Novobiocin is a potent inhibitor for human organic anion transporters

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Published on: August 31, 2015

Peng Duan1, Guofeng You

  • 1Department of Pharmaceutics, Rutgers, the State University of New Jersey, Piscataway, NJ 08854, USA.

Drug Metabolism and Disposition: the Biological Fate of Chemicals
|March 14, 2009
PubMed

Insights

Novobiocin inhibits organic anion transporters (OATs) by competitively binding to their substrate sites, impacting drug and toxin transport. This interaction is crucial for researchers using novobiocin to study breast cancer resistance proteins (BCRP).

Area of Science:

  • Pharmacology and Toxicology
  • Molecular Biology
  • Drug Metabolism and Transport

Background:

  • Organic anion transporters (OATs) are critical for eliminating diverse toxins and drugs.
  • Novobiocin, a known breast cancer resistance protein (BCRP) inhibitor, was previously observed to affect organic anion transport.
  • The specific interactions between novobiocin and individual OATs remained uncharacterized.

Purpose of the Study:

  • To investigate and characterize the inhibitory effects of novobiocin on human organic anion transporters (hOAT1, hOAT3, and hOAT4).
  • To determine the kinetic parameters and mechanism of inhibition for novobiocin's interaction with hOATs.
  • To assess whether novobiocin alters transporter protein abundance on the plasma membrane.

Main Methods:

  • Functional characterization of hOAT1, hOAT3, and hOAT4 using novobiocin as an inhibitor.
  • Kinetic analysis to determine inhibition constants (K(i)) and half-maximal inhibitory concentrations (IC(50)).
  • Cis- and trans-inhibition assays to elucidate the interaction mechanism.
  • Assessment of transporter protein abundance via membrane fraction analysis.

Main Results:

  • Novobiocin competitively inhibited OAT-mediated uptake with specific K(i) values for hOAT1 (14.87 ± 0.40 µM), hOAT3 (4.77 ± 1.12 µM), and hOAT4 (90.50 ± 7.50 µM).
  • Novobiocin acted as a potent inhibitor, not a substrate, for hOAT1, hOAT3, and hOAT4, with IC(50) values ranging from 4.99 to 92.68 µM.
  • The inhibitory effects were not due to changes in transporter protein levels on the plasma membrane.

Conclusions:

  • Novobiocin interacts with the substrate-binding sites of hOAT1, hOAT3, and hOAT4 from both intracellular and extracellular sides.
  • This interaction reduces the availability of functional transporters for their substrates, impacting organic anion transport.
  • The significant inhibitory effect of novobiocin on OATs must be considered when using it as a selective BCRP inhibitor in studies involving tissues co-expressing OATs.

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