Cloning and Functional Expression of a Human Kidney Na+:HCO3−Cotransporter

Burnham, Charles E.; Amlal, Hassane; Wang, Zhaohui; Shull, Gary E.; Soleimani, Manoocher

doi:10.1074/jbc.272.31.19111

Cited by 187 publications

(157 citation statements)

References 22 publications

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“…Oocyte Experiments: hkNBCe1 and S427L cDNAs-The hkNBCe1 cDNA was generated by RT-PCR using oligo(dT)-primed human kidney poly(A) ϩ RNA (Clontech) and primers corresponding to the start and stop of the known sequence (19): F10 (5Ј-ATgTCCACTgAAAATgTggAAgggAAgCCC), R10 (5Ј-TTATCAgCATgATgTgTggCgTTC).…”

Section: Methodsmentioning

confidence: 99%

A Novel Missense Mutation in the Sodium Bicarbonate Cotransporter (NBCe1/SLC4A4) Causes Proximal Tubular Acidosis and Glaucoma through Ion Transport Defects

Dinour

Chang²,

Satoh³

et al. 2004

Journal of Biological Chemistry

165

182

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In humans and terrestrial vertebrates, the kidney controls systemic pH in part by absorbing filtered bicarbonate in the proximal tubule via an electrogenic Na ؉ /HCO 3 ؊ cotransporter (NBCe1/SLC4A4). Recently, human genetics revealed that NBCe1 is the major renal contributor to this process. Homozygous point mutations in NBCe1 cause proximal renal tubular acidosis (pRTA), glaucoma, and cataracts (Igarashi, T., Inatomi, J., Sekine, T., Cha, S. H., Kanai, Y., Kunimi, M., Tsukamoto, K., Satoh, H., Shimadzu, M., Tozawa, F., Mori, T., Shiobara, M., Seki, G., and Endou, H. (1999) Nat. Genet. 23, 264 -266). We have identified and functionally characterized a novel, homozygous, missense mutation (S427L) in NBCe1, also resulting in pRTA and similar eye defects without mental retardation. To understand the pathophysiology of the syndrome, we expressed wild-type (WT) NBCe1 and S427L-NBCe1 in Xenopus oocytes. Function was evaluated by measuring intracellular pH (HCO 3 ؊ transport) and membrane currents using microelectrodes. HCO 3 ؊ -elicited currents for S427L were ϳ10% of WT NBCe1, and CO 2 -induced acidification was ϳ4-fold faster. Na ؉ -dependent HCO 3 ؊ transport (currents and acidification) was also ϳ10% of WT. Current-voltage (I-V) analysis reveals that S427L has no reversal potential in HCO 3 ؊ , indicating that under physiological ion gradient conditions, NaHCO 3 could not move out of cells as is needed for renal HCO 3 ؊ absorption and ocular pressure homeostasis. I-V analysis without Na ؉ further shows that the S427L-mediated NaHCO 3 efflux mode is depressed or absent. These experiments reveal that voltage-and Na ؉ -dependent transport by S427L-hkNBCe1 is unfavorably altered, thereby causing both insufficient HCO 3 ؊ absorption by the kidney (proximal RTA) and inappropriate anterior chamber fluid transport (glaucoma).

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Section: Methodsmentioning

confidence: 99%

A Novel Missense Mutation in the Sodium Bicarbonate Cotransporter (NBCe1/SLC4A4) Causes Proximal Tubular Acidosis and Glaucoma through Ion Transport Defects

Dinour

Chang²,

Satoh³

et al. 2004

Journal of Biological Chemistry

165

182

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“…Expression in HEK293 cells demonstrated that Pendrin can function as a Cl Ϫ /OH Ϫ , Cl Ϫ / HCO 3 Ϫ , and Cl Ϫ /formate exchanger (16). Sodium/bicarbonate co-transporters have been characterized in the kidney (56,57). Sequence alignment of the extreme carboxyl-terminal tail of bicarbonate transport proteins (Fig.…”

