{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,8]],"date-time":"2026-05-08T21:28:37Z","timestamp":1778275717293,"version":"3.51.4"},"reference-count":24,"publisher":"American Physiological Society","issue":"3","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["American Journal of Physiology-Renal Physiology"],"published-print":{"date-parts":[[2007,9]]},"abstract":"<jats:p>NHE8 is expressed in the apical membrane of the proximal tubule and is predicted to be a Na<jats:sup>+<\/jats:sup>\/H<jats:sup>+<\/jats:sup>exchanger on the basis of its primary amino acid sequence. Functional characterization of native NHE8 in mammalian cells has not been possible to date. We screened a number of polarized renal cell lines for the plasma membrane Na<jats:sup>+<\/jats:sup>\/H<jats:sup>+<\/jats:sup>exchangers (NHE1, 2, 3, 4, and 8) and found only NHE1 and NHE8 transcripts in NRK cells by RT-PCR. NHE8 protein is expressed in the apical membrane of NRK cells as demonstrated by immunoblots, confocal fluorescent immunocytochemistry, and immunoelectron microscopy. NHE1, on the other hand, is expressed primarily in the basolateral membrane. Bilateral perfusion of NRK cells grown on permeable supports shows Na<jats:sup>+<\/jats:sup>\/H<jats:sup>+<\/jats:sup>exchange activity on both the apical and basolateral membranes. NHE8-specific small interfering RNA knocks down NHE8 protein expression but does not affect NHE1 protein levels. Knockdown of NHE8 protein is accompanied by a commensurate reduction in apical NHE activity, without altered basolateral NHE activity. Conversely, transfection of NHE1-specific small interfering RNA knocks down NHE1 protein expression without affecting NHE8 protein levels and reduces basolateral NHE activity without affecting apical NHE activity. NHE8 is the only apical membrane Na<jats:sup>+<\/jats:sup>\/H<jats:sup>+<\/jats:sup>exchanger in NRK cells. NHE8 activity is Na<jats:sup>+<\/jats:sup>dependent, displaying a cooperative sigmoidal relationship, and is highly sensitive to 5-( N-ethyl- n-isopropyl)-amiloride (EIPA). NRK cells provide a useful system where NHE8 can be studied in its native environment.<\/jats:p>","DOI":"10.1152\/ajprenal.00117.2007","type":"journal-article","created":{"date-parts":[[2007,6,21]],"date-time":"2007-06-21T01:44:19Z","timestamp":1182390259000},"page":"F761-F766","source":"Crossref","is-referenced-by-count":40,"title":["Characterization of Na<sup>+<\/sup>\/H<sup>+<\/sup>exchanger NHE8 in cultured renal epithelial cells"],"prefix":"10.1152","volume":"293","author":[{"given":"Jianning","family":"Zhang","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ion Alexandru","family":"Bobulescu","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sunita","family":"Goyal","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Peter S.","family":"Aronson","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Michel G.","family":"Baum","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Orson W.","family":"Moe","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"24","reference":[{"key":"R1","doi-asserted-by":"publisher","DOI":"10.1085\/jgp.86.5.613"},{"key":"R2","doi-asserted-by":"publisher","DOI":"10.1038\/ki.1995.404"},{"key":"R3","doi-asserted-by":"publisher","DOI":"10.1203\/00006450-199204000-00021"},{"key":"R4","doi-asserted-by":"publisher","DOI":"10.1152\/ajprenal.1995.268.5.F815"},{"key":"R5","doi-asserted-by":"crossref","unstructured":"Becker AM, Zhang J, Goyal S, Dwarakanath V, Aronson PS, Moe OW, Baum M.Ontogeny of NHE8 in the rat proximal tubule.Am J Physiol Renal Physiol(April 11, 2007). doi:10.1152\/ajprenal.00400.2006.","DOI":"10.1152\/ajprenal.00400.2006"},{"key":"R6","doi-asserted-by":"publisher","DOI":"10.1152\/ajprenal.1993.265.5.F736"},{"key":"R7","doi-asserted-by":"publisher","DOI":"10.1097\/01.mnh.0000174146.52915.5d"},{"key":"R8","doi-asserted-by":"publisher","DOI":"10.1152\/ajprenal.00447.2004"},{"key":"R9","doi-asserted-by":"publisher","DOI":"10.1016\/j.semnephrol.2006.07.001"},{"key":"R10","doi-asserted-by":"publisher","DOI":"10.1152\/ajpcell.00360.2004"},{"key":"R11","doi-asserted-by":"publisher","DOI":"10.1172\/JCI116748"},{"key":"R12","doi-asserted-by":"publisher","DOI":"10.1172\/JCI9260"},{"key":"R13","doi-asserted-by":"publisher","DOI":"10.1152\/ajprenal.00229.2004"},{"key":"R14","doi-asserted-by":"publisher","DOI":"10.1152\/ajprenal.00352.2002"},{"key":"R15","doi-asserted-by":"crossref","unstructured":"Kang'Ethe W, Aimanova KG, Pullikuth AK, Gill SS.NHE8 mediates amiloride sensitive Na+\/H+exchange across mosquito Malpighian tubules and catalyzes Na+and K+transport in reconstituted proteoliposomes.Am J Physiol Renal Physiol(Feb 6, 2007). doi:10.1152\/ajprenal.00487.2005.","DOI":"10.1152\/ajprenal.00487.2005"},{"key":"R16","doi-asserted-by":"crossref","unstructured":"Levine SA, Montrose MH, Tse CM, Donowitz M.Kinetics and regulation of three cloned mammalian Na+\/H+exchangers stably expressed in a fibroblast cell line.J Biol Chem268: 25527\u201325535, 1993.","DOI":"10.1016\/S0021-9258(19)74423-8"},{"key":"R17","doi-asserted-by":"publisher","DOI":"10.1172\/JCI115487"},{"key":"R18","doi-asserted-by":"publisher","DOI":"10.1074\/jbc.M410041200"},{"key":"R19","doi-asserted-by":"crossref","unstructured":"Orlowski J.Heterologous expression and functional properties of amiloride high affinity (NHE-1) and low affinity (NHE-3) isoforms of the rat Na\/H exchanger.J Biol Chem268: 16369\u201316377, 1993.","DOI":"10.1016\/S0021-9258(19)85430-3"},{"key":"R20","doi-asserted-by":"publisher","DOI":"10.1007\/s00424-003-1110-3"},{"key":"R21","doi-asserted-by":"crossref","unstructured":"Otsu K, Kinsella JL, Heller P, Froehlich JP.Sodium dependence of the Na+-H+exchanger in the pre-steady state. 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