title: Molecular cloning and functional characterization of a polyspecific organic anion transporter from Caenorhabditis elegans.
abstract: We have cloned a polyspecific organic anion transporter from Caenorhabditis 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 transports p-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 alpha-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.
authors.affiliation: Department of Physiology and Endocrinology, Medical College of Georgia, Augusta, Georgia, USA.
authors.forename: R L
authors.initials: RL
authors.lastname: George
authors.forename: X
authors.initials: X
authors.lastname: Wu
authors.forename: W
authors.initials: W
authors.lastname: Huang
authors.forename: Y J
authors.initials: YJ
authors.lastname: Fei
authors.forename: F H
authors.initials: FH
authors.lastname: Leibach
authors.forename: V
authors.initials: V
authors.lastname: Ganapathy
mesh_terms: D000818:Animals; D000838:Anions / Q000493:pharmacokinetics*; D016588:Anticarcinogenic Agents / Q000378:metabolism; D001483:Base Sequence; D001693:Biological Transport, Active / Q000235:genetics*; D017173:Caenorhabditis elegans / Q000235:genetics*; D003001:Cloning, Molecular / Q000379:methods; D003998:Dicarboxylic Acids / Q000493:pharmacokinetics; D004305:Dose-Response Relationship, Drug; D005650:Fumarates / Q000378:metabolism; D066298:In Vitro Techniques; D007474:Ion Exchange; D007656:Ketoglutaric Acids / Q000378:metabolism; D008969:Molecular Sequence Data; D011837:Radiation-Protective Agents / Q000378:metabolism; D012964:Sodium / Q000502:physiology; D010130:p-Aminohippuric Acid / Q000493:pharmacokinetics*
chemical_list: D000838:Anions; D016588:Anticarcinogenic Agents; D003998:Dicarboxylic Acids; D005650:Fumarates; D007656:Ketoglutaric Acids; D011837:Radiation-Protective Agents; C032005:fumaric acid; D012964:Sodium; D010130:p-Aminohippuric Acid