thus, we aimed to investigate the effect of ICWs on endothelial permeability. ICW activity was triggered in immortalized and primary brain endothelial cells by lowering the extracellular Ca(2+) concentration. Low extracellular Ca(2+) increased the endothelial permeability and this was significantly suppressed by buffering [Ca(2+)](i) with BAPTA-AM, indicating a central role of [Ca(2+)](i) changes. The endothelial permeability increase was furthermore inhibited by the connexin channel blocking peptide Gap27, which also blocked the ICWs, and by inhibiting protein kinase C (PKC), Ca(2+)/calmodulin-dependent kinase II (CaMKII) and actomyosin contraction. We compared these observations with the [Ca(2+)](i) changes and permeability alterations provoked by the inflammatory agent bradykinin (BK), which triggers oscillatory [Ca(2+)](i) changes without wave activity. BK-associated [Ca(2+)](i) changes and the endothelial permeability increase were significantly smaller than those associated with ICWs, and the permeability increase was not influenced by inhibition of PKC, CaMKII or actomyosin contraction. We conclude that ICWs significantly increase endothelial permeability and therefore, the connexins that underlie wave propagation form an interesting target to limit BBB alterations. This article is part of a Special Issue entitled Electrical Synapses.
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175
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Characterization of gap junction proteins in the bladder of Cx43 mutant mouse models of oculodentodigital dysplasia. J Membr Biol 2012; 245:345-55. [PMID: 22752022 DOI: 10.1007/s00232-012-9455-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2012] [Accepted: 06/08/2012] [Indexed: 12/31/2022]
Abstract
Oculodentodigital dysplasia (ODDD) is a rare developmental disease resulting from germline mutations in the GJA1 gene that encodes the gap junction protein connexin43 (Cx43). In addition to the classical ODDD symptoms that affect the eyes, teeth, bone and digits, in some cases ODDD patients have reported bladder impairments. Thus, we chose to characterize the bladder in mutant mouse models of ODDD that harbor two distinct Cx43 mutations, G60S and I130T. Histological assessment revealed no difference in bladder detrusor wall thickness in mutant compared to littermate control mice. The overall localization of Cx43 in the lamina propria and detrusor also appeared to be similar in the bladders of mutant mice with the exception that the G60S mice had more instances of intracellular Cx43. However, both mutant mouse lines exhibited a significant reduction in the phosphorylated P1 and P2 isoforms of Cx43, while only the I130T mice exhibited a reduction in total Cx43 levels. Interestingly, Cx26 levels and distribution were not altered in mutant mice as it was localized to intracellular compartments and restricted to the basal cell layers of the urothelium. Our studies suggest that these two distinct genetically modified mouse models of ODDD probably mimic patients who lack bladder defects or other factors, such as aging or co-morbidities, are necessary to reveal a bladder phenotype.
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176
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Wagner C, Kurtz A. Distribution and functional relevance of connexins in renin-producing cells. Pflugers Arch 2012; 465:71-7. [DOI: 10.1007/s00424-012-1134-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Revised: 06/13/2012] [Accepted: 06/15/2012] [Indexed: 10/28/2022]
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177
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Donnelly S, English G, de Zwart-Storm EA, Lang S, van Steensel MAM, Martin PE. Differential susceptibility of Cx26 mutations associated with epidermal dysplasias to peptidoglycan derived from Staphylococcus aureus and Staphylococcus epidermidis. Exp Dermatol 2012; 21:592-8. [PMID: 22643125 DOI: 10.1111/j.1600-0625.2012.01521.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/27/2012] [Indexed: 12/28/2022]
Abstract
Mutations in Connexin26 (Cx26) give rise to a spectrum of dominantly inherited hyperproliferating skin disorders, the severest being keratitis-ichthyosis-deafness (KID) syndrome, an inflammatory skin disorder, with patients prone to opportunistic infections. We compared the effects of peptidoglycan (PGN) extracted from the skin commensal Staphylococcus epidermidis and the opportunistic pathogen Staphylococcus aureus on interleukin-6 and connexin expression in HaCaT cells (a keratinocyte cell line) and connexin channel activity in HaCaT and HeLa (connexin deficient) cells transfected to express KID and non-KID Cx26 mutations. In both cell types, PGN from S. aureus induced hemichannel activity in cells expressing KID mutants as monitored by ATP release assays following 15-min challenge, while that from S. epidermidis evoked a response in HeLa cells. In KID mutant expressing cells, ATP release was significantly higher than in cells transfected with wild-type Cx26. No ATP release was observed in non-KID mutant transfected cells or in the presence of carbenoxolone, a connexin channel blocker. PGN isolated from S. aureus but not S. epidermidis induced interleukin-6 and Cx26 expression in HaCaT cells following 6-h challenge. Challenge by PGN from S. aureus evoked a greater interleukin-6 response in cells expressing KID mutants than in cells expressing wtCx26 or non-KID mutants. This response returned to basal levels if acute KID hemichannel signalling was blocked prior to PGN challenge. Thus, KID mutants form channels that can be triggered by the pro-inflammatory mediator PGN from opportunistic pathogens but not skin commensals, providing further insight into the genotype-phenotype relationship of Cx26 disorders.
