The Antiviral Nucleotide Analogs Cidofovir and Adefovir Are Novel Substrates for Human and Rat Renal Organic Anion Transporter 1
- Tomas Cihlar1,
- Deborah C. Lin1,
- John B. Pritchard2,
- Michael D. Fuller1,
- Dirk B. Mendel1 and
- Douglas H. Sweet2
- 1Gilead Sciences, Foster City, California (T.C., D.C.L., M.D.F., D.B.M.); and 2Laboratory of Pharmacology and Chemistry, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina (J.B.P., D.H.S)
Abstract
Nephrotoxicity is the dose-limiting clinical adverse effect of cidofovir and adefovir, two potent antiviral therapeutics. Because renal uptake likely plays a role in the etiology of cidofovir- and adefovir-associated nephrotoxicity, we attempted to identify a renal transporter capable of interacting with these therapeutics. A cDNA clone was isolated from a human renal library and designated human organic anion transporter 1 (hOAT1). Northern analysis detected a specific 2.5-kilobase pair hOAT1 transcript only in human kidney. However, reverse transcription-polymerase chain reaction revealed hOAT1 expression in human brain and skeletal muscle, as well. Immunoblot analysis of human kidney cortex demonstrated that hOAT1 is an 80- to 90-kilodalton heterogeneous protein modified by abundantN-glycosylation. Xenopus laevis oocytes expressing hOAT1 supported probenecid-sensitive uptake of [3H]p-aminohippurate (Km = 4 μM), which wastrans-stimulated in oocytes preloaded with glutarate. Importantly, both hOAT1 and rat renal organic anion transporter 1 (rROAT1) mediated saturable, probenecid-sensitive uptake of cidofovir, adefovir, and other nucleoside phosphonate antivirals. The affinity of hOAT1 toward cidofovir and adefovir (Km = 46 and 30 μM, respectively) was 5- to 9-fold higher compared with rROAT1 (Km = 238 and 270 μM, respectively). These data indicate that hOAT1 may significantly contribute to the accumulation of cidofovir and adefovir in renal proximal tubules and, thus, play an active role in the mechanism of nephrotoxicity associated with these antiviral therapeutics.
Footnotes
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Send reprint requests to: Dr. Tomas Cihlar, Gilead Sciences, 333 Lakeside Dr., Foster City, CA 94404. E-mail:tomas_cihlar{at}gilead.com
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The nucleotide sequence reported in this paper has been submitted to the GenBank/EBI Data Bank with accession numberAF124373.
- Abbreviations:
- rROAT1
- rat renal organic anion transporter 1
- α-KG
- α-ketoglutarate
- bp
- base
- CKII
- casein kinase II
- EST
- expressed sequence tag
- hPAHT
- human p-aminohippurate transporter
- kb
- kilobase pair
- oatp
- organic anion transporting polypeptide
- OR-2
- oocyte Ringer’s 2
- PAH
- p-aminohippurate
- PBS-M
- phosphate-buffered saline/5% dry milk
- PCR
- polymerase chain reaction
- PKA
- protein kinase A
- PKC
- protein kinase C
- PMEG
- 9-(2-phosphonylmethoxyethyl)guanine
- PMEDAP
- 9-(2-phosphonylmethoxyethyl)diaminopurine
- RT-PCR
- reverse transcription-PCR
- SSC
- sodium chloride/sodium citrate solution
- TK
- tyrosine kinase
- UTR
- untranslated region
- hOAT1
- human renal organic anion transporter 1
- mNKT(mROAT1)
- mouse renal organic anion transporter 1
- fROAT1
- winter flounder renal organic anion transporter 1
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- Received April 5, 1999.
- Accepted June 17, 1999.
- U.S. Government