Section: Figmentioning

confidence: 99%

A Transport Metabolon

Sterling

Reithmeier

Casey

2001

Journal of Biological Chemistry

336

153

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The cytoplasmic carboxyl-terminal domain of AE1, the plasma membrane chloride/bicarbonate exchanger of erythrocytes, contains a binding site for carbonic anhydrase II (CAII). To examine the physiological role of the AE1/CAII interaction, anion exchange activity of transfected HEK293 cells was monitored by following the changes in intracellular pH associated with AE1-mediated bicarbonate transport. AE1-mediated chloride/bicarbonate exchange was reduced 50 -60% by inhibition of endogenous carbonic anhydrase with acetazolamide, which indicates that CAII activity is required for full anion transport activity. AE1 mutants, unable to bind CAII, had significantly lower transport activity than wild-type AE1 (10% of wild-type activity), suggesting that a direct interaction was required. To determine the effect of displacement of endogenous wild-type CAII from its binding site on AE1, AE1-transfected HEK293 cells were co-transfected with cDNA for a functionally inactive CAII mutant, V143Y. AE1 activity was maximally inhibited 61 ؎ 4% in the presence of V143Y CAII. A similar effect of V143Y CAII was found for AE2 and AE3cardiac anion exchanger isoforms. We conclude that the binding of CAII to the AE1 carboxyl-terminus potentiates anion transport activity and allows for maximal transport. The interaction of CAII with AE1 forms a transport metabolon, a membrane protein complex involved in regulation of bicarbonate metabolism and transport.Carbon dioxide, the metabolic end product of oxidative respiration, must be effectively cleared from the human body. CO 2 diffuses out of cells into the blood stream and into erythrocytes, where it is hydrated by cytosolic carbonic anhydrase (CA). 1 The resulting membrane-impermeant HCO 3 Ϫ is exported into the plasma by the plasma membrane Cl Ϫ /HCO 3 Ϫ anion exchanger (AE1), thus increasing the blood capacity for carrying CO 2 . Upon returning to the lungs the process is reversed; HCO 3 Ϫ is transported into the erythrocyte in exchange for Cl Ϫ by AE1 and dehydrated by CA, and the resulting CO 2 diffuses across the erythrocyte and alveolar membranes to be expired from the body. The 5 ϫ 10 4 s Ϫ1 turnover rate of AE1 (1) and the high content of AE1 in the membrane (2) facilitate completion of bicarbonate transport within 50 ms during passage of an erythrocyte through a capillary (3).AE1 is a 911-amino acid polytopic glycoprotein that facilitates the one for one electroneutral exchange of Cl Ϫ for HCO 3

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“…These findings indicate that NBC1 has essential roles not only in whole-body acid-base balance but also in the maintenance of homeostasis in several tissues. There are two major splicing variants of NBC1, pancreastype NBC1 (pNBC1) (9) and kidney-type NBC1 (kNBC1) (10)(11)(12). pNBC1 and kNBC1 are 93% identical, but the N-terminal 85 aa of pNBC1 are replaced by 41 different amino acids in kNBC1.…”

mentioning

confidence: 99%

IRBIT, an inositol 1,4,5-trisphosphate receptor-binding protein, specifically binds to and activates pancreas-type Na ⁺ /HCO ₃ ⁻ cotransporter 1 (pNBC1)