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Affiliation(s)
- Steven Donnelly
- Department of Life Sciences, School of Health and Life Sciences, Glasgow Caledonian University, Scotland, UK
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178
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Li C, Meng Q, Yu X, Jing X, Xu P, Luo D. Regulatory effect of connexin 43 on basal Ca2+ signaling in rat ventricular myocytes. PLoS One 2012; 7:e36165. [PMID: 22577485 PMCID: PMC3338611 DOI: 10.1371/journal.pone.0036165] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2011] [Accepted: 03/28/2012] [Indexed: 11/19/2022] Open
Abstract
Background It has been found that gap junction-associated intracellular Ca2+ [Ca2+]i disturbance contributes to the arrhythmogenesis and hyperconstriction in diseased heart. However, whether functional gaps are also involved in the regulation of normal Ca2+ signaling, in particular the basal [Ca2+]i activities, is unclear. Methods and Results Global and local Ca2+ signaling and gap permeability were monitored in cultured neonatal rat ventricular myocytes (NRVMs) and freshly isolated mouse ventricular myocytes by Fluo4/AM and Lucifer yellow (LY), respectively. The results showed that inhibition of gap communication by heptanol, Gap 27 and flufenamic acid or interference of connexin 43 (Cx43) with siRNA led to a significant suppression of LY uptake and, importantly, attenuations of global Ca2+ transients and local Ca2+ sparks in monolayer NRVMs and Ca2+ sparks in adult ventricular myocytes. In contrast, overexpression of rat-Cx43 in NRVMs induced enhancements in the above measurements, and so did in HEK293 cells expressing rat Cx43. Additionally, membrane-permeable inositol 1,4,5-trisphosphate (IP3 butyryloxymethyl ester) and phenylephrine, an agonist of adrenergic receptor, could relieve the inhibited Ca2+ signal and LY uptake by gap uncouplers, whereas blockade of IP3 receptor with xestospongin C or 2-aminoethoxydiphenylborate mimicked the effects of gap inhibitors. More importantly, all these gap-associated effects on Ca2+ signaling were also found in single NRVMs that only have hemichannels instead of gap junctions. Further immunostaining/immunoblotting single myocytes with antibody against Cx43 demonstrated apparent increases in membrane labeling of Cx43 and non-junctional Cx43 in overexpressed cells, suggesting functional hemichannels exist and also contribute to the Ca2+ signaling regulation in cardiomyocytes. Conclusions These data demonstrate that Cx43-associated gap coupling plays a role in the regulation of resting Ca2+ signaling in normal ventricular myocytes, in which IP3/IP3 receptor coupling is involved. This finding may provide a novel regulatory pathway for mediation of spontaneous global and local Ca2+ activities in cardiomyocytes.
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MESH Headings
- Adrenergic Agonists/pharmacology
- Animals
- Calcium/metabolism
- Calcium Signaling
- Cell Communication/drug effects
- Cells, Cultured
- Connexin 43/antagonists & inhibitors
- Connexin 43/genetics
- Connexin 43/metabolism
- Fluorescent Dyes/chemistry
- Fluorescent Dyes/metabolism
- Gap Junctions/metabolism
- HEK293 Cells
- Heart Ventricles/cytology
- Humans
- Inositol 1,4,5-Trisphosphate/pharmacology
- Inositol 1,4,5-Trisphosphate Receptors/antagonists & inhibitors
- Inositol 1,4,5-Trisphosphate Receptors/metabolism
- Isoquinolines/chemistry
- Isoquinolines/metabolism
- Myocytes, Cardiac/drug effects
- Myocytes, Cardiac/metabolism
- Phenylephrine/pharmacology
- RNA Interference
- RNA, Small Interfering/metabolism
- Rats
- Rats, Sprague-Dawley
- Receptors, Adrenergic/chemistry
- Receptors, Adrenergic/metabolism
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Affiliation(s)
- Chen Li
- Department of Pharmacology, School of Chemical Biology & Pharmaceutical Sciences, Capital Medical University, Beijing, China
| | - Qingli Meng
- Department of Pharmacology, School of Chemical Biology & Pharmaceutical Sciences, Capital Medical University, Beijing, China
| | - Xinfeng Yu
- Department of Pharmacology, School of Chemical Biology & Pharmaceutical Sciences, Capital Medical University, Beijing, China
| | - Xian Jing
- Department of Pharmacology, School of Chemical Biology & Pharmaceutical Sciences, Capital Medical University, Beijing, China
| | - Pingxiang Xu
- Department of Pharmacology, School of Chemical Biology & Pharmaceutical Sciences, Capital Medical University, Beijing, China
| | - Dali Luo
- Department of Pharmacology, School of Chemical Biology & Pharmaceutical Sciences, Capital Medical University, Beijing, China
- * E-mail:
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179
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De Bock M, Wang N, Bol M, Decrock E, Ponsaerts R, Bultynck G, Dupont G, Leybaert L. Connexin 43 hemichannels contribute to cytoplasmic Ca2+ oscillations by providing a bimodal Ca2+-dependent Ca2+ entry pathway. J Biol Chem 2012; 287:12250-66. [PMID: 22351781 PMCID: PMC3320976 DOI: 10.1074/jbc.m111.299610] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Revised: 02/16/2012] [Indexed: 11/06/2022] Open
