NHE1 (gene symbol SLC9A1) encodes an isoform of the amiloride-sensitive Na+-H+ exchanger that is present in many cells and the basolateral membrane of renal epithelia. Expression of NHE1 is modulated in response to chronic metabolic acidosis, growth factors, and phorbol esters. To begin examining the molecular basis for this regulation, a rabbit genomic clone that contained 6 kb of 5′ flanking region, the first exon, and a portion of the first intervening sequence of NHE1 was obtained. The principal transcription start site in native rabbit tissues was located 798 by 5' to the initiation codon. The sequence of the proximal 5′ flanking region of rabbit NHE1 was similar to the human sequence and contained a TATA-box, (G + C)-boxes, homopyrimidine direct repeats, and a putative AP-1 site. When ligated to luciferase and transfected into porcine renal epithelial cells (LLC-PK1), 708 by of proximal 5′ flanking region exhibited orientation-dependent promoter activity.
Bibliographical noteFunding Information:
This study was supporLed by NIH grant RO1 DK-42921. This work was performed in partial fulfillment of the requirements for an M.D. degree from Yale University (to M.C.B.). We thank J. Elsemore and M. Sadowski for expert technical assistance, K. McDonaugh for providing pUC007L-A A5', S. Subramani for providing pSV2-LUC, and M. Pucci for secretarial assistance. M.C.B. was a recipient of a Student Scholarship in the Kidney in Cardiovascular Disease from the American Heart Association (AHA). N.A.R. was the recipient of a postdoctoral fellowship from the Funda~ao de Amparo h Pesquisa do Estado de S~o Paulo. P.I. was a recipient of a New Investigator Award from the AHA Connecticut Affiliate, Inc.
- Carrier protein
- LLC-PK cell
- Sodium-hydrogen antiporter