Publications

• Structure, function, and genomic organization of human Na(+)-dependent high-affinity dicarboxylate transporter.

  Wang H., Fei Y.-J., Kekuda R., Yang-Feng T.L., Devoe L.D., Leibach F.H., Prasad P.D., Ganapathy V.

  We have cloned and functionally characterized the human Na(+)-dependent high-affinity dicarboxylate transporter (hNaDC3) from placenta. The hNaDC3 cDNA codes for a protein of 602 amino acids with 12 transmembrane domains. When expressed in mammalian cells, the cloned transporter mediates the trans ... >> More

  We have cloned and functionally characterized the human Na(+)-dependent high-affinity dicarboxylate transporter (hNaDC3) from placenta. The hNaDC3 cDNA codes for a protein of 602 amino acids with 12 transmembrane domains. When expressed in mammalian cells, the cloned transporter mediates the transport of succinate in the presence of Na(+) [concentration of substrate necessary for half-maximal transport (K(t)) for succinate = 20+/-1 microM]. Dimethylsuccinate also interacts with hNaDC3. The Na(+)-to-succinate stoichiometry is 3:1 and concentration of Na(+) necessary for half-maximal transport (K(Na(+))(0.5)) is 49+/-1 mM as determined by uptake studies with radiolabeled succinate. When expressed in Xenopus laevis oocytes, hNaDC3 induces Na(+)-dependent inward currents in the presence of succinate and dimethylsuccinate. At a membrane potential of -50 mV, K(Suc)(0.5) is 102+/-20 microM and K(Na(+))(0.5) is 22+/-4 mM as determined by the electrophysiological approach. Simultaneous measurements of succinate-evoked charge transfer and radiolabeled succinate uptake in hNaDC3-expressing oocytes indicate a charge-to-succinate ratio of 1:1 for the transport process, suggesting a Na(+)-to-succinate stoichiometry of 3:1. pH titration of citrate-induced currents shows that hNaDC3 accepts preferentially the divalent anionic form of citrate as a substrate. Li(+) inhibits succinate-induced currents in the presence of Na(+). Functional analysis of rat-human and human-rat NaDC3 chimeric transporters indicates that the catalytic domain of the transporter lies in the carboxy-terminal half of the protein. The human NaDC3 gene is located on chromosome 20q12-13.1, as evidenced by fluorescent in situ hybridization. The gene is >80 kbp long and consists of 13 exons and 12 introns. << Less

  Am. J. Physiol. 278:C1019-C1030(2000) [PubMed] [EuropePMC]

  This publication is cited by 3 other entries.

• Cloning and functional characterization of a high-affinity Na(+)/dicarboxylate cotransporter from mouse brain.

  Pajor A.M., Gangula R., Yao X.

  Neurons contain a high-affinity Na(+)/dicarboxylate cotransporter for absorption of neurotransmitter precursor substrates, such as alpha-ketoglutarate and malate, which are subsequently metabolized to replenish pools of neurotransmitters, including glutamate. We have isolated the cDNA coding for a ... >> More

  Neurons contain a high-affinity Na(+)/dicarboxylate cotransporter for absorption of neurotransmitter precursor substrates, such as alpha-ketoglutarate and malate, which are subsequently metabolized to replenish pools of neurotransmitters, including glutamate. We have isolated the cDNA coding for a high-affinity Na(+)/dicarboxylate cotransporter from mouse brain, called mNaDC-3. The mRNA coding for mNaDC-3 is found in brain and choroid plexus as well as in kidney and liver. The mNaDC-3 transporter has a broad substrate specificity for dicarboxylates, including succinate, alpha-ketoglutarate, fumarate, malate, and dimethylsuccinate. The transport of citrate is relatively insensitive to pH, but the transport of succinate is inhibited by acidic pH. The Michaelis-Menten constant for succinate in mNaDC-3 is 140 microM in transport assays and 16 microM at -50 mV in two-electrode voltage clamp assays. Transport is dependent on sodium, although lithium can partially substitute for sodium. In conclusion, mNaDC-3 likely codes for the high-affinity Na(+)/dicarboxylate cotransporter in brain, and it has some unusual electrical properties compared with the other members of the family. << Less

  Am. J. Physiol. 280:C1215-C1223(2001) [PubMed] [EuropePMC]

  This publication is cited by 3 other entries.