Abstract
Many cellular functions are driven by changes in the intracellular Ca(2+) concentration ([Ca(2+)](i)) that are highly organized in time and space. Ca(2+) oscillations are particularly important in this respect and are based on positive and negative [Ca(2+)](i) feedback on inositol 1,4,5-trisphosphate receptors (InsP(3)Rs). Connexin hemichannels are Ca(2+)-permeable plasma membrane channels that are also controlled by [Ca(2+)](i). We aimed to investigate how hemichannels may contribute to Ca(2+) oscillations. Madin-Darby canine kidney cells expressing connexin-32 (Cx32) and Cx43 were exposed to bradykinin (BK) or ATP to induce Ca(2+) oscillations. BK-induced oscillations were rapidly (minutes) and reversibly inhibited by the connexin-mimetic peptides (32)Gap27/(43)Gap26, whereas ATP-induced oscillations were unaffected. Furthermore, these peptides inhibited the BK-triggered release of calcein, a hemichannel-permeable dye. BK-induced oscillations, but not those induced by ATP, were dependent on extracellular Ca(2+). Alleviating the negative feedback of [Ca(2+)](i) on InsP(3)Rs using cytochrome c inhibited BK- and ATP-induced oscillations. Cx32 and Cx43 hemichannels are activated by <500 nm [Ca(2+)](i) but inhibited by higher concentrations and CT9 peptide (last 9 amino acids of the Cx43 C terminus) removes this high [Ca(2+)](i) inhibition. Unlike interfering with the bell-shaped dependence of InsP(3)Rs to [Ca(2+)](i), CT9 peptide prevented BK-induced oscillations but not those triggered by ATP. Collectively, these data indicate that connexin hemichannels contribute to BK-induced oscillations by allowing Ca(2+) entry during the rising phase of the Ca(2+) spikes and by providing an OFF mechanism during the falling phase of the spikes. Hemichannels were not sufficient to ignite oscillations by themselves; however, their contribution was crucial as hemichannel inhibition stopped the oscillations.
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Affiliation(s)
- Marijke De Bock
- From the Department of Basic Medical Sciences, Physiology Group, Ghent University 9000 Ghent, Belgium
| | - Nan Wang
- From the Department of Basic Medical Sciences, Physiology Group, Ghent University 9000 Ghent, Belgium
| | - Melissa Bol
- From the Department of Basic Medical Sciences, Physiology Group, Ghent University 9000 Ghent, Belgium
| | - Elke Decrock
- From the Department of Basic Medical Sciences, Physiology Group, Ghent University 9000 Ghent, Belgium
| | - Raf Ponsaerts
- Department of Molecular Cell Biology, Laboratory of Molecular and Cellular Signaling, KULeuven, 3000 Leuven, Belgium, and
| | - Geert Bultynck
- Department of Molecular Cell Biology, Laboratory of Molecular and Cellular Signaling, KULeuven, 3000 Leuven, Belgium, and
| | - Geneviève Dupont
- Theoretical Chronobiology Unit, Université Libre de Bruxelles, 1050 Brussels, Belgium
| | - Luc Leybaert
- From the Department of Basic Medical Sciences, Physiology Group, Ghent University 9000 Ghent, Belgium
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180
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Ponsaerts R, Wang N, Himpens B, Leybaert L, Bultynck G. The contractile system as a negative regulator of the connexin 43 hemichannel. Biol Cell 2012; 104:367-77. [DOI: 10.1111/boc.201100079] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2011] [Accepted: 02/21/2012] [Indexed: 02/04/2023]
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181
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Halidi N, Alonso F, Burt JM, Bény JL, Haefliger JA, Meister JJ. Intercellular calcium waves in primary cultured rat mesenteric smooth muscle cells are mediated by connexin43. CELL COMMUNICATION & ADHESION 2012; 19:25-37. [PMID: 22642233 PMCID: PMC3804248 DOI: 10.3109/15419061.2012.690792] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Intercellular Ca(2+) wave propagation between vascular smooth muscle cells (SMCs) is associated with the propagation of contraction along the vessel. Here, we characterize the involvement of gap junctions (GJs) in Ca(2+) wave propagation between SMCs at the cellular level. Gap junctional communication was assessed by the propagation of intercellular Ca(2+) waves and the transfer of Lucifer Yellow in A7r5 cells, primary rat mesenteric SMCs (pSMCs), and 6B5N cells, a clone of A7r5 cells expressing higher connexin43 (Cx43) to Cx40 ratio. Mechanical stimulation induced an intracellular Ca(2+) wave in pSMC and 6B5N cells that propagated to neighboring cells, whereas Ca(2+) waves in A7r5 cells failed to progress to neighboring cells. We demonstrate that Cx43 forms the functional GJs that are involved in mediating intercellular Ca(2+) waves and that co-expression of Cx40 with Cx43, depending on their expression ratio, may interfere with Cx43 GJ formation, thus altering junctional communication.
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Affiliation(s)
- Nadia Halidi
- Laboratory of Cell Biophysics, Ecole Polytechnique Fédérale de Lausanne, Switzerland.
