301
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Begandt D, Bader A, Dreyer L, Eisert N, Reeck T, Ngezahayo A. Biphasic increase of gap junction coupling induced by dipyridamole in the rat aortic A-10 vascular smooth muscle cell line. J Cell Commun Signal 2013; 7:151-60. [PMID: 23483357 DOI: 10.1007/s12079-013-0196-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Accepted: 02/18/2013] [Indexed: 12/11/2022] Open
Abstract
The rat aortic smooth muscle cell line A-10 was used to investigate the effect of dipyridamole on the gap junction coupling of smooth muscle cells. The scrape loading/dye transfer (SL/DT) technique revealed that dipyridamole concentrations between 5 μM and 100 μM significantly increased gap junction coupling. The adenosine receptor antagonist MRS 1754, as well as the PKA inhibitors Rp-cAMPS and H-89 were able to inhibit the dipyridamole-related increase in coupling, while forskolin and Br-cAMP also induced an enhancement of the gap junction coupling. Regarding the time-dependent behaviour of dipyridamole, a short-term effect characterised by an oscillatory reaction was observed for application times of less than 5 h, while applications times of at least 6 h resulted in a long-term effect, characterised by a constant increase of gap junction coupling to its maximum levels. This increase was not altered by prolonged presence of dipyridamole. In parallel, a short application of dipyridamole for at least 15 min was found to be sufficient to evoke the long-term effect measured 6 h after drug washout. We propose that in both the short-term and long-term effect, cAMP-related pathways are activated. The short-term phase could be related to an oscillatory cAMP effect, which might directly affect connexin trafficking, assembly and/or gap junction gating. The long-term effect is most likely related to the new expression and synthesis of connexins. With previous data from a bovine aortic endothelial cell line, the present results show that gap junction coupling of vascular cells is a target for dipyridamole.
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Affiliation(s)
- Daniela Begandt
- Institute of Biophysics, Leibniz University Hannover, Herrenhäuserstr. 2, 30419, Hannover, Germany
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302
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Syed-Picard FN, Jayaraman T, Lam RSK, Beniash E, Sfeir C. Osteoinductivity of calcium phosphate mediated by connexin 43. Biomaterials 2013; 34:3763-74. [PMID: 23465492 DOI: 10.1016/j.biomaterials.2013.01.095] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Accepted: 01/26/2013] [Indexed: 11/25/2022]
Abstract
Recent reports have alluded to the osteoinductive properties of calcium phosphate, yet the cellular processes behind this are not well understood. To gain insight into the molecular mechanisms of this phenomenon, we have conducted a series of in vitro and in vivo experiments using a scaffoldless three dimensional (3D) dental pulp cell (DPC) construct as a physiologically relevant model. We demonstrate that amorphous calcium phosphate (ACP) alters cellular functions and 3D spatial tissue differentiation patterns by increasing local calcium concentration, which modulates connexin 43 (Cx43)-mediated gap junctions. These observations indicate a chemical mechanism for osteoinductivity of calcium phosphates. These results provide new insights for possible roles of mineral phases in bone formation and remodeling. This study also emphasizes the strong effect of scaffold materials on cellular functions and is expected to advance the design of future tissue engineering materials.
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Affiliation(s)
- Fatima N Syed-Picard
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15260, USA
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303
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Zhao JQ, Sun FJ, Liu SS, Yang J, Wu YQ, Li GS, Chen QY, Wang JX. Expression of Connexin 43 and E-cadherin Protein and mRNA in Non-small Cell Lung Cancers in Chinese Patients. Asian Pac J Cancer Prev 2013; 14:639-43. [DOI: 10.7314/apjcp.2013.14.2.639] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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304
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Lee D, Oka T, Hunter B, Robinson A, Papp S, Nakamura K, Srisakuldee W, Nickel BE, Light PE, Dyck JRB, Lopaschuk GD, Kardami E, Opas M, Michalak M. Calreticulin induces dilated cardiomyopathy. PLoS One 2013; 8:e56387. [PMID: 23437120 PMCID: PMC3577809 DOI: 10.1371/journal.pone.0056387] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Accepted: 01/08/2013] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Calreticulin, a Ca(2+)-buffering chaperone of the endoplasmic reticulum, is highly expressed in the embryonic heart and is essential for cardiac development. After birth, the calreticulin gene is sharply down regulated in the heart, and thus, adult hearts have negligible levels of calreticulin. In this study we tested the role of calreticulin in the adult heart. METHODOLOGY/PRINCIPAL FINDINGS We generated an inducible transgenic mouse in which calreticulin is targeted to the cardiac tissue using a Cre/loxP system and can be up-regulated in adult hearts. Echocardiography analysis of hearts from transgenic mice expressing calreticulin revealed impaired left ventricular systolic and diastolic function and impaired mitral valve function. There was altered expression of Ca(2+) signaling molecules and the gap junction proteins, Connexin 43 and 45. Sarcoplasmic reticulum associated Ca(2+)-handling proteins (including the cardiac ryanodine receptor, sarco/endoplasmic reticulum Ca(2+)-ATPase, and cardiac calsequestrin) were down-regulated in the transgenic hearts with increased expression of calreticulin. CONCLUSIONS/SIGNIFICANCE We show that in adult heart, up-regulated expression of calreticulin induces cardiomyopathy in vivo leading to heart failure. This is due to an alternation in changes in a subset of Ca(2+) handling genes, gap junction components and left ventricle remodeling.
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Affiliation(s)
- Dukgyu Lee
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
| | - Tatsujiro Oka
- Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada
| | - Beth Hunter
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada
| | - Alison Robinson
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
| | - Sylvia Papp
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
| | - Kimitoshi Nakamura
- Department of Pediatrics, Kumamoto University School of Medicine, Kumamoto, Japan
| | - Wattamon Srisakuldee
- Department of Human Anatomy and Cell Sciences, and Physiology and Institute of Cardiovascular Sciences, St. Boniface Research Centre, University of Manitoba, Winnipeg, Canada
| | - Barbara E. Nickel
- Department of Human Anatomy and Cell Sciences, and Physiology and Institute of Cardiovascular Sciences, St. Boniface Research Centre, University of Manitoba, Winnipeg, Canada
| | - Peter E. Light
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada
| | - Jason R. B. Dyck
- Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada
| | - Gary D. Lopaschuk
- Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada
| | - Elissavet Kardami
- Department of Human Anatomy and Cell Sciences, and Physiology and Institute of Cardiovascular Sciences, St. Boniface Research Centre, University of Manitoba, Winnipeg, Canada
| | - Michal Opas
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
| | - Marek Michalak
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
- * E-mail:
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305
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Ke Q, Li L, Cai B, Liu C, Yang Y, Gao Y, Huang W, Yuan X, Wang T, Zhang Q, Harris AL, Tao L, Xiang AP. Connexin 43 is involved in the generation of human-induced pluripotent stem cells. Hum Mol Genet 2013; 22:2221-33. [PMID: 23420013 DOI: 10.1093/hmg/ddt074] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Although somatic cells can be successfully programmed to create pluripotent stem cells by ectopically expressing defined transcriptional factors, reprogramming efficiency is low and the reprogramming mechanism remains unclear. Previous reports have shown that almost all human connexin (CX) isoforms are expressed by human embryonic stem (hES) cells and that gap junctional intercellular communication (GJIC) is important for ES cell survival and differentiation. However, the CX expression profiles in human induced pluripotent stem (iPS) cells and the role of CXs in the process of reprogramming back to iPS cells remains unknown. Here, we determined the expression levels of most forms of CX in human embryonic fibroblasts (hEFs) and in the hEF-derived iPS cells. A scrape loading/dye transfer assay showed that human iPS cells contained functional gap junctions (GJs) that could be affected by pharmacological inhibitors of GJ function. We found that CX43 was the most dramatically upregulated CX following reprogramming. Most importantly, the ectopic expression of CX43 significantly enhanced the reprogramming efficiency, whereas shRNA-mediated knockdown of endogenous CX43 expression greatly reduced the efficiency. In addition, we found that CX43 overexpression or knockdown affected the expression of E-CADHERIN, a marker of the mesenchymal-to-epithelial transition (MET), during reprogramming. In conclusion, our data indicate that CX43 expression is important for reprogramming and may mediate the MET that is associated with the acquisition of pluripotency.
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Affiliation(s)
- Qiong Ke
- Center for Stem Cell Biology and Tissue Engineering, Key Laboratory for Stem Cells and Tissue Engineering, Ministry of Education
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306
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Penna C, Perrelli MG, Pagliaro P. Mitochondrial pathways, permeability transition pore, and redox signaling in cardioprotection: therapeutic implications. Antioxid Redox Signal 2013; 18:556-99. [PMID: 22668069 DOI: 10.1089/ars.2011.4459] [Citation(s) in RCA: 125] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Reperfusion therapy is the indispensable treatment of acute myocardial infarction (AMI) and must be applied as soon as possible to attenuate the ischemic insult. However, reperfusion is responsible for additional myocardial damage likely involving opening of the mitochondrial permeability transition pore (mPTP). A great part of reperfusion injury occurs during the first minute of reperfusion. The prolonged opening of mPTP is considered one of the endpoints of the cascade to myocardial damage, causing loss of cardiomyocyte function and viability. Opening of mPTP and the consequent oxidative stress due to reactive oxygen and nitrogen species (ROS/RNS) are considered among the major mechanisms of mitochondrial and myocardial dysfunction. Kinases and mitochondrial components constitute an intricate network of signaling molecules and mitochondrial proteins, which interact in response to stressors. Cardioprotective pathways are activated by stimuli such as preconditioning and postconditioning (PostC), obtained with brief intermittent ischemia or with pharmacological agents, which drastically reduce the lethal ischemia/reperfusion injury. The protective pathways converging on mitochondria may preserve their function. Protection involves kinases, adenosine triphosphate-dependent potassium channels, ROS signaling, and the mPTP modulation. Some clinical studies using ischemic PostC during angioplasty support its protective effects, and an interesting alternative is pharmacological PostC. In fact, the mPTP desensitizer, cyclosporine A, has been shown to induce appreciable protections in AMI patients. Several factors and comorbidities that might interfere with cardioprotective signaling are considered. Hence, treatments adapted to the characteristics of the patient (i.e., phenotype oriented) might be feasible in the future.
