Abstract
Organic anion transporters (OATs) mediate the body disposition of a diverse array of environmental toxins and clinically important drugs. Previous studies have shown that novobiocin, an inhibitor for breast cancer resistance proteins (BCRP), inhibited organic anion transport. However, its interactions with specific OATs are unknown. In the current study, we characterized the inhibitory effects of novobiocin on the function of human OATs (hOAT)1, hOAT3, and hOAT4. Kinetic study revealed that novobiocin inhibited OAT-mediated uptake in a competitive manner, with Ki of 14.87 ± 0.40 μM for hOAT1, Ki of 4.77 ± 1.12 μM for hOAT3, and Ki of 90.50 ± 7.50 μM for hOAT4. Furthermore, the cis- and trans-inhibition feature of novobiocin demonstrated that novobiocin was a potent inhibitor but not a substrate for hOAT1 (IC50 = 34.76 ± 0.31 μM), hOAT3 (IC50 = 4.987 ± 0.35 μM), and hOAT4 (IC50 = 92.68 ± 0.34 μM). We further showed that the effects of novobiocin on OATs were not mediated through a change in transporter protein abundance on the plasma membrane. Taken together, we conclude that novobiocin seems to interact with the substrate-binding sites of OATs from both the intracellular and the extracellular sides, and this interaction interferes with the substrate-binding site(s) on respective carriers, leading to an apparent reduction in carriers available for the substrates. Because BCRP is often expressed in the same tissue where multiple OATs are identified such as liver, kidney and placenta, when dissecting the contribution of BCRP to drug disposition using novobiocin as an inhibitor, its inhibitory effect to OATs has to be taken into consideration.
Footnotes
-
This work was supported in part by the National Institutes of Health National Institute of Diabetes and Digestive and Kidney Diseases [Grant R01-DK60034] (to G.Y.); and the National Institutes of Health National Institute of General Medical Sciences [Grant R01-GM079123] (to G.Y.).
-
Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
-
doi:10.1124/dmd.109.026880.
-
ABBREVIATIONS: OAT, organic anion transporter; BCRP, breast cancer resistance proteins; hOAT, human OAT; PAH, [3H]ρ-aminohippuric acid; ES, estrone sulfate; DHEA, dehydroepiandrosterone-3-sulfate; FBS, fetal bovine serum; PBS, phosphate-buffered saline; sulfo-NHS-SS-biotin, sulfosuccinimidyl 2-(biotinamido)-ethyl-1,3-dithiopropionate.
- Received January 23, 2009.
- Accepted March 10, 2009.
- The American Society for Pharmacology and Experimental Therapeutics
DMD articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|