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182
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Abstract
Cell-to-cell interactions via gap junctional communication and connexon hemichannels are involved in the pathogenesis of diabetes. Gap junctions are highly specialized transmembrane structures that are formed by connexon hemichannels, which are further assembled from proteins called “connexins.” In this paper, we discuss current knowledge about connexins in diabetes. We also discuss mechanisms of connexin influence and the role of individual connexins in various tissues and how these are affected in diabetes. Connexins may be a future target by both genetic and pharmacological approaches to develop treatments for the treatment of diabetes and its complications.
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183
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Desplantez T, Verma V, Leybaert L, Evans WH, Weingart R. Gap26, a connexin mimetic peptide, inhibits currents carried by connexin43 hemichannels and gap junction channels. Pharmacol Res 2012; 65:546-52. [PMID: 22406236 DOI: 10.1016/j.phrs.2012.02.002] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Revised: 02/06/2012] [Accepted: 02/13/2012] [Indexed: 10/28/2022]
Abstract
Connexin mimetic peptides corresponding to short conserved extracellular loop sequences of connexins have been used widely as reversible inhibitors of gap junctional intercellular communication. These peptides also block movement of ATP and Ca(2+) across connexin hemichannels, i.e. hexameric channels yet to dock with partners in aligned cells and to generate the gap junction cell-cell conduit. By means of electrophysiology, we compared the effects of Gap26, a mimetic peptide corresponding to a short linear sequence in the first extracellular loop of connexin43, on connexin channel function in HeLa cells expressing connexin43. We demonstrate that Gap26 inhibited electrical coupling in cell pairs mediated by gap junctions after exposure for 30min. In contrast, Gap26 applied to single cells, inhibited hemichannel currents evoked in low Ca(2+) solution with a response time of less than 5min. The results further support the view that the likely primary and direct inhibitory effect of Gap26 is on connexin hemichannels, with gap junctions becoming inhibited later. The mechanism of action of Gap26 in blocking hemichannels and gap junction channels is discussed in the context of their different functions and locations.
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Affiliation(s)
- T Desplantez
- Institute of Physiology, University of Bern, Bühlplatz 5, CH-3012 Bern, Switzerland.
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184
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Baroja-Mazo A, Barberà-Cremades M, Pelegrín P. The participation of plasma membrane hemichannels to purinergic signaling. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1828:79-93. [PMID: 22266266 DOI: 10.1016/j.bbamem.2012.01.002] [Citation(s) in RCA: 131] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Revised: 12/30/2011] [Accepted: 01/04/2012] [Indexed: 12/17/2022]
Abstract
The field of hemichannels is closely related to the purinergic signaling and both areas have been growing in parallel. Hemichannels open in response to a wide range of stressful conditions, such as ischemia, pressure or swelling. Hemichannels represent an important mechanism for the cellular release of adenosine 5'-triphosphate (ATP), which is an agonist of the P2Y and P2X family of purinergic receptors. Therefore, hemichannels are key molecules in the regulation of purinergic receptor activation, during physiological and pathophysiological conditions. Furthermore, purinergic receptor activation can also lead to the opening of hemichannels and the subsequent amplification of purinergic signaling via a positive signaling feedback loop, giving rise to the concept of ATP-induced ATP release. Purinergic receptor signaling is involved in regulating many physiological and pathophysiological processes. P2Y receptors activate inositol trisphosphate and transiently increase intracellular calcium. This signaling opens both connexin and pannexin channels, therefore contributing to the expansion of calcium waves across astrocytes and epithelial cells. In addition, several of the P2X receptor subtypes, including the P2X2, P2X4 and P2X7 receptors, activate select cellular permeation pathways to large molecules, including the pannexin-1 channels, which are involved in the initiation of inflammatory responses and cell death. Consequently, the interplay between purinergic receptors and hemichannels could represent a novel target with substantial therapeutic implications in areas such as chronic pain, inflammation or atherosclerosis. This article is part of a Special Issue entitled: The communicating junctions, roles and dysfunctions.
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Affiliation(s)
- Alberto Baroja-Mazo
- University Hospital Virgen de la Arrixaca, Fundación Formación Investigación Sanitaria Región Murcia, Murcia, Spain
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185
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Schalper KA, Riquelme MA, Brañes MC, Martínez AD, Vega JL, Berthoud VM, Bennett MVL, Sáez JC. Modulation of gap junction channels and hemichannels by growth factors. MOLECULAR BIOSYSTEMS 2012; 8:685-98. [PMID: 22218428 DOI: 10.1039/c1mb05294b] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Gap junction hemichannels and cell-cell channels have roles in coordinating numerous cellular processes, due to their permeability to extra and intracellular signaling molecules. Another mechanism of cellular coordination is provided by a vast array of growth factors that interact with relatively selective cell membrane receptors. These receptors can affect cellular transduction pathways, including alteration of intracellular concentration of free Ca(2+) and free radicals and activation of protein kinases or phosphatases. Connexin and pannexin based channels constitute recently described targets of growth factor signal transduction pathways, but little is known regarding the effects of growth factor signaling on pannexin based channels. The effects of growth factors on these two channel types seem to depend on the cell type, cell stage and connexin and pannexin isoform expressed. The functional state of hemichannels and gap junction channels are affected in opposite directions by FGF-1 via protein kinase-dependent mechanisms. These changes are largely explained by channels insertion in or withdrawal from the cell membrane, but changes in open probability might also occur due to changes in phosphorylation and redox state of channel subunits. The functional consequence of variation in cell-cell communication via these membrane channels is implicated in disease as well as normal cellular responses.