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Affiliation(s)
- Claudia Penna
- Department of Clinical and Biological Sciences, University of Turin, Orbassano, Italy
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307
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Skyschally A, Walter B, Schultz Hansen R, Heusch G. The antiarrhythmic dipeptide ZP1609 (danegaptide) when given at reperfusion reduces myocardial infarct size in pigs. Naunyn Schmiedebergs Arch Pharmacol 2013; 386:383-91. [PMID: 23397587 DOI: 10.1007/s00210-013-0840-9] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Accepted: 01/28/2013] [Indexed: 12/12/2022]
Abstract
Connexin 43 is located in the cardiomyocyte sarcolemma and in the mitochondrial membrane. Sarcolemmal connexin 43 contributes to the spread of myocardial ischemia/reperfusion injury, whereas mitochondrial connexin 43 contributes to cardioprotection. We have now investigated the antiarrhythmic dipeptide ZP1609 (danegaptide), which is an analog of the connexin 43 targeting antiarrhythmic peptide rotigaptide (ZP123), in an established and clinically relevant experimental model of ischemia/reperfusion in pigs. Pigs were subjected to 60 min coronary occlusion and 3 h reperfusion. ZP1609 (n = 10) was given 10 min prior to reperfusion (75 μg/kg b.w. bolus i.v. + 57 μg/kg/min i.v. infusion for 3 h). Immediate full reperfusion (IFR, n = 9) served as control. Ischemic postconditioning (PoCo, n = 9; 1 min LAD reocclusion after 1 min reperfusion; four repetitions) was used as a positive control of cardioprotection. Infarct size (TTC) was determined as the end point of cardioprotection. Systemic hemodynamics and regional myocardial blood flow during ischemia were not different between groups. PoCo and ZP1609 reduced infarct size vs. IFR (IFR, 46 ± 4 % of area at risk; mean ± SEM; PoCo, 31 ± 4 %; ZP1609, 25 ± 5 %; both p < 0.05 vs. IFR; ANOVA). There were only few arrhythmias during reperfusion such that no antiarrhythmic action of ZP1609 was observed. ZP1609 when given before reperfusion reduces infarct size to a similar extent as ischemic postconditioning. Further studies are necessary to define the mechanism/action of ZP1609 on connexin 43 in cardiomyocytes.
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Affiliation(s)
- Andreas Skyschally
- Institut für Pathophysiologie, Universitätsklinikum Essen, Hufelandstr. 55, 45122 Essen, Germany
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308
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Wang Z, Han J, David LL, Schey KL. Proteomics and phosphoproteomics analysis of human lens fiber cell membranes. Invest Ophthalmol Vis Sci 2013; 54:1135-43. [PMID: 23349431 DOI: 10.1167/iovs.12-11168] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
PURPOSE The human lens fiber cell insoluble membrane fraction contains important membrane proteins, cytoskeletal proteins, and cytosolic proteins that are strongly associated with the membrane. The purpose of this study was to characterize the lens fiber cell membrane proteome and phosphoproteome from human lenses. METHODS HPLC-mass spectrometry-based multidimensional protein identification technology (MudPIT), without or with phosphopeptide enrichment, was applied to study the proteome and phosphoproteome of lens fiber cell membranes, respectively. RESULTS In total, 951 proteins were identified, including 379 integral membrane and membrane-associated proteins. Enriched gene categories and pathways based on the proteomic analysis include carbohydrate metabolism (glycolysis/gluconeogenesis, pentose phosphate pathway, pyruvate metabolism), proteasome, cell-cell signaling and communication (GTP binding, gap junction, focal adhesion), glutathione metabolism, and actin regulation. The combination of TiO(2) phosphopeptide enrichment and MudPIT analysis revealed 855 phosphorylation sites on 271 proteins, including 455 phosphorylation sites that have not been previously identified. PKA, PKC, CKII, p38MAPK, and RSK are predicted as the major kinases for phosphorylation on the sites identified in the human lens membrane fraction. CONCLUSIONS The results presented herein significantly expand the characterized proteome and phosphoproteome of the human lens fiber cell and provide a valuable reference for future research in studies of lens development and disease.
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Affiliation(s)
- Zhen Wang
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA
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309
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Johnson KE, Mitra S, Katoch P, Kelsey LS, Johnson KR, Mehta PP. Phosphorylation on Ser-279 and Ser-282 of connexin43 regulates endocytosis and gap junction assembly in pancreatic cancer cells. Mol Biol Cell 2013; 24:715-33. [PMID: 23363606 PMCID: PMC3596244 DOI: 10.1091/mbc.e12-07-0537] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The molecular mechanisms regulating the assembly of connexins (Cxs) into gap junctions are poorly understood. Using human pancreatic tumor cell lines BxPC3 and Capan-1, which express Cx26 and Cx43, we show that, upon arrival at the cell surface, the assembly of Cx43 is impaired. Connexin43 fails to assemble, because it is internalized by clathrin-mediated endocytosis. Assembly is restored upon expressing a sorting-motif mutant of Cx43, which does not interact with the AP2 complex, and by expressing mutants that cannot be phosphorylated on Ser-279 and Ser-282. The mutants restore assembly by preventing clathrin-mediated endocytosis of Cx43. Our results also document that the sorting-motif mutant is assembled into gap junctions in cells in which the expression of endogenous Cx43 has been knocked down. Remarkably, Cx43 mutants that cannot be phosphorylated on Ser-279 or Ser-282 are assembled into gap junctions only when connexons are composed of Cx43 forms that can be phosphorylated on these serines and forms in which phosphorylation on these serines is abolished. Based on the subcellular fate of Cx43 in single and contacting cells, our results document that the endocytic itinerary of Cx43 is altered upon cell-cell contact, which causes Cx43 to traffic by EEA1-negative endosomes en route to lysosomes. Our results further show that gap-junctional plaques formed of a sorting motif-deficient mutant of Cx43, which is unable to be internalized by the clathrin-mediated pathway, are predominantly endocytosed in the form of annular junctions. Thus the differential phosphorylation of Cx43 on Ser-279 and Ser-282 is fine-tuned to control Cx43's endocytosis and assembly into gap junctions.
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Affiliation(s)
- Kristen E Johnson
- Department of Biochemistry and Molecular Biology, Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE 68198, USA
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310
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Munger SJ, Kanady JD, Simon AM. Absence of venous valves in mice lacking Connexin37. Dev Biol 2013; 373:338-48. [PMID: 23142761 PMCID: PMC3533519 DOI: 10.1016/j.ydbio.2012.10.032] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Revised: 10/30/2012] [Accepted: 10/31/2012] [Indexed: 12/31/2022]
Abstract
Venous valves play a crucial role in blood circulation, promoting the one-way movement of blood from superficial and deep veins towards the heart. By preventing retrograde flow, venous valves spare capillaries and venules from being subjected to damaging elevations in pressure, especially during skeletal muscle contraction. Pathologically, valvular incompetence or absence of valves are common features of venous disorders such as chronic venous insufficiency and varicose veins. The underlying causes of these conditions are not well understood, but congenital venous valve aplasia or agenesis may play a role in some cases. Despite progress in the study of cardiac and lymphatic valve morphogenesis, the molecular mechanisms controlling the development and maintenance of venous valves remain poorly understood. Here, we show that in valved veins of the mouse, three gap junction proteins (Connexins, Cxs), Cx37, Cx43, and Cx47, are expressed exclusively in the valves in a highly polarized fashion, with Cx43 on the upstream side of the valve leaflet and Cx37 on the downstream side. Surprisingly, Cx43 expression is strongly induced in the non-valve venous endothelium in superficial veins following wounding of the overlying skin. Moreover, we show that in Cx37-deficient mice, venous valves are entirely absent. Thus, Cx37, a protein involved in cell-cell communication, is one of only a few proteins identified so far as critical for the development or maintenance of venous valves. Because Cxs are necessary for the development of valves in lymphatic vessels as well, our results support the notion of common molecular pathways controlling valve development in veins and lymphatic vessels.
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Affiliation(s)
| | - John D. Kanady
- Department of Physiology, University of Arizona, Tucson, AZ 85724, USA
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311
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Aktuğ H, Bozok Çetintaş V, Uysal A, Oltulu F, Yavaşoğlu A, Akarca SÖ, Kosova B. Evaluation of the Effects of STZ-Induced Diabetes on In Vitro Fertilization and Early Embryogenesis Processes. J Diabetes Res 2013; 2013:603813. [PMID: 23671879 PMCID: PMC3647572 DOI: 10.1155/2013/603813] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Revised: 02/12/2013] [Accepted: 02/25/2013] [Indexed: 01/23/2023] Open
Abstract
The aim of this study was to investigate the effects of experimentally induced diabetes on (a) germ cells, (b) in vitro fertilization (IVF) success rate, and (c) gap junction and cell adhesion molecule gene and protein expressions during the early blastocyst period. Germ cells were obtained from healthy and diabetic rats, analyzed for number, motility, and morphology, and used for IVF. After reaching the early blastocyst stage, the expressions of genes encoding gap junction proteins and cell adhesion molecules were analyzed by quantitative RT-PCR. Histomorphologically and immunohistochemically analyses were also performed. Diabetes significantly affected sperm number and motility and the development of oocytes. Gene expressions of β -catenin and connexin family members and protein expressions of E-cadherin and connexin-43 significantly decreased in groups including germ cells isolated from diabetic rats. Connective tissue growth factor expression increased in groups that included sperm cells isolated from diabetic male rats, whereas mucin-1 expression increased in the group that included oocytes isolated from diabetic female rats paired with sperm cells isolated from healthy male rats. In summary, experimentally induced diabetes was found to influence gap junctions, cell adhesion molecules, and associated proteins which all have important roles in germ cell maturation, fertilization, and development.
