Cloning, functional characterization, and localization of a rat renal Na⁺-dicarboxylate transporter

Abstract

We report here the isolation, functional characterization, tissue distribution, and membrane localization of rat renal Na+-dicarboxylate transporter (rNaDC-1). rNaDC-1 consists of 2,245 nucleotides, and the deduced amino acid sequence showed 73% and 75% identity to rabbit and human NaDC-1, respectively. When expressed in Xenopus laevis oocytes, rNaDC-1 mediated sodium-dependent uptake of di- and tricarboxylates. Substrates of rNaDC-1 evoked inward currents in oocytes expressed with rNaDC-1; succinate, α-ketoglutarate, and glutarate were relatively high-affinity substrates, and citrate was a low-affinity substrate of rNaDC-1. The coupling ratio of citrate to charge was determined to be 1:1 at pH 7.4; influx of one positive charge per citrate molecule suggests a symport of three Na+with a divalent citrate. Expression of rNaDC-1 mRNA was detected in the kidney and the small and large intestines. Immunohistochemistry using polyclonal antibodies raised against the 14 amino acids at the COOH terminus of rNaDC-1 revealed that rNaDC-1 is localized exclusively in the luminal membrane of S2 and S3.

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

“…The degree of identity of the fNaDC-3 protein with the functional Na ϩ -dicarboxylate cotransporters is around 45% (in detail: 46% with X. laevis NaDC-2; 43, 44, and 43% with rat, rabbit, and human NaDC-1, respectively). The lower amino acid identity to the not yet functionally characterized Ri-19 (36%) might be attributable to possible frameshifts as discussed by Sekine et al (15). On the other hand, the human renal NaDC-1 has a strikingly higher homology not only to rabbit and rat NaDC-1 (78 and 77% identity, respectively), but also to X. laevis intestinal NaDC-2 (66% identity).…”

“…3), the other being the rat renal Na ϩ -sulfate cotransporter NaSi-1. Of these, the rat and rabbit NaDC-1 (15,31), as well as NaSi-1 (32), have so far been associated with the luminal membrane of the epithelium. The degree of identity of the fNaDC-3 protein with the functional Na ϩ -dicarboxylate cotransporters is around 45% (in detail: 46% with X. laevis NaDC-2; 43, 44, and 43% with rat, rabbit, and human NaDC-1, respectively).…”

“…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.…”

Primary Structure and Functional Characteristics of a Mammalian Sodium-coupled High Affinity Dicarboxylate Transporter

“…There have been several reports on the cloning and functional characterization of the low affinity sodium/dicarboxylate transporter from mammalian kidney (13)(14)(15)(16) and intestine (17). This transporter has been designated as either NaDC1 (Na ϩ /dicarboxylate cotransporter 1) or SDCT1 (sodium/dicarboxylate transporter 1).…”

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

“…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.…”