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Chen H, Li YX, Wong RS, Esseltine JL, Bai D. Genetically engineered human embryonic kidney cells as a novel vehicle for dual patch clamp study of human gap junction channels. Biochem J 2024; 481:741-758. [PMID: 38752978 DOI: 10.1042/bcj20240016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2024] [Revised: 04/29/2024] [Accepted: 05/16/2024] [Indexed: 06/11/2024]
Abstract
Mutations in more than half of human connexin genes encoding gap junction (GJ) subunits have been linked to inherited human diseases. Functional studies of human GJ channels are essential for revealing mechanistic insights into the etiology of disease-linked connexin mutants. However, the commonly used Xenopus oocytes, N2A, HeLa, and other model cells for recombinant expression of human connexins have different and significant limitations. Here we developed a human cell line (HEK293) with each of the endogenous connexins (Cx43 and Cx45) knocked out using the CRISPR-Cas9 system. Double knockout HEK293 cells showed no background GJ coupling, were easily transfected with several human connexin genes (such as those encoding Cx46, Cx50, Cx37, Cx45, Cx26, and Cx36) which successfully formed functional GJs and were readily accessible for dual patch clamp analysis. Single knockout Cx43 or Cx45 HEK cell lines could also be used to characterize human GJ channels formed by Cx45 or Cx43, respectively, with an expression level suitable for studying macroscopic and single channel GJ channel properties. A cardiac arrhythmia linked Cx45 mutant R184G failed to form functional GJs in DKO HEK293 cells with impaired localizations. These genetically engineered HEK293 cells are well suited for patch clamp study of human GJ channels.
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Affiliation(s)
- Honghong Chen
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada N6A 5C1
| | - Yi X Li
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada N6A 5C1
| | - Robert S Wong
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada N6A 5C1
| | - Jessica L Esseltine
- Division of BioMedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada A1B 3V6
| | - Donglin Bai
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada N6A 5C1
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2
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Nielsen MS, van Opbergen CJM, van Veen TAB, Delmar M. The intercalated disc: a unique organelle for electromechanical synchrony in cardiomyocytes. Physiol Rev 2023; 103:2271-2319. [PMID: 36731030 PMCID: PMC10191137 DOI: 10.1152/physrev.00021.2022] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 01/24/2023] [Accepted: 01/30/2023] [Indexed: 02/04/2023] Open
Abstract
The intercalated disc (ID) is a highly specialized structure that connects cardiomyocytes via mechanical and electrical junctions. Although described in some detail by light microscopy in the 19th century, it was in 1966 that electron microscopy images showed that the ID represented apposing cell borders and provided detailed insight into the complex ID nanostructure. Since then, much has been learned about the ID and its molecular composition, and it has become evident that a large number of proteins, not all of them involved in direct cell-to-cell coupling via mechanical or gap junctions, reside at the ID. Furthermore, an increasing number of functional interactions between ID components are emerging, leading to the concept that the ID is not the sum of isolated molecular silos but an interacting molecular complex, an "organelle" where components work in concert to bring about electrical and mechanical synchrony. The aim of the present review is to give a short historical account of the ID's discovery and an updated overview of its composition and organization, followed by a discussion of the physiological implications of the ID architecture and the local intermolecular interactions. The latter will focus on both the importance of normal conduction of cardiac action potentials as well as the impact on the pathophysiology of arrhythmias.
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Affiliation(s)
- Morten S Nielsen
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Chantal J M van Opbergen
- The Leon Charney Division of Cardiology, New York University Grossmann School of Medicine, New York, New York, United States
| | - Toon A B van Veen
- Department of Medical Physiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Mario Delmar
- The Leon Charney Division of Cardiology, New York University Grossmann School of Medicine, New York, New York, United States
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Pan L, Ni H, Jin W, Su X. Inhibition of ERK or Akt ameliorates intimal hyperplasia via up-regulation of Cx37 and down-regulation of Cx43 in balloon injury rat model. Cardiovasc Diagn Ther 2020; 10:658-666. [PMID: 32968622 DOI: 10.21037/cdt-20-345] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Background Connexins (Cxs) are reported to participate in atherosclerosis associated intimal hyperplasia (IH), while their function involved in the balloon injury (BI) induced IH and restenosis is less reported. Methods Forty-eight male Sprague-Dawley rats were randomly assigned to not injured (NI) group and BI group, which were further administrated with ERK-inhibitor U0216 and Akt-inhibitor MIK2206. Western blot and RT-PCR were utilized to detect the expression of Cx30, Cx37, Cx40, and Cx43 at 6 hours, 24 hours, 7 days, and 14 days post-surgery. H&E staining and related intima area, media area, and luminal area measurement were applied to indicate neointima formation and IH. ERK and Akt phosphorylation levels and proliferating cell nuclear antigen (PCNA) immunostaining were also detected. Results Among the four Cxs detected, Cx37 showed down-regulated, and Cx43 showed up-regulated temporal expression pattern in BI rats with confirmed neointima formation. Up-regulated p-ERK (P<0.01) and p-Akt (P<0.01) can be detected in BI rats compared with NI rats. Meanwhile, U0216 and MIK2206 can significantly reduce Cx43 expression and increase CX37 expression accompanied with reduced neointima formation and PCNA staining (P<0.05 or P<0.01) in BI rats. Conclusions ERK or Akt inhibition can alleviate BI-induced IH via up-regulation of Cx37 and down-regulation of Cx43.
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Affiliation(s)
- Lemen Pan
- Department of Vascular Surgery, the First Affiliated Hospital of Wenzhou Medical University, Wenzhou, China
| | - Haizhen Ni
- Department of Vascular Surgery, the First Affiliated Hospital of Wenzhou Medical University, Wenzhou, China
| | - Wenxu Jin
- Department of Vascular Surgery, the First Affiliated Hospital of Wenzhou Medical University, Wenzhou, China
| | - Xiang Su
- Department of Vascular Surgery, the First Affiliated Hospital of Wenzhou Medical University, Wenzhou, China
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PUFAs supplementation affects the renal expression of pannexin 1 and connexins in diabetic kidney of rats. Histochem Cell Biol 2019; 153:165-175. [PMID: 31858211 DOI: 10.1007/s00418-019-01838-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/14/2019] [Indexed: 12/26/2022]
Abstract
In diabetic nephropathy (DN), intercellular communication is disrupted. Connexins (Cx) have a crucial role in that process. Dietary ratios and supplementation with polyunsaturated fatty acids (PUFAs) can alleviate diabetic complications and cause alterations in Cx levels. Although pannexins (Panx) share similarities with members of the Cx family, their function in diabetic nephropathy has still not been fully determined. We studied the influence of PUFA supplementation on the immunoexpression of Px1 and Cx family members in diabetic kidneys of rats. Four groups of rats in experimental DM1 model were supplemented with different dietary n-6/n-3 ratios; ≈7 in control (C) and diabetic groups (STZ), ≈ 60 in the STZ + N6 group and ≈ 1 (containing 16% EPA and 19% DHA) in the STZ + N3 group. Immunoexpression of Cx40, Cx43, Cx45 and Panx1 was evaluated in the renal tissue of diabetic rats using immunohistochemistry. Diabetes significantly decreased the protein expression of Cx40 and Cx43 and increased Panx1 protein expression in the renal cortex (p < 0.05-p < 0.01). There was a significant impact of diet on Cx and Panx1 immunoexpression. Dietary supplementation with a high n-6/n-3 ratio downregulated the protein expression of Cx45 and Panx1 in diabetic rats (p < 0.05-p < 0.01), while Cx43 immunoexpression was increased in diabetic rats fed with high and low n-6/n-3 ratios (p < 0.01-p < 0.001). Hyperglycaemic conditions in DN interfere with cell-to-cell communication and disturb the connection between cells and their immediate environment due to variations in connexin and pannexin immunoexpression. These variations can be regulated by PUFA dietary intake, suggesting their beneficial effect and possible therapeutic option.
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Santos-Miranda A, Noureldin M, Bai D. Effects of temperature on transjunctional voltage-dependent gating kinetics in Cx45 and Cx40 gap junction channels. J Mol Cell Cardiol 2019; 127:185-193. [PMID: 30594539 DOI: 10.1016/j.yjmcc.2018.12.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Revised: 11/29/2018] [Accepted: 12/26/2018] [Indexed: 02/01/2023]
Abstract
Gap junctions (GJs) are intercellular channels directly linking neighbouring cells and are dodecamers of connexins. In the human heart, connexin40 (Cx40), Cx43, and Cx45 are expressed in different regions of the heart forming GJs ensuring rapid propagation of action potentials in the myocardium. Two of these connexins, Cx40 and Cx45, formed functional GJs with prominent transjunctional voltage-dependent gating (Vj-gating), which can be a mechanism to down regulate coupling conductance (Gj). It is not clear the effects of temperature on Vj-gating properties. We expressed Cx40 or Cx45 in N2A cells to study the Vj-gating extent, the kinetics of deactivation, and the recovery time course from deactivation at 22 °C, 28 °C, and 32 °C. Dynamic uncoupling between cell pairs were evaluated at different temperatures, junctional delays, and/or repeating frequencies. Cx40 or Cx45 GJs showed little changes in the extent of Vj-gating, but in both cases with a faster deactivation kinetics at high temperatures. The recovery from deactivation was faster at higher temperatures for Cx45 GJs, but not for Cx40 GJs. Cx45 GJs, but not Cx40 GJs, were dynamically uncoupled when sufficient junctional delays and/or repeating frequency in all tested temperatures. Gap junction specific dynamic uncoupling could play an important role in regulating action potential propagation speed in Cx45 enriched nodal cells in the heart.
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Affiliation(s)
- Artur Santos-Miranda
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
| | - Mahmoud Noureldin
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
| | - Donglin Bai
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada.
