AB157. The environmental endocrine disruptor p-nitrophenol interacts with FKBP51, a positive regulator of androgen receptor and inhibits androgen receptor signaling in human cells

OBJECTIVE: Although it was shown that p-nitrophenol is anti-androgenic in vivo, the molecular details of how p-nitrophenol inhibits AR signaling are still not quite clear. In this report, we want to figure out this signaling in human cells. METHODS: (I) Cell viability assay; (II) endogenous expression of androgen-activated genes; (III) expression, and purification of the FK1 domain of FKBP51; (IV) fluorescence quenching assay; (V) crystallization and data collection; (VI) structure determination; (VII) molecular dynamics (MD) simulation; (VIII) the free energy calculation. RESULTS: we show that p-nitrophenol inhibits the androgen dependent cell growth and down-regulates the expression levels of AR target genes. Furthermore, we identified that p-nitrophenol binds with micromolar affinity to the Hsp90 co-chaperone FKBP51, a protein essential for AR activation. Crystal structure of FKBP51 in complex with p-nitrophenol revealed that p-nitrophenol occupies a hydrophobic pocket of FKBP51 that is vital for AR activity enhancement. Molecular dynamics simulation indicate that p-nitrophenol is stably bound to the FKBP51 pocket and the hotspot residues that involved p-nitrophenol binding are mainly hydrophobic and overlap with the AR interaction site. CONCLUSIONS: our results demonstrate the anti-androgenic activity of p-nitrophenol in human cells and illustrate the binding mechanism between p-nitrophenol and its potential molecular target FKBP51, providing guidelines for assessing the long term health risks of p-nitrophenol and its derivatives.