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Affiliation(s)
- Hüseyin Aktuğ
- Department of Histology and Embryology, Ege University Medical School, 35100 Izmir, Turkey
- *Hüseyin Aktuğ:
| | | | - Ayşegül Uysal
- Department of Histology and Embryology, Ege University Medical School, 35100 Izmir, Turkey
| | - Fatih Oltulu
- Department of Histology and Embryology, Ege University Medical School, 35100 Izmir, Turkey
| | - Altuğ Yavaşoğlu
- Department of Histology and Embryology, Ege University Medical School, 35100 Izmir, Turkey
| | - Saadet Özen Akarca
- Department of Histology and Embryology, Ege University Medical School, 35100 Izmir, Turkey
| | - Buket Kosova
- Department of Medical Biology, Ege University Medical School, 35100 Izmir, Turkey
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312
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Bloemendal S, Kück U. Cell-to-cell communication in plants, animals, and fungi: a comparative review. THE SCIENCE OF NATURE - NATURWISSENSCHAFTEN 2013. [PMID: 23128987 DOI: 10.1007/s00114-012-0988] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 04/28/2023]
Abstract
Cell-to-cell communication is a prerequisite for differentiation and development in multicellular organisms. This communication has to be tightly regulated to ensure that cellular components such as organelles, macromolecules, hormones, or viruses leave the cell in a precisely organized way. During evolution, plants, animals, and fungi have developed similar ways of responding to this biological challenge. For example, in higher plants, plasmodesmata connect adjacent cells and allow communication to regulate differentiation and development. In animals, two main general structures that enable short- and long-range intercellular communication are known, namely gap junctions and tunneling nanotubes, respectively. Finally, filamentous fungi have also developed specialized structures called septal pores that allow intercellular communication via cytoplasmic flow. This review summarizes the underlying mechanisms for intercellular communication in these three eukaryotic groups and discusses its consequences for the regulation of differentiation and developmental processes.
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Affiliation(s)
- Sandra Bloemendal
- Lehrstuhl für Allgemeine und Molekulare Botanik, Ruhr-Universität Bochum, ND7/131, Universitätsstraße 150, Bochum, 44780, Germany
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313
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Plotkin LI, Bellido T. Beyond gap junctions: Connexin43 and bone cell signaling. Bone 2013; 52:157-66. [PMID: 23041511 PMCID: PMC3513515 DOI: 10.1016/j.bone.2012.09.030] [Citation(s) in RCA: 100] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2012] [Revised: 09/20/2012] [Accepted: 09/25/2012] [Indexed: 12/31/2022]
Abstract
Connexin43 (Cx43) is the most abundant gap junction protein expressed in bone cells and plays a central role in cell-to-cell communication in the skeleton. Findings of the last decade uncovered functions of Cx43 hemichannels expressed on unopposed plasma cell membranes as mediators of the communication between bone cells and their extracellular milieu. Additionally, through its cytoplasmic C-terminus domain, Cx43 serves as a scaffolding protein that associates with structural and signaling molecules leading to regulation of intracellular signaling, independent of channel activity. This perspective discusses the evidence demonstrating that via these diverse mechanisms Cx43 is a key component of the intracellular machinery responsible for signal transduction in bone in response to pharmacologic, hormonal and mechanical stimuli. This advance in the knowledge of the role of connexins increases our understanding of the pathophysiological mechanisms that regulate bone cell function and provides new opportunities to treat bone diseases.
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Affiliation(s)
- Lilian I. Plotkin
- Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN
| | - Teresita Bellido
- Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN
- Department of Medicine, Division of Endocrinology, Indiana University School of Medicine, Indianapolis, IN
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314
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Radice GL. N-cadherin-mediated adhesion and signaling from development to disease: lessons from mice. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2013; 116:263-89. [PMID: 23481199 PMCID: PMC6047516 DOI: 10.1016/b978-0-12-394311-8.00012-1] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Of the 20 classical cadherin subtypes identified in mammals, the functions of the two initially identified family members E- (epithelial) and N- (neural) cadherin have been most extensively studied. E- and N-Cadherin have mostly mutually exclusive expression patterns, with E-cadherin expressed primarily in epithelial cells, whereas N-cadherin is found in a variety of cells, including neural, muscle, and mesenchymal cells. N-Cadherin function, in particular, appears to be cell context-dependent, as it can mediate strong cell-cell adhesion in the heart but induces changes in cell behavior in favor of a migratory phenotype in the context of epithelial-mesenchymal transition (EMT). The ability of tumor cells to alter their cadherin expression profile, for example, E- to N-cadherin, is critical for malignant progression. Recent advances in mouse molecular genetics, and specifically tissue-specific knockout and knockin alleles of N-cadherin, have provided some unexpected results. This chapter highlights some of the genetic studies that explored the complex role of N-cadherin in embryonic development and disease.
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Affiliation(s)
- Glenn L Radice
- Department of Medicine, Center for Translational Medicine, Jefferson Medical College, Philadelphia, Pennsylvania, USA
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315
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Zucker SN, Bancroft TA, Place DE, Des Soye B, Bagati A, Berezney R. A dominant negative Cx43 mutant differentially affects tumorigenic and invasive properties in human metastatic melanoma cells. J Cell Physiol 2012; 228:853-9. [DOI: 10.1002/jcp.24235] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2012] [Accepted: 09/20/2012] [Indexed: 02/02/2023]
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316
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Cell motility in models of wounded human skin is improved by Gap27 despite raised glucose, insulin and IGFBP-5. Exp Cell Res 2012; 319:390-401. [PMID: 23262023 DOI: 10.1016/j.yexcr.2012.12.013] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Revised: 12/12/2012] [Accepted: 12/13/2012] [Indexed: 11/21/2022]
Abstract
Reducing Cx43 expression stimulates skin wound healing. This is mimicked in models when Cx43 function is blocked by the connexin mimetic peptide Gap27. IGF-I also stimulates wound healing with IGFBP-5 attenuating its actions. Further, the IGF-I to IGFBP-5 ratio is altered in diabetic skin, where wound closure is impaired. We investigated whether Gap27 remains effective in augmenting scrape-wound closure in human skin wound models simulating diabetes-induced changes, using culture conditions with raised glucose, insulin and IGFBP-5. Gap27 increased scrape-wound closure in normal glucose and insulin (NGI) and to a lesser extent in high glucose and insulin (HGI). IGF-I enhanced scrape-wound closure in keratinocytes whereas IGFBP-5 inhibited this response. Gap27 overcame the inhibitory effects of IGFBP-5 on IGF-I activity. Connexin-mediated communication (CMC) was reduced in HGI, despite raised Cx43, and Gap27 significantly decreased CMC in NGI and HGI. IGF-I and IGFBP-5 did not affect CMC. IGF-I increased keratinocyte proliferation in NGI, and Gap27 increased proliferation in NGI to a greater extent than in HGI. We conclude that IGF-I and Gap27 stimulate scrape-wound closure by independent mechanisms with Gap27 inhibiting Cx43 function. Gap27 can enhance wound closure in diabetic conditions, irrespective of the IGF-I:IGFBP-5 balance.
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317
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Kim E, Fishman GI. Designer gap junctions that prevent cardiac arrhythmias. Trends Cardiovasc Med 2012; 23:33-8. [PMID: 23245912 DOI: 10.1016/j.tcm.2012.08.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Revised: 08/01/2012] [Accepted: 08/02/2012] [Indexed: 12/28/2022]
Abstract
Cardiac gap junctions are specialized membrane structures comprised of arrays of intercellular channels responsible for propagation of the cardiac impulse. These channels are formed by oligomerization of individual protein subunits known as connexins. In response to a broad array of pathologic stressors, gap junction expression is disturbed, resulting in aberrant cardiac conduction and increased propensity for rhythm disturbances. In this article, we review some of the recently identified molecular regulators of connexin assembly, membrane targeting, and degradation, focusing on the role of post-translational phosphorylation of connexin 43, the major gap junctional protein expressed in ventricular myocardium. We also describe efforts to engineer "designer" gap junctions that are resistant to pathologic remodeling.
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Affiliation(s)
- Eugene Kim
- Leon H. Charney Division of Cardiology, New York University School of Medicine, New York, NY 10016, USA
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318
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Fang JS, Dai C, Kurjiaka DT, Burt JM, Hirschi KK. Connexin45 regulates endothelial-induced mesenchymal cell differentiation toward a mural cell phenotype. Arterioscler Thromb Vasc Biol 2012; 33:362-8. [PMID: 23220276 DOI: 10.1161/atvbaha.112.255950] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE The focus of this study was to investigate the role of connexin (Cx) 45 in endothelial-induced mural cell differentiation. METHODS AND RESULTS We created mural cell precursors that stably express only Cx45 in Cx43-deficient mesenchymal cells (ReCx45), and used our in vitro model of blood vessel assembly to assess the capacity of this Cx to support endothelial-induced mural cell differentiation. Lucifer Yellow dye injection and dual whole-cell patch clamping revealed that functional gap junctions exhibiting properties of Cx45-containing channels formed among ReCx45 transfectants, and between ReCx45 and endothelial cells. Heterocellular Cx45-containing gap junction channels enabled transforming growth factor-β activation and promoted the upregulation of mural cell-specific proteins in the mesenchymal precursors. CONCLUSIONS These studies reveal a critical role for Cx45 in the regulation of endothelial-induced mural cell differentiation, which is consistent with the phenotype of Cx45-deficient embryos that exhibit dysregulated transforming growth factor-β and lack mural cell development.