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Bai D, Yue B, Aoyama H. Crucial motifs and residues in the extracellular loops influence the formation and specificity of connexin docking. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1860:9-21. [PMID: 28693896 DOI: 10.1016/j.bbamem.2017.07.003] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 06/25/2017] [Accepted: 07/03/2017] [Indexed: 12/19/2022]
Abstract
Most of the early studies on gap junction (GJ) channel function and docking compatibility were on rodent connexins, while recent research on GJ channels gradually shifted from rodent to human connexins largely due to the fact that mutations in many human connexin genes are found to associate with inherited human diseases. The studies on human connexins have revealed some key differences from those found in rodents, calling for a comprehensive characterization of human GJ channels. Functional studies revealed that docking and formation of functional GJ channels between two hemichannels are possible only between docking-compatible connexins. Two groups of docking-compatible rodent connexins have been identified. Compatibility is believed to be due to their amino acid residue differences at the extracellular loop domains (E1 and E2). Sequence alignment of the E1 and E2 domains of all connexins known to make GJs revealed that they are highly conserved and show high sequence identity with human Cx26, which is the only connexin with near atomic resolution GJ structure. We hypothesize that different connexins have a similar structure as that of Cx26 at the E1 and E2 domains and use the corresponding residues in their E1 and E2 domains for docking. Based on the Cx26 GJ structure and sequence analysis of well-studied connexins, we propose that the E1-E1 docking interactions are staggered with each E1 interacting with two E1s on the docked connexon. The putative E1 docking residues are conserved in both docking-compatible and -incompatible connexins, indicating that E1 does not likely serve a role in docking compatibility. However, in the case of E2-E2 docking interactions, the putative docking residues are only conserved within the docking-compatible connexins, suggesting the E2 is likely to serve the function of docking compatibility. Docking compatibility studies on human connexins have attracted a lot of attention due to the fact that putative docking residues are mutational hotspots for several connexin-linked human diseases. This article is part of a Special Issue entitled: Gap Junction Proteins edited by Jean Claude Herve.
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Affiliation(s)
- Donglin Bai
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada.
| | - Benny Yue
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
| | - Hiroshi Aoyama
- Graduate School of Pharmaceutical Sciences, Osaka University, Osaka, Japan
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Zhong G, Akoum N, Appadurai DA, Hayrapetyan V, Ahmed O, Martinez AD, Beyer EC, Moreno AP. Mono-Heteromeric Configurations of Gap Junction Channels Formed by Connexin43 and Connexin45 Reduce Unitary Conductance and Determine both Voltage Gating and Metabolic Flux Asymmetry. Front Physiol 2017; 8:346. [PMID: 28611680 PMCID: PMC5447054 DOI: 10.3389/fphys.2017.00346] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Accepted: 05/11/2017] [Indexed: 11/29/2022] Open
Abstract
In cardiac tissues, the expression of multiple connexins (Cx40, Cx43, Cx45, and Cx30.2) is a requirement for proper development and function. Gap junctions formed by these connexins have distinct permeability and gating mechanisms. Since a single cell can express more than one connexin isoform, the formation of hetero-multimeric gap junction channels provides a tissue with an enormous repertoire of combinations to modulate intercellular communication. To study further the perm-selectivity and gating properties of channels containing Cx43 and Cx45, we studied two monoheteromeric combinations in which a HeLa cell co-transfected with Cx43 and Cx45 was paired with a cell expressing only one of these connexins. Macroscopic measurements of total conductance between cell pairs indicated a drastic reduction in total conductance for mono-heteromeric channels. In terms of Vj dependent gating, Cx43 homomeric connexons facing heteromeric connexons only responded weakly to voltage negativity. Cx45 homomeric connexons exhibited no change in Vj gating when facing heteromeric connexons. The distributions of unitary conductances (γj) for both mono-heteromeric channels were smaller than predicted, and both showed low permeability to the fluorescent dyes Lucifer yellow and Rhodamine123. For both mono-heteromeric channels, we observed flux asymmetry regardless of dye charge: flux was higher in the direction of the heteromeric connexon for MhetCx45 and in the direction of the homomeric Cx43 connexon for MhetCx43. Thus, our data suggest that co-expression of Cx45 and Cx43 induces the formation of heteromeric connexons with greatly reduced permeability and unitary conductance. Furthermore, it increases the asymmetry for voltage gating for opposing connexons, and it favors asymmetric flux of molecules across the junction that depends primarily on the size (not the charge) of the crossing molecules.
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Affiliation(s)
- Guoqiang Zhong
- Department of Cardiology, First Affiliated Hospital of Guangxi Medical UniversityGuangxi, China
| | - Nazem Akoum
- University Medical Center, University of WashingtonSeattle, WA, United States
| | | | | | - Osman Ahmed
- Atlanta Heart SpecialistsAtlanta, GA, United States
| | - Agustin D Martinez
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de ValparaísoValparaíso, Chile
| | - Eric C Beyer
- Department of Pediatrics, University of ChicagoChicago, IL, United States
| | - Alonso P Moreno
- Cardiovascular Research and Training Institute (CVRTI), Department of Bioengineering, University of UtahSalt Lake Citiy, UT, United States
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Xu Q, Lin X, Matiukas A, Zhang X, Veenstra RD. Specificity of the connexin W3/4 locus for functional gap junction formation. Channels (Austin) 2016; 10:453-65. [PMID: 27304225 PMCID: PMC5034775 DOI: 10.1080/19336950.2016.1200775] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Revised: 05/23/2016] [Accepted: 06/08/2016] [Indexed: 10/21/2022] Open
Abstract
The N-terminal (NT) domain of the connexins forms an essential transjunctional voltage (Vj) sensor and pore-forming domain that when truncated, tagged, or mutated often leads to formation of a nonfunctional channel. The NT domain is relatively conserved among the connexins though the α- and δ-group connexins possess a G2 residue not found in the β- and γ-group connexins. Deletion of the connexin40 G2 residue (Cx40G2Δ) affected the Vj gating, increased the single channel conductance (γj), and decreased the relative K(+)/Cl(-) permeability (PK/PCl) ratio of the Cx40 gap junction channel. The conserved α/β-group connexin D2/3 and W3/4 loci are postulated to anchor the NT domain within the pore via hydrophilic and hydrophobic interactions with adjacent connexin T5 and M34 residues. Cx40D3N and D3R mutations produced limited function with progressive reductions in Vj gating and noisy low γj gap junction channels that reduced the γj of wild-type Cx40 channels from 150 pS to < 50 pS when coexpressed. Surprisingly, hydrophobic Cx40 W4F and W4Y substitution mutations were not compatible with function despite their ability to form gap junction plaques. These data are consistent with minor and major contributions of the G2 and D3 residues to the Cx40 channel pore structure, but not with the postulated hydrophobic W4 intermolecular interactions. Our results indicate an absolute requirement for an amphipathic W3/4 residue that is conserved among all α/β/δ/γ-group connexins. We alternatively hypothesize that the connexin D2/3-W3/4 locus interacts with the highly conserved FIFR M1 motif to stabilize the NT domain within the pore.
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Affiliation(s)
- Qin Xu
- Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY, USA
| | - Xianming Lin
- Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY, USA
| | - Arvydas Matiukas
- Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY, USA
| | - Xian Zhang
- Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY, USA
| | - Richard D. Veenstra
- Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY, USA
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, NY, USA
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9
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Connexin 43, breast cancer tumor suppressor: Missed connections? Cancer Lett 2016; 374:117-126. [DOI: 10.1016/j.canlet.2016.02.008] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Revised: 01/28/2016] [Accepted: 02/03/2016] [Indexed: 12/21/2022]
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Jassim A, Aoyama H, Ye WG, Chen H, Bai D. Engineered Cx40 variants increased docking and function of heterotypic Cx40/Cx43 gap junction channels. J Mol Cell Cardiol 2016; 90:11-20. [PMID: 26625713 DOI: 10.1016/j.yjmcc.2015.11.026] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Revised: 10/30/2015] [Accepted: 11/24/2015] [Indexed: 02/06/2023]
Abstract
Gap junction (GJ) channels provide low resistance passages for rapid action potential propagation in the heart. Both connexin40 (Cx40) and Cx43 are abundantly expressed in and frequently co-localized between atrial myocytes, possibly forming heterotypic GJ channels. However, conflicting results have been obtained on the functional status of heterotypic Cx40/Cx43 GJs. Here we provide experimental evidence that the docking and formation of heterotypic Cx40/Cx43 GJs can be substantially increased by designed Cx40 variants on the extracellular domains (E1 and E2). Specifically, Cx40 D55N and P193Q, substantially increased the probability to form GJ plaque-like structures at the cell-cell interfaces with Cx43 in model cells. More importantly the coupling conductance (Gj) of D55N/Cx43 and P193Q/Cx43 GJ channels are significantly increased from the Gj of Cx40/Cx43 in N2A cells. Our homology models indicate the electrostatic interactions and surface structures at the docking interface are key factors preventing Cx40 from docking to Cx43. Improving heterotypic Gj of these atrial connexins might be potentially useful in improving the coupling and synchronization of atrial myocardium.
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Affiliation(s)
- Arjewan Jassim
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
| | - Hiroshi Aoyama
- Graduate School of Pharmaceutical Sciences, Osaka University, Osaka, Japan
| | - Willy G Ye
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
| | - Honghong Chen
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
| | - Donglin Bai
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada.
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Lin X, Xu Q, Veenstra RD. Functional formation of heterotypic gap junction channels by connexins-40 and -43. Channels (Austin) 2015; 8:433-43. [PMID: 25483586 DOI: 10.4161/19336950.2014.949188] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Connexin40 (Cx40) and connexin43 (Cx43) are co-expressed in the cardiovascular system, yet their ability to form functional heterotypic Cx43/Cx40 gap junctions remains controversial. We paired Cx43 or Cx40 stably-transfected N2a cells to examine the formation and biophysical properties of heterotypic Cx43/Cx40 gap junction channels. Dual whole cell patch clamp recordings demonstrated that Cx43 and Cx40 form functional heterotypic gap junctions with asymmetric transjunctional voltage (Vj) dependent gating properties. The heterotypic Cx43/Cx40 gap junctions exhibited less Vj gating when the Cx40 cell was positive and pronounced gating when negative. Endogenous N2a cell connexin expression levels were 1,000-fold lower than exogenously expressed Cx40 and Cx43 levels, measured by real-time PCR and Western blotting methods, suggestive of heterotypic gap junction formation by exogenous Cx40 and Cx43. Imposing a [KCl] gradient across the heterotypic gap junction modestly diminished the asymmetry of the macroscopic normalized junctional conductance - voltage (Gj-Vj) curve when [KCl] was reduced by 50% on the Cx43 side and greatly exacerbated the Vj gating asymmetries when lowered on the Cx40 side. Pairing wild-type (wt) Cx43 with the Cx40 E9,13K mutant protein produced a nearly symmetrical heterotypic Gj-Vj curve. These studies conclusively demonstrate the ability of Cx40 and Cx43 to form rectifying heterotypic gap junctions, owing primarily to alternate amino-terminal (NT) domain acidic and basic amino acid differences that may play a significant role in the physiology and/or pathology of the cardiovascular tissues including cardiac conduction properties and myoendothelial intercellular communication.
