Institute of General Zoology and Endocrinology, Ulm University, Albert Einstein Allee 11, 89069 Ulm, Germany.
J Cell Biochem. 2010 Apr 15;109(6):1192-200. doi: 10.1002/jcb.22500.
The androgen receptor (AR) is a ligand-dependent transcription factor belonging to the steroid hormone receptor superfamily. Under normal conditions, in the absence of a ligand, the AR is localized to the cytoplasm and is actively transported into the nucleus upon binding of androgens. In advanced prostate cancer (PCa) cell lines, an increased sensitivity to dihydrotestosterone (DHT), enabling the cells to proliferate under sub-physiological levels of androgens, has been associated with increased stability and nuclear localization of the AR. There is experimental evidence that the glycogen synthase kinase-3beta (GSK-3beta), a multifunctional serine/threonine kinase is involved in estrogen and AR stability. As demonstrated in the following study by immunoprecipitation analysis, GSK-3beta binds to the AR forming complexes in the cytoplasm and in the nucleus. Furthermore, inhibition of GSK-3beta activity by pharmacological inhibitors like the maleimide SB216761, the chloromethyl-thienyl-ketone GSK-3 inhibitor VI or the aminopyrazol GSK-3 inhibitor XIII in cells grown in the presence of DHT triggered a rapid nuclear export of endogenous AR as well as of green fluorescent AR-EosFP. The nuclear export of AR following GSK-3beta inhibition could be blocked by leptomycin B suggesting a CRM1-dependent export mechanism. This assumption is supported by the localization of a putative CRM1 binding site at the C-terminus of the AR protein. The results suggest that GSK-3beta is an important element not only in AR stability but also significantly alters nuclear translocation of the AR, thereby modulating the androgenic response of human PCa cells.
雄激素受体（AR）是一种配体依赖性转录因子，属于甾体激素受体超家族。在正常情况下，在没有配体的情况下，AR 位于细胞质中，并在与雄激素结合后被主动转运到细胞核中。在晚期前列腺癌（PCa）细胞系中，对二氢睾酮（DHT）的敏感性增加，使细胞能够在低于生理水平的雄激素下增殖，这与 AR 的稳定性和核定位增加有关。有实验证据表明，糖原合酶激酶-3β（GSK-3β），一种多功能丝氨酸/苏氨酸激酶，参与雌激素和 AR 的稳定性。正如以下研究中的免疫沉淀分析所示，GSK-3β与 AR 结合形成细胞质和细胞核中的复合物。此外，在 DHT 存在下生长的细胞中，通过药理学抑制剂如马来酰亚胺 SB216761、氯甲基-噻吩基-酮 GSK-3 抑制剂 VI 或氨基吡唑 GSK-3 抑制剂 XIII 抑制 GSK-3β 活性，会触发内源性 AR 以及绿色荧光 AR-EosFP 的快速核输出。GSK-3β 抑制后 AR 的核输出可以被莱普霉素 B 阻断，表明存在 CRM1 依赖性的输出机制。这一假设得到了 AR 蛋白 C 末端存在假定的 CRM1 结合位点的定位的支持。结果表明，GSK-3β不仅是 AR 稳定性的重要组成部分，而且还显著改变了 AR 的核转位，从而调节人 PCa 细胞的雄激素反应。
