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Expression of transfected human Na + /H + exchanger (NHE‐1) in the basolateral membrane of opossum kidney cells
Author(s) -
Takaichi Kenmei,
Miyajima Yoshihiro,
Hanai JunIchi,
Kurokawa Kiyoshi,
Fujita Toshiro,
Warnock David G.
Publication year - 1999
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/(sici)1097-4652(199901)178:1<44::aid-jcp6>3.0.co;2-o
Subject(s) - epithelial polarity , amiloride , transfection , apical membrane , dids , chemistry , sodium–hydrogen antiporter , intracellular ph , epithelial sodium channel , cell culture , microbiology and biotechnology , membrane , biochemistry , biophysics , biology , intracellular , sodium , genetics , organic chemistry , gene
Some epithelial cells have Na + /H + exchanger (NHE) activity in both apical and basolateral membranes. Amiloride‐sensitive NHE‐1 is generally identified in the basolateral membrane. The renal cell line, OK7a, targets amiloride‐resistant NHE predominantly to the apical membrane. It is controversial whether the transfected NHE‐1 is targeted preferentially to the basolateral membrane in OK7a cells, when human NHE‐1 is chronically expressed under control of constitutively active promoters. We tried to identify the membranes in which the transfected human NHE‐1 could be detected following acute expression in OK7a cells. We have always observed small Na + ‐dependent pH recovery in the basolateral membrane in OK7a cells. It is, however, controversial whether or not OK7a cells express NHE activity in the basolateral membrane. We also characterized Na + ‐dependent pH recovery in the basolateral membrane. It was not inhibited by [4,4′‐diisothiocyanatostilbene‐2,2′‐disulfonic acid] (DIDS), [4‐acetamido‐4′‐isothiocyanatostilbene‐2,2′‐disulfonic acid] (SITS), or contralateral amiloride. Li + but not K + , chol + , or NMG + could replace Na + . These results are consistent with the presence of the NHE in the basolateral membrane. NHE activities were predominant in the apical membrane and those in both membranes were resistant to amiloride analogs. After stable transfection with human NHE‐1 in a vector utilizing the metallothionein promoter, overnight induction with Zn 2+ increased the NHE activity and its sensitivity to amiloride only in the basolateral membrane in OK7a cells. We conclude that the transfected human NHE‐1 is exclusively targeted to the basolateral membrane of OK7a cells during acute induction. J Cell Physiol 178:44–50, 1999. © 1999 Wiley‐Liss, Inc.