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Key Words
- Connexin40
- Cx37, connexin37
- Cx40, connexin40; Cx43, connexin43
- Cx45, connexin45
- E1, first extracellular loop domain
- EDTA, Ethylenediaminetetraacetic acid
- FITC, fluorescein isothiocyante
- GAPDH, glyceraldehyde-3-phosphate dehydrogenase
- Gj, normalized junctional conductance
- Gj,max, maximum normalized gj
- Gj,min, mimimum normalized gj
- I1 and I2, whole cell currents for cell 1 and cell 2
- Ij, junctional current
- Kon, inactivation on-rate
- N2a, mouse Neuro2a
- NT, N-terminal domain
- Popen, open probability
- RT-PCR, real-time PCR
- Rel1 and Rel2, whole cell patch electrode resistance values for cell 1 and cell 2
- Rin, renal insulinoma
- TBS, Tris buffered saline
- TRITC, tetramethylrhodamine isothiocyanate
- V1 and V2, command voltage clamp potentials for cell 1 and cell 2
- V1/2, half-inactivation voltage
- Vj, transjunctional voltage
- connexin43
- gap junctions
- gj, junctional conductance
- heterotypic
- ij, single gap junction channel current
- mCx30.2/hCx31.9, mouse connexin30.2/human connexin31.9
- pS, picoSiemen
- spermine
- transjunctional voltage gating
- wt, wild-type
- ΔI2, change in I2 in response to an applied Vj gradient produced by changing V1
- γj, single gap junction channel conductance
- τdecay, exponential decay time constant
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Affiliation(s)
- Xianming Lin
- a Department of Pharmacology ; SUNY Upstate Medical University ; Syracuse , NY USA
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Ampey BC, Morschauser TJ, Lampe PD, Magness RR. Gap junction regulation of vascular tone: implications of modulatory intercellular communication during gestation. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 814:117-32. [PMID: 25015806 DOI: 10.1007/978-1-4939-1031-1_11] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
In the vasculature, gap junctions (GJ) play a multifaceted role by serving as direct conduits for cell-cell intercellular communication via the facilitated diffusion of signaling molecules. GJs are essential for the control of gene expression and coordinated vascular development in addition to vascular function. The coupling of endothelial cells to each other, as well as with vascular smooth muscle cells via GJs, plays a relevant role in the control of vasomotor tone, tissue perfusion and arterial blood pressure. The regulation of cell-signaling is paramount to cardiovascular adaptations of pregnancy. Pregnancy requires highly developed cell-to-cell coupling, which is affected partly through the formation of intercellular GJs by Cx43, a gap junction protein, within adjacent cell membranes to help facilitate the increase of uterine blood flow (UBF) in order to ensure adequate perfusion for nutrient and oxygen delivery to the placenta and thus the fetus. One mode of communication that plays a critical role in regulating Cx43 is the release of endothelial-derived vasodilators such as prostacyclin (PGI2) and nitric oxide (NO) and their respective signaling mechanisms involving second messengers (cAMP and cGMP, respectively) that are likely to be important in maintaining UBF. Therefore, the assertion we present in this review is that GJs play an integral if not a central role in maintaining UBF by controlling rises in vasodilators (PGI2 and NO) via cyclic nucleotides. In this review, we discuss: (1) GJ structure and regulation; (2) second messenger regulation of GJ phosphorylation and formation; (3) pregnancy-induced changes in cell-signaling; and (4) the role of uterine arterial endothelial GJs during gestation. These topics integrate the current knowledge of this scientific field with interpretations and hypotheses regarding the vascular effects that are mediated by GJs and their relationship with vasodilatory vascular adaptations required for modulating the dramatic physiological rises in uteroplacental perfusion and blood flow observed during normal pregnancy.
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Affiliation(s)
- Bryan C Ampey
- Perinatal Research Laboratories, Department of Obstetrics & Gynecology, School Medicine and Public Health, University of Wisconsin - Madison, Madison, WI, 53715, USA
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Functional Role of Connexins and Pannexins in the Interaction Between Vascular and Nervous System. J Cell Physiol 2014; 229:1336-45. [DOI: 10.1002/jcp.24563] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Accepted: 01/16/2014] [Indexed: 01/22/2023]
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14
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Sun Y, Tong X, Chen H, Huang T, Shao Q, Huang W, Laird DW, Bai D. An atrial-fibrillation-linked connexin40 mutant is retained in the endoplasmic reticulum and impairs the function of atrial gap-junction channels. Dis Model Mech 2014; 7:561-9. [PMID: 24626989 PMCID: PMC4007407 DOI: 10.1242/dmm.013813] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Accepted: 03/11/2014] [Indexed: 12/18/2022] Open
Abstract
Connexin40 (Cx40)-containing gap-junction channels are expressed in the atrial myocardium and provide a low-resistance passage for rapid impulse propagation. A germline mutation in the GJA5 gene, which encodes Cx40, resulting in a truncated Cx40 (Q49X) was identified in a large Chinese family with lone (idiopathic) atrial fibrillation (AF). This mutation co-segregated with seven AF probands in an autosomal-dominant way over generations. To test the hypothesis that this Cx40 mutant affects the distribution and function of atrial gap junctions, we studied the Q49X mutant in gap-junction-deficient HeLa and N2A cells. The Q49X mutant, unlike wild-type Cx40, was typically localized in the cytoplasm and failed to form gap-junction plaques at cell-cell interfaces. When the Q49X mutant was co-expressed with Cx40 or Cx43, the mutant substantially reduced the gap-junction plaque formation of Cx40 and Cx43. Electrophysiological studies revealed no electrical coupling of cell pairs expressing the mutant alone and a significant decrease in the coupling conductance when the mutant was co-expressed with Cx40 or Cx43. Further colocalization experiments with the organelle residential proteins indicate that Q49X was retained in the endoplasmic reticulum. These findings provide evidence that the Q49X mutant is capable of impairing gap-junction distribution and function of key atrial connexins, which might play a role in the predisposition to and onset of AF.
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Affiliation(s)
- Yiguo Sun
- Department of Physiology and Pharmacology, The University of Western Ontario, London, ON N6A 5C1, Canada
| | - Xiaoling Tong
- Department of Physiology and Pharmacology, The University of Western Ontario, London, ON N6A 5C1, Canada
| | - Honghong Chen
- Department of Physiology and Pharmacology, The University of Western Ontario, London, ON N6A 5C1, Canada
| | - Tao Huang
- Anatomy and Cell Biology, The University of Western Ontario, London, ON N6A 5C1, Canada
| | - Qing Shao
- Anatomy and Cell Biology, The University of Western Ontario, London, ON N6A 5C1, Canada
| | - Weixiong Huang
- Department of Physiology and Pharmacology, The University of Western Ontario, London, ON N6A 5C1, Canada
| | - Dale W. Laird
- Department of Physiology and Pharmacology, The University of Western Ontario, London, ON N6A 5C1, Canada
- Anatomy and Cell Biology, The University of Western Ontario, London, ON N6A 5C1, Canada
| | - Donglin Bai
- Department of Physiology and Pharmacology, The University of Western Ontario, London, ON N6A 5C1, Canada
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15
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McCain ML, Desplantez T, Kléber AG. Engineering Cardiac Cell JunctionsIn Vitroto Study the Intercalated Disc. ACTA ACUST UNITED AC 2014; 21:181-91. [DOI: 10.3109/15419061.2014.905931] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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16
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Bai D. Atrial fibrillation-linked GJA5/connexin40 mutants impaired gap junctions via different mechanisms. FEBS Lett 2014; 588:1238-43. [PMID: 24656738 DOI: 10.1016/j.febslet.2014.02.064] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Revised: 02/05/2014] [Accepted: 02/06/2014] [Indexed: 01/08/2023]
Abstract
The gap junctions (GJs) formed by Cx40 and Cx43 provide a low resistance passage allowing for rapid propagation of action potentials. Sporadic somatic mutations in GJA5 (encoding Cx40) have been identified in lone atrial fibrillation (AF) patients. More recently germline autosomal dominantly inherited mutations in GJA5 have been found in early onset lone AF patients in several families over generations. Characterizations of these AF-linked Cx40 mutants in model cells and in patient tissues revealed that some of the mutants reduced GJ channel function due to an impaired trafficking or channel formation. While others showed a gain-of-function in hemichannels. These functional alterations in GJs or hemichannel may play an important role in the pathogenesis of AF in the mutant carriers.
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Affiliation(s)
- Donglin Bai
- Department of Physiology and Pharmacology, Western University, London, Ontario N6A 5C1, Canada.
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17
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Koval M, Molina SA, Burt JM. Mix and match: investigating heteromeric and heterotypic gap junction channels in model systems and native tissues. FEBS Lett 2014; 588:1193-204. [PMID: 24561196 DOI: 10.1016/j.febslet.2014.02.025] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Revised: 02/12/2014] [Accepted: 02/13/2014] [Indexed: 12/12/2022]
Abstract
This review is based in part on a roundtable discussion session: "Physiological roles for heterotypic/heteromeric channels" at the 2013 International Gap Junction Conference (IGJC 2013) in Charleston, South Carolina. It is well recognized that multiple connexins can specifically co-assemble to form mixed gap junction channels with unique properties as a means to regulate intercellular communication. Compatibility determinants for both heteromeric and heterotypic gap junction channel formation have been identified and associated with specific connexin amino acid motifs. Hetero-oligomerization is also a regulated process; differences in connexin quality control and monomer stability are likely to play integral roles to control interactions between compatible connexins. Gap junctions in oligodendrocyte:astrocyte communication and in the cardiovascular system have emerged as key systems where heterotypic and heteromeric channels have unique physiologic roles. There are several methodologies to study heteromeric and heterotypic channels that are best applied to either heterologous expression systems, native tissues or both. There remains a need to use and develop different experimental approaches in order to understand the prevalence and roles for mixed gap junction channels in human physiology.