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Affiliation(s)
- Jennifer S Fang
- Yale Cardiovascular Research Center, Yale Stem Cell Center, Yale University School of Medicine, New Haven, CT 06510, USA
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319
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Tiscornia GC, Moretta R, Argenziano MA, Amorena CE, Garcia Gras EA. Inhibition of connexin 43 in cardiac muscle during intense physical exercise. Scand J Med Sci Sports 2012. [PMID: 23206241 DOI: 10.1111/sms.12017] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Endurance training is accompanied by important adaptations in both cardiovascular and autonomic nervous systems. Previous works have shown that the main component of gap junctions in the ventricular myocardium (connexin 43 (Cx43) can be regulated by adrenergic stimulus. On the other hand, training raises vagal and decreases sympathetic tone, while augmenting myocardial sensitivity to sympathetic stimulation during exercise. We therefore evaluated the regulation of Cx43 expression by sympathetic tone during exercise in trained and sedentary mice. Training induced an increase in the protein level of Cx43 by 45-70% under resting conditions. The expression of Cx43 was inhibited in trained but not in untrained mice in response to a 60 min exercise bout. Normal basal expression was restored after 60 min of resting. Cx43 reached a minimum that was not different from basal expression in untrained mice. In accordance, electrocardiography and action potential analysis did not reveal major electrophysiological implications for the drop in Cx43 abundance in trained-exercise mice. We prevented Cx43 inhibition using propranolol, and observed increased basal mRNA levels of β-adrenergic receptors without significant changes in the ratio β1 to β2. In conclusion, we showed that Cx43 expression is transiently inhibited by β-adrenergic stimulus in trained mice during acute exercise.
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Affiliation(s)
- G C Tiscornia
- CESyMA, ECyT, National University of San Martin, San Martin, Buenos Aires, Argentina
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320
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Peng YS, Ding HC, Lin YT, Syu JP, Chen Y, Wang SM. Uremic toxin p-cresol induces disassembly of gap junctions of cardiomyocytes. Toxicology 2012; 302:11-7. [DOI: 10.1016/j.tox.2012.07.004] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2012] [Revised: 06/29/2012] [Accepted: 07/08/2012] [Indexed: 11/29/2022]
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321
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Bloemendal S, Kück U. Cell-to-cell communication in plants, animals, and fungi: a comparative review. Naturwissenschaften 2012; 100:3-19. [PMID: 23128987 DOI: 10.1007/s00114-012-0988-z] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Revised: 10/22/2012] [Accepted: 10/25/2012] [Indexed: 12/30/2022]
Abstract
Cell-to-cell communication is a prerequisite for differentiation and development in multicellular organisms. This communication has to be tightly regulated to ensure that cellular components such as organelles, macromolecules, hormones, or viruses leave the cell in a precisely organized way. During evolution, plants, animals, and fungi have developed similar ways of responding to this biological challenge. For example, in higher plants, plasmodesmata connect adjacent cells and allow communication to regulate differentiation and development. In animals, two main general structures that enable short- and long-range intercellular communication are known, namely gap junctions and tunneling nanotubes, respectively. Finally, filamentous fungi have also developed specialized structures called septal pores that allow intercellular communication via cytoplasmic flow. This review summarizes the underlying mechanisms for intercellular communication in these three eukaryotic groups and discusses its consequences for the regulation of differentiation and developmental processes.
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Affiliation(s)
- Sandra Bloemendal
- Lehrstuhl für Allgemeine und Molekulare Botanik, Ruhr-Universität Bochum, ND7/131, Universitätsstraße 150, Bochum, 44780, Germany
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322
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A functional interaction between the MAGUK protein hDlg and the gap junction protein connexin 43 in cervical tumour cells. Biochem J 2012; 446:9-21. [PMID: 22657348 DOI: 10.1042/bj20111144] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Gap junctions, composed of Cxs (connexins), allow direct intercellular communication. Gap junctions are often lost during the development of malignancy, although the processes behind this are not fully understood. Cx43 is a widely expressed Cx with a long cytoplasmic C-terminal tail that contains several potential protein-interaction domains. Previously, in a model of cervical carcinogenesis, we showed that the loss of gap junctional communication correlated with relocalization of Cx43 to the cytoplasm late in tumorigenesis. In the present study, we demonstrate a similar pattern of altered expression for the hDlg (human discs large) MAGUK (membrane-associated guanylate kinase) family tumour suppressor protein in cervical tumour cells, with partial co-localization of Cx43 and hDlg in an endosomal/lysosomal compartment. Relocalization of these proteins is not due to a general disruption of cell membrane integrity or Cx targeting. Cx43 (via its C-terminus) and hDlg interact directly in vitro and can form a complex in cells. This novel interaction requires the N- and C-termini of hDlg. hDlg is not required for Cx43 internalization in W12GPXY cells. Instead, hDlg appears to have a role in maintaining a cytoplasmic pool of Cx43. These results demonstrate that hDlg is a physiologically relevant regulator of Cx43 in transformed epithelial cells.
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323
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Andrysík Z, Procházková J, Kabátková M, Umannová L, Šimečková P, Kohoutek J, Kozubík A, Machala M, Vondráček J. Aryl hydrocarbon receptor-mediated disruption of contact inhibition is associated with connexin43 downregulation and inhibition of gap junctional intercellular communication. Arch Toxicol 2012; 87:491-503. [DOI: 10.1007/s00204-012-0963-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Accepted: 10/11/2012] [Indexed: 11/29/2022]
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324
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Braganza O, Bedner P, Hüttmann K, von Staden E, Friedman A, Seifert G, Steinhäuser C. Albumin is taken up by hippocampal NG2 cells and astrocytes and decreases gap junction coupling. Epilepsia 2012; 53:1898-906. [PMID: 22967085 DOI: 10.1111/j.1528-1167.2012.03665.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
PURPOSE Dysfunction of the blood-brain barrier (BBB) and albumin extravasation have been suggested to play a role in the etiology of human epilepsy. In this context, dysfunction of glial cells attracts increasing attention. Our study was aimed to analyze in the hippocampus (1) which cell types internalize albumin injected into the lateral ventricle in vivo, (2) whether internalization into astrocytes impacts their coupling and expression of connexin 43 (Cx43), and (3) whether expression of Kir4.1, the predominating astrocytic K(+) channel subunit, is altered by albumin. METHODS The patch-clamp method was combined with single cell tracer filling to investigate electrophysiologic properties and gap junction coupling (GJC). For cell identification, mice with cell type-specific expression of a fluorescent protein (NG2kiEYFP mice) and immunohistochemistry were employed. Semiquantitative real time polymerase chain reaction (RT-PCR) allowed analysis of Kir4.1 and Cx43 transcript levels. KEY FINDINGS We show that fluorescently labeled albumin is taken up by astrocytes, NG2 cells, and neurons, with NG2 cells standing out in terms of the quantity of uptake. Within 5 days postinjection (dpi), intracellular albumin accumulation was largely reduced suggesting rapid degradation. Electrophysiologic analysis of astrocytes and NG2 cells revealed no changes in their membrane properties at either time point. However, astrocytic GJC was significantly decreased at 1 dpi but returned to control levels within 5 dpi. We found no changes in hippocampal Cx43 transcript expression, suggesting that other mechanisms account for the observed changes in coupling. Kir4.1 mRNA was regulated oppositely in the CA1 stratum radiatum, with a strong increase at 1 dpi followed by a decrease at 5 dpi. SIGNIFICANCE The present study demonstrates that extravasal albumin in the hippocampus induces rapid changes of astrocyte function, which can be expected to impair ion and transmitter homeostasis and contribute to hyperactivity and epileptogenesis. Therefore, astrocytes may represent alternative targets for antiepileptic therapeutic approaches.
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Affiliation(s)
- Oliver Braganza
- Institute of Cellular Neurosciences, University of Bonn, Sigmund Freud Strasse 25, Bonn, Germany
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325
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Gap junctions and non-neoplastic liver disease. J Hepatol 2012; 57:655-62. [PMID: 22609308 DOI: 10.1016/j.jhep.2012.02.036] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Revised: 02/15/2012] [Accepted: 02/17/2012] [Indexed: 12/30/2022]
Abstract
Because of their critical role as goalkeepers of hepatic homeostasis, gap junctions are frequent targets in liver disease. This concept has been demonstrated on many occasions in the light of hepatocarcinogenesis. Relatively little focus has been put on the fate of gap junctions in other liver pathologies, including hepatitis, liver fibrosis and cirrhosis, cholestasis and hepatic ischemia and reperfusion injury. The present paper provides an in-depth description of the multiple changes in expression, localization and function of connexins, the molecular constituents of gap junctions. The use of connexins as biomarkers and therapeutic targets in liver disease is also illustrated.
