Binding and Activation of Estrogen-Related Receptor ?: A Novel Molecular Mechanism for the Estrogenic Disruption Effects of DDT and Its Metabolites

DDT and its metabolites (DDTs) can induce estrogenic effects. Previous mechanistic investigations mainly concentrated on activating the genomic transcription of estrogen receptor (ER) pathways. Here, we identified whether estrogen-related receptor gamma (ERR gamma), an orphan nuclear receptor, is a potential target of DDTs by receptor binding, transcriptional activity, and receptor-mediated pathway assays. Fluorescence polarization-based binding assays showed that all eight DDTs bound to ERR gamma directly, with Kd values ranging from 0.73-168.82 mu M. Among them, 2,2-bis(4-chlorophenyl)ethanol (4,4 '-DDOH) exhibited the highest binding affinity, which was 2.5-fold stronger than GSK4716, a well-known ERR gamma agonist. Eight DDTs exhibited agonistic activity toward the ERR gamma pathway, with 4,4 '-DDOH showing the strongest potency. In silico studies revealed that DDTs tended to bind with ERR gamma in the agonistic conformation. Using a SKBR3 breast cancer cell model, we further found that nanomolar or micromolar levels of DDTs significantly activated the ERR gamma pathway in cells and induced cell proliferation through the ERR gamma-modulated cell cycle. These results indicated that the binding and activation of DDTs to ERR gamma might serve as molecular initiating events for subsequent ERR gamma-mediated signaling pathways and adverse outcomes. Overall, our results demonstrated that ERR gamma might be a crucial pathway involved in the estrogenic disruption effects of DDTs.