Regulation of Na/K-ATPase beta1-subunit gene expression by ouabain and other hypertrophic stimuli in neonatal rat cardiac myocytes.
Partial inhibition of Na/K-ATPase by ouabain causes hypertrophic growth and regulates several early and late response genes, including that of Na/K-ATPase alpha3 subunit, in cultured neonatal rat cardiac myocytes. The aim of this work was to determine whether ouabain and other hypertrophic stimuli affect Na/K-ATPase beta1 subunit gene expression. When myocytes were exposed to non-toxic concentrations of ouabain, ouabain increased beta1 subunit mRNA in a dose- and time-dependent manner. Like the alpha3 gene, beta1 mRNA was also regulated by several other well-known hypertrophic stimuli including phenylephrine, a phorbol ester, endothelin-1, and insulin-like growth factor, suggesting involvement of growth signals in regulation of beta1 expression. Ouabain failed to increase beta1 subunit mRNA in the presence of actinomycin D. Using a luciferase reporter gene that is directed by the 5'-flanking region of the beta1 subunit gene, transient transfection assay showed that ouabain augmented the expression of luciferase. These data support the proposition that ouabain regulates the beta1 subunit through a transcriptional mechanism. The effect of ouabain on beta1 subunit induction, like that on alpha3 repression, was dependent on extracellular Ca2+ and on calmodulin. Inhibitions of PKC, Ras, and MEK, however, had different quantitive effects on ouabain-induced regulations of beta1 and alpha3 subunits. The findings show that partial inhibition of Na/K-ATPase activates multiple signaling pathways that regulate growth-related genes, including those of two subunit isoforms of Na/K-ATPase, in a gene-specific manner.
Kometiani
P
P
Department of Pharmacology, Medical College of Ohio, Toledo 43614-5804, USA.
Tian
J
J
Li
J
J
Nabih
Z
Z
Gick
G
G
Xie
Z
Z
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D000831:Animals, Newborn; D015152:Blotting, Northern; D002118:Calcium / Q000494:pharmacology; D002147:Calmodulin / Q000378:metabolism; D002455:Cell Division; D003609:Dactinomycin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D019332:Endothelin-1 / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D017930:Genes, Reporter; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D008156:Luciferases / Q000378:metabolism; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D009206:Myocardium / Q000166:cytology*; D010042:Ouabain / Q000494:pharmacology*; D010656:Phenylephrine / Q000494:pharmacology; D020033:Protein Isoforms; D011493:Protein Kinase C / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000096:biosynthesis* / Q000235:genetics*; D013997:Time Factors; D014158:Transcription, Genetic; D014162:Transfection; D015854:Up-Regulation; D018631:ras Proteins / Q000378:metabolism
D002147:Calmodulin; D019332:Endothelin-1; D020033:Protein Isoforms; D012333:RNA, Messenger; D003609:Dactinomycin; D010656:Phenylephrine; D010042:Ouabain; D007334:Insulin-Like Growth Factor I; D012964:Sodium; D008156:Luciferases; D011493:Protein Kinase C; D020929:Mitogen-Activated Protein Kinase Kinases; D018631:ras Proteins; D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium