title: Molecular identification and functional characterization of rat multidrug and toxin extrusion type transporter 1 as an organic cation/H+ antiporter in the kidney.
abstract: We have cloned and functionally characterized the rat ortholog of multidrug and toxin extrusion type transporter 1 (rMATE1). The mRNA of rMATE1 was strongly expressed in kidney and detectable in the various tissues such as brain, stomach, colon, lung, liver, spleen, skeletal muscle, and prostate. When stably expressed in HEK293 cells, rMATE1 could mediate the transport of tetraethylammonium (TEA) and cimetidine under the condition where the membrane potential was disrupted by a high concentration of potassium ion and intracellular pH was reduced by NH(4)Cl pretreatment. When extracellular pH was changed from 5.5 to 8.5, the transport of TEA by rMATE1 was greatest at pH 7.5. Kinetic analyses showed that the transports of TEA and cimetidine mediated by rMATE1 were both saturable with a K(m) of 260 +/- 10 and 3.01 +/- 0.21 muM, respectively. It was found that cimetidine is the most potent inhibitor of rMATE1, and many other organic cations, such as 1-methyl-4-phenylpyridinium, amiloride, imipramine, and quinidine, are also effective as inhibitors. Pretreatment of the cells expressing rMATE1 with p-chloromercuribenzene sulfonate significantly reduced TEA transport, but this effect was totally reversed by subsequent treatment with dithiothreitol. These results indicate that the functional nature of rMATE1 is consistent with that of the hypothetical organic cation/H(+) antiporter system in the brush-border membrane of the renal tubular epithelial cells. Accordingly, these results suggest that rMATE1 is an electroneutral and multispecific organic cation transporter energized by the trans-proton gradient, and plays a physiological role in renal secretion of organic cations, including clinically used cationic drugs.
authors.affiliation: Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Nagoya, Japan.
authors.forename: Kin-Ya
authors.initials: KY
authors.lastname: Ohta
authors.forename: Katsuhisa
authors.initials: K
authors.lastname: Inoue
authors.forename: Yayoi
authors.initials: Y
authors.lastname: Hayashi
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Yuasa
mesh_terms: D000818:Animals; D017920:Antiporters / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D001692:Biological Transport; D015152:Blotting, Northern; D002412:Cations / Q000378:metabolism*; D002460:Cell Line; D002927:Cimetidine / Q000493:pharmacokinetics; D003001:Cloning, Molecular; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007668:Kidney / Q000378:metabolism*; D027701:Organic Cation Transport Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D012313:RNA / Q000378:metabolism; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013379:Substrate Specificity; D019789:Tetraethylammonium / Q000493:pharmacokinetics; D014162:Transfection
chemical_list: D017920:Antiporters; D002412:Cations; D027701:Organic Cation Transport Proteins; C515734:Slc47a1 protein, rat; D012313:RNA; D019789:Tetraethylammonium; D002927:Cimetidine