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Affiliation(s)
- Michael Koval
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, Emory University, Atlanta, GA, United States; Department of Cell Biology, Emory University, Atlanta, GA, United States.
| | - Samuel A Molina
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, Emory University, Atlanta, GA, United States
| | - Janis M Burt
- Department of Physiology, University of Arizona, Tucson, AZ, United States
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18
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Syndromic and non-syndromic disease-linked Cx43 mutations. FEBS Lett 2014; 588:1339-48. [PMID: 24434540 DOI: 10.1016/j.febslet.2013.12.022] [Citation(s) in RCA: 106] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Accepted: 12/30/2013] [Indexed: 01/05/2023]
Abstract
There are now at least 14 distinct diseases linked to germ line mutations in the 21 genes that encode the connexin (Cx) family of gap junction proteins. This review focuses on the links between germ-line mutations in the gene encoding Cx43 (GJA1) and the human disease termed oculodentodigital dysplasia (ODDD). This disease is clinically characterized by soft tissue fusion of the digits, abnormal craniofacial bone development, small eyes and loss of tooth enamel. However, the disease is considerably more complex and somewhat degenerative as patients often suffer from other syndromic effects that include incontinence, glaucoma, skin diseases and neuropathies that become more pronounced during aging. The challenge continues to be understanding how distinct Cx43 gene mutations cause such a diverse range of tissue phenotypes and pathophysiological changes while other Cx43-rich organs are relatively unaffected. This review will provide an overview of many of these studies and distill some themes and outstanding questions that need to be addressed in the coming years.
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19
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Beyer EC, Lin X, Veenstra RD. Interfering amino terminal peptides and functional implications for heteromeric gap junction formation. Front Pharmacol 2013; 4:67. [PMID: 23734129 PMCID: PMC3659311 DOI: 10.3389/fphar.2013.00067] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Accepted: 04/29/2013] [Indexed: 02/05/2023] Open
Abstract
Connexin43 (Cx43) is widely expressed in many different tissues of the human body. In cells of some organs, Cx43 is co-expressed with other connexins (Cx), including Cx46 and Cx50 in lens, Cx40 in atrium, Purkinje fibers, and the blood vessel wall, Cx45 in heart, and Cx37 in the ovary. Interactions with the co-expressed connexins may have profound functional implications. The abilities of Cx37, Cx45, Cx46, and Cx50 to function in heteromeric gap junction combinations with Cx43 are well documented. Different studies disagree regarding the ability of Cx43 and Cx40 to produce functional heteromeric gap junctions with each other. We review previous studies regarding the heteromeric interactions of Cx43. The possibility of negative functional interactions between the cytoplasmic pore-forming amino-terminal (NT) domains of these connexins was assessed using pentameric connexin sequence-specific NT domain [interfering NT (iNT)] peptides applied to cells expressing homomeric Cx40, Cx37, Cx45, Cx46, and Cx50 gap junctions. A Cx43 iNT peptide corresponding to amino acids 9–13 (Ac-KLLDK-NH2) specifically inhibited the electrical coupling of Cx40 gap junctions in a transjunctional voltage (Vj)-dependent manner without affecting the function of homologous Cx37, Cx46, Cx50, and Cx45 gap junctions. A Cx40 iNT (Ac-EFLEE-OH) peptide counteracted the Vj-dependent block of Cx40 gap junctions, whereas a similarly charged Cx50 iNT (Ac-EEVNE-OH) peptide did not, suggesting that these NT domain interactions are not solely based on electrostatics. These data are consistent with functional Cx43 heteromeric gap junction formation with Cx37, Cx45, Cx46, and Cx50 and suggest that Cx40 uniquely experiences functional suppressive interactions with a Cx43 NT domain sequence. These findings present unique functional implications about the heteromeric interactions between Cx43 and Cx40 that may influence cardiac conduction in atrial myocardium and the specialized conduction system.
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Affiliation(s)
- Eric C Beyer
- Department of Pediatrics, University of Chicago Chicago, IL, USA
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20
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Lemcke H, Nittel ML, Weiss DG, Kuznetsov SA. Neuronal differentiation requires a biphasic modulation of gap junctional intercellular communication caused by dynamic changes of connexin43 expression. Eur J Neurosci 2013; 38:2218-28. [PMID: 23607708 DOI: 10.1111/ejn.12219] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2012] [Revised: 03/12/2013] [Accepted: 03/14/2013] [Indexed: 11/30/2022]
Abstract
It was suggested that gap junctional intercellular communication (GJIC) and connexin (Cx) proteins play a crucial role in cell proliferation and differentiation. However, the mechanisms of cell coupling in regulating cell fate during embryonic development are poorly understood. To study the role of GJIC in proliferation and differentiation, we used a human neural progenitor cell line derived from the ventral mesencephalon. Fluorescence recovery after photobleaching (FRAP) showed that dye coupling was extensive in proliferating cells but diminished after the induction of differentiation, as indicated by a 2.5-fold increase of the half-time of fluorescence recovery. Notably, recovery half-time decreased strongly (five-fold) in the later stage of differentiation. Western blot analysis revealed a similar time-dependent expression profile of Cx43, acting as the main gap junction-forming protein. Interestingly, large amounts of cytoplasmic Cx43 were retained mainly in the Golgi network during proliferation but decreased when differentiation was induced. Furthermore, down-regulation of Cx43 by small interfering RNA reduced functional cell coupling, which in turn resulted in a 50% decrease of both the proliferation rate and neuronal differentiation. Our findings suggest a dual function of Cx43 and GJIC in the neural development of ReNcell VM197 human progenitor cells. GJIC accompanied by high Cx43 expression is necessary (1) to maintain cells in a proliferative state and (2) to complete neuronal differentiation, including the establishment of a neural network. However, uncoupling of cells is crucial in the early stage of differentiation during cell fate commitment.
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Affiliation(s)
- Heiko Lemcke
- Department of Animal Physiology, Cell Biology and Biosystems Technology, Institute of Biological Sciences, University of Rostock, Albert-Einstein-Str. 3, D-18059, Rostock, Germany
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21
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Gemel J, Nelson TK, Burt JM, Beyer EC. Inducible coexpression of connexin37 or connexin40 with connexin43 selectively affects intercellular molecular transfer. J Membr Biol 2012; 245:231-41. [PMID: 22729648 PMCID: PMC3501935 DOI: 10.1007/s00232-012-9444-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Accepted: 06/01/2012] [Indexed: 12/17/2022]
Abstract
Many tissues express multiple gap junction proteins, or connexins (Cx); for example, Cx43, Cx40, and Cx37 are coexpressed in vascular cells. This study was undertaken to elucidate the consequences of coexpression of Cx40 or Cx37 with Cx43 at different ratios. EcR-293 cells (which endogenously produce Cx43) were transfected with ecdysone-inducible plasmids encoding Cx37 or Cx40. Immmunoblotting showed a ponasterone dose-dependent induction of Cx37 or Cx40 while constant levels of Cx43 were maintained. The coexpressed connexins colocalized at appositional membranes. Double whole-cell patch clamp recordings showed no significant change in total junctional conductances in cells treated with 0, 0.5, or 4 μM ponasterone; however, they did show a diversity of unitary channel sizes consistent with the induced connexin expression. In cells with induced expression of either Cx40 or Cx37, intercellular transfer of microinjected Lucifer yellow was reduced, but transfer of NBD-TMA (2-(4-nitro-2,1,3-benzoxadiol-7-yl)[aminoethyl]trimethylammonium) was not affected. In cocultures containing uninduced EcR cells together with cells induced to coexpress Cx37 or Cx40, Lucifer yellow transfer was observed only between the cells expressing Cx43 alone. These data show that induced expression of either Cx37 or Cx40 in Cx43-expressing cells can selectively alter the intercellular exchange of some molecules without affecting the transfer of others.
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Affiliation(s)
- Joanna Gemel
- Department of Pediatrics, University of Chicago, Chicago, IL, USA
| | - Tasha K. Nelson
- Department of Physiology, University of Arizona, Tucson, AZ, USA
| | - Janis M. Burt
- Department of Physiology, University of Arizona, Tucson, AZ, USA
| | - Eric C. Beyer
- Department of Pediatrics, University of Chicago, Chicago, IL, USA
- Section of Pediatric Hematology/Oncology, University of Chicago, 900 E 57th St., KCBD 5152, Chicago, IL 60637, USA
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22
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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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23
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Igarashi T, Finet JE, Takeuchi A, Fujino Y, Strom M, Greener ID, Rosenbaum DS, Donahue JK. Connexin gene transfer preserves conduction velocity and prevents atrial fibrillation. Circulation 2012; 125:216-25. [PMID: 22158756 PMCID: PMC3260348 DOI: 10.1161/circulationaha.111.053272] [Citation(s) in RCA: 162] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Several lines of evidence have suggested that maintenance of atrial fibrillation (AF) depends on reentrant mechanisms. Maintenance of reentry necessitates a sufficiently short refractory period and/or delayed conduction, and AF has been associated with both alterations. Fibrosis, cellular dysfunction, and gap junction protein alterations occur in AF and cause conduction delay. We performed this study to test the hypothesis that gap junction protein overexpression would improve conduction and prevent AF. METHODS AND RESULTS Thirty Yorkshire swine were randomized into 2 groups (sinus rhythm and AF), and each group into 3 subgroups: sham-operated control, gene therapy with adenovirus expressing connexin (Cx) 40, and gene therapy with adenovirus expressing Cx43 (n=5 per subgroup). All animals had epicardial gene painting; the AF group had burst atrial pacing. All animals underwent terminal study 7 days after gene transfer. Sinus rhythm animals had strong transgene expression but no atrial conduction changes. In AF animals, controls had reduced and lateralized Cx43 expression, and Cx43 gene transfer restored expression and cellular location to sinus rhythm control levels. In the AF group, both Cx40 and Cx43 gene transfer improved conduction and reduced AF relative to controls. CONCLUSIONS Connexin gene therapy preserved atrial conduction and prevented AF.
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Affiliation(s)
- Tomonori Igarashi
- Heart and Vascular Research Center, MetroHealth Campus, Case Western Reserve University, Cleveland, Ohio, USA
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24
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Furuta N, Ikeda M, Hirayanagi K, Fujita Y, Amanuma M, Okamoto K. A novel GJA1 mutation in oculodentodigital dysplasia with progressive spastic paraplegia and sensory deficits. Intern Med 2012; 51:93-8. [PMID: 22214631 DOI: 10.2169/internalmedicine.51.5770] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Oculodentodigital dysplasia (ODDD) is a rare autosomal dominant inherited disorder mainly affecting the development of the face, eyes, dentition, limbs, hair and heart. GJA1 (the gap junction protein α-1) has been determined to be a causative gene of ODDD, mapped to chromosome 6q22-24 identified as the connexin 43 gene (Cx43). We found a novel GJA1 mutation (W25C) as the possible causative gene in this sporadic ODDD patient with neurological features of motor deficits by pyramidal tract signs, and sensory deficits due to peripheral nerve disturbance. It is also notable that the MRI of this patient demonstrated widespread aberrant signal lesions in the brain and brainstem.
