RESUMO
Steroids can induce both transcription-dependent (genomic) and independent (nongenomic) signaling. Here, several classical androgen receptor ligands were tested for their ability to modulate genomic and nongenomic responses, focusing on the role of the oocyte-expressed Xenopus classical androgen receptor (XeAR) in mediating these processes. Cellular fractionation and immunohistochemistry revealed that the XeAR was located throughout oocytes, including within the plasma membrane. RNA interference and oocyte maturation studies suggested that androgen-induced maturation was mediated in part by the XeAR in a transcription-independent fashion, perhaps by altering G protein-mediated signaling. While inducing minimal transcription in oocytes, all AR ligands promoted significant XeAR-mediated transcription in CV1 cells. In contrast, only testosterone and androstenedione potently induced oocyte maturation, whereas dihydrotestosterone and R1881 actually inhibited testosterone and human chorionic gonadotropin-induced maturation and signaling. These results suggest that the nature of a steroid-induced signal (genomic vs. nongenomic) may depend on the type of target cell, the receptor location within cells, as well as the ligand itself. The identification of molecules capable of selectively altering genomic vs. nongenomic signaling may be useful in delineating the roles of these pathways in mediating androgen responses and might lead to the development of novel compounds that specifically modulate these signals in vivo.
