Abstract
We have cloned a polyspecific organic anion transporter fromCaenorhabditis elegans and elucidated its functional characteristics. The C. elegans anion transporter (CeOAT1) codes for a protein of 526 amino acids containing 12 putative transmembrane domains. It exhibits significant homology at the level of amino acid sequence to the C. elegans organic cation transporter and to the mammalian organic cation and anion transporters. The function of CeOAT1 was investigated by expressing the transporter heterologously in mammalian cells. CeOAT1 transportsp-aminohippurate (PAH) in a Na+-independent manner. The transport mechanism appears to involve anion exchange because CeOAT1-mediated PAH transport is stimulated by a cell-to-medium concentration gradient of α-ketoglutarate or fumarate generated by coexpression in the cells of a mammalian Na+-coupled dicarboxylate transporter. CeOAT1 exhibits broad specificity, accepting anions such as folate, indomethacin, furosemide, probenecid, and benzylpenicillin as substrates. The Michaelis-Menten constant for the prototypical organic anion PAH is 0.43 ± 0.07 mM. This constitutes the first report of the molecular and functional identification of a polyspecific organic anion transporter in C. elegans.
Footnotes
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Send reprint requests to: Dr. Vadivel Ganapathy, Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA. E-mail: vganapat{at}mail.mcg.edu
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↵1 This work was supported by National Institutes of Health Grant DA 10045.
- Abbreviations:
- PAH
- p-aminohippurate
- CeOAT
- Caenorhabditis elegans organic anion transporter
- OAT
- organic anion transporter
- rNaDC3
- rat Na+-coupled dicarboxylate transporter 3
- OCT
- organic cation transporter
- OCTN
- novel organic cation transporter
- MPP+
- 1-methyl-4-phenylpyridinium ion
- MPTP
- 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine
- TEA
- tetraethylammonium
- RT-PCR
- reverse transcription-polymerase chain reaction
- bp
- base pair(s)
- Received May 25, 1999.
- Accepted July 8, 1999.
- The American Society for Pharmacology and Experimental Therapeutics
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