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Affiliation(s)
- Natsumi Furuta
- Department of Neurology, Gunma University Graduate School of Medicine, Japan
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25
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Carnarius C, Kreir M, Krick M, Methfessel C, Moehrle V, Valerius O, Brüggemann A, Steinem C, Fertig N. Green fluorescent protein changes the conductance of connexin 43 (Cx43) hemichannels reconstituted in planar lipid bilayers. J Biol Chem 2011; 287:2877-86. [PMID: 22139870 DOI: 10.1074/jbc.m111.319871] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
In mammalian tissues, connexin 43 (Cx43) is the most prominent member of the connexin family. In a single lipid bilayer, six connexin subunits assemble into a hemichannel (connexon). Direct communication of apposing cells is realized by two adjacent hemichannels, which can form gap junction channels. Here, we established an expression system in Pichia pastoris to recombinantly produce and purify Cx43 as well as Cx43 fused to green fluorescent protein (GFP). Proteins were isolated from crude cell membrane fractions via affinity chromatography. Cx43 and Cx43-GFP hemichannels were reconstituted in giant unilamellar vesicles as proven by fluorescence microscopy, and their electrophysiological behavior was analyzed on the single channel level by planar patch clamping. Cx43 and Cx43-GFP both showed an ohmic behavior and a voltage-dependent open probability. Cx43 hemichannels exhibited one major mean conductance of 224 ± 26 picosiemens (pS). In addition, a subconductance state at 124 ± 5 pS was identified. In contrast, the analysis of Cx43-GFP single channels revealed 10 distinct conductance states in the range of 15 to 250 pS, with a larger open probability at 0 mV as compared with Cx43, which suggests that intermolecular interactions between the GFP molecules alter the electrophysiology of the protein.
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Affiliation(s)
- Christian Carnarius
- Institute of Organic and Biomolecular Chemistry, University of Göttingen, Tammannstrasse 2, 37077 Göttingen, Germany
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26
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Langer J, Stephan J, Theis M, Rose CR. Gap junctions mediate intercellular spread of sodium between hippocampal astrocytes in situ. Glia 2011; 60:239-52. [DOI: 10.1002/glia.21259] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2011] [Accepted: 09/29/2011] [Indexed: 01/01/2023]
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27
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Lübkemeier I, Machura K, Kurtz L, Neubauer B, Dobrowolski R, Schweda F, Wagner C, Willecke K, Kurtz A. The connexin 40 A96S mutation causes renin-dependent hypertension. J Am Soc Nephrol 2011; 22:1031-40. [PMID: 21597036 PMCID: PMC3103723 DOI: 10.1681/asn.2010101047] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2010] [Accepted: 01/16/2011] [Indexed: 11/03/2022] Open
Abstract
Deletion of the gap-junction-forming protein connexin40 leads to renin-dependent hypertension in mice, but whether observed human variants in connexin40, such as A96S, promote hypertension is unknown. Here, we generated mice with the A96S variant in the mouse connexin40 gene. Although mice homozygous for the A96S mutations had normal expression patterns of connexin40 in the kidney, they were hypertensive, had sixfold higher plasma renin concentrations, and had 40% higher levels of renin mRNA than controls. Renin-expressing cells were aberrantly located outside the media layer of afferent arterioles, and increased renal perfusion pressure did not inhibit renin secretion from kidneys isolated from homozygous A96S mice. Treatment with a low-salt diet in combination with an ACE inhibitor increased renin mRNA levels, plasma renin concentrations, and the number of aberrantly localized renin-producing cells. Taken together, these findings suggest that the A96S mutation in connexin40 leads to renin-dependent hypertension in mice. Modulation of renin secretion by BP critically depends on functional connexin40; with the A96S mutation, the aberrant extravascular localization of renin-secreting cells in the kidney likely impairs the pressure-mediated inhibition of renin secretion.
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Affiliation(s)
| | | | - Lisa Kurtz
- Department of Internal Medicine, University of Regensburg, Regensburg, Germany
| | | | | | | | | | - Klaus Willecke
- Institute of Genetics, University of Bonn, Bonn, Germany; and
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28
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Koval M, Billaud M, Straub AC, Johnstone SR, Zarbock A, Duling BR, Isakson BE. Spontaneous lung dysfunction and fibrosis in mice lacking connexin 40 and endothelial cell connexin 43. THE AMERICAN JOURNAL OF PATHOLOGY 2011; 178:2536-46. [PMID: 21641379 PMCID: PMC3124229 DOI: 10.1016/j.ajpath.2011.02.045] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2010] [Revised: 12/30/2010] [Accepted: 02/01/2011] [Indexed: 12/31/2022]
Abstract
Gap junction proteins (connexins) facilitate intercellular communication and serve several roles in regulation of tissue function and remodeling. To examine the physiologic effects of depleting two prominent endothelial connexins, Cx40 and Cx43, transgenic mice were generated by breeding Cx40-deficient mice (Cx40(-/-)) with a vascular endothelial cell (VEC)-specific Cx43-deficient mouse strain (VEC Cx43(-/-)) to produce double-connexin knockout mice (VEC Cx43(-/-)/Cx40(-/-)). The life span in VEC Cx43(-/-)/Cx40(-/-) mice was dramatically shortened, which correlated with severe spontaneous lung abnormalities as the mice aged including increased fibrosis, aberrant alveolar remodeling, and increased lung fibroblast content. Moreover, VEC Cx43(-/-)/Cx40(-/-) mice exhibited cardiac hypertrophy and hypertension. Because VEC Cx43(-/-)/Cx40(-/-) mice demonstrated phenotypic hallmarks that were remarkably similar to those in mice deficient in caveolin-1, pulmonary caveolin expression was examined. Lungs from VEC Cx43(-/-)/Cx40(-/-) mice demonstrated significantly decreased expression of caveolin-1 and caveolin-2. This suggests that expression of caveolin-1 may be linked to expression of Cx40 and endothelial Cx43. Moreover, the phenotype of caveolin-1(-/-) mice and VEC Cx43(-/-)/Cx40(-/-) mice may arise via a common mechanism.
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Affiliation(s)
- Michael Koval
- Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia
- Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia
| | - Marie Billaud
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, Virginia
| | - Adam C. Straub
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, Virginia
| | - Scott R. Johnstone
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, Virginia
| | - Alexander Zarbock
- Department of Anesthesiology and Critical Care Medicine, University of Münster, Münster, Germany
- Max-Planck-Institute of Molecular Biomedicine, Münster, Germany
| | - Brian R. Duling
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, Virginia
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, Virginia
| | - Brant E. Isakson
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, Virginia
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, Virginia
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29
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Pries AR, Höpfner M, le Noble F, Dewhirst MW, Secomb TW. The shunt problem: control of functional shunting in normal and tumour vasculature. Nat Rev Cancer 2010; 10:587-93. [PMID: 20631803 PMCID: PMC3109666 DOI: 10.1038/nrc2895] [Citation(s) in RCA: 185] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Networks of blood vessels in normal and tumour tissues have heterogeneous structures, with widely varying blood flow pathway lengths. To achieve efficient blood flow distribution, mechanisms for the structural adaptation of vessel diameters must be able to inhibit the formation of functional shunts (whereby short pathways become enlarged and flow bypasses long pathways). Such adaptation requires information about tissue metabolic status to be communicated upstream to feeding vessels, through conducted responses. We propose that impaired vascular communication in tumour microvascular networks, leading to functional shunting, is a primary cause of dysfunctional microcirculation and local hypoxia in cancer. We suggest that anti-angiogenic treatment of tumours may restore vascular communication and thereby improve or normalize flow distribution in tumour vasculature.
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Affiliation(s)
- Axel R Pries
- Department of Physiology and the Centre for Cardiovascular Research, Charité Berlin, Thielallee 71, D-14195 Berlin, Germany.
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30
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Bouvier D, Spagnol G, Chenavas S, Kieken F, Vitrac H, Brownell S, Kellezi A, Forge V, Sorgen PL. Characterization of the structure and intermolecular interactions between the connexin40 and connexin43 carboxyl-terminal and cytoplasmic loop domains. J Biol Chem 2009; 284:34257-71. [PMID: 19808665 PMCID: PMC2797195 DOI: 10.1074/jbc.m109.039594] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2009] [Revised: 09/10/2009] [Indexed: 11/06/2022] Open
Abstract
Gap junctions are intercellular channels that allow the passage of ions, small molecules, and second messengers that are essential for the coordination of cellular function. They are formed by two hemichannels, each constituted by the oligomerization of six connexins (Cx). Among the 21 different human Cx isoforms, studies have suggested that in the heart, Cx40 and Cx43 can oligomerize to form heteromeric hemichannels. The mechanism of heteromeric channel regulation has not been clearly defined. Tissue ischemia leads to intracellular acidification and closure of Cx43 and Cx40 homomeric channels. However, coexpression of Cx40 and Cx43 in Xenopus oocytes enhances the pH sensitivity of the channel. This phenomenon requires the carboxyl-terminal (CT) part of both connexins. In this study we used different biophysical methods to determine the structure of the Cx40CT and characterize the Cx40CT/Cx43CT interaction. Our results revealed that the Cx40CT is an intrinsically disordered protein similar to the Cx43CT and that the Cx40CT and Cx43CT can interact. Additionally, we have identified an interaction between the Cx40CT and the cytoplasmic loop of Cx40 as well as between the Cx40CT and the cytoplasmic loop of Cx43 (and vice versa). Our studies support the "particle-receptor" model for pH gating of Cx40 and Cx43 gap junction channels and suggest that interactions between cytoplasmic regulatory domains (both homo- and hetero-connexin) could be important for the regulation of heteromeric channels.
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Affiliation(s)
- Denis Bouvier
- From the Department of Biochemistry and Molecular Biology and
| | - Gaelle Spagnol
- From the Department of Biochemistry and Molecular Biology and
| | - Sylvie Chenavas
- From the Department of Biochemistry and Molecular Biology and
| | - Fabien Kieken
- From the Department of Biochemistry and Molecular Biology and
| | - Heidi Vitrac
- the Laboratoire de Chimie et Biologie des Métaux (UMR 5249), Commissariat à l'Energie Atomique, 17 rue des Martyrs, Grenoble F-38054, France
| | - Sarah Brownell
- From the Department of Biochemistry and Molecular Biology and
| | - Admir Kellezi
- the Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198 and
| | - Vincent Forge
- the Laboratoire de Chimie et Biologie des Métaux (UMR 5249), Commissariat à l'Energie Atomique, 17 rue des Martyrs, Grenoble F-38054, France
| | - Paul L. Sorgen
- From the Department of Biochemistry and Molecular Biology and
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31
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Heyman NS, Kurjiaka DT, Ek Vitorin JF, Burt JM. Regulation of gap junctional charge selectivity in cells coexpressing connexin 40 and connexin 43. Am J Physiol Heart Circ Physiol 2009; 297:H450-9. [PMID: 19465552 PMCID: PMC2711728 DOI: 10.1152/ajpheart.00287.2009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/24/2009] [Accepted: 05/20/2009] [Indexed: 11/22/2022]
Abstract
Expression of connexin 40 (Cx40) and Cx43 in cardiovascular tissues varies as a function of age, injury, and development with unknown consequences on the selectivity of junctional communication and its acute regulation. We investigated the PKC-dependent regulation of charge selectivity in junctions composed of Cx43, Cx40, or both by simultaneous assessment of junctional permeance rate constants (B(dye)) for dyes of similar size but opposite charge, N,N,N-trimethyl-2-[methyl-(7-nitro-2,1,3-benzoxadiol-4-yl)amino]ethanaminium (NBD-M-TMA; +1) and Alexa 350 (-1). The ratio of dye rate constants (B(NBD-M-TMA)/B(Alexa 350)) indicated that Cx40 junctions are cation selective (10.7 +/- 0.5), whereas Cx43 junction are nonselective (1.22 +/- 0.14). In coexpressing cells, a broad range of junctional selectivities was observed with mean cation selectivity increasing as the Cx40 to Cx43 expression ratio increased. PKC activation reduced or eliminated dye permeability of Cx43 junctions without altering their charge selectivity, had no effect on either permeability or charge selectivity of Cx40 junctions, and significantly increased the cation selectivity of junctions formed by coexpressing cells (approaching charge selectivity of Cx40 junctions). Junctions composed of Cx43 truncated at residue 257 (Cx43tr) were also not charge selective, but when Cx43tr was coexpressed with Cx40, a broad range of junctional selectivities that was unaffected by PKC activation was observed. Thus, whereas the charge selectivities of homomeric/homotypic Cx43 and Cx40 junctions appear invariant, the selectivities of junctions formed by cells coexpressing Cx40 and Cx43 vary considerably, reflecting both their relative expression levels and phosphorylation-dependent regulation. Such regulation could represent a mechanism by which coexpressing cells such as vascular endothelium and atrial cells regulate acutely the selective intercellular communication mediated by their gap junctions.
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Isakson BE. Localized expression of an Ins(1,4,5)P3 receptor at the myoendothelial junction selectively regulates heterocellular Ca2+ communication. J Cell Sci 2009; 121:3664-73. [PMID: 18946029 DOI: 10.1242/jcs.037481] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Inositol (1,4,5)-trisphosphate [Ins(1,4,5)P(3)] originating in the vascular smooth-muscle cells (VSMCs) has been shown to modulate the Ca(2+) stores in endothelial cells (ECs). However, the reverse is not found, suggesting that Ins(1,4,5)P(3) movement might be unidirectional across gap junctions at the myoendothelial junction (MEJ), or that distribution of the Ins(1,4,5)P(3) receptor [Ins(1,4,5)P(3)-R] is different between the two cell types. To study trans-junctional communication at the MEJ, we used a vascular-cell co-culture model system and selectively modified the connexin composition in gap junctions in the two cell types. We found no correlation between modification of connexin expression and Ins(1,4,5)P(3) signaling between ECs and VSMCs. We next explored the distribution of Ins(1,4,5)P(3)-R isoforms in the two cell types and found that Ins(1,4,5)P(3)-R1 was selectively localized to the EC side of the MEJ. Using siRNA, selective knockdown of Ins(1,4,5)P(3)-R1 in ECs eliminated the secondary Ins(1,4,5)P(3)-induced response in these cells. By contrast, siRNA knockdown of Ins(1,4,5)P(3)-R2 or Ins(1,4,5)P(3)-R3 in ECs did not alter the EC response to VSMC stimulation. The addition of 5-phosphatase inhibitor (5-PI) to ECs that were transfected with Ins(1,4,5)P(3)-R1 siRNA rescued the Ins(1,4,5)P(3) response, indicating that metabolic degradation of Ins(1,4,5)P(3) is an important part of EC-VSMC coupling. To test this concept, VSMCs were loaded with 5-PI and BAPTA-loaded ECs were stimulated, inducing an Ins(1,4,5)P(3)-mediated response in VSMCs; this indicated that Ins(1,4,5)P(3) is bidirectional across the gap junction at the MEJ. Therefore, localization of Ins(1,4,5)P(3)-R1 on the EC side of the MEJ allows the ECs to respond to Ins(1,4,5)P(3) from VSMCs, whereas Ins(1,4,5)P(3) moving from ECs to VSMCs is probably metabolized before binding to a receptor. This data implicates the MEJ as being a unique cell-signaling domain in the vasculature.
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Affiliation(s)
- Brant E Isakson
- Robert M. Berne Cardiovascular Research Center, and Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, P.O. Box 801394, Charlottesville, VA 22908, USA.
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Abstract
Direct intercellular communication via gap junctions is critical in the control and coordination of vascular function. In the cardiovascular system, gap junctions are made up of one or more of four connexin proteins: Cx37, Cx40, Cx43, and Cx45. The expression of more than one gap-junction protein in the vasculature is not redundant. Rather, vascular connexins work in concert, first during the development of the cardiovascular system, and then in integrating smooth muscle and endothelial cell function, and in coordinating cell function along the length of the vessel wall. In addition, connexin-based channels have emerged as an important signaling pathway in the astrocyte-mediated neurovascular coupling. Direct electrical communication between endothelial cells and vascular smooth muscle cells via gap junctions is thought to play a relevant role in the control of vasomotor tone, providing the signaling pathway known as endothelium-derived hyperpolarizing factor (EDHF). Consistent with the importance of gap junctions in the regulation of vasomotor tone and arterial blood pressure, the expression of connexins is altered in diseases associated with vascular complications. In this review, we discuss the participation of connexin-based channels in the control of vascular function in physiologic and pathologic conditions, with a special emphasis on hypertension and diabetes.
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Affiliation(s)
- Xavier F Figueroa
- Departamento de Ciencias Fisiológicas, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.
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Johnstone S, Isakson B, Locke D. Biological and biophysical properties of vascular connexin channels. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2009; 278:69-118. [PMID: 19815177 PMCID: PMC2878191 DOI: 10.1016/s1937-6448(09)78002-5] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Intercellular channels formed by connexin proteins play a pivotal role in the direct movement of ions and larger cytoplasmic solutes between vascular endothelial cells, between vascular smooth muscle cells, and between endothelial and smooth muscle cells. Multiple genetic and epigenetic factors modulate connexin expression levels and/or channel function, including cell-type-independent and cell-type-specific transcription factors, posttranslational modifications, and localized membrane targeting. Additionally, differences in protein-protein interactions, including those between connexins, significantly contribute to both vascular homeostasis and disease progression. The biophysical properties of the connexin channels identified in the vasculature, those formed by Cx37, Cx40, Cx43 and/or Cx45 proteins, are discussed in this chapter in the physiological and pathophysiological context of vessel function.
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Affiliation(s)
- Scott Johnstone
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA 29908
| | - Brant Isakson
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA 29908
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA 29908
| | - Darren Locke
- Department of Pharmacology and Physiology, New Jersey Medical School, University of Medicine and Dentistry of New Jersey, Newark, NJ 07103
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35
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36
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Burt JM, Nelson TK, Simon AM, Fang JS. Connexin 37 profoundly slows cell cycle progression in rat insulinoma cells. Am J Physiol Cell Physiol 2008; 295:C1103-12. [PMID: 18753315 PMCID: PMC2584977 DOI: 10.1152/ajpcell.299.2008] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2008] [Accepted: 08/23/2008] [Indexed: 12/19/2022]
Abstract
In addition to providing a pathway for intercellular communication, the gap junction-forming proteins, connexins, can serve a growth-suppressive function that is both connexin and cell-type specific. To assess its potential growth-suppressive function, we stably introduced connexin 37 (Cx37) into connexin-deficient, tumorigenic rat insulinoma (Rin) cells under the control of an inducible promoter. Proliferation of these iRin37 cells, when induced to express Cx37, was profoundly slowed: cell cycle time increased from 2 to 9 days. Proliferation and cell cycle time of Rin cells expressing Cx40 or Cx43 did not differ from Cx-deficient Rin cells. Cx37 suppressed Rin cell proliferation irrespective of cell density at the time of induced expression and without causing apoptosis. All phases of the cell cycle were prolonged by Cx37 expression, and progression through the G(1)/S checkpoint was delayed, resulting in accumulation of cells at this point. Serum deprivation augmented the effect of Cx37 to accumulate cells in late G(1). Cx43 expression also affected cell cycle progression of Rin cells, but its effects were opposite to Cx37, with decreases in G(1) and increases in S-phase cells. These effects of Cx43 were also augmented by serum deprivation. Cx-deficient Rin cells were unaffected by serum deprivation. Our results indicate that Cx37 expression suppresses cell proliferation by significantly increasing cell cycle time by extending all phases of the cell cycle and accumulating cells at the G(1)/S checkpoint.
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Affiliation(s)
- Janis M Burt
- Dept. of Physiology, P. O. Box 245051, Univ. of Arizona, Tucson, AZ 85724, USA.
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37
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Schulte JS, Scheffler A, Rojas-Gomez D, Mohr FW, Dhein S. Neonatal rat cardiomyocytes show characteristics of nonhomotypic gap junction channels. CELL COMMUNICATION & ADHESION 2008; 15:13-25. [PMID: 18649175 DOI: 10.1080/15419060802014404] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Neonatal rat cardiomyocytes mainly coexpress the connexins Cx40, Cx43, and to a small amount Cx45, leading to potential formation of mixed (heteromeric/heterotypic) gap junction channels. Using the dual-voltage clamp technique with switching clamp circuits, the authors investigated voltage sensitivity of gap junction channels between cell pairs of Cx40, Cx43, and Cx45 stably transfected HeLa cells and compared those data to data obtained from cell pairs of cultured neonatal rat cardiomyocytes. In accordance to previously published data, the relationship between normalized conductance and transjunctional voltage (g/V(j)) was quasisymmetrical for the transfected HeLa cells, indicating homotypic gap junction channels. Boltzmann curves fitted to data obtained from neonatal rat cardiomyocyte pairs expressing both Cx40 and Cx43 showed an asymmetrical inactivation pattern, which cannot be explained by the presence of pure populations of homotypic gap junction channels of either isoform. In conclusion the authors assume the additional presence of heterotypic and possibly even heteromeric gap junction channels in neonatal rat cardiomyocytes.
