Regulation of the nhe-1 promoter in the mammalian myocardium.
Yang, Weidong, Jason R. B. Dyck, Huayan Wang, and Larry Fliegel.
Departments of Biochemistry and Pediatrics, Faculty of Medicine,
University of Alberta, 417 Heritage Medical Research Center,
Edmonton, Alberta, Canada, T6G 2S2
APStracts 2:0416H, 1995.
The Na/H exchanger 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 was contained
within both the 1.1 kb and the 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 while external acidosis had no
direct effect on the promoter.
Received 28 October 1994; accepted in final form 10 July 1995.
APS Manuscript Number H960-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 September 1995.