Regulation of NHE-1 promoter in mammalian myocardium.
The Na+/H exchanger (NHE-1) is an integral membrane protein responsible for intracellular pH regulation in the myocardium and other tissues. The NHE-1 isoform is universally distributed in mammalian cells. We examined regulation of a 1.1-kb fragment of the NHE-1 promoter in neonatal rat cardiomyocytes. Deletion of most of the promoter up to an AP-2 site reduced activity 75%. Further deletion of the promoter or mutation of the AP-2 site reduced or eliminated activity almost completely. Gel mobility shift assay showed that purified AP-2 protein or AP-2-like protein from nuclear extracts of isolated myocytes can bind to DNA of the NHE-1 protein. External acidosis did not cause increased transcription from the promoter. Removal of serum from the medium reduced activity of the NHE-1 promoter. The elements responsible for activation of the promoter by serum were contained within both the 1.1-kb and AP-2-containing region. The results show that the cis-acting putative AP-2 site and the presence of serum are important in NHE-1 expression, whereas external acidosis had no direct effect on the promoter.
Yang
W
W
Department of Biochemistry, Faculty of Medicine, University of Alberta, Edmonton, Canada.
Dyck
J R
JR
Wang
H
H
Fliegel
L
L
D000138:Acidosis / Q000378:metabolism / Q000473:pathology; D000818:Animals; D001483:Base Sequence; D001790:Blood Physiological Phenomena; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000502:physiology; D006321:Heart / Q000502:physiology*; D015335:Molecular Probes / Q000235:genetics; D008969:Molecular Sequence Data; D009206:Myocardium / Q000166:cytology / Q000378:metabolism / Q000473:pathology; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics* / Q000378:metabolism; D050656:Transcription Factor AP-2; D014157:Transcription Factors / Q000502:physiology; D014158:Transcription, Genetic; D014162:Transfection
D004268:DNA-Binding Proteins; D015335:Molecular Probes; D012333:RNA, Messenger; D017923:Sodium-Hydrogen Exchangers; D050656:Transcription Factor AP-2; D014157:Transcription Factors; C069139:growth factor-activatable Na-H exchanger NHE-1