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Affiliation(s)
- Jan Sebastian Schulte
- Institut fur Pharmakologie und Toxikologie, Universitatsklinikum Münster, Münster, Germany.
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38
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Bouvier D, Kieken F, Kellezi A, Sorgen P. Structural changes in the carboxyl terminus of the gap junction protein connexin 40 caused by the interaction with c-Src and zonula occludens-1. CELL COMMUNICATION & ADHESION 2008; 15:107-18. [PMID: 18649183 PMCID: PMC2917908 DOI: 10.1080/15419060802014347] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
c-Src can disrupt the connexin 43 (Cx43) and zonula occludens-1 (ZO-1) interaction, leading to down-regulation of gap junction intercellular communication. Previously, the authors characterized the interaction of domains from these proteins with the carboxyl terminus of Cx43 (Cx43CT) and found that binding of the c-Src SH3 domain to Cx43CT disrupted the Cx43CT/ZO-1 PDZ-2 domain complex. Because Cx43 and Cx40 form heteromeric connexons and display similar mechanisms of pH regulation, the authors addressed whether Cx40CT interacts with these domains in a similar manner as Cx43CT. Nuclear magnetic resonance (NMR) data indicate that Cx40CT is an intrinsically disordered protein. NMR titrations determined that PDZ-2 affected the last 28 Cx40CT residues and SH3 shifted numerous amino-terminal Cx40CT residues. Finally, the Cx40CT/PDZ-2 complex was unaffected by SH3 and both domains interacted simultaneously with Cx40CT. This result differs from when the same experiment was performed with Cx43CT, suggesting different mechanisms of regulation exist between connexin isoforms, even when involving the same molecular partners.
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Affiliation(s)
- Denis Bouvier
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE 68198
| | - Fabien Kieken
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE 68198
| | - Admir Kellezi
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE 68198
| | - Paul Sorgen
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE 68198
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39
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Mathias RT, White TW, Brink PR. Chapter 3 The Role of Gap Junction Channels in the Ciliary Body Secretory Epithelium. CURRENT TOPICS IN MEMBRANES 2008. [DOI: 10.1016/s1063-5823(08)00403-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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40
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Penuela S, Bhalla R, Gong XQ, Cowan KN, Celetti SJ, Cowan BJ, Bai D, Shao Q, Laird DW. Pannexin 1 and pannexin 3 are glycoproteins that exhibit many distinct characteristics from the connexin family of gap junction proteins. J Cell Sci 2007; 120:3772-83. [PMID: 17925379 DOI: 10.1242/jcs.009514] [Citation(s) in RCA: 331] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Pannexins are mammalian orthologs of the invertebrate gap junction proteins innexins and thus have been proposed to play a role in gap junctional intercellular communication. Localization of exogenously expressed pannexin 1 (Panx1) and pannexin 3 (Panx3), together with pharmacological studies, revealed a cell surface distribution profile and life cycle dynamics that were distinct from connexin 43 (Cx43, encoded by Gja1). Furthermore, N-glycosidase treatment showed that both Panx1 (approximately 41-48 kD species) and Panx3 (approximately 43 kD) were glycosylated, whereas N-linked glycosylation-defective mutants exhibited a decreased ability to be transported to the cell surface. Tissue surveys revealed the expression of Panx1 in several murine tissues--including in cartilage, skin, spleen and brain--whereas Panx3 expression was prevalent in skin and cartilage with a second higher-molecular-weight species present in a broad range of tissues. Tissue-specific localization patterns of Panx1 and Panx3 ranging from distinct cell surface clusters to intracellular profiles were revealed by immunostaining of skin and spleen sections. Finally, functional assays in cultured cells transiently expressing Panx1 and Panx3 were incapable of forming intercellular channels, but assembled into functional cell surface channels. Collectively, these studies show that Panx1 and Panx3 have many characteristics that are distinct from Cx43 and that these proteins probably play an important biological role as single membrane channels.
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Affiliation(s)
- Silvia Penuela
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON, N6A 5C1, Canada
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41
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Hindered diffusion through an aqueous pore describes invariant dye selectivity of Cx43 junctions. Biophys J 2007; 94:840-54. [PMID: 17921206 DOI: 10.1529/biophysj.107.115634] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The permselectivity (permeance/conductance) of Cx43-comprised gap junctions is a variable parameter of junctional function. To ascertain whether this variability in junctional permselectivity is explained by heterogeneous charge or size selectivity of the comprising channels, the permeance of individual Cx43 gap junctions to combinations of two dyes differing in either size or charge was determined in four cell types: Rin43, NRKe, HeLa43, and cardiac myocytes. The results show that Cx43 junctions are size- but not charge-selective and that both selectivities are constant parameters of junctional function. The consistency of dye selectivities indicates that the large continuum of measured junctional permselectivities cannot be ascribed to an equivalent continuum of individual channel selectivities. Further, the relative dye permeance sequence of NBD-M-TMA approximately Alexa 350 > Lucifer yellow > Alexa 488 >> Alexa 594 (Stokes radii of 4.3 A, 4.4 A, 4.9 A, 5.8 A, and 7.4 A, respectively) and the conductance sequence of KCl > TEACl approximately Kglutamate are well described by hindered diffusion through an aqueous pore with radius approximately 10 A and length 160 A. The permselectivity and dye selectivity data suggest the variable presence in Cx43-comprised junctions of conductive channels that are either dye-impermeable or dye-permeable.
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42
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Duffy HS, Wit AL. Is there a role for remodeled connexins in AF? No simple answers. J Mol Cell Cardiol 2007; 44:4-13. [PMID: 17935733 DOI: 10.1016/j.yjmcc.2007.08.016] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2007] [Revised: 08/20/2007] [Accepted: 08/22/2007] [Indexed: 01/19/2023]
Abstract
Gap junctions provide direct cytoplasmic continuity between cells forming a low resistivity barrier to electrical propagation. As such, aberrant regulation of these low resistive conduits has been blamed for electrical conduction disorders in diseased myocardium. While there is a plethora of evidence that abnormalities in gap junctional communication underlie many forms of ventricular arrhythmias, the role of gap junctions in atrial conduction disorders has been less well studied. The atria are the most heterogeneous cardiac structures in terms of the gap junction proteins, connexins (Cx), which are present. Cx40 is the primary, or most abundant, gap junction protein in atria although Cx43 is also abundantly expressed. Cx45 is also expressed in atria, although at low levels. This heterogeneity in connexins leads to a complexity that makes understanding the role of cell coupling in conduction disorders and arrhythmogenesis difficult. In this review we focus on what is known about atrial connexins and their role in atrial fibrillation but also on the challenges presented in understanding the complex interplay between the individual connexin isoforms.
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43
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Desplantez T, Dupont E, Severs NJ, Weingart R. Gap junction channels and cardiac impulse propagation. J Membr Biol 2007; 218:13-28. [PMID: 17661127 DOI: 10.1007/s00232-007-9046-8] [Citation(s) in RCA: 121] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2007] [Accepted: 05/15/2007] [Indexed: 11/25/2022]
Abstract
The role of gap junction channels on cardiac impulse propagation is complex. This review focuses on the differential expression of connexins in the heart and the biophysical properties of gap junction channels under normal and disease conditions. Structural determinants of impulse propagation have been gained from biochemical and immunocytochemical studies performed on tissue extracts and intact cardiac tissue. These have defined the distinctive connexin coexpression patterns and relative levels in different cardiac tissues. Functional determinants of impulse propagation have emerged from electrophysiological experiments carried out on cell pairs. The static properties (channel number and conductance) limit the current flow between adjacent cardiomyocytes and thus set the basic conduction velocity. The dynamic properties (voltage-sensitive gating and kinetics of channels) are responsible for a modulation of the conduction velocity during propagated action potentials. The effect is moderate and depends on the type of Cx and channel. For homomeric-homotypic channels, the influence is small to medium; for homomeric-heterotypic channels, it is medium to strong. Since no data are currently available on heteromeric channels, their influence on impulse propagation is speculative. The modulation by gap junction channels is most prominent in tissues at the boundaries between cardiac tissues such as sinoatrial node-atrial muscle, atrioventricular node-His bundle, His bundle-bundle branch and Purkinje fibers-ventricular muscle. The data predict facilitation of orthodromic propagation.
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Affiliation(s)
- Thomas Desplantez
- Institute of Physiology, University of Bern, Bühlplatz 5, Bern, Switzerland
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44
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Locke D, Jamieson S, Stein T, Liu J, Hodgins MB, Harris AL, Gusterson B. Nature of Cx30-containing channels in the adult mouse mammary gland. Cell Tissue Res 2007; 328:97-107. [PMID: 17120054 DOI: 10.1007/s00441-006-0301-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2006] [Accepted: 07/12/2006] [Indexed: 10/23/2022]
Abstract
Oligonucleotide microarray analysis uniquely shows that several members of the connexin family of gap junction proteins are expressed by the epithelium during mouse mammary gland development. Connexin 26 (Cx26) is present throughout pregnancy and lactation, is then undetectable shortly after weaning, but reappears during involution. Additionally, Cx30 is abundant in late-pregnant and early lactating gland epithelium. From mid-pregnancy into early lactation, Cx26 and Cx30 co-localize in junctional plaques between epithelial cells, forming hemichannels of mixed connexin content. Microarray analysis also shows Cx32 is developmentally restricted to parturition, suggesting that specific modification of gap junction channel composition and/or intercellular communication pathways occurs at parturition. Specifically, heteromeric channels of all pairwise combinations are formed when these connexins are expressed within the same cells. Of these hemichannels, Cx26/Cx32 pores are increasingly sensitive to closure by taurine (an osmolyte implicated in milk protein synthesis) with increasing Cx26 content. In contrast, physiological taurine concentrations have no effect on Cx26/Cx30 and Cx30/Cx32 channel activity. Such changes in connexin expression and channel composition and their chemical modulation are discussed in relation to the various stages of mammary gland development in the adult mouse.
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Affiliation(s)
- Darren Locke
- Department of Pharmacology and Physiology, New Jersey Medical School, UMDNJ, Newark, NJ 07103, USA.
