Wnt-1 regulation of connexin43 in cardiac myocytes.
Gap junction channels composed of connexin43 (Cx43) are essential for normal heart formation and function. We studied the potential role of the Wnt family of secreted polypeptides as regulators of Cx43 expression and gap junction channel function in dissociated myocytes and intact hearts. Neonatal rat cardiomyocytes responded to Li(+), which mimics Wnt signaling, by accumulating the effector protein beta-catenin and by inducing Cx43 mRNA and protein markedly. Induction of Cx43 expression was also observed in cardiomyocytes cocultured with Rat-2 fibroblasts or N2A neuroblastoma cells programmed to secrete bioactive Wnt-1. By transfecting a Cx43 promoter-reporter gene construct into cardiomyocytes, we demonstrated that the inductive effect of Wnt signaling was transcriptionally mediated. Enhanced expression of Cx43 increased cardiomyocyte cell coupling, as determined by Lucifer Yellow dye transfer and by calcium wave propagation. Conversely, in a transgenic cardiomyopathic mouse model that exhibits ventricular arrhythmias and gap junctional remodeling, beta-catenin and Cx43 expression were downregulated concordantly. In response to Wnt signaling, the accumulating Cx43 colocalized with beta-catenin in the junctional membrane; moreover, forced expression of Cx43 in cardiomyocytes reduced the transactivation potential of beta-catenin. These findings demonstrate that Wnt signaling is an important modulator of Cx43-dependent intercellular coupling in the heart, and they support the hypothesis that dysregulated signaling contributes to altered impulse propagation and arrhythmia in the myopathic heart.
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Section of Myocardial Biology, Zena and Michael A. Wiener Cardiovascular Institute, Department of Medicine, Mount Sinai School of Medicine, New York, New York 10029, USA.
Fischer
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Spray
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Brown
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Fishman
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D000818:Animals; D000831:Animals, Newborn; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002478:Cells, Cultured; D018920:Coculture Techniques; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism*; D000242:Cyclic AMP / Q000494:pharmacology; D003598:Cytoskeletal Proteins / Q000037:antagonists & inhibitors / Q000235:genetics; D005456:Fluorescent Dyes; D017629:Gap Junctions / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D017930:Genes, Reporter / Q000187:drug effects; D038362:Glycogen Synthase Kinase 3; D018021:Lithium Chloride / Q000494:pharmacology; D051379:Mice; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism* / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects; D015534:Trans-Activators; D014162:Transfection; D051153:Wnt Proteins; D051155:Wnt1 Protein; D029961:Zebrafish Proteins; D051176:beta Catenin
D000911:Antibodies, Monoclonal; C495267:CTNNB1 protein, mouse; D018031:Connexin 43; C495268:Ctnnb1 protein, rat; D003598:Cytoskeletal Proteins; D005456:Fluorescent Dyes; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D015534:Trans-Activators; D051153:Wnt Proteins; D051155:Wnt1 Protein; C495246:Wnt1 protein, mouse; C495245:Wnt1 protein, rat; D029961:Zebrafish Proteins; D051176:beta Catenin; D000242:Cyclic AMP; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D038362:Glycogen Synthase Kinase 3; D018021:Lithium Chloride; D002118:Calcium