Identification and Characterization of Human Organic Anion Transporter 3 Expressing Predominantly in the Kidney

  1. Seok Ho Cha1,
  2. Takashi Sekine1,
  3. Jun-ichi Fukushima2,
  4. Yoshikatsu Kanai1,2,
  5. Yukari Kobayashi,
  6. Tomoyuki Goya2 and
  7. Hitoshi Endou1
  1. 1Department of Pharmacology and Toxicology (S.H.C., T. S., Y. K., H. E.) and 2Second Department of Surgery (J.F., Y.K., T.G.), Kyorin University School of Medicine, Shinkawa, Mitaka, Tokyo, Japan

    Abstract

    A cDNA encoding a multispecific organic anion transporter 3 (hOAT3) was isolated from a human kidney cDNA library. The hOAT3 cDNA consisted of 2179 base pairs that encoded a 543-amino-acid residue protein with 12 putative transmembrane domains. The deduced amino acid sequence of hOAT3 showed 36 to 51% identity to those of other members of the OAT family. Northern blot analysis revealed that hOAT3 mRNA is expressed in the kidney, brain, and skeletal muscle. When expressed inXenopus laevis oocytes, hOAT3 mediated the transport of estrone sulfate (K m = 3.1 μM),p-aminohippurate (K m = 87.2 μM), methotrexate (K m = 10.9 μM), and cimetidine (K m = 57.4 μM) in a sodium-independent manner. hOAT3 also mediated the transport of dehydroepiandrosterone sulfate, ochratoxin A, PGE2, estradiol glucuronide, taurocholate, glutarate, cAMP and uric acid. Estrone sulfate did not show any trans-stimulatory effects on either influx or efflux of [3H]estrone sulfate via hOAT3. hOAT3 interacted with chemically heterogeneous anionic compounds, such as nonsteroidal anti-inflammatory drugs, diuretics, sulfobromophthalein, penicillin G, bile salts and tetraethyl ammonium bromide. The hOAT3 protein was shown to be localized in the basolateral membrane of renal proximal tubules and the hOAT3 gene was determined to be located on the human chromosome 11q12-q13.3 by fluorescent in situ hybridization analysis. These results suggest an important role of hOAT3 in the excretion/detoxification of endogenous and exogenous organic anions in the kidney.

    Footnotes

    • Send reprint requests to: Dr. Hitoshi Endou, Dept. of Pharmacology and Toxicology, Kyorin University School of Medicine, 6–20-2 Shinkawa, Mitaka, Tokyo, 181-8611, Japan. E-mail:endouh{at}kyorin-u.ac.jp

    • This work was supported in part by grants from the Japanese Ministry of Education Science, Sports and Culture, Grants-in-Aids for Scientific Research, and High-Tech Research Center from the Science Research Promotion Fund of the Japan Private School Promotion Foundation, and Research on Health Sciences focusing on Drug Innovation from the Japan Health Sciences Foundation.

    • The nucleotide sequence reported in this article has been submitted to the GenBank/EBI Data bank with accession number AB042505.

    • Abbreviations:
      hOAT
      human organic anion transporter
      PAH
      para-aminohippurate
      rOAT
      rat organic anion transporter
      DHEA
      dehydroepiandrosterone
      PG
      prostaglandin
      TEA
      tetraethylammonium
      PCR
      polymerase chain reaction
      EST
      expressed sequence tag
      SSC
      standard saline citrate
      FISH
      fluorescent in situ hybridization
      MES
      4-morpholineethanesulfonic acid
      MTX
      methotrexate
      DAPI
      4,6-diamidino-2-phenylindole
      oatp
      organic anion transporting polypeptide
      Mrp
      multidrug resistance associated protein
      • Received August 28, 2000.
      • Accepted January 26, 2001.
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    1. Molecular Pharmacology May 1, 2001 vol. 59 no. 5 1277-1286
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