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Affiliation(s)
- Kurt A Schalper
- Clínica Alemana de Santiago, Universidad del Desarrollo, Santiago, Chile
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186
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Regulation of Intercellular Calcium Signaling Through Calcium Interactions with Connexin-Based Channels. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 740:777-94. [DOI: 10.1007/978-94-007-2888-2_34] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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187
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Parsons SP, Kunze WA, Huizinga JD. Maxi-channels recorded in situ from ICC and pericytes associated with the mouse myenteric plexus. Am J Physiol Cell Physiol 2011; 302:C1055-69. [PMID: 22159087 DOI: 10.1152/ajpcell.00334.2011] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Ion channels are fundamental to gastrointestinal pacemaking by interstitial cells of Cajal (ICC). Previously, we have recorded a high-conductance chloride channel (HCCC) from ICC, both in culture and in situ, associated with the myenteric plexus. The biophysical properties of the HCCC (conductance, subconductances, voltage- and time-dependent inactivation) suggest it is a member of a class called the maxi-anion channels. In this study we further investigated the properties of the HCCC in situ. Our main finding was that the HCCC is not strictly a chloride channel but has a relative sodium-chloride permeability (P(Na/Cl)) of 0.76 to 1.64 (depending on the method of measurement). Therefore, we have renamed the HCCC the "maxi-channel." A maxi-channel was also expressed by pericytes associated with the vasculature near the myenteric plexus. This had a lower P(Na/Cl) (0.33 to 0.49, depending on the method of measurement) but similar conductance (326 ± 7 vs. 316 ± 24 pS for ICC). This is the first report of cation permeability equaling anion permeability in a maxi-anion channel. As such, the properties of the maxi-channels described in this article may have implications for the maxi-anion channel field, as well as for studies of their role in ICC and pericytes.
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Affiliation(s)
- Sean P Parsons
- Farncombe Family Digestive Health Research Institute, McMaster University, Hamilton, ON, Canada
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188
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Becker DL, Thrasivoulou C, Phillips ARJ. Connexins in wound healing; perspectives in diabetic patients. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:2068-75. [PMID: 22155211 DOI: 10.1016/j.bbamem.2011.11.017] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Revised: 11/07/2011] [Accepted: 11/18/2011] [Indexed: 11/19/2022]
Abstract
Skin lesions are common events and we have evolved to rapidly heal them in order to maintain homeostasis and prevent infection and sepsis. Most acute wounds heal without issue, but as we get older our bodies become compromised by poor blood circulation and conditions such as diabetes, leading to slower healing. This can result in stalled or hard-to-heal chronic wounds. Currently about 2% of the Western population develop a chronic wound and this figure will rise as the population ages and diabetes becomes more prevalent [1]. Patient morbidity and quality of life are profoundly altered by chronic wounds [2]. Unfortunately a significant proportion of these chronic wounds fail to respond to conventional treatment and can result in amputation of the lower limb. Life quality and expectancy following amputation is severely reduced. These hard to heal wounds also represent a growing economic burden on Western society with published estimates of costs to healthcare services in the region of $25B annually [3]. There exists a growing need for specific and effective therapeutic agents to improve healing in these wounds. In recent years the gap junction protein Cx43 has been shown to play a pivotal role early on in the acute wound healing process at a number of different levels [4-7]. Conversely, abnormal expression of Cx43 in wound edge keratinocytes was shown to underlie the poor rate of healing in diabetic rats, and targeting its expression with an antisense gel restored normal healing rates [8]. The presence of Cx43 in the wound edge keratinocytes of human chronic wounds has also been reported [9]. Abnormal Cx43 biology may underlie the poor healing of human chronic wounds and be amenable therapeutic intervention [7]. This article is part of a Special Issue entitled: The Communicating junctions, composition, structure and characteristics.
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Affiliation(s)
- David L Becker
- Department of Cell and Developmental Biology, University College, London, WC1E 6BT, UK.
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189
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The gap junction protein Cx43 is involved in the bone-targeted metastatic behaviour of human prostate cancer cells. Clin Exp Metastasis 2011; 29:111-22. [PMID: 22080401 DOI: 10.1007/s10585-011-9434-4] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2011] [Accepted: 11/01/2011] [Indexed: 01/20/2023]
Abstract
For decades, cancer was associated with gap-junction defects. However, more recently it appeared that the gap junction proteins (connexins) could be re-expressed and participate to cancer cell dissemination during the late stages of tumor progression. Since primary tumors of prostate cancer (PCa) are known to be connexin deficient, it was interesting to verify whether their bone-targeted metastatic behaviour could be influenced by the re-expression of the connexin type (connexin43) which is originally present in prostate tissue and highly expressed in bone where it participates to the differentiation of osteoblastic cells. Thus, we investigated the effect of the increased Cx43 expression, by retroviral infection, on the metastatic behaviour of two well-characterized cell lines (PC-3 and LNCaP) representing different stages of PCa progression. It appeared that Cx43 differently behaved in those cell lines and induced different phenotypes. In LNCaP, Cx43 was functional, localized at the plasma membrane and its high expression was correlated with a more aggressive phenotype both in vitro and in vivo. In particular, those Cx43-expressing LNCaP cells exhibited a high incidence of osteolytic metastases generated by bone xenografts in mice. Interestingly, LNCaP cells were also able to decrease the proliferation of cocultured osteoblastic cells. In contrast, the increased expression of Cx43 in PC-3 cells led to an unfunctional, cytoplasmic localization of the protein and was correlated with a reduction of proliferation, adhesion and invasion of the cells. In conclusion, the localization and the functionality of Cx43 may govern the ability of PCa cells to metastasize in bones.
