Astapova Olga, Seger Christina, Hammes Stephen R
Division of Endocrinology and Metabolism, Department of Medicine, University of Rochester Medical Center, Rochester, New York 14642, USA.
J Endocr Soc. 2021 Mar 5;5(5):bvab035. doi: 10.1210/jendso/bvab035. eCollection 2021 May 1.
Androgens are important in female reproduction, but the molecular actions of androgens in female reproductive tissues are not fully understood. We investigated the androgen-responsive transcriptome in human and mouse granulosa cells (GCs) and surprisingly found that the gene-regulation activity of androgen receptor (AR) in these cells is negligible. We then investigated extranuclear actions of AR and found that in human and mouse GCs, as well as in prostate cancer cells, dihydrotestosterone (DHT) dramatically increases the half-life of its own receptor protein. Using the human granulosa-like KGN cells, we show that this effect is not the result of increased gene transcription or protein synthesis, nor is it fully abrogated by proteasome inhibition. Knockdown of PTEN, which contributes to degradation of cytoplasmic AR, did not diminish AR accumulation in the presence of DHT. Using immunofluorescence cellular localization studies, we show that nuclear AR is selectively protected from degradation in the presence of DHT. Knockdown of importin 7 expression, a potential regulator of AR nuclear import, does not affect DHT-mediated nuclear accumulation of AR, suggesting importin 7-independent nuclear import of AR in GCs. Further, DNA binding is not required for this protective mechanism. In summary, we show that ligand binding sequesters AR in the nucleus through enhanced nuclear localization independent of DNA binding, thereby protecting it from proteasome degradation in the cytoplasm. This phenomenon distinguishes AR from other sex steroid receptors and may have physiological significance through a positive feedback loop in which androgen induces its own activity in male and female reproductive tissues.
雄激素在女性生殖过程中起着重要作用，但雄激素在女性生殖组织中的分子作用尚未完全明确。我们研究了人和小鼠颗粒细胞（GCs）中的雄激素反应转录组，令人惊讶地发现雄激素受体（AR）在这些细胞中的基因调控活性可忽略不计。然后我们研究了AR的核外作用，发现在人和小鼠的GCs以及前列腺癌细胞中，二氢睾酮（DHT）显著延长了其自身受体蛋白的半衰期。利用人颗粒细胞样KGN细胞，我们发现这种作用并非基因转录增加或蛋白质合成增加的结果，蛋白酶体抑制也不能完全消除这种作用。敲低参与细胞质AR降解的PTEN，在存在DHT的情况下并不会减少AR的积累。通过免疫荧光细胞定位研究，我们发现核AR在存在DHT的情况下可被选择性地保护不被降解。敲低作为AR核输入潜在调节因子的输入蛋白7的表达，并不影响DHT介导的AR核内积累，这表明在GCs中AR的核输入不依赖于输入蛋白7。此外，这种保护机制不需要DNA结合。总之，我们发现配体结合通过增强不依赖于DNA结合的核定位将AR隔离在细胞核中，从而保护其免受细胞质中的蛋白酶体降解。这种现象将AR与其他性类固醇受体区分开来，并且可能通过雄激素在雄性和雌性生殖组织中诱导自身活性的正反馈回路而具有生理意义。
