Novel amiloride-sensitive sodium-dependent proton secretion in the mouse proximal convoluted tubule

Choi, Joo Young; Shah, Mehul; Lee, Min Goo; Schultheis, Patrick J.; Shull, Gary E.; Muallem, Shmuel; Baum, Michel

doi:10.1172/jci9260

Cited by 111 publications

(111 citation statements)

References 29 publications

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“…4A) using the Cl-NHE-specific probe revealed expression in several epithelial and non-epithelial tissues including proximal colon, heart, lung, kidney, and liver. Second, perfusion studies of proximal renal tubule in NHE-2, NHE-3, and NHE-2/ NHE-3 knockout mice that were performed in the presence of luminal chloride demonstrated sodium-dependent proton secretion that was inhibited by low concentrations of EIPA (30). These findings of an unidentified NHE representing ϳ50% of total NHE activity in proximal tubule are consistent with the potential presence of Cl-NHE.…”

Section: Identification Of a Chloride-dependent Nasupporting

confidence: 61%

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 Nasupporting

confidence: 61%

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

Sangan¹,

Rajendran²,

Geibel³

et al. 2002

Journal of Biological Chemistry

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“…Another HCO 3 Ϫ -transporting mechanism in tissues that express CFTR is HCO 3 Ϫ -absorbing processes that may function as HCO 3 Ϫ salvage mechanisms in the resting state (8). In the pancreatic duct (8) and the kidney proximal tubule (9), 50% of HCO 3 Ϫ absorption is mediated by the Na ϩ /H ϩ exchanger isoform 3 (NHE3) and 50% by a novel, yet unidentified, Na ϩ -dependent mechanism. Hence, HCO 3 Ϫ homeostasis in secretory epithelia is accomplished by both HCO 3 Ϫ -absorbing (resting state) and HCO 3 Ϫ -secretory (stimulated state) mechanisms.…”

Section: Patients (1) Cf Is Caused By Mutations In the Cystic Fibrosmentioning

confidence: 99%

Regulatory Interaction between the Cystic Fibrosis Transmembrane Conductance Regulator and HCO 3− Salvage Mechanisms in Model Systems and the Mouse Pancreatic Duct

Ahn

Kim

Lee

et al. 2001

Journal of Biological Chemistry

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105

114

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The pancreatic duct expresses cystic fibrosis transmembrane conductance regulator (CFTR) and HCO 3 ؊ secretory and salvage mechanisms in the luminal membrane. Although CFTR plays a prominent role in HCO 3 ؊ secretion, the role of CFTR in HCO 3 ؊ salvage is not known. In the present work, we used molecular, biochemical, and functional approaches to study the regulatory interaction between CFTR and the HCO 3 ؊ salvage mechanism Na ؉ /H ؉ exchanger isoform 3 (NHE3) in heterologous expression systems and in the native pancreatic duct. We found that CFTR regulates NHE3 activity by both acute and chronic mechanisms. In the pancreatic duct, CFTR increases expression of NHE3 in the luminal membrane. Thus, luminal expression of NHE3 was reduced by 53% in ducts of homozygote ⌬F508 mice. Accordingly, luminal Na ؉ -dependent and HOE694-sensitive recovery from an acid load was reduced by 60% in ducts of ⌬F508 mice. CFTR and NHE3 were coimmunoprecipitated from PS120 cells expressing both proteins and the pancreatic duct of wild type mice but not from PS120 cells lacking CFTR or the pancreas of ⌬F508 mice. The interaction between CFTR and NHE3 required the COOH-terminal PDZ binding motif of CFTR, and mutant CFTR proteins lacking the C terminus were not co-immunoprecipitated with NHE3. Furthermore, when expressed in PS120 cells, wild type CFTR, but not CFTR mutants lacking the C-terminal PDZ binding motif, augmented cAMP-dependent inhibition of NHE3 activity by 31%. These findings reveal that CFTR controls overall HCO 3 ؊ homeostasis by regulating both pancreatic ductal HCO 3 ؊ secretory and salvage mechanisms.Fluid secretion and the control of the ionic composition of biological fluids are essential for the function of many secretory epithelia, including the respiratory, digestive, and reproductive systems. HCO 3 Ϫ is an important constituent of secreted fluids by virtue of its function as the biological pH buffer and its effect on the solubility of proteins and ions in biological fluids. Accordingly, the mechanisms underlying HCO 3 Ϫ homeostasis at rest and during stimulation have attracted much attention in recent years. The importance of HCO 3 Ϫ homeostasis is evident from the marked reduction in Cl Ϫ -and HCO 3 Ϫ

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“…All NHEs have a predicted N-terminal hydrophobic ion-translocating domain and a variable C-terminal hydrophilic domain that harbors regulatory sequences (15)(16)(17)(18). NHE3 is the isoform in the apical membrane based on antigenic (19,20) and functional data (21)(22)(23)(24). Non-NHE3-mediated Na ϩ /H ϩ exchange activity in the proximal tubule apical membrane (24) can theoretically be caused by NHE8 (14), but definitive data are still forthcoming.…”

mentioning

confidence: 99%

“…NHE3 is the isoform in the apical membrane based on antigenic (19,20) and functional data (21)(22)(23)(24). Non-NHE3-mediated Na ϩ /H ϩ exchange activity in the proximal tubule apical membrane (24) can theoretically be caused by NHE8 (14), but definitive data are still forthcoming. The current study focuses on NHE3.…”

mentioning

confidence: 99%