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326
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Firestone GL, Kapadia BJ. Minireview: regulation of gap junction dynamics by nuclear hormone receptors and their ligands. Mol Endocrinol 2012; 26:1798-807. [PMID: 22935924 DOI: 10.1210/me.2012-1065] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Gap junctions are plasma membrane channels comprising connexin proteins that mediate intercellular permeability and communication. The presence, composition, and function of gap junctions can be regulated by diverse sets of physiological signals. Evidence from many hormone-responsive tissues has shown that connexin expression, modification, stability, and localization can be targeted by nuclear hormone receptors and their ligands through both transcriptional and nontranscriptional mechanisms. The focus of this review is to discuss molecular, cellular, and physiological studies that directly link receptor- and ligand-triggered signaling pathways to the regulation of gap junction dynamics.
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Affiliation(s)
- Gary L Firestone
- Department of Molecular and Cell Biology, 591 LSA, The University of California at Berkeley, Berkeley, California 94720-3200, USA.
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327
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Chen CH, Beard RS, Bearden SE. Homocysteine impairs endothelial wound healing by activating metabotropic glutamate receptor 5. Microcirculation 2012; 19:285-95. [PMID: 22221504 DOI: 10.1111/j.1549-8719.2012.00159.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
OBJECTIVE Hcy is an independent risk factor for cerebrovascular disease and cognitive impairment. The purpose of this study was to elucidate the role of mGluR5 in Hcy-mediated impairment of cerebral endothelial wound repair. METHODS Mouse CMVECs (bEnd.3) were used in conjunction with directed pharmacology and shRNA. AutoDock was used to simulate the docking of ligand-receptor interactions. RESULTS Hcy (20 μM) significantly increased Cx43-pS368 by mGluR5- and PKC-dependent mechanisms. Hcy attenuated wound repair by an mGluR5-dependent mechanism over the six-day study period but did not alter cell proliferation in a proliferation assay, suggesting that the attenuation of wound repair may be due to dysfunctional migration in HHcy. Hcy increased the expression of Cx43 and Cx43-pS368 at the wound edge by activating mGluR5. Direct activation of mGluR5, using the specific agonist CHPG, was sufficient to reproduce the results whereas KO of mGluR5 with shRNA, or inhibition with MPEP, blocked the response to Hcy. CONCLUSIONS Inhibition of mGluR5 activation could be a novel strategy for promoting endothelial wound repair in patients with HHcy. Activation of mGluR5 may be a viable strategy for disrupting angiogenesis.
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Affiliation(s)
- Cheng-Hung Chen
- Department of Biological Sciences, Idaho State University, Pocatello, Idaho 83209-8007, USA
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328
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Cea LA, Riquelme MA, Cisterna BA, Puebla C, Vega JL, Rovegno M, Sáez JC. Connexin- and pannexin-based channels in normal skeletal muscles and their possible role in muscle atrophy. J Membr Biol 2012; 245:423-36. [PMID: 22850938 DOI: 10.1007/s00232-012-9485-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2012] [Accepted: 06/28/2012] [Indexed: 12/13/2022]
Abstract
Precursor cells of skeletal muscles express connexins 39, 43 and 45 and pannexin1. In these cells, most connexins form two types of membrane channels, gap junction channels and hemichannels, whereas pannexin1 forms only hemichannels. All these channels are low-resistance pathways permeable to ions and small molecules that coordinate developmental events. During late stages of skeletal muscle differentiation, myofibers become innervated and stop expressing connexins but still express pannexin1 hemichannels that are potential pathways for the ATP release required for potentiation of the contraction response. Adult injured muscles undergo regeneration, and connexins are reexpressed and form membrane channels. In vivo, connexin reexpression occurs in undifferentiated cells that form new myofibers, favoring the healing process of injured muscle. However, differentiated myofibers maintained in culture for 48 h or treated with proinflammatory cytokines for less than 3 h also reexpress connexins and only form functional hemichannels at the cell surface. We propose that opening of these hemichannels contributes to drastic changes in electrochemical gradients, including reduction of membrane potential, increases in intracellular free Ca(2+) concentration and release of diverse metabolites (e.g., NAD(+) and ATP) to the extracellular milieu, contributing to multiple metabolic and physiologic alterations that characterize muscles undergoing atrophy in several acquired and genetic human diseases. Consequently, inhibition of connexin hemichannels expressed by injured or denervated skeletal muscles might reduce or prevent deleterious changes triggered by conditions that promote muscle atrophy.
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Affiliation(s)
- Luis A Cea
- Departamento de Fisiología, Pontificia Universidad Católica de Chile, Alameda 340, Santiago, Chile,
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329
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Evans WH, Bultynck G, Leybaert L. Manipulating connexin communication channels: use of peptidomimetics and the translational outputs. J Membr Biol 2012; 245:437-49. [PMID: 22886208 PMCID: PMC3456916 DOI: 10.1007/s00232-012-9488-5] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Accepted: 07/07/2012] [Indexed: 12/22/2022]
Abstract
Gap junctions are key components underpinning multicellularity. They provide cell to cell channel pathways that enable direct intercellular communication and cellular coordination in tissues and organs. The channels are constructed of a family of connexin (Cx) membrane proteins. They oligomerize inside the cell, generating hemichannels (connexons) composed of six subunits arranged around a central channel. After transfer to the plasma membrane, arrays of Cx hemichannels (CxHcs) interact and couple with partners in neighboring attached cells to generate gap junctions. Cx channels have been studied using a range of technical approaches. Short peptides corresponding to sequences in the extra- and intracellular regions of Cxs were used first to generate epitope-specific antibodies that helped studies on the organization and functions of gap junctions. Subsequently, the peptides themselves, especially Gap26 and -27, mimetic peptides derived from each of the two extracellular loops of connexin43 (Cx43), a widely distributed Cx, have been extensively applied to block Cx channels and probe the biology of cell communication. The development of a further series of short peptides mimicking sequences in the intracellular loop, especially the extremity of the intracellular carboxyl tail of Cx43, followed. The primary inhibitory action of the peptidomimetics occurs at CxHcs located at unapposed regions of the cell's plasma membrane, followed by inhibition of cell coupling occurring across gap junctions. CxHcs respond to a range of environmental conditions by increasing their open probability. Peptidomimetics provide a way to block the actions of CxHcs with some selectivity. Furthermore, they are increasingly applied to address the pathological consequences of a range of environmental stresses that are thought to influence Cx channel operation. Cx peptidomimetics show promise as candidates in developing new therapeutic approaches for containing and reversing damage inflicted on CxHcs, especially in hypoxia and ischemia in the heart and in brain functions.
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Affiliation(s)
- W Howard Evans
- Institute of Infection and Immunity, Cardiff University School of Medicine, Heath Park, Cardiff, Wales CF14 4XN, UK.
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330
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Opposing roles of connexin43 in glioma progression. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:2058-67. [DOI: 10.1016/j.bbamem.2011.10.022] [Citation(s) in RCA: 88] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2011] [Revised: 10/17/2011] [Accepted: 10/24/2011] [Indexed: 12/12/2022]
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331
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Posttranscriptional regulation of connexin-43 expression. Arch Biochem Biophys 2012; 524:23-9. [DOI: 10.1016/j.abb.2012.03.012] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Revised: 03/10/2012] [Accepted: 03/12/2012] [Indexed: 12/26/2022]
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332
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Falk MM, Fong JT, Kells RM, O'Laughlin MC, Kowal TJ, Thévenin AF. Degradation of endocytosed gap junctions by autophagosomal and endo-/lysosomal pathways: a perspective. J Membr Biol 2012; 245:465-76. [PMID: 22825714 DOI: 10.1007/s00232-012-9464-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Accepted: 06/13/2012] [Indexed: 12/24/2022]
Abstract
Gap junctions (GJs) are composed of tens to many thousands of double-membrane spanning GJ channels that cluster together to form densely packed channel arrays (termed GJ plaques) in apposing plasma membranes of neighboring cells. In addition to providing direct intercellular communication (GJIC, their hallmark function), GJs, based on their characteristic double-membrane-spanning configuration, likely also significantly contribute to physical cell-to-cell adhesion. Clearly, modulation (up-/down-regulation) of GJIC and of physical cell-to-cell adhesion is as vitally important as the basic ability of GJ formation itself. Others and we have previously described that GJs can be removed from the plasma membrane via the internalization of entire GJ plaques (or portions thereof) in a cellular process that resembles clathrin-mediated endocytosis. GJ endocytosis results in the formation of double-membrane vesicles [termed annular gap junctions (AGJs) or connexosomes] in the cytoplasm of one of the coupled cells. Four recent independent studies, consistent with earlier ultrastructural analyses, demonstrate the degradation of endocytosed AGJ vesicles via autophagy. However, in TPA-treated cells others report degradation of AGJs via the endo-/lysosomal degradation pathway. Here we summarize evidence that supports the concept that autophagy serves as the cellular default pathway for the degradation of internalized GJs. Furthermore, we highlight and discuss structural criteria that seem required for an alternate degradation via the endo-/lysosomal pathway.
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Affiliation(s)
- Matthias M Falk
- Department of Biological Sciences, Lehigh University, 111 Research Drive, Iacocca Hall, D-218, Bethlehem, PA 18015, USA.
