title: Functional characterization of rat organic anion transporter 5 (Slc22a19) at the apical membrane of renal proximal tubules.
abstract: A novel member of the organic anion transporter (OAT) family, Oat5 (Slc22a19), has been reported to transport a naturally occurring mycotoxin, ochratoxin A (OTA). However, neither its endogenous substrate and driving force nor physiological functions have been determined. Herein, we report the functional characterization of rat Oat5 (rOat5), as well as its intrarenal distribution and membrane localization. When expressed in Xenopus laevis oocytes, rOat5 mediated the transport of sulfate conjugates of steroids such as estrone-3-sulfate (E(1)S; K(m) = 18.9 +/- 3.9 microM) and dehydroepiandrosterone sulfate (K(m) = 2.3 +/- 0.2 microM) in a sodium-independent manner, in addition to OTA. The rOat5-mediated E(1)S transport was strongly inhibited by four-carbon (C4) dicarboxylate succinate and longer dicarboxylates (C7-C9). The uptake of [(3)H]E(1)S via rOat5 was significantly trans-stimulated by succinate, and the efflux of [(14)C]succinate was significantly trans-stimulated by E(1)S. A similar trans-stimulatory effect of preloaded succinate on E(1)S uptake was also detected in cells stably expressing rOat5 (S(2) rOat5). rOat5 interacted with chemically heterogenous anionic compounds. The rOat5-mediated E(1)S transport was inhibited by several sulfate conjugates, such as 4-methylumbelliferyl sulfate and beta-estradiol sulfate, but not by glucuronide conjugates. An immunohistochemical study showed that rOat5 was localized at the apical membrane of renal proximal tubules in the corticomedullary region. rOat5 mRNA was expressed in the late segments (S(2) and S(3)) of proximal tubules. These results indicate that rOat5 is renal organic anion/dicarboxylates exchanger and, under physiological conditions, may function as an apical reabsorptive pathway for organic anions in proximal tubules driven by an outward gradient of dicarboxylates.
authors.affiliation: Department of Pharmacology and Toxicology, Kyorin University School of Medicine, Mitaka-shi, Tokyo, Japan.
authors.forename: Naohiko
authors.initials: N
authors.lastname: Anzai
authors.forename: Promsuk
authors.initials: P
authors.lastname: Jutabha
authors.forename: Atsushi
authors.initials: A
authors.lastname: Enomoto
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Yokoyama
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nonoguchi
authors.forename: Taku
authors.initials: T
authors.lastname: Hirata
authors.forename: Katsuko
authors.initials: K
authors.lastname: Shiraya
authors.forename: Xin
authors.initials: X
authors.lastname: He
authors.forename: Seok Ho
authors.initials: SH
authors.lastname: Cha
authors.forename: Michio
authors.initials: M
authors.lastname: Takeda
authors.forename: Hiroki
authors.initials: H
authors.lastname: Miyazaki
authors.forename: Takeshi
authors.initials: T
authors.lastname: Sakata
authors.forename: Kimio
authors.initials: K
authors.lastname: Tomita
authors.forename: Takashi
authors.initials: T
authors.lastname: Igarashi
authors.forename: Yoshikatsu
authors.initials: Y
authors.lastname: Kanai
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Endou
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D018076:DNA, Complementary / Q000096:biosynthesis / Q000235:genetics; D019314:Dehydroepiandrosterone Sulfate / Q000378:metabolism; D029382:Dicarboxylic Acid Transporters / Q000378:metabolism*; D004970:Estrone / Q000031:analogs & derivatives / Q000378:metabolism; D020224:Expressed Sequence Tags; D007150:Immunohistochemistry; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D007700:Kinetics; D008566:Membranes / Q000378:metabolism; D009399:Nephrons / Q000166:cytology / Q000378:metabolism; D009865:Oocytes / Q000378:metabolism; D018075:RNA, Complementary / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013386:Succinates / Q000378:metabolism; D014162:Transfection; D014982:Xenopus laevis
chemical_list: D018076:DNA, Complementary; D029382:Dicarboxylic Acid Transporters; D018075:RNA, Complementary; C506835:Slc22a24 protein, rat; D013386:Succinates; D004970:Estrone; D019314:Dehydroepiandrosterone Sulfate; C017296:estrone sulfate