By using a yeast detection system for androgenic and antiandrogenic effects of chemicals, we identified bisphenol A (BPA) and nonylphenol (NP) as antiandrogens. In this study, we report molecular mechanisms for the antiandrogenic action of BPA and NP. In the ARhLBD-activating signal cointegrator 1 (ASC1) yeast two-hybrid system, which reflects the androgen-dependent interaction between androgen receptor (AR) and its coactivator, ASC1, BPA and NP acted as potent AR antagonists comparable to a known strong antagonist, cyproterone acetate. Ligand competition assays revealed that [3H]5alpha-dihydroxytestosterone (DHT) binding to AR is inhibited a maximum of 30 and 40% at approximately 5 nM of NP and 50 nM of BPA, respectively. In addition, the nuclear translocation of green fluorescent protein (GFP)-AR fusion protein in the presence of testosterone was affected by the addition of BPA and NP, which cause rather dispersed distribution of GFP-AR between the nuclear and the cytoplasmic compartments. Furthermore, in transient transfection assays, BPA and NP inhibited androgen-induced AR transcriptional activity. Taken together, the results suggest that BPA and NP affect multiple steps of the activation and function of AR, thereby inhibiting the binding of native androgens to AR, AR nuclear localization, AR interaction with its coregulator, and its subsequent transactivation. These data may help us better understand the biological alterations induced by these environmental compounds.

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ARR19 (androgen receptor corepressor-19 kDa), a leucinerich protein whose expression is down-regulated by luteinizing hormone and cAMP, is differentially expressed during the development of Leydig cells and inhibits testicular steroidogenesis by reducing the expression of steroidogenic enzymes. However, the molecular events behind the suppression of testicular steroidogenesis are unknown. In the present study, we demonstrate that ARR19 inhibits the transactivation of orphan nuclear receptor Nur77, which is one of the major transcription factors that regulate the expression of steroidogenic enzyme genes in Leydig cells. ARR19 physically interacts with Nur77 and suppresses Nur77-induced promoter activity of steroidogenic enzyme genes including StAR, P450c17, and 3␤-HSD in Leydig cells. Transient transfection and chromatin immunoprecipitation assays revealed that ARR19-mediated reduced expression of steroidogenic enzyme genes was likely due to the interference of SRC-1 recruitment to Nur77 protein on the promoter of steroidogenic enzyme genes. These findings suggest that ARR19 acts as a novel coregulator of Nur77, in turn regulating Nur77-induced testicular steroidogenesis, and may play an important role in the development and function of testicular Leydig cells.

Androgen receptor (AR) that mediates androgen action is a crucial factor in male reproductive functions. Here, we report a novel AR corepressor ARR19 (androgen receptor corepressor-19 kDa), which has been isolated as a putative androgen-induced gene from murine testis. ARR19 encoding a leucine-rich protein is expressed only in male reproductive organs such as testis and prostate. ARR19 expression in the testis is developmentally regulated. Functional analysis conducted by the transient transfection of mammalian cells shows that ARR19 represses AR transactivation in a dose-dependent manner. Furthermore, yeast two-hybrid and glutathione S-transferase pull-down analyses reveal that ARR19 directly associates with AR through the N-terminal and leucine zipper-containing regions of ARR19 and the DNA binding-hinge domain of AR. Interestingly, ARR19 localized in the cytoplasmic compartment cotranslocates into the nucleus with AR upon androgen exposure. The ARR19 repression of AR transactivation is through the recruitment of histone deacetylase 4 (HDAC4) by ARR19. Overexpression of HDAC4 further inhibits the ARR19-repressed AR transactivation. In addition, ARR19 directly interacts with HDAC4 in vitro. Furthermore, DNA-protein complex immunoprecipitation assays reveal that HDAC4 is recruited to an androgen-regulated promoter through ARR19. Taken together, the results suggest that ARR19 may act as an AR corepressor in vivo and play an important role in male reproductive functions.

Background:The androgen receptor (AR) is the primary drug target for prostate cancer treatment. Results: We have identified a novel AR antagonist, the compound 6-(3,4-dihydro-1H-isoquinolin-2-yl)-N-(6-methylpyridin-2-yl)nicotinamide (DIMN) that inhibits the growth of AR-positive prostate cancer cells. Conclusion: DIMN has been identified as a new lead structure targeting the AR. Significance: This novel AR antagonist could be a useful therapeutic agent for prostate cancer treatment.