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333
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Shao Q, Liu Q, Lorentz R, Gong XQ, Bai D, Shaw GS, Laird DW. Structure and functional studies of N-terminal Cx43 mutants linked to oculodentodigital dysplasia. Mol Biol Cell 2012; 23:3312-21. [PMID: 22809623 PMCID: PMC3431933 DOI: 10.1091/mbc.e12-02-0128] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Mutations in the connexin-43 gap junction protein cause the developmental disease known as oculodentodigital dysplasia. Structure and function approaches are used to demonstrate that the nature of the missense mutation in the amino-terminal domain of connexin-43 governs the mechanism that leads to loss of connexin-43 function. Mutations in the gene encoding connexin-43 (Cx43) cause the human development disorder known as oculodentodigital dysplasia (ODDD). In this study, ODDD-linked Cx43 N-terminal mutants formed nonfunctional gap junction–like plaques and exhibited dominant-negative effects on the coupling conductance of coexpressed endogenous Cx43 in reference cell models. Nuclear magnetic resonance (NMR) protein structure determination of an N-terminal 23–amino acid polypeptide of wild-type Cx43 revealed that it folded in to a kinked α-helical structure. This finding predicted that W4 might be critically important in intramolecular and intermolecular interactions. Thus we engineered and characterized a W4A mutant and found that this mutant formed a regular, nonkinked α-helix but did not form functional gap junctions. Furthermore, a G2V variant peptide of Cx43 showed a kinked helix that now included V2 interactions with W4, resulting in the G2V mutant forming nonfunctional gap junctions. Also predicted from the NMR structures, a G2S mutant was found to relieve these interactions and allowed the protein to form functional gap junctions. Collectively, these studies suggest that the nature of the mutation conveys loss of Cx43 function by distinctly different mechanisms that are rooted in the structure of the N-terminal region.
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Affiliation(s)
- Qing Shao
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON N6A 5C1, Canada
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334
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Wasielewski B, Jensen A, Roth-Härer A, Dermietzel R, Meier C. Neuroglial activation and Cx43 expression are reduced upon transplantation of human umbilical cord blood cells after perinatal hypoxic-ischemic injury. Brain Res 2012; 1487:39-53. [PMID: 22796290 DOI: 10.1016/j.brainres.2012.05.066] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2012] [Accepted: 05/31/2012] [Indexed: 12/15/2022]
Abstract
Glial cells play a crucial role in the pathomechanism of perinatal hypoxic-ischemic brain injury (HI) and are involved in the maintenance of a chronic state of inflammation that causes delayed neuronal damage. Activation of astrocytes is one factor prolonging brain damage and contributing to the formation of a glial scar that limits neuronal plasticity. In this context, the major astrocytic gap junction protein Connexin 43 (Cx43) has been ascribed various functions including regulation of astrocytic migration and proliferation. Here, we investigate glial responses like microglia/macrophages and astrocytic activation in a rat model of neonatal HI and characterize changes of these parameters upon transplantation of human umbilical cord blood cells (hUCB). As an alleviation of motor function in lesioned rats has previously been described in transplanted animals, we analyze the putative correlation between motor function and glial activation over time. The lesion-induced impairment of motor function, assessed by forelimb use bias, muscle strength and distal spasticity, was alleviated upon transplantation of hUCB short and long term. HI induced an acute inflammatory reaction with activation of microglia/macrophages and reactive astrogliosis associated with perilesional upregulation of Cx43 that slowly declined during the chronic post-ischemic phase. hUCB transplantation accelerated the regression of inflammatory events, narrowed the perilesional astrocytic wall and led to a downregulation of the investigated astrocytic proteins. Thus, in the immature brain, hUCB may indirectly reduce secondary cell death upon hypoxia-ischemia and facilitate post-ischemic plasticity through the attenuation of reactive gliosis. This article is part of a Special Issue entitled Electrical Synapses.
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Affiliation(s)
- Bianca Wasielewski
- Department of Neuroanatomy and Molecular Brain Research, Ruhr-University Bochum, D-44801 Bochum, Germany
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335
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Degradation of connexins through the proteasomal, endolysosomal and phagolysosomal pathways. J Membr Biol 2012; 245:389-400. [PMID: 22772442 DOI: 10.1007/s00232-012-9461-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Accepted: 06/20/2012] [Indexed: 01/23/2023]
Abstract
Connexins comprise gap junction channels, which create a direct conduit between the cytoplasms of adjacent cells and provide for intercellular communication. Therefore, the level of total cellular connexin protein can have a direct influence on the level of intercellular communication. Control of connexin protein levels can occur through different mechanisms during the connexin life cycle, such as by regulation of connexin gene expression and turnover of existing protein. The degradation of connexins has been extensively studied, revealing proteasomal, endolysosomal and more recently autophagosomal degradation mechanisms that modulate connexin turnover and, subsequently, affect intercellular communication. Here, we review the current knowledge of connexin degradation pathways.
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336
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Characterization of gap junction proteins in the bladder of Cx43 mutant mouse models of oculodentodigital dysplasia. J Membr Biol 2012; 245:345-55. [PMID: 22752022 DOI: 10.1007/s00232-012-9455-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2012] [Accepted: 06/08/2012] [Indexed: 12/31/2022]
Abstract
Oculodentodigital dysplasia (ODDD) is a rare developmental disease resulting from germline mutations in the GJA1 gene that encodes the gap junction protein connexin43 (Cx43). In addition to the classical ODDD symptoms that affect the eyes, teeth, bone and digits, in some cases ODDD patients have reported bladder impairments. Thus, we chose to characterize the bladder in mutant mouse models of ODDD that harbor two distinct Cx43 mutations, G60S and I130T. Histological assessment revealed no difference in bladder detrusor wall thickness in mutant compared to littermate control mice. The overall localization of Cx43 in the lamina propria and detrusor also appeared to be similar in the bladders of mutant mice with the exception that the G60S mice had more instances of intracellular Cx43. However, both mutant mouse lines exhibited a significant reduction in the phosphorylated P1 and P2 isoforms of Cx43, while only the I130T mice exhibited a reduction in total Cx43 levels. Interestingly, Cx26 levels and distribution were not altered in mutant mice as it was localized to intracellular compartments and restricted to the basal cell layers of the urothelium. Our studies suggest that these two distinct genetically modified mouse models of ODDD probably mimic patients who lack bladder defects or other factors, such as aging or co-morbidities, are necessary to reveal a bladder phenotype.
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337
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Johnstone SR, Billaud M, Lohman AW, Taddeo EP, Isakson BE. Posttranslational modifications in connexins and pannexins. J Membr Biol 2012; 245:319-32. [PMID: 22739962 DOI: 10.1007/s00232-012-9453-3] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2012] [Accepted: 06/08/2012] [Indexed: 01/17/2023]
Abstract
Posttranslational modification is a common cellular process that is used by cells to ensure a particular protein function. This can happen in a variety of ways, e.g., from the addition of phosphates or sugar residues to a particular amino acid, ensuring proper protein life cycle and function. In this review, we assess the evidence for ubiquitination, glycosylation, phosphorylation, S-nitrosylation as well as other modifications in connexins and pannexin proteins. Based on the literature, we find that posttranslational modifications are an important component of connexin and pannexin regulation.
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Affiliation(s)
- Scott R Johnstone
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
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338
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Dyce PW, Norris RP, Lampe PD, Kidder GM. Phosphorylation of serine residues in the C-terminal cytoplasmic tail of connexin43 regulates proliferation of ovarian granulosa cells. J Membr Biol 2012; 245:291-301. [PMID: 22729691 DOI: 10.1007/s00232-012-9450-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 06/01/2012] [Indexed: 10/28/2022]
Abstract
Connexin43 (Cx43) forms gap junctions that couple the granulosa cells of ovarian follicles. In Cx43 knockout mice, follicle growth is restricted as a result of impaired granulosa cell proliferation. We have used these mice to examine the importance of specific Cx43 phosphorylation sites in follicle growth. Serines at residues 255, 262, 279, and 282 are MAP kinase substrates that, when phosphorylated, reduce junctional conductance. Mutant forms of Cx43 were constructed with these serines replaced with amino acids that cannot be phosphorylated. These mutants were transduced into Cx43 knockout ovarian somatic cells that were combined with wild-type oocytes and grafted into immunocompromised female mice permitting follicle growth in vivo. Despite residues 255 or 262 being mutated to prevent their being phosphorylated, recombinant ovaries constructed with these mutants were able to rescue the null phenotype, restoring complete folliculogenesis. In contrast, Cx43 with serine to alanine mutations at both residues 279 and 282 or at all four residues failed to rescue folliculogenesis; the mutant molecules were largely confined to intracellular sites, with few gap junctions. Using an in vitro proliferation assay, we confirmed a decrease in proliferation of granulosa cells expressing the double mutant construct. These results indicate that Cx43 phosphorylation by MAP kinase at serines 279 and 282 occurs in granulosa cells of early follicles and that this is involved in regulating follicle development.
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Affiliation(s)
- Paul W Dyce
- Department of Physiology and Pharmacology, The University of Western Ontario and Children's Health Research Institute, London, ON N6C 2V5, Canada
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339
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Connexin43 cardiac gap junction remodeling: lessons from genetically engineered murine models. J Membr Biol 2012; 245:275-81. [PMID: 22722763 DOI: 10.1007/s00232-012-9448-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2012] [Accepted: 06/01/2012] [Indexed: 10/28/2022]
Abstract
Sudden cardiac death is responsible for several hundred thousand deaths each year in the United States. Multiple lines of evidence suggest that perturbation of gap junction expression and function in the heart, or what has come to be known as cardiac gap junction remodeling, plays a key mechanistic role in the pathophysiology of clinically significant cardiac arrhythmias. Here we review recent studies from our laboratory using genetically engineered murine models to explore mechanisms implicated in pathologic gap junction remodeling and their proarrhythmic consequences, with a particular focus on aberrant posttranslational phosphorylation of connexin43.
