Molecular Mechanisms for Species Differences in Organic Anion Transporter 1, OAT1: Implications for Renal Drug Toxicity<sup><a href="#FN3" rid="FN3" class=" fn"><img alt="An external file that holds a picture, illustration, etc. Object name is sbox.jpg" src="/pmc/articles/PMC5987998/bin/sbox.jpg"></a></sup>
Abstract
Species differences in renal drug transporters continue to plague drug development with animal models failing to adequately predict renal drug toxicity. For example, adefovir, a renally excreted antiviral drug, failed clinical studies for human immunodeficiency virus due to pronounced nephrotoxicity in humans. In this study, we demonstrated that there are large species differences in the kinetics of interactions of a key class of antiviral drugs, acyclic nucleoside phosphonates (ANPs), with organic anion transporter 1 [(OAT1) SLC22A6] and identified a key amino acid residue responsible for these differences. In OAT1 stably transfected human embryonic kidney 293 cells, the Km value of tenofovir for human OAT1 (hOAT1) was significantly lower than for OAT1 orthologs from common preclinical animals, including cynomolgus monkey, mouse, rat, and dog. Chimeric and site-directed mutagenesis studies along with comparative structure modeling identified serine at position 203 (S203) in hOAT1 as a determinant of its lower Km value. Furthermore, S203 is conserved in apes, and in contrast alanine at the equivalent position is conserved in preclinical animals and Old World monkeys, the most related primates to apes. Intriguingly, transport efficiencies are significantly higher for OAT1 orthologs from apes with high serum uric acid (SUA) levels than for the orthologs from species with low serum uric acid levels. In conclusion, our data provide a molecular mechanism underlying species differences in renal accumulation of nephrotoxic ANPs and a novel insight into OAT1 transport function in primate evolution.
Acknowledgments
We thank Dr. John Witte and Dr. Sara Rashkin at University of California, San Francisco, for the consultation on statistical analysis.
Abbreviations
ANP | acyclic nucleoside phosphonate |
A203 | alanine at position 203 |
6CF | 6-carboxyfluorescein |
cyOAT1 | cynomolgus monkey organic anion transporter 1 |
HBSS | Hanks’ balanced salt solution |
HEK293 | human embryonic kidney 293 |
hOAT1 | human organic anion transporter 1 |
OAT1 | organic anion transporter 1 |
SNP | single-nucleotide polymorphism |
S203 | serine at position 203 |
SUA | serum uric acid |
Authorship Contributions
Participated in research design: Zou, Stecula, Gupta, Stahl, Fenner, Giacomini.
Conducted experiments: Zou, Stecula, Prasad, Chien, Wang.
Contributed new reagents or analytic tools: Unadkat.
Performed data analysis: Zou, Stecula, Gupta, Prasad, Yee, Giacomini.
Wrote or contributed to the writing of the manuscript: Zou, Stecula, Gupta, Prasad, Unadkat, Stahl, Fenner, Giacomini.
Footnotes
Funding for this project was provided by AstraZeneca UK Ltd. and the National Institutes of Health [Grant R01-DK103729] (to K.M.G.).
https://doi.org/10.1124/mol.117.111153.
This article has supplemental material available at molpharm.aspetjournals.org.