Sequence and Functional Characterization of a Renal Sodium/Dicarboxylate Cotransporter

Abstract

The cDNA coding for a rabbit renal Na+/dicarboxylate cotransporter, designated NaDC-1, was isolated by functional expression in Xenopus oocytes. NaDC-1 cDNA is approximately 2.3 kilobases in length and codes for a protein of 593 amino acids. NaDC-1 protein contains eight putative transmembrane domains, and the sequence and secondary structure are related to the renal Na+/sulfate transporter, NaSi-1. Northern analysis shows that the NaDC-1 message is abundant in kidney and small intestine, and related transporters may be found in liver, lung, and adrenal. The transport of succinate by NaDC-1 was sodium-dependent, sensitive to inhibition by lithium, and inhibited by a range of di- and tricarboxylic acids. This transporter also carries citrate, but it does not transport lactate. In kinetic experiments, the Km for succinate was around 0.4 mM and the Vmax was 15 nmol/oocyte/h, while the Hill coefficient of Na+ activation of succinate transport was 1.9. The transport of succinate by NaDC-1 was insensitive to changes in pH, whereas the transport of citrate increased with decreasing pH, in parallel with the concentration of divalent citrate in the medium. The results of the functional characterization indicate that NaDC-1 likely corresponds to the renal brush-border Na+/dicarboxylate cotransporter.

Role of Conserved Prolines in the Structure and Function of the Na+/Dicarboxylate Cotransporter 1, NaDC1

“…The kinetic values for the mutant represent mean ± range of two independent experiments. The rbNaDC1 kinetic parameters compare well with the K m of 0.5 mM measured in our previous studies (17).…”

“…Rabbit (rb) NaDC1 in pcDNA3.1 vector was used as a template (17). We were unable to make the P327A mutant.…”

Expression Cloning and Characterization of a Novel Sodium-Dicarboxylate Cotransporter from Winter Flounder Kidney

“…In recent years, the luminal dicarboxylate transporters from rabbit, NaDC-1 (13), human, hNaDC-1 (14), and rat kidney, rNaDC-1 (15) or SDCT1 (16), as well as homologous transporters from rat, Ri-19 (17), and Xenopus laevis intestine, NaDC-2 (18), have been cloned. In contrast, the basolateral transporter has not yet been characterized on the molecular level.…”

The Renal Na+-Dependent Dicarboxylate Transporter, NaDC-3, Translocates Dimethyl- and Disulfhydryl-Compounds and Contributes to Renal Heavy Metal Detoxification

“…In contrast, 2,3-DMS was a very weak inhibitor of dicarboxylate transport at the luminal membrane (K i , 3.76 Ϯ 0.73 mM) (19). Within the cloned NaDC-1 orthologs, DMS analogs left either radiolabeled succinate uptake unaffected (41,45,46) or induced currents comparable in magnitude to succinate under two-electrode voltage clamp conditions (44,47,48). In contrast, NaDC-3 orthologs were generally sensitive to DMS analogs (12)(13)(14)(15)(16).…”

“…The Na ϩ -dependent dicarboxylate transporter located at the brush-border membrane of intestinal and renal epithelial cells exhibits a K 0.5 of 0.2 to 1 mM for succinate. This transporter, designated NaDC-1, has been cloned from various species and functionally characterized ( [41][42][43][44][45]. The high-affinity Na ϩ -dependent dicarboxylate transporter with a K 0.5 Ͻ 0.2 mM for succinate is located at the basolateral membrane of renal proximal tubular cells, sinusoidal membrane of hepatocytes, brain synaptosomes, and the maternal-facing brush border membrane of the placental syncytiotrophoblast.…”