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340
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Investigation on the effects of experimental STZ-induced diabetic rat model on basal membrane structures and gap junctions of skin. Int J Diabetes Dev Ctries 2012. [DOI: 10.1007/s13410-012-0070-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
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341
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Yeganeh A, Stelmack GL, Fandrich RR, Halayko AJ, Kardami E, Zahradka P. Connexin 43 phosphorylation and degradation are required for adipogenesis. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1823:1731-44. [PMID: 22705883 DOI: 10.1016/j.bbamcr.2012.06.009] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2012] [Revised: 06/06/2012] [Accepted: 06/07/2012] [Indexed: 11/25/2022]
Abstract
Connexin-43 (Cx43) is a membrane phosphoprotein that mediates direct inter-cellular communication by forming gap junctions. In this way Cx43 can influence gene expression, differentiation and growth. Its role in adipogenesis, however, is poorly understood. In this study, we established that Cx43 becomes highly phosphorylated in early adipocyte differentiation and translocates to the plasma membrane from the endoplasmic reticulum. As preadipocytes differentiate, Cx43 phosphorylation declines, the protein is displaced from the plasma membrane, and total cellular levels are reduced via proteosomal degradation. Notably, we show that inhibiting Cx43 degradation or constitutively over-expressing Cx43 blocks adipocyte differentiation. These data reveal that transient activation of Cx43 via phosphorylation followed by its degradation is vital for preadipocyte differentiation and maturation of functional adipocytes.
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Affiliation(s)
- Azadeh Yeganeh
- Department of Human Nutritional Sciences, University of Manitoba, Winnipeg, Canada
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342
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Wilhelmsen K, Mesa KR, Lucero J, Xu F, Hellman J. ERK5 protein promotes, whereas MEK1 protein differentially regulates, the Toll-like receptor 2 protein-dependent activation of human endothelial cells and monocytes. J Biol Chem 2012; 287:26478-94. [PMID: 22707717 DOI: 10.1074/jbc.m112.359489] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Endothelial cell (EC) Toll-like receptor 2 (TLR2) activation up-regulates the expression of inflammatory mediators and of TLR2 itself and modulates important endothelial functions, including coagulation and permeability. We defined TLR2 signaling pathways in EC and tested the hypothesis that TLR2 signaling differs in EC and monocytes. We found that ERK5, heretofore unrecognized as mediating TLR2 activation in any cell type, is a central mediator of TLR2-dependent inflammatory signaling in human umbilical vein endothelial cells, primary human lung microvascular EC, and human monocytes. Additionally, we observed that, although MEK1 negatively regulates TLR2 signaling in EC, MEK1 promotes TLR2 signaling in monocytes. We also noted that activation of TLR2 led to the up-regulation of intracellularly expressed TLR2 and inflammatory mediators via NF-κB, JNK, and p38-MAPK. Finally, we found that p38-MAPK, JNK, ERK5, and NF-κB promote the attachment of human neutrophils to lung microvascular EC that were pretreated with TLR2 agonists. This study newly identifies ERK5 as a key regulator of TLR2 signaling in EC and monocytes and indicates that there are fundamental differences in TLR signaling pathways between EC and monocytes.
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Affiliation(s)
- Kevin Wilhelmsen
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, California 94143,USA.
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343
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Johnstone SR, Kroncke BM, Straub AC, Best AK, Dunn CA, Mitchell LA, Peskova Y, Nakamoto RK, Koval M, Lo CW, Lampe PD, Columbus L, Isakson BE. MAPK phosphorylation of connexin 43 promotes binding of cyclin E and smooth muscle cell proliferation. Circ Res 2012; 111:201-11. [PMID: 22652908 DOI: 10.1161/circresaha.112.272302] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
RATIONALE Dedifferentiation of vascular smooth muscle cells (VSMC) leading to a proliferative cell phenotype significantly contributes to the development of atherosclerosis. Mitogen-activated protein kinase (MAPK) phosphorylation of proteins including connexin 43 (Cx43) has been associated with VSMC proliferation in atherosclerosis. OBJECTIVE To investigate whether MAPK phosphorylation of Cx43 is directly involved in VSMC proliferation. METHODS AND RESULTS We show in vivo that MAPK-phosphorylated Cx43 forms complexes with the cell cycle control proteins cyclin E and cyclin-dependent kinase 2 (CDK2) in carotids of apolipoprotein-E receptor null (ApoE(-/-)) mice and in C57Bl/6 mice treated with platelet-derived growth factor-BB (PDGF). We tested the involvement of Cx43 MAPK phosphorylation in vitro using constructs for full-length Cx43 (Cx43) or the Cx43 C-terminus (Cx43(CT)) and produced null phosphorylation Ser>Ala (Cx43(MK4A)/Cx43(CTMK4A)) and phospho-mimetic Ser>Asp (Cx43(MK4D)/Cx43(CTMK4D)) mutations. Coimmunoprecipitation studies in primary VSMC isolated from Cx43 wild-type (Cx43(+/+)) and Cx43 null (Cx43(-/-)) mice and analytic size exclusion studies of purified proteins identify that interactions between cyclin E and Cx43 requires Cx43 MAPK phosphorylation. We further demonstrate that Cx43 MAPK phosphorylation is required for PDGF-mediated VSMC proliferation. Finally, using a novel knock-in mouse containing Cx43-MK4A mutation, we show in vivo that interactions between Cx43 and cyclin E are lost and VSMC proliferation does not occur after treatment of carotids with PDGF and that neointima formation is significantly reduced in carotids after injury. CONCLUSIONS We identify MAPK-phosphorylated Cx43 as a novel interacting partner of cyclin E in VSMC and show that this interaction is critical for VSMC proliferation. This novel interaction may be important in the development of atherosclerotic lesions.
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Affiliation(s)
- Scott R Johnstone
- Robert M. Berne Cardiovascular Research Center, Charlottesville, VA 22908, USA
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344
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Gap junction proteins on the move: connexins, the cytoskeleton and migration. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1828:94-108. [PMID: 22613178 DOI: 10.1016/j.bbamem.2012.05.014] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Revised: 04/25/2012] [Accepted: 05/04/2012] [Indexed: 01/08/2023]
Abstract
Connexin43 (Cx43) has roles in cell-cell communication as well as channel independent roles in regulating motility and migration. Loss of function approaches to decrease Cx43 protein levels in neural cells result in reduced migration of neurons during cortical development in mice and impaired glioma tumor cell migration. In other cell types, correlations between Cx43 expression and cell morphology, adhesion, motility and migration have been noted. In this review we will discuss the common themes that have been revealed by a detailed comparison of the published results of neuronal cells with that of other cell types. In brief, these comparisons clearly show differences in the stability and directionality of protrusions, polarity of movement, and migration, depending on whether a) residual Cx43 levels remain after siRNA or shRNA knockdown, b) Cx43 protein levels are not detectable as in cells from Cx43(-/-) knockout mice or in cells that normally have no endogenous Cx43 expression, c) gain-of-function approaches are used to express Cx43 in cells that have no endogenous Cx43 and, d) Cx43 is over-expressed in cells that already have low endogenous Cx43 protein levels. What is clear from our comparisons is that Cx43 expression influences the adhesiveness of cells and the directionality of cellular processes. These observations are discussed in light of the ability of cells to rearrange their cytoskeleton and move in an organized manner. This article is part of a Special Issue entitled: The Communicating junctions, roles and dysfunctions.
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345
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Abstract
Decreases in cardiac connexin43 (Cx43) play a critical role in abnormal cell-to-cell communication and have been linked to the resistance of the female heart to arrhythmias. We therefore hypothesized that Cx43 expression would be greater in female cardiomyocytes than in male cardiomyocytes under pathologic conditions. Adult ventricular myocytes were isolated from male and female rats and treated with phenylephrine (PE), a well-established pathologic stimulus. Cx43 gene and protein expression was determined. The expression of micro-RNA-1 (miR-1), a micro-RNA known to control Cx43 protein expression in cardiomyocytes, was also determined. Cx43 mRNA and protein levels were significantly higher in the female cardiomyocytes than in the male cardiomyocytes (mRNA: 1.4-fold; Protein: 5-fold, both P < 0.05) under both basal and pathologic conditions. PE treatment increased Cx43 expression only in female cardiomyocytes. Cx43 phosphorylation, a marker of preserved Cx43 function, was also higher (P < 0.05), and The expression of miR-1 was lower (P < 0.05) in the female cardiomyocytes after PE treatment. The expression of miR-1 was unchanged by PE treatment in male cardiomyocytes. Thus, a sex difference in miR-1 may be responsible for the sex difference in Cx43 expression in cardiomyocytes under pathologic conditions. Taken together, our results demonstrate a sex difference in Cx43 expression and site-specific phosphorylation that favors cardioprotection in female cardiomyocytes.