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190
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Sood A, Salih S, Roh D, Lacharme-Lora L, Parry M, Hardiman B, Keehan R, Grummer R, Winterhager E, Gokhale PJ, Andrews PW, Abbott C, Forbes K, Westwood M, Aplin JD, Ingham E, Papageorgiou I, Berry M, Liu J, Dick AD, Garland RJ, Williams N, Singh R, Simon AK, Lewis M, Ham J, Roger L, Baird DM, Crompton LA, Caldwell MA, Swalwell H, Birch-Machin M, Lopez-Castejon G, Randall A, Lin H, Suleiman MS, Evans WH, Newson R, Case CP. Signalling of DNA damage and cytokines across cell barriers exposed to nanoparticles depends on barrier thickness. NATURE NANOTECHNOLOGY 2011; 6:824-33. [PMID: 22056725 DOI: 10.1038/nnano.2011.188] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Accepted: 09/28/2011] [Indexed: 05/28/2023]
Abstract
The use of nanoparticles in medicine is ever increasing, and it is important to understand their targeted and non-targeted effects. We have previously shown that nanoparticles can cause DNA damage to cells cultured below a cellular barrier without crossing this barrier. Here, we show that this indirect DNA damage depends on the thickness of the cellular barrier, and it is mediated by signalling through gap junction proteins following the generation of mitochondrial free radicals. Indirect damage was seen across both trophoblast and corneal barriers. Signalling, including cytokine release, occurred only across bilayer and multilayer barriers, but not across monolayer barriers. Indirect toxicity was also observed in mice and using ex vivo explants of the human placenta. If the importance of barrier thickness in signalling is a general feature for all types of barriers, our results may offer a principle with which to limit the adverse effects of nanoparticle exposure and offer new therapeutic approaches.
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Affiliation(s)
- A Sood
- Bristol Musculoskeletal Research Unit, Clinical Science at North Bristol University of Bristol, Avon Orthopaedic Centre, Southmead Hospital, Bristol
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191
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Halidi N, Boittin FX, Bény JL, Meister JJ. Propagation of fast and slow intercellular Ca2+ waves in primary cultured arterial smooth muscle cells. Cell Calcium 2011; 50:459-67. [DOI: 10.1016/j.ceca.2011.08.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2011] [Revised: 08/02/2011] [Accepted: 08/02/2011] [Indexed: 11/30/2022]
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192
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Mese G, Sellitto C, Li L, Wang HZ, Valiunas V, Richard G, Brink PR, White TW. The Cx26-G45E mutation displays increased hemichannel activity in a mouse model of the lethal form of keratitis-ichthyosis-deafness syndrome. Mol Biol Cell 2011; 22:4776-86. [PMID: 22031297 PMCID: PMC3237621 DOI: 10.1091/mbc.e11-09-0778] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Mutations in the GJB2 gene (Cx26) cause deafness in humans. Most are loss-of-function mutations and cause nonsyndromic deafness. Some mutations produce a gain of function and cause syndromic deafness associated with skin disorders, such as keratitis-ichthyosis-deafness syndrome (KIDS). Cx26-G45E is a lethal mutation linked to KIDS that forms constitutively active connexin hemichannels. The pathomechanism(s) by which mutant Cx26 hemichannels perturb normal epidermal cornification are poorly understood. We created an animal model for KIDS by generating an inducible transgenic mouse expressing Cx26-G45E in keratinocytes. Cx26-G45E mice displayed reduced viability, hyperkeratosis, scaling, skin folds, and hair loss. Histopathology included hyperplasia, acanthosis, papillomatosis, increased cell size, and osteal plugging. These abnormalities correlated with human KIDS pathology and were associated with increased hemichannel currents in transgenic keratinocytes. These results confirm the pathogenic nature of the G45E mutation and provide a new model for studying the role of aberrant connexin hemichannels in epidermal differentiation and inherited connexin disorders.