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45
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Moreno AP, Lau AF. Gap junction channel gating modulated through protein phosphorylation. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2007; 94:107-19. [PMID: 17507079 PMCID: PMC1973155 DOI: 10.1016/j.pbiomolbio.2007.03.004] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
As a ubiquitous post-translation modification process, protein phosphorylation has proven to be a key mechanism in regulating the function of several membrane proteins, including transporters and channels. Connexins, pannexins, and innexins are protein families that form gap junction channels essential for intercellular communication. Connexins have been intensely studied, and most of their isoforms are known to be phosphorylated by protein kinases that lead to modifications in tyrosine, serine, and threonine residues, which have been reported to affect, in one way or another, intercellular communication. Despite the abundant reports on changes in intercellular communication due to the activation or inactivation of numerous kinases, the molecular mechanisms by which phosphorylation alters channel gating properties have not been elucidated completely. Hence, this chapter will cover some of the current, relevant research that attempt to explain how phosphorylation triggers and/or modulates gap junction channel gating.
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Affiliation(s)
- Alonso P Moreno
- Department of Internal Medicine, University of Utah, Nora Eccles Cardiovascular Research and Training Institute, Salt Lake City, UT 84112, USA.
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46
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Rackauskas M, Kreuzberg MM, Pranevicius M, Willecke K, Verselis VK, Bukauskas FF. Gating properties of heterotypic gap junction channels formed of connexins 40, 43, and 45. Biophys J 2007; 92:1952-65. [PMID: 17189315 PMCID: PMC1861779 DOI: 10.1529/biophysj.106.099358] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2006] [Accepted: 12/04/2006] [Indexed: 11/18/2022] Open
Abstract
Connexins (Cxs) 40, 43, and 45 are expressed in many different tissues, but most abundantly in the heart, blood vessels, and the nervous system. We examined formation and gating properties of heterotypic gap junction (GJ) channels assembled between cells expressing wild-type Cx40, Cx43, or Cx45 and their fusion forms tagged with color variants of green fluorescent protein. We show that these Cxs, with exception of Cxs 40 and 43, are compatible to form functional heterotypic GJ channels. Cx40 and Cx43 hemichannels are unable or effectively impaired in their ability to dock and/or assemble into junctional plaques. When cells expressing Cx45 contacted those expressing Cx40 or Cx43 they readily formed junctional plaques with cell-cell coupling characterized by asymmetric junctional conductance dependence on transjunctional voltage, V(j). Cx40/Cx45 heterotypic GJ channels preferentially exhibit V(j)-dependent gating transitions between open and residual states with a conductance of approximately 42 pS; transitions between fully open and closed states with conductance of approximately 52 pS in magnitude occur at substantially lower ( approximately 10-fold) frequency. Cx40/Cx45 junctions demonstrate electrical signal transfer asymmetry that can be modulated between unidirectional and bidirectional by small changes in the difference between holding potentials of the coupled cells. Furthermore, both fast and slow gating mechanisms of Cx40 exhibit a negative gating polarity.
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Affiliation(s)
- Mindaugas Rackauskas
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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Kreuzberg MM, Willecke K, Bukauskas FF. Connexin-mediated cardiac impulse propagation: connexin 30.2 slows atrioventricular conduction in mouse heart. Trends Cardiovasc Med 2007; 16:266-72. [PMID: 17055382 PMCID: PMC3615414 DOI: 10.1016/j.tcm.2006.05.002] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/20/2006] [Revised: 05/26/2006] [Accepted: 05/30/2006] [Indexed: 10/24/2022]
Abstract
In mouse heart, four connexins (Cxs), Cx30.2, Cx40, Cx43, and Cx45, form gap junction (GJ) channels for electric and metabolic cell-to-cell signaling. Extent and pattern of Cx isoform expression together with cytoarchitecture and excitability of cells determine the velocity of excitation spread in different regions of the heart. In the SA node, cell-cell coupling is mediated by Cx30.2 and Cx45, which form low-conductance (approximately 9 and 32 pS, respectively) GJ channels. In contrast, the working cardiomyocytes of atria and ventricles express mainly Cx40 and Cx43, which form GJ channels of high conductance (approximately 180 and 115 pS, respectively) that facilitate the fast conduction necessary for efficient mechanical contraction. In the AV node, cell-cell coupling is mediated by abundantly expressed Cx30.2 and Cx45 and Cx40, which is expressed to a lesser extent. Cx30.2 and Cx45 may determine higher intercellular resistance and slower conduction in the SA- and AV-nodal regions than in the ventricular conduction system or the atrial and ventricular working myocardium. Cx30.2 and its putative human ortholog, Cx31.9, under physiologic conditions form unapposed hemichannels in nonjunctional plasma membrane; these hemichannels have a conductance of approximately 20 pS and are permeable to cationic dyes up to approximately 400 Da in molecular mass. Genetic ablation of Cxs confirmed that Cx40 and Cx43 are important in determining the high conduction velocities in atria and ventricles, whereas the deletion of the Cx30.2 complementary DNA led to accelerated conduction in the AV node and reduced the Wenckebach period. We suggest that these effects are caused by (1) a dominant-negative effect of Cx30.2 on junctional conductance via formation of low-conductance homotypic and heterotypic GJ channels, and (2) open Cx30.2 hemichannels in non-junctional membranes, which shorten the space constant and depolarize the excitable membrane.
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Affiliation(s)
- Maria M. Kreuzberg
- Institut für Genetik, Abteilung Molekulargenetik, Universität Bonn, 53117 Bonn, Germany
| | - Klaus Willecke
- Institut für Genetik, Abteilung Molekulargenetik, Universität Bonn, 53117 Bonn, Germany
| | - Feliksas F. Bukauskas
- Address correspondence to: Dr. Feliksas Bukauskas, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY, 10461, USA. Tel.: (+1) 718-430-4130; fax: (+1) 718-430-8944; ,
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Abstract
Second messenger signaling between endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) is poorly understood, but intracellular Ca2+ concentrations ([Ca2+]i) in the 2 cells are coordinated, possibly through gap junctions at the myoendothelial junction. To study heterocellular calcium signaling, we used a vascular cell coculture model composed of monolayers of ECs and VSMCs. Stimulation of either cell type leads to an increase in [Ca2+]i in the stimulated cell and a secondary increase in [Ca2+]i in the other cell type that was blocked by gap junction inhibitors. To determine which second messengers are involved, we initially depleted Ca2+ stores in the endoplasmic reticulum Ca2+ with thapsigargin in ECs or VSMCs, but this had no effect on heterocellular calcium signaling. Alternatively, we loaded ECs or VSMCs with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) to buffer changes in [Ca2+]i. BAPTA loading of ECs inhibited agonist-induced increases in intracellular calcium concentration ([Ca2+]i), in both ECs and VSMCs. In contrast, BAPTA loading of the VSMCs blunted the VSMC response but did not alter the secondary increase in EC [Ca2+]i. Xestospongin C (an inositol 1,4,5-trisphosphate receptor inhibitor) had no effect on the secondary Ca2+ response, but when xestospongin C or thapsigargin was loaded into ECs and BAPTA into VSMCs, intercellular Ca2+ signaling was completely blocked. We conclude that 1,4,5-trisphosphate and Ca2+ originating in the VSMCs induces the secondary increase in EC [Ca2+]i but stimulation of the ECs generates a Ca2+ dependent response in the VSMCs.
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MESH Headings
- Animals
- Calcium/physiology
- Calcium Signaling/physiology
- Cell Communication/physiology
- Cells, Cultured
- Endothelium, Vascular/cytology
- Endothelium, Vascular/metabolism
- Endothelium, Vascular/physiology
- Gap Junctions/physiology
- Inositol 1,4,5-Trisphosphate/physiology
- Mice
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/metabolism
- Muscle, Smooth, Vascular/physiology
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Affiliation(s)
- Brant E Isakson
- Department of Molecular Physiology and Biological Physics, Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville 22908, USA.
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Affiliation(s)
- Xavier F Figueroa
- Unidad de Regulación Neurohumoral, Departamento de Ciencias Fisiológicas, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
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Isakson BE, Kronke G, Kadl A, Leitinger N, Duling BR. Oxidized phospholipids alter vascular connexin expression, phosphorylation, and heterocellular communication. Arterioscler Thromb Vasc Biol 2006; 26:2216-21. [PMID: 16857951 DOI: 10.1161/01.atv.0000237608.19055.53] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE In endothelial cells (EC) and vascular smooth muscle cells (VSMC) from atherosclerotic mice, connexin (Cx) expression becomes distorted. Lipoprotein-derived phospholipid oxidation products (OxPAPC) play a critical role in atherosclerosis, and we hypothesized that they may act as trigger molecules causing the changes in connexin expression. METHODS AND RESULTS We applied OxPAPC to murine carotid arteries in vivo and vascular cell cocultures. OxPAPC applied to carotids induced an upregulation of both Cx37 and Cx43 in the VSMC. In EC, Cx43 was upregulated and Cx37 was downregulated, whereas Cx40 in EC remained constant. In the vascular cell coculture, OxPAPC caused similar changes in Cx37 and Cx43 but caused a decrease in Cx40 in EC and an elevation of Cx40 in VSMC. In the coculture model, OxPAPC treatment led to the selective disappearance of Cx40 at the myoendothelial junction. Biocytin dye transfer between EC and VSMC coupling was dramatically reduced by OxPAPC. The decrease in dye transfer after OxPAPC treatment was correlated with an increase in tyrosine 265 phosphorylation of Cx43, especially at the in vitro myoendothelial junction. CONCLUSIONS We conclude that OxPAPC could be responsible for the changes in connexin expression previously reported in atherosclerosis.
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MESH Headings
- Animals
- Blood Vessels/cytology
- Blood Vessels/drug effects
- Blood Vessels/metabolism
- Carotid Arteries/drug effects
- Carotid Arteries/metabolism
- Cell Communication/physiology
- Cells, Cultured
- Coculture Techniques
- Connexin 43/metabolism
- Connexins/metabolism
- Endothelial Cells/drug effects
- Endothelial Cells/metabolism
- Gap Junctions/drug effects
- Gap Junctions/metabolism
- Lysine/analogs & derivatives
- Lysine/pharmacokinetics
- Mice
- Mice, Inbred C57BL
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/metabolism
- Permeability/drug effects
- Phosphatidylcholines/pharmacology
- Phosphorylation
- Gap Junction alpha-5 Protein
- Gap Junction alpha-4 Protein
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Affiliation(s)
- Brant E Isakson
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA.
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