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346
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Saidi Brikci-Nigassa A, Clement MJ, Ha-Duong T, Adjadj E, Ziani L, Pastre D, Curmi PA, Savarin P. Phosphorylation Controls the Interaction of the Connexin43 C-Terminal Domain with Tubulin and Microtubules. Biochemistry 2012; 51:4331-42. [DOI: 10.1021/bi201806j] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Amal Saidi Brikci-Nigassa
- Institut National de la Santé
et de la Recherche Médicale (INSERM), UMR829, Université Evry-Val d’Essonne, Laboratoire
Structure-Activité des Biomolécules Normales et Pathologiques,
Evry 91025, France
| | - Marie-Jeanne Clement
- Institut National de la Santé
et de la Recherche Médicale (INSERM), UMR829, Université Evry-Val d’Essonne, Laboratoire
Structure-Activité des Biomolécules Normales et Pathologiques,
Evry 91025, France
| | - Tap Ha-Duong
- Centre
National de la Recherche
Scientifique (CNRS), UMR 8587, Université Evry-Val d’Essonne, Laboratoire Analyse et Modélisation
pour la Biologie et l’Environnement, Evry 91025, France
| | - Elisabeth Adjadj
- Institut National de la Santé
et de la Recherche Médicale (INSERM), UMR829, Université Evry-Val d’Essonne, Laboratoire
Structure-Activité des Biomolécules Normales et Pathologiques,
Evry 91025, France
| | - Latifa Ziani
- Institut National de la Santé
et de la Recherche Médicale (INSERM), UMR829, Université Evry-Val d’Essonne, Laboratoire
Structure-Activité des Biomolécules Normales et Pathologiques,
Evry 91025, France
| | - David Pastre
- Institut National de la Santé
et de la Recherche Médicale (INSERM), UMR829, Université Evry-Val d’Essonne, Laboratoire
Structure-Activité des Biomolécules Normales et Pathologiques,
Evry 91025, France
| | - Patrick A. Curmi
- Institut National de la Santé
et de la Recherche Médicale (INSERM), UMR829, Université Evry-Val d’Essonne, Laboratoire
Structure-Activité des Biomolécules Normales et Pathologiques,
Evry 91025, France
| | - Philippe Savarin
- Institut National de la Santé
et de la Recherche Médicale (INSERM), UMR829, Université Evry-Val d’Essonne, Laboratoire
Structure-Activité des Biomolécules Normales et Pathologiques,
Evry 91025, France
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347
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Wu Y, Gu EW, Zhu Y, Zhang L, Liu XQ, Fang WP. Sufentanil limits the myocardial infarct size by preservation of the phosphorylated connexin 43. Int Immunopharmacol 2012; 13:341-6. [PMID: 22561119 DOI: 10.1016/j.intimp.2012.04.009] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Revised: 03/10/2012] [Accepted: 04/18/2012] [Indexed: 11/18/2022]
Abstract
Sufentanil, with a potent analgesia effect, has been wildly used in anesthesia and analgesia, especially for the cardiovascular surgeries. The aim of the study was to evaluate whether sufentanil provides cardioprotection and the effect of connexin 43 on the cardiac infarct size reduction. Sufentanil post-conditioning (bolus injection at 0.1, 0.3, 1, 3, 10 μg/kg) or ischemic post-conditioning (3 cycles of a 10s reperfusion alternating with a 10s ischemia) was induced in an intact rat heart model of ischemia-reperfusion injury. Both ischemic and sufentanil post-conditioning reduced the myocardial infarct size compared with control group. The infarct size limitation of sufentanil was dose-dependent, 1 μg/kg has the optimal effect and increasing dosage could not afford further cardioprotection. Connexin 43 underwent dephosphorylation in response to ischemia-reperfusion measured by Western blot at the anterior myocardium tissues of left ventricle while sufentanil preserved the phosphorylation of connexin 43. The results demonstrated that sufentanil limits myocardial infarct size which is similar with ischemic post-conditioning at the dosage of 1 μg/kg. Preservation of phosphorylation of connexin 43 plays an important role in the cardioprotection of ischemic and sufentanil post-conditioning.
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Affiliation(s)
- Yun Wu
- Department of Anesthesiology, The First Affiliated Hospital of Anhui Medical University, 218 Jixi Road, Hefei, China
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348
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Larsen AP, Sciuto KJ, Moreno AP, Poelzing S. The voltage-sensitive dye di-4-ANEPPS slows conduction velocity in isolated guinea pig hearts. Heart Rhythm 2012; 9:1493-500. [PMID: 22537886 DOI: 10.1016/j.hrthm.2012.04.034] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Indexed: 11/19/2022]
Abstract
BACKGROUND Voltage-sensitive dyes are important tools for mapping electrical activity in the heart. However, little is known about the effects of voltage-sensitive dyes on cardiac electrophysiology. OBJECTIVE To test the hypothesis that the voltage-sensitive dye di-4-ANEPPS modulates cardiac impulse propagation. METHODS Electrical and optical mapping experiments were performed in isolated Langendorff perfused guinea pig hearts. The effect of di-4-ANEPPS on conduction velocity and anisotropy of propagation was quantified. HeLa cells expressing connexin 43 were used to evaluate the effect of di-4-ANEPPS on gap junctional conductance. RESULTS In electrical mapping experiments, di-4-ANEPPS (7.5 μM) was found to decrease both longitudinal and transverse conduction velocities significantly compared with control. No change in the anisotropy of propagation was observed. Similar results were obtained in optical mapping experiments. In these experiments, the effect of di-4-ANEPPS was dose dependent. di-4-ANEPPS had no detectable effect on connexin 43-mediated gap junctional conductance in transfected HeLa cells. CONCLUSION Our results demonstrate that the voltage-sensitive dye di-4-ANEPPS directly and dose-dependently modulates cardiac impulse propagation. The effect is not likely mediated by connexin 43 inhibition. Our results highlight an important caveat that should be taken into account when interpreting data obtained using di-4-ANEPPS in cardiac preparations.
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Affiliation(s)
- Anders Peter Larsen
- Nora Eccles-Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, Utah 84112, USA
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349
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Ishikawa S, Kuno A, Tanno M, Miki T, Kouzu H, Itoh T, Sato T, Sunaga D, Murase H, Miura T. Role of connexin-43 in protective PI3K-Akt-GSK-3β signaling in cardiomyocytes. Am J Physiol Heart Circ Physiol 2012; 302:H2536-44. [PMID: 22505645 DOI: 10.1152/ajpheart.00940.2011] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Sarcolemmal connexin-43 (Cx43) and mitochondrial Cx43 play distinct roles: formation of gap junctions and production of reactive oxygen species (ROS) for redox signaling. In this study, we examined the hypothesis that Cx43 contributes to activation of a major cytoprotective signal pathway, phosphoinositide 3-kinase (PI3K)-Akt-glycogen synthase kinase-3β (GSK-3β) signaling, in cardiomyocytes. A δ-opioid receptor agonist {[d-Ala(2),d-Leu(5)]enkephalin acetate (DADLE)}, endothelin-1 (ET-1), and insulin-like growth factor-1 (IGF-1) induced phosphorylation of Akt and GSK-3β in H9c2 cardiomyocytes. Reduction of Cx43 protein to 20% of the normal level by Cx43 small interfering RNA abolished phosphorylation of Akt and GSK-3β induced by DADLE or ET-1 but not that induced by IGF-1. DADLE and IGF-1 protected H9c2 cells from necrosis after treatment with H(2)O(2) or antimycin A. The protection by DADLE or ET-1, but not that by IGF-1, was lost by reduction of Cx43 protein expression. In contrast to Akt and GSK-3β, PKC-ε, ERK and p38 mitogen-activated protein kinase were phosphorylated by ET-1 in Cx43-knocked-down cells. Like diazoxide, an activator of the mitochondrial ATP-sensitive K(+) channel, DADLE and ET-1 induced significant ROS production in mitochondria, although such an effect was not observed for IGF-1. Cx43 knockdown did not attenuate the mitochondrial ROS production by DADLE or ET-1. Cx43 was coimmunoprecipitated with the β-subunit of G protein (Gβ), and knockdown of Gβ mimicked the effect of Cx43 knockdown on ET-1-induced phosphorylation of Akt and GSK-3β. These results suggest that Cx43 contributes to activation of class I(B) PI3K in PI3K-Akt-GSK-3β signaling possibly as a cofactor of Gβ in cardiomyocytes.
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Affiliation(s)
- Satoko Ishikawa
- Division of Cardiology, Second Department of Internal Medicine, Sapporo Medical University, School of Medicine, Sapporo, Japan
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350
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Bivi N, Lezcano V, Romanello M, Bellido T, Plotkin LI. Connexin43 interacts with βarrestin: a pre-requisite for osteoblast survival induced by parathyroid hormone. J Cell Biochem 2012; 112:2920-30. [PMID: 21630325 DOI: 10.1002/jcb.23208] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Parathyroid hormone (PTH) promotes osteoblast survival through a mechanism that depends on cAMP-mediated signaling downstream of the G protein-coupled receptor PTHR1. We present evidence herein that PTH-induced survival signaling is impaired in cells lacking connexin43 (Cx43). Thus, expression of functional Cx43 dominant negative proteins or Cx43 knock-down abolished the expression of cAMP-target genes and anti-apoptosis induced by PTH in osteoblastic cells. In contrast, cells lacking Cx43 were still responsive to the stable cAMP analog dibutyril-cAMP. PTH survival signaling was rescued by transfecting wild type Cx43 or a truncated dominant negative mutant of βarrestin, a PTHR1-interacting molecule that limits cAMP signaling. On the other hand, Cx43 mutants lacking the cytoplasmic domain (Cx43(Δ245)) or unable to be phosphorylated at serine 368 (Cx43(S368A)), a residue crucial for Cx43 trafficking and function, failed to restore the anti-apoptotic effect of PTH in Cx43-deficient cells. In addition, overexpression of wild type βarrestin abrogated PTH survival signaling in Cx43-expressing cells. Moreover, βarrestin physically associated in vivo to wild type Cx43 and to a lesser extent to Cx43(S368A) ; and this association and the phosphorylation of Cx43 in serine 368 were reduced by PTH. Furthermore, induction of Cx43(S368) phosphorylation or overexpression of wild type Cx43, but not Cx43(Δ245) or Cx43(S368A) , reduced the interaction between βarrestin and the PTHR1. These studies demonstrate that βarrestin is a novel Cx43-interacting protein and suggest that, by sequestering βarrestin, Cx43 facilitates cAMP signaling, thereby exerting a permissive role on osteoblast survival induced by PTH.
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Affiliation(s)
- Nicoletta Bivi
- Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202-5120, USA
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