Low external K+ regulates Na,K-ATPase alpha 1 and beta 1 gene expression in rat cardiac myocytes.
Incubation of mammalian cells in medium containing low K+ is often associated with an increase in Na,K-ATPase activity and content. In the present studies, we investigated the effect of low K+ on the regulation of Na,K-ATPase alpha 1 and beta 1 gene expression in primary cultures of neonatal rat cardiac myocytes. Northern blot hybridization analysis indicated that exposure of cardiocytes to a medium containing 0.3 mmol/L K+ for 72 h resulted in 1.8- and 3.3-fold increases in the abundance of alpha 1 and beta 1 mRNAs, respectively, compared with control cells exposed to 5.4 mmol/L K+. To investigate the molecular mechanism of the low K effect on beta 1 mRNA content, we constructed chimeric genes with a full-length and deleted portion of the 5' end of the rat beta 1 gene linked to the firefly luciferase gene. Transient transfection experiments using these constructs indicated that beta 1 gene sequences between -102 and +151 base pairs (bp) are required for low K(+)-induced trans-activation of reporter gene expression. Taken together, these results indicate that low K+ induction of beta 1 mRNA abundance in neonatal rat cardiac myocytes is mediated by regulatory DNA sequences in close proximity to the site of transcription initiation of the beta 1 gene.
Qin
X
X
Department of Biochemistry, State University of New York Health Science Center at Brooklyn 11203.
Liu
B
B
Gick
G
G
D000818:Animals; D000831:Animals, Newborn; D015152:Blotting, Northern; D004247:DNA / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D066298:In Vitro Techniques; D008156:Luciferases / Q000032:analysis; D009206:Myocardium / Q000166:cytology / Q000201:enzymology*; D011188:Potassium / Q000502:physiology*; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics*; D014162:Transfection; D001616:beta-Galactosidase / Q000032:analysis
D012333:RNA, Messenger; D004247:DNA; D008156:Luciferases; D001616:beta-Galactosidase; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium