Cloning and functional characterization of a novel rat organic anion transporter mediating basolateral uptake of methotrexate in the kidney

Hideyuki Salto, Satohiro Masuda, Ken Ichi Inui

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187 Citations (Scopus)

Abstract

We have cloned a cDNA coding for a novel member of organic anion transporter, designated OAT-K1, expressed specifically in the kidney of rats. The rat OAT-K1 cDNA (2788 base pairs) had an open reading frame encoding for a 669-amino acid protein (calculated molecular mass of 74 kDa) which shows 72% identity with the cloned rat liver organic anion transporter, oatp. Northern hybridization and reverse transcription-coupled polymerase chain reaction revealed that the rat OAT-K1 messenger RNA transcript is expressed predominantly in the kidney. By use of stable LLC-PK1 cell monolayers transfected with the rat OAT-K1 cDNA, the transporter was suggested to mediate basolateral uptake of methotrexate, an anionic anticancer drug, but not taurocholate, p-aminohippurate, prostaglandin E2, and leukotriene C4. The methotrexate transport by rat OAT-K1 was unaffected by the presence of Na+ or Cl- gradient. The methotrexate accumulation by the OAT-K1-expressing cells showed saturability with the apparent K(m) value of 1.0 μM. Folate, sulfobromophthalein, and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) inhibited the methotrexate accumulation markedly. These findings suggest that the rat OAT-KI is localized in the basolateral membranes of renal tubules, where it mediates renal clearance of methotrexate from the blood.

Original languageEnglish
Pages (from-to)20719-20725
Number of pages7
JournalJournal of Biological Chemistry
Volume271
Issue number34
DOIs
Publication statusPublished - 1996

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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