SAT-718 Inhibition of Androgen Receptor Activity by DDE Is Affected by Mutations in the BF3 Site

The androgen receptor (AR) plays an important role in the development of the male phenotype and traits. Some diphenyl compounds inhibit AR activity by binding to a hydrophobic surface binding site, BF3. A similar diphenyl structure is found in 4,4’ DDT and its breakdown product 4,4’ DDE. Previous results showed that DDT and DDE induced the release of bound dihydrotestosterone from the AR ligand binding domain, with IC(50) values ranging from 54 to 82uM. This suggested that DDT and related compounds may act as endocrine disrupting chemicals by binding to the BF3 site and inducing allosteric changes in the AR structure, disrupting binding of the steroid to the ligand binding domain. Here, an AR reporter system was transiently transfected into HEK293 cells and AR activity was measured using a dual luciferase assay. The system was used to measure the response of the AR protein to varying concentrations of dihydrotestosterone in the presence and absence of DDE. DDE inhibited the activation of AR by dihydrotestosterone under these conditions. Five mutant AR genes with amino acid changes in the BF3 site were tested for alterations in the ability of DDE to disrupt AR activity. The five mutations tested were F673K, F673W, G724R, G724M, and L830D. The ability of DDE to inhibit AR activity was reduced by the mutations in the BF3 site. These results suggest that DDE acts as an endocrine disrupting chemical (EDC) by binding to the BF3 site and allosterically regulating AR activity.