Structure/function studies of the epithelial isoforms of the mammalian Na+/H+ exchanger gene family

Tse, Ming; Levine, Stuart M.; Yun, Chris; Brant, Steve; Counillon, Laurent; Pouysségur, Jacques; Donowitz, Mark

doi:10.1007/bf00231435

Cited by 136 publications

(69 citation statements)

References 78 publications

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“…Because Cl-NHE activity in both colonic AMV and during crypt microperfusion studies is inhibited by NPPB, a nonspecific Cl Ϫ channel blocker, an additional study was performed with 500 M NPPB that significantly reduced sodium/chloridedependent pH i recovery to an acid load by Ϫ59 Ϯ 3%. Thus, the pharmacological profile distinguishes the novel Cl-NHE from all other known NHE isoforms and particularly from the closely related NHE-1 isoform (3,14). More importantly, the functional and pharmacological properties of this novel NHE isoform closely resemble those of the recently described Cl-dependent Na ϩ -H ϩ exchange in apical membranes of colon crypts strongly suggesting that this newly identified cDNA encodes the transport protein expressing Cl-NHE function in apical membranes of colonic crypts (12)(13)(14).…”

Section: Identification Of a Chloride-dependent Namentioning

confidence: 60%

“…At least seven NHE isoforms have been cloned to date and functionally expressed with a length ranging from 669 to 898 amino acids with 10 -12 putative transmembrane domains (1)(2)(3)(4)(5). NHE-1 isoform is ubiquitous and linked to intracellular pH (pH i ) and cell volume regulation, whereas other isoforms (e.g.…”

Section: Namentioning

confidence: 99%

“…By using both crypt AMV and microperfusion, we demonstrated that both [H ϩ ] gradient-driven 22 Na ϩ uptake and sodium-dependent recovery of pH i from an acid load, respectively, had an absolute requirement for chloride (12)(13)(14). Additional studies established that the chloride dependence of chloride-dependent Na ϩ -H ϩ exchange (Cl-NHE) most likely involves one or more Cl Ϫ channels, including cystic fibrosis transmembrane regulator, and not a Cl Ϫ -HCO 3 Ϫ exchange, as follows: 1) Cl-NHE activity in AMV was inhibited by both Cl Ϫ channel blockers and partially by a polyclonal antibody to cystic fibrosis transmembrane regulator (13); 2) Cl Ϫ -HCO 3 Ϫ exchangers are not present in crypt AMV (15); and 3) Cl-NHE activity was not inhibited by 100 M 4,4Ј-diisothiocyanostilbene-2,2Ј-disulfonic acid, a concentration that only inhibits chloride anion exchanges but not Cl Ϫ channels (13). As the characteristics and the kinetic properties of the colonic Cl-NHE differed from those of other known NHE isoforms (14) and NHE-2 but not the NHE-3 isoform has been localized to the apical membrane of colonic crypt cells, it was likely that chloride-dependent Na ϩ -H ϩ exchange transport protein was mediated by a previously unidentified NHE isoform.…”

Section: Namentioning

confidence: 99%

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Cloning and Expression of a Chloride-dependent Na+-H+ Exchanger

Sangan¹,

Rajendran²,

Geibel³

et al. 2002

Journal of Biological Chemistry

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Electroneutral Na؉ -H ؉ exchange is present in virtually all cells, mediating the exchange of extracellular Na ؉ for intracellular H ؉ and, thus, plays an important role in the regulation of intracellular pH, cell volume, and transepithelial Na ؉ absorption. Recent transport studies demonstrated the presence of a novel chloridedependent Na ؉ -H ؉ exchange in the apical membrane of crypt cells of rat distal colon. We describe the cloning of a 2.5-kb full-length cDNA from rat distal colon that encodes 438 amino acids and has six putative transmembrane spanning domains. Of the 438 amino acids 375 amino acids at the N-terminal region are identical to Na ؉ -H ؉ exchange (NHE)-1 isoform with the remaining 63 amino acids comprising a completely novel C terminus. In situ hybridization revealed that this transcript is expressed in colonic crypt cells, whereas Northern blot analysis established the presence of its 2.5-kb mRNA in multiple tissues. Despite its much smaller size compared with all other known Na ؉ -H ؉ exchange isoforms, NHEdeficient PS120 fibroblasts stably transfected with this cDNA exhibited Na ؉ -dependent intracellular pH recovery to an acid load that was chloride-dependent and inhibited both by 5-ethylisopropylamiloride, an amiloride analogue, and by 5-nitro-2-(3-phenylproplyamino)-benzoic acid, a Cl ؊ channel blocker, but only minimally affected by 25 M 3-methylsulfonyl-4piperidonbenzoyl-guanidine, an NHE-1 and NHE-2 isoform inhibitor.