• The transport properties of the human renal Na(+)- dicarboxylate cotransporter under voltage-clamp conditions.

  Yao X., Pajor A.M.

  The transport properties of the human Na(+)-dicarboxylate cotransporter, (hNaDC-1), expressed in Xenopus laevis oocytes were characterized using the two-electrode voltage clamp technique. Steady-state succinate-evoked inward currents in hNaDC-1 were dependent on the concentrations of succinate and ... >> More

  The transport properties of the human Na(+)-dicarboxylate cotransporter, (hNaDC-1), expressed in Xenopus laevis oocytes were characterized using the two-electrode voltage clamp technique. Steady-state succinate-evoked inward currents in hNaDC-1 were dependent on the concentrations of succinate and sodium, and on the membrane potential. At -50 mV, the half-saturation constant for succinate (K(0.5)(succinate)) was 1.1 mM and the half-saturation constant for sodium (K(0.5)(sodium)) was 65 mM. The Hill coefficient was 2.3, which is consistent with a transport stoichiometry of 3 Na(+):1 divalent anion substrate. The hNaDC-1 exhibits a high-cation selectivity. Sodium is the preferred cation and other cations, such as lithium, were not able to support transport of succinate. The preferred substrates of hNaDC-1 are fumarate (K(0.5) 1.8 mM) and succinate, followed by methylsuccinate (K(0.5) 2.8 mM), citrate (K(0. 5) 6.8 mM) and alpha-ketoglutarate (K(0.5) 16 mM). The hNaDC-1 may also transport sodium ions through an uncoupled leak pathway, which is sensitive to phloretin inhibition. We propose a transport model for hNaDC-1 in which the binding of three sodium ions is followed by substrate binding. << Less

  Am. J. Physiol. 279:F54-F64(2000) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• Substrate specificity of the human renal sodium dicarboxylate cotransporter, hNaDC-3, under voltage-clamp conditions.

  Burckhardt B.C., Lorenz J., Kobbe C., Burckhardt G.

  Proximal tubule cells extract dicarboxylates from filtrate and blood, using cotransporters located in the brush border [sodium dicarboxylate cotransporter (NaDC-1)] and basolateral cell membrane (NaDC-3). We expressed the human NaDC-3 (hNaDC-3) in Xenopus laevis oocytes and characterized it by the ... >> More

  Proximal tubule cells extract dicarboxylates from filtrate and blood, using cotransporters located in the brush border [sodium dicarboxylate cotransporter (NaDC-1)] and basolateral cell membrane (NaDC-3). We expressed the human NaDC-3 (hNaDC-3) in Xenopus laevis oocytes and characterized it by the two-electrode voltage-clamp technique. At -60 mV, succinate (4 carbons) and glutarate (5 carbons) generated inward currents due to translocation of three sodium ions and one divalent dicarboxylate, whereas oxalate (2 carbons) and malonate (3 carbons) did not. The cis-dicarboxylate maleate produced currents smaller in magnitude, whereas the trans-dicarboxylate fumarate generated currents similar to succinate. The substituted succinate derivatives, malate, 2,2- and 2,3-dimethylsuccinate, and 2,3-dimercaptosuccinate elicited inward currents, whereas aspartate and guanidinosuccinate showed hardly detectable currents. The C-5 dicarboxylates glutarate and alpha-ketoglutarate produced larger currents than succinate; glutamate and folate failed to cause inward currents. Kinetic analysis revealed, at -60 mV, K(0.5) values of 25 +/-12 microM for succinate and 45 +/-13 microM for alpha-ketoglutarate, values close to the plasma concentration of these compounds. For both compounds, the K(0.5) was independent of voltage, whereas the maximal current increased with hyperpolarization. As opposed to the rat and flounder orthologs, hNaDC-3 was hardly inhibited by lithium concentrations up to 5 mM. In the absence of sodium, however, lithium can mediate succinate-dependent currents. The narrow substrate specificity prevents interaction of drugs with dicarboxylate-like structure with hNaDC-3 and ensures sufficient support of the proximal tubule cells with alpha-ketoglutarate for anion secretion via organic anion transporter 1 or 3. << Less

  Am. J. Physiol. 288:F792-F799(2005) [PubMed] [EuropePMC]

  This publication is cited by 7 other entries.