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Affiliation(s)
- Gulistan Mese
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY 11794, USA
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193
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Orellana JA, Sáez PJ, Cortés-Campos C, Elizondo RJ, Shoji KF, Contreras-Duarte S, Figueroa V, Velarde V, Jiang JX, Nualart F, Sáez JC, García MA. Glucose increases intracellular free Ca(2+) in tanycytes via ATP released through connexin 43 hemichannels. Glia 2011; 60:53-68. [PMID: 21987367 DOI: 10.1002/glia.21246] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Revised: 08/26/2011] [Accepted: 08/31/2011] [Indexed: 11/10/2022]
Abstract
The ventromedial hypothalamus is involved in regulating feeding and satiety behavior, and its neurons interact with specialized ependymal-glial cells, termed tanycytes. The latter express glucose-sensing proteins, including glucose transporter 2, glucokinase, and ATP-sensitive K(+) (K(ATP) ) channels, suggesting their involvement in hypothalamic glucosensing. Here, the transduction mechanism involved in the glucose-induced rise of intracellular free Ca(2+) concentration ([Ca(2+) ](i) ) in cultured β-tanycytes was examined. Fura-2AM time-lapse fluorescence images revealed that glucose increases the intracellular Ca(2+) signal in a concentration-dependent manner. Glucose transportation, primarily via glucose transporters, and metabolism via anaerobic glycolysis increased connexin 43 (Cx43) hemichannel activity, evaluated by ethidium uptake and whole cell patch clamp recordings, through a K(ATP) channel-dependent pathway. Consequently, ATP export to the extracellular milieu was enhanced, resulting in activation of purinergic P2Y(1) receptors followed by inositol trisphosphate receptor activation and Ca(2+) release from intracellular stores. The present study identifies the mechanism by which glucose increases [Ca(2+) ](i) in tanycytes. It also establishes that Cx43 hemichannels can be rapidly activated under physiological conditions by the sequential activation of glucosensing proteins in normal tanycytes.
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Affiliation(s)
- Juan A Orellana
- Departamento de Fisiología, Pontificia Universidad Católica de Chile, Santiago, Chile.
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194
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Abstract
Extracellular signaling molecules have crucial roles in development and homeostasis, and their incorrect deployment can lead to developmental defects and disease states. Signaling molecules are released from sending cells, travel to target cells, and act over length scales of several orders of magnitude, from morphogen-mediated patterning of small developmental fields to hormonal signaling throughout the organism. We discuss how signals are modified and assembled for transport, which routes they take to reach their targets, and how their range is affected by mobility and stability.
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Affiliation(s)
- Patrick Müller
- Department of Molecular and Cellular Biology, Harvard Stem Cell Institute, Broad Institute, Center for Brain Science, FAS Center for Systems Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA.
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195
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Wu A, Green CR, Rupenthal ID, Moalem-Taylor G. Role of gap junctions in chronic pain. J Neurosci Res 2011; 90:337-45. [DOI: 10.1002/jnr.22764] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2011] [Revised: 06/15/2011] [Accepted: 07/15/2011] [Indexed: 11/10/2022]
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196
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Gairhe S, Bauer NN, Gebb SA, McMurtry IF. Myoendothelial gap junctional signaling induces differentiation of pulmonary arterial smooth muscle cells. Am J Physiol Lung Cell Mol Physiol 2011; 301:L527-35. [DOI: 10.1152/ajplung.00091.2011] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Myoendothelial gap junctions are involved in regulating systemic arterial smooth muscle cell phenotype and function, but their role in the regulation of pulmonary arterial smooth muscle cell (PASMC) phenotype is unknown. We therefore investigated in cocultured pulmonary arterial endothelial cells (PAECs) and PASMCs whether myoendothelial gap junctional signaling played a role in PAEC-dependent regulation of PASMC phenotype. Rat PAECs and PASMCs were cocultured on opposite sides of a porous Transwell membrane that permitted formation of heterotypic cell-cell contacts. Immunostaining showed expression of the gap junctional protein connexin 43 (Cx43) on projections extending into the membrane from both cell types. Dye transfer exhibited functional gap junctional communication from PAECs to PASMCs. PASMCs cocultured with PAECs had a more contractile-like phenotype (spindle shape and increased expression of the contractile proteins myosin heavy chain, H1-calponin, and α-smooth muscle cell-actin) than PASMCs cocultured with PASMCs or cocultured without direct contact with PAECs. Transforming growth factor (TGF)-β1 signaling was activated in PASMCs cocultured with PAECs, and the PASMC differentiation was inhibited by TGF-β type I receptor blockade. Inhibition of gap junctional communication pharmacologically or by knock down of Cx43 in PAECs blocked TGF-β signaling and PASMC differentiation. These results implicate myoendothelial gap junctions as a gateway for PAEC-derived signals required for maintaining TGF-β-dependent PASMC differentiation. This study identifies an alternative pathway to paracrine signaling to convey regulatory signals from PAECs to PASMCs and raises the possibility that dysregulation of this direct interaction is involved in the pathogenesis of hypertensive pulmonary vascular remodeling.
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Affiliation(s)
- Salina Gairhe
- Departments of 1Pharmacology,
- Center for Lung Biology, College of Medicine, University of South Alabama, Mobile, Alabama
| | - Natalie N. Bauer
- Departments of 1Pharmacology,
- Center for Lung Biology, College of Medicine, University of South Alabama, Mobile, Alabama
| | - Sarah A. Gebb
- Cell Biology and Neuroscience, and
- Center for Lung Biology, College of Medicine, University of South Alabama, Mobile, Alabama
| | - Ivan F. McMurtry
- Departments of 1Pharmacology,
- Medicine and
- Center for Lung Biology, College of Medicine, University of South Alabama, Mobile, Alabama
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197
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Abstract
The appearance of multicellular organisms imposed the development of several mechanisms for cell-to-cell communication, whereby different types of cells coordinate their function. Some of these mechanisms depend on the intercellular diffusion of signal molecules in the extracellular spaces, whereas others require cell-to-cell contact. Among the latter mechanisms, those provided by the proteins of the connexin family are widespread in most tissues. Connexin signaling is achieved via direct exchanges of cytosolic molecules between adjacent cells at gap junctions, for cell-to-cell coupling, and possibly also involves the formation of membrane "hemi-channels," for the extracellular release of cytosolic signals, direct interactions between connexins and other cell proteins, and coordinated influence on the expression of multiple genes. Connexin signaling appears to be an obligatory attribute of all multicellular exocrine and endocrine glands. Specifically, the experimental evidence we review here points to a direct participation of the Cx36 isoform in the function of the insulin-producing β-cells of the endocrine pancreas, and of the Cx40 isoform in the function of the renin-producing juxtaglomerular epithelioid cells of the kidney cortex.