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Section: Identification Of a Chloride-dependent Namentioning

confidence: 60%

Section: Namentioning

confidence: 99%

Section: Namentioning

confidence: 99%

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Cloning and Expression of a Chloride-dependent Na+-H+ Exchanger

Sangan¹,

Rajendran²,

Geibel³

et al. 2002

Journal of Biological Chemistry

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“…NHE2, NHE3, and NHE4 mRNAs show a more limited pattern of expression. They are preferentially found in the gastrointestinal tract and in the kidney (5,6,8). The targeting of NHE2 in polarized renal and intestinal epithelial cells is controversial, with some studies reporting basolateral (19) and others apical (brush border) localization (20).…”

Section: Tissue and Subcellular Distributionmentioning

confidence: 99%

Na+/H+ Exchangers of Mammalian Cells

Orlowski¹,

Grinstein²

1997

Journal of Biological Chemistry

551

429

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“…Na + /H + antiports are expressed in all mammalian cells. Six isoforms of the Na + /H + antiports have been identified and named NHE1 -6 (Sardet et al, 1989;Orlowski et al, 1992;Tse et al, 1992;Tse et al, 1993;Wang et al, 1993;Klanke et al, 1995;Numata et al, 1998). While NHE1 is found in most cells, NHE2-5 are tissue specific and NHE6 is expressed in mitochondria (Counillon and Pouyssegur, 2000).…”

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confidence: 99%

Cytostatic potential of novel agents that inhibit the regulation of intracellular pH

Wong

Hw²,

Tannock

2002

Br J Cancer

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Cells within the acidic extracellular environment of solid tumours maintain their intracellular pH (pHi) through the activity of membrane-based ion exchange mechanisms including the Na + /H + antiport and the Na + -dependent Cl 7 /HCO 3 7 exchanger. Inhibition of these regulatory mechanisms has been proposed as an approach to tumour therapy. Previously available inhibitors of these exchangers were toxic (e.g. 4,4-diisothiocyanstilbene-2,2-disulphonic acid), and/or non-specific (e.g. 5-N-ethyl-Nisopropyl amiloride). Using two human (MCF7, MDA-MB231) and one murine (EMT6) breast cancer cell lines, we evaluated the influence of two new agents, cariporide (an inhibitor of the Na + /H + antiport) and S3705 (an inhibitor of the Na + -dependent Cl 7 /HCO 3 7 exchanger) on the regulation of intracellular pH (pHi). The cytotoxicity of the two agents was assessed by using clonogenic assays. Our results suggest that cariporide has similar efficacy and potency to 5-N-ethyl-Nisopropyl amiloride for inhibition of Na + /H + exchange while S3705 is more potent and efficient than 4,4-diisothiocyanstilbene-2,2-disulphonic acid in inhibiting Na+-dependent Cl 7 /HCO3 7 exchange. The agents inhibited the growth of tumour cells when they were incubated at low pHe (7.0 -6.8), but were non-toxic to cells grown at doses that inhibited the regulation of pHi. Our results indicate that cariporide and S3705 are selective cytostatic agents under in vitro conditions that reflect the slightly acidic microenvironment found in solid tumours.

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Structure/function studies of the epithelial isoforms of the mammalian Na+/H+ exchanger gene family

Cited by 136 publications

References 78 publications

Cloning and Expression of a Chloride-dependent Na+-H+ Exchanger

Cloning and Expression of a Chloride-dependent Na+-H+ Exchanger

Na+/H+ Exchangers of Mammalian Cells

Cytostatic potential of novel agents that inhibit the regulation of intracellular pH

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