title: Regulation of apical membrane Na+/H+ exchangers NHE2 and NHE3 in intestinal epithelial cell line C2/bbe.
abstract: We examined the regulation of the Na+/H+ exchangers (NHEs) NHE2 and NHE3 by expressing them in human intestinal C2/bbe cells, which spontaneously differentiate and have little basal apical NHE activity. Unidirectional apical membrane 22Na+ influxes were measured in NHE2-transfected (C2N2) and NHE3-transfected (C2N3) cells under basal and stimulated conditions, and their activities were distinguished as the HOE-642-sensitive and -insensitive components of 5-(N,N-dimethyl)amiloride-inhibitable flux. Both C2N2 and C2N3 cells exhibited increased apical membrane NHE activity under non-acid-loaded conditions compared with nontransfected control cells. NHE2 was inhibited by 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate and thapsigargin, was stimulated by serum, and was unaffected by cGMP- and protein kinase C-dependent pathways. In contrast, NHE3 was inhibited by all regulatory pathways examined. Under acid-loaded conditions (which increase apical Na+ influx), NHE2 and NHE3 exhibited similar patterns of regulation, suggesting that the second messenger effects observed were not secondary to effects on cell pH. Thus, in contrast to their expression in nonepithelial cells, NHE2 and NHE3 expressed in an epithelial cell line behave similarly to endogenously expressed intestinal apical membrane NHEs. We conclude that physiological regulation and function of epithelium-specific NHEs are dependent on tissue-specific factors and/or conditional requirements.
authors.affiliation: Section of Gastroenterology, Department of Medicine, University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: R L
authors.initials: RL
authors.lastname: McSwine
authors.forename: M W
authors.initials: MW
authors.lastname: Musch
authors.forename: C
authors.initials: C
authors.lastname: Bookstein
authors.forename: Y
authors.initials: Y
authors.lastname: Xie
authors.forename: M
authors.initials: M
authors.lastname: Rao
authors.forename: E B
authors.initials: EB
authors.lastname: Chang
mesh_terms: D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D006152:Cyclic GMP / Q000378:metabolism; D006146:Guanidines / Q000494:pharmacology; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism*; D007700:Kinetics; D010641:Phenotype; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D015290:Second Messenger Systems / Q000187:drug effects / Q000502:physiology; D012964:Sodium / Q000378:metabolism*; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000096:biosynthesis / Q000378:metabolism*; D013450:Sulfones / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology; D013997:Time Factors; D014162:Transfection
chemical_list: D006146:Guanidines; D011994:Recombinant Proteins; C081517:SLC9A2 protein, human; C000613385:SLC9A3 protein, human; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D013450:Sulfones; D013873:Thionucleotides; C039465:5-dimethylamiloride; C015929:8-((4-chlorophenyl)thio)cyclic-3',5'-AMP; D019284:Thapsigargin; D000584:Amiloride; C093373:cariporide; D012964:Sodium; D000242:Cyclic AMP; D006152:Cyclic GMP; D013755:Tetradecanoylphorbol Acetate