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Affiliation(s)
- Domenico Bosco
- Department of Surgery, University of Geneva Medical School, Geneva, Switzerland
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198
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Mendoza-Naranjo A, Bouma G, Pereda C, Ramírez M, Webb KF, Tittarelli A, López MN, Kalergis AM, Thrasher AJ, Becker DL, Salazar-Onfray F. Functional gap junctions accumulate at the immunological synapse and contribute to T cell activation. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2011; 187:3121-32. [PMID: 21844382 PMCID: PMC3173876 DOI: 10.4049/jimmunol.1100378] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Gap junction (GJ) mediates intercellular communication through linked hemichannels from each of two adjacent cells. Using human and mouse models, we show that connexin 43 (Cx43), the main GJ protein in the immune system, was recruited to the immunological synapse during T cell priming as both GJs and stand-alone hemichannels. Cx43 accumulation at the synapse was Ag specific and time dependent, and required an intact actin cytoskeleton. Fluorescence recovery after photobleaching and Cx43-specific inhibitors were used to prove that intercellular communication between T cells and dendritic cells is bidirectional and specifically mediated by Cx43. Moreover, this intercellular cross talk contributed to T cell activation as silencing of Cx43 with an antisense or inhibition of GJ docking impaired intracellular Ca(2+) responses and cytokine release by T cells. These findings identify Cx43 as an important functional component of the immunological synapse and reveal a crucial role for GJs and hemichannels as coordinators of the dendritic cell-T cell signaling machinery that regulates T cell activation.
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Affiliation(s)
- Ariadna Mendoza-Naranjo
- Institute of Biomedical Sciences, Faculty of Medicine, University of Chile, 8380453 Santiago, Chile.
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199
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Pathological hemichannels associated with human Cx26 mutations causing Keratitis-Ichthyosis-Deafness syndrome. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:2014-9. [PMID: 21933663 DOI: 10.1016/j.bbamem.2011.09.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2011] [Revised: 08/30/2011] [Accepted: 09/06/2011] [Indexed: 12/25/2022]
Abstract
Connexin (Cx) proteins form intercellular gap junction channels by first assembling into single membrane hemichannels that then dock to connect the cytoplasm of two adjacent cells. Gap junctions are highly specialized structures that allow the direct passage of small molecules between cells to maintain tissue homeostasis. Functional activity of nonjunctional hemichannels has now been shown in several experimental systems. Hemichannels may constitute an important diffusional exchange pathway with the extracellular space, but the extent of their normal physiological role is currently unknown. Aberrant hemichannel activity has been linked to mutations of connexin proteins involved in genetic diseases. Here, we review a proposed role for hemichannels in the pathogenesis of Keratitis-Ichthyosis-Deafness (KID) syndrome associated with connexin26 (Cx26) mutations. Continued functional evaluation of mutated hemichannels linked to human hereditary disorders may provide additional insights into the mechanisms governing their regulation in normal physiology and dysregulation in disease. This article is part of a Special Issue entitled: The Communicating junctions, composition, structure and characteristics.
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200
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Abstract
The distal nephron plays a critical role in the renal control of homeostasis. Until very recently most studies focused on the control of Na(+), K(+), and water balance by principal cells of the collecting duct and the regulation of solute and water by hormones from the renin-angiotensin-aldosterone system and by antidiuretic hormone. However, recent studies have revealed the unexpected importance of renal intercalated cells, a subtype of cells present in the connecting tubule and collecting ducts. Such cells were thought initially to be involved exclusively in acid-base regulation. However, it is clear now that intercalated cells absorb NaCl and K(+) and hence may participate in the regulation of blood pressure and potassium balance. The second paradigm-challenging concept we highlight is the emerging importance of local paracrine factors that play a critical role in the renal control of water and electrolyte balance.
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Affiliation(s)
- Dominique Eladari
- Centre de Recherche des Cordeliers, Université Paris Descartes, INSERM UMRS 872, Equipe 3, F-75006, Paris, France; ,
- Université Pierre et Marie Curie, CNRS ERL7226, F-75006, Paris, France
- Département de Physiologie, Hôpital Européen Georges Pompidou, Assistance Publique-Hôpitaux de Paris, F-75015, Paris, France
| | - Régine Chambrey
- Centre de Recherche des Cordeliers, Université Paris Descartes, INSERM UMRS 872, Equipe 3, F-75006, Paris, France; ,
- Université Pierre et Marie Curie, CNRS ERL7226, F-75006, Paris, France
| | - Janos Peti-Peterdi
- Department of Physiology and Biophysics, Keck School of Medicine, Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California 90033;
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