Direct evidence revealing structural elements essential for the high binding ability of bisphenol A to human estrogen-related receptor-gamma

Environ Health Perspect. 2008 Jan;116(1):32-8. doi: 10.1289/ehp.10587.

Abstract

Background: Various lines of evidence have shown that bisphenol A [BPA; HO-C6H4-C(CH3)2-C6H4-OH] acts as an endocrine disruptor when present in very low doses. We have recently demonstrated that BPA binds strongly to human estrogen-related receptor-gamma (ERR-gamma ) in a binding assay using [3H]4-hydroxytamoxifen ([3H]4-OHT). We also demonstrated that BPA inhibits the deactivation activity of 4-OHT.

Objectives: In the present study, we intended to obtain direct evidence that BPA interacts with ERR-gamma as a strong binder, and also to clarify the structural requirements of BPA for its binding to ERR-gamma.

Methods: We examined [3H]BPA in the saturation binding assay using the ligand binding domain of ERR-gamma and analyzed the result using Scatchard plot analysis. A number of BPA derivatives were tested in the competitive binding assay using [3H]BPA as a tracer and in the luciferase reporter gene assay.

Results: [3H]BPA showed a KD of 5.50 nM at a Bmax of 14.4 nmol/mg. When we examined BPA derivatives to evaluate the structural essentials required for the binding of BPA to ERR-gamma , we found that only one of the two phenol-hydroxyl groups was essential for the full binding. The maximal activity was attained when one of the methyl groups was removed. All of the potent BPA derivatives retained a high constitutive basal activity of ERR-gamma in the luciferase reporter gene assay and exhibited a distinct inhibitory activity against 4-OHT.

Conclusion: These results indicate that the phenol derivatives are potent candidates for the endocrine disruptor that binds to ERR-gamma.

Keywords: bisphenol A; constitutive activity; endocrine disruptor; estrogen receptor; estrogen-related receptor-γ; inverse agonist; nuclear receptor.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Benzhydryl Compounds
  • Binding, Competitive
  • Endocrine Disruptors / chemistry
  • Endocrine Disruptors / metabolism*
  • Estrogens, Non-Steroidal / chemistry
  • Estrogens, Non-Steroidal / metabolism*
  • HeLa Cells
  • Humans
  • Phenols / chemistry
  • Phenols / metabolism*
  • Receptors, Cytoplasmic and Nuclear / metabolism*
  • Receptors, Estrogen / metabolism*
  • Tamoxifen / analogs & derivatives
  • Tamoxifen / metabolism

Substances

  • Benzhydryl Compounds
  • ESRRG protein, human
  • Endocrine Disruptors
  • Estrogens, Non-Steroidal
  • Phenols
  • Receptors, Cytoplasmic and Nuclear
  • Receptors, Estrogen
  • Tamoxifen
  • afimoxifene
  • bisphenol A