Li Pengfei, Lee Heehyoung, Guo Shaodong, Unterman Terry G, Jenster Guido, Bai Wenlong
Department of Pathology, University of South Florida College of Medicine, and Program of Molecular Oncology and Drug Discovery, H. Lee Moffitt Cancer Center, Tampa 33612-4799, USA.
Mol Cell Biol. 2003 Jan;23(1):104-18. doi: 10.1128/MCB.23.1.104-118.2003.
Recent studies suggested that the protection of cell apoptosis by AKT involves phosphorylation and inhibition of FKHR and related FOXO forkhead transcription factors and that androgens provide an AKT-independent cell survival signal in prostate cancer cells. Here, we report receptor-dependent repression of FKHR function by androgens in prostate cancer cells. Transcriptional analysis demonstrated that activation of the androgen receptor caused an inhibition of both wild-type FKHR and a mutant in which all three known AKT sites were mutated to alanines, showing that the repression is AKT independent. In vivo and in vitro coprecipitation studies demonstrated that the repression is mediated through protein-protein interaction between FKHR and the androgen receptor. Mapping analysis localized the interacting domains to the carboxyl terminus between amino acids 350 and 655 of FKHR and to the amino-terminal A/B region and the ligand binding domain of the receptor. Further analysis demonstrated that the activated androgen receptor blocked FKHR's DNA binding activity and impaired its ability to induce Fas ligand expression and prostate cancer cell apoptosis and cell cycle arrest. These studies identify a new mechanism for androgen-mediated prostate cancer cell survival that appears to be independent of the activity of the receptor on androgen response element-mediated transcription and establish FKHR and related FOXO forkhead proteins as important nuclear targets for both AKT-dependent and -independent survival signals in prostate cancer cells.
最近的研究表明，AKT对细胞凋亡的保护作用涉及对FKHR及相关FOXO叉头转录因子的磷酸化和抑制，并且雄激素在前列腺癌细胞中提供了一种不依赖AKT的细胞存活信号。在此，我们报告雄激素在前列腺癌细胞中通过受体依赖性方式抑制FKHR功能。转录分析表明，雄激素受体的激活导致野生型FKHR和一个将所有三个已知AKT位点突变为丙氨酸的突变体均受到抑制，这表明这种抑制不依赖AKT。体内和体外共沉淀研究表明，这种抑制是通过FKHR与雄激素受体之间的蛋白质-蛋白质相互作用介导的。定位分析将相互作用结构域定位于FKHR氨基酸350至655之间的羧基末端以及受体的氨基末端A/B区域和配体结合结构域。进一步分析表明，激活的雄激素受体阻断了FKHR的DNA结合活性，并损害了其诱导Fas配体表达以及前列腺癌细胞凋亡和细胞周期停滞的能力。这些研究确定了雄激素介导的前列腺癌细胞存活的一种新机制——该机制似乎独立于受体对雄激素反应元件介导的转录的活性，并确立了FKHR及相关FOXO叉头蛋白是前列腺癌细胞中依赖AKT和不依赖AKT的存活信号的重要核靶点。
