Identification of a novel voltage-driven organic anion transporter present at apical membrane of renal proximal tubule.
A novel transport protein with the properties of voltage-driven organic anion transport was isolated from pig kidney cortex by expression cloning in Xenopus laevis oocytes. A cDNA library was constructed from size-fractionated poly(A)+ RNA and screened for p-aminohippurate (PAH) transport in high potassium medium. A 1856-base pair cDNA encoding a 467-amino acid peptide designated as OATV1 (voltage-driven organic anion transporter 1) was isolated. The predicted amino acid sequence of OATV1 exhibited 60-65% identity to those of human, rat, rabbit, and mouse sodium-dependent phosphate cotransporter type 1 (NPT1), although OATV1 did not transport phosphate. The homology of this transporter to known members of the organic anion transporter family (OAT family) was about 25-30%. OATV1-mediated PAH transport was affected by the changes in membrane potential. The transport was Na+-independent and enhanced at high concentrations of extracellular potassium and low concentrations of extracellular chloride. Under the voltage clamp condition, extracellularly applied PAH induced outward currents in oocytes expressing OATV1. The current showed steep voltage dependence, consistent with the voltage-driven transport of PAH by OATV1. The PAH transport was inhibited by various organic anions but not by organic cations, indicating the multispecific nature of OATV1 for anionic compounds. This transport protein is localized at the apical membrane of renal proximal tubule, consistent with the proposed localization of a voltage-driven organic anion transporter. Therefore, it is proposed that OATV1 plays an important role to excrete drugs, xenobiotics, and their metabolites driven by membrane voltage through the apical membrane of the tubular epithelial cells into the urine.
Department of Pharmacology and Toxicology, Kyorin University School of Medicine, 6-20-2 Shinkawa, Mitaka, Tokyo, 181-8611, Japan.
Promsuk
P
Jutabha
Yoshikatsu
Y
Kanai
Makoto
M
Hosoyamada
Arthit
A
Chairoungdua
Do Kyung
DK
Kim
Yuji
Y
Iribe
Ellappan
E
Babu
Ju Young
JY
Kim
Naohiko
N
Anzai
Varanuj
V
Chatsudthipong
Hitoshi
H
Endou
D000818:Animals; D001692:Biological Transport; D015152:Blotting, Northern; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism*; D002713:Chlorine / Q000494:pharmacology; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D004847:Epithelial Cells / Q000378:metabolism; D015723:Gene Library; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007150:Immunohistochemistry; D017136:Ion Transport; D007477:Ions; D007668:Kidney / Q000378:metabolism; D007684:Kidney Tubules / Q000378:metabolism*; D007700:Kinetics; D008564:Membrane Potentials; D051379:Mice; D009865:Oocytes / Q000378:metabolism; D027361:Organic Anion Transporters / Q000737:chemistry* / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000737:chemistry; D011061:Poly A; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology; D018075:RNA, Complementary / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D012964:Sodium / Q000378:metabolism; D050608:Sodium-Phosphate Cotransporter Proteins; D050609:Sodium-Phosphate Cotransporter Proteins, Type I; D050611:Sodium-Phosphate Cotransporter Proteins, Type III; D013379:Substrate Specificity; D013552:Swine; D027981:Symporters / Q000737:chemistry; D013997:Time Factors; D014981:Xenopus; D014982:Xenopus laevis; D010130:p-Aminohippuric Acid / Q000378:metabolism
D018076:DNA, Complementary; D007477:Ions; D027361:Organic Anion Transporters; D010455:Peptides; D018075:RNA, Complementary; C493546:SLC17A1 protein, human; C493547:Slc17a1 protein, mouse; D050608:Sodium-Phosphate Cotransporter Proteins; D050609:Sodium-Phosphate Cotransporter Proteins, Type I; D050611:Sodium-Phosphate Cotransporter Proteins, Type III; D027981:Symporters; D011061:Poly A; D002713:Chlorine; D012964:Sodium; D011188:Potassium; D010130:p-Aminohippuric Acid