Shirakabe¹,

Priori²,

Yamada

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

159

222

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Inositol 1,4,5-trisphosphate (IP3) receptors (IP3Rs) are IP3-gated Ca 2؉ channels that are located on intracellular Ca 2؉ stores. We previously identified an IP 3R binding protein, termed IP3R binding protein released with IP3 (IRBIT). Because IRBIT is released from IP3R by physiological concentrations of IP3, we hypothesized that IRBIT is a signaling molecule that is released from IP3R and regulates downstream target molecules in response to the production of IP3. Therefore, in this study, we attempted to identify the target molecules of IRBIT, and we succeeded in identifying Na ؉ ͞HCO3 ؊ cotransporter 1 (NBC1) as an IRBIT binding protein. Of the two major splicing variants of NBC1, pancreas-type NBC1 (pNBC1) and kidney-type NBC1 (kNBC1), IRBIT was found to bind specifically to pNBC1 and not to bind to kNBC1. IRBIT binds to the N-terminal pNBC1-specific domain, and its binding depends on the phosphorylation of multiple serine residues of IRBIT. Also, an electrophysiological analysis in Xenopus oocytes revealed that pNBC1 requires coexpression of IRBIT to manifest substantial activity comparable with that of kNBC1, which displays substantial activity independently of IRBIT. These results strongly suggest that pNBC1 is the target molecule of IRBIT and that IRBIT has an important role in pH regulation through pNBC1. Also, our findings raise the possibility that the regulation through IRBIT enables NBC1 variants to have different physiological roles.pH ͉ acidosis ͉ phosphorylation I nositol 1,4,5-trisphosphate (IP 3 ) receptors (IP 3 Rs) are intracellular Ca 2ϩ -release channels that are located on intracellular Ca 2ϩ -storage organelles, mainly the endoplasmic reticulum (ER) (1). IP 3 Rs release Ca 2ϩ from the ER into the cytoplasm and increase the cytoplasmic concentration of Ca 2ϩ in response to the binding of a second messenger, IP 3 . This IP 3 -Ca 2ϩ pathway regulates many biological processes, including cell growth, cell differentiation, apoptosis, synaptic plasticity, secretion, and fertilization (1).We identified (2) an IP 3 R binding protein, termed IP 3 R binding protein released with IP 3 (IRBIT). IRBIT consists of an N-terminal domain (residues 1-104), which contains a serine͞threonine-rich region, and a C-terminal domain (residues 105-530), which has homology with the methylation pathway enzyme S-adenosylhomocysteine hydrolase. We found (2) that the N-terminal amino acids 1-277 of IRBIT are sufficient for the interaction with the IP 3 R and that the interaction between IRBIT and the IP 3 R is inhibited by physiological concentrations of IP 3 , indicating that IRBIT interacts with the IP 3 R in the resting state and dissociates from the IP 3 R when IP 3 production is induced by extracellular stimuli. Therefore, we speculated that IRBIT acts as a signaling molecule that dissociates from the IP 3 R and regulates target proteins in response to IP 3 production, raising the possibility of the existence of an unidentified pathway, the IP 3 -IRBIT pathway.The Na ϩ ͞HCO 3 Ϫ cotransporter 1 (NBC1) is a membrane...

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Cloning and Functional Expression of a Human Kidney Na+:HCO3−Cotransporter

Cited by 187 publications

References 22 publications

A Novel Missense Mutation in the Sodium Bicarbonate Cotransporter (NBCe1/SLC4A4) Causes Proximal Tubular Acidosis and Glaucoma through Ion Transport Defects

A Novel Missense Mutation in the Sodium Bicarbonate Cotransporter (NBCe1/SLC4A4) Causes Proximal Tubular Acidosis and Glaucoma through Ion Transport Defects

A Transport Metabolon

IRBIT, an inositol 1,4,5-trisphosphate receptor-binding protein, specifically binds to and activates pancreas-type Na ⁺ /HCO ₃ ⁻ cotransporter 1 (pNBC1)

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Cloning and Functional Expression of a Human Kidney Na+:HCO3−Cotransporter

Cited by 187 publications

References 22 publications

A Novel Missense Mutation in the Sodium Bicarbonate Cotransporter (NBCe1/SLC4A4) Causes Proximal Tubular Acidosis and Glaucoma through Ion Transport Defects

A Novel Missense Mutation in the Sodium Bicarbonate Cotransporter (NBCe1/SLC4A4) Causes Proximal Tubular Acidosis and Glaucoma through Ion Transport Defects

A Transport Metabolon

IRBIT, an inositol 1,4,5-trisphosphate receptor-binding protein, specifically binds to and activates pancreas-type Na + /HCO 3 − cotransporter 1 (pNBC1)

Contact Info

Product

Resources

About

IRBIT, an inositol 1,4,5-trisphosphate receptor-binding protein, specifically binds to and activates pancreas-type Na ⁺ /HCO ₃ ⁻ cotransporter 1 (pNBC1)