Yang Liu, Jeong Kwang Won
Gachon Institute of Pharmaceutical Sciences, College of Pharmacy, Gachon University, Incheon 21936, Republic of Korea.
Endocr J. 2019 Jan 28;66(1):65-74. doi: 10.1507/endocrj.EJ18-0343. Epub 2018 Oct 26.
The human homologue of flightless-I (FLII) belong to the gelsolin protein family and contain a gelsolin-like domain at the C-terminus and a leucine-rich repeat (LRR) domain at the N-terminus. FLII regulates estrogen receptor alpha (ERα) and glucocorticoid receptor (GR)-mediated transcription by direct interaction through different domains, suggestive of its potential role in the crosstalk between the ERα and GR signaling pathway. Here, we demonstrate that FLII plays a critical role in GR-mediated repression of ERα target gene expression. In FLII-depleted cells, the reduction in 17-β-estradiol (E2)-induced ERα occupancy following treatment with dexamethasone (Dex) at the estrogen responsive element (ERE) site of the ERα target gene was significantly inhibited. The ERE binding of GR by the cotreatment with E2 and Dex was significantly inhibited by FLII depletion, indicating that FLII is required for the recruitment of GR at the ERE sites of ERα target genes. In addition, the recruitment of ERα-induced FLII to ERE sites was significantly reduced by Dex treatment. In protein binding assays, GR inhibited the E2-induced interaction between ERα and FLII, suggesting that GR interferes with the binding of ERα and FLII at the ERα target genes, resulting in the release of ERα and FLII from EREs. Taken together, our data reveal an unknown mechanism by which the transcription coactivator FLII regulates the GR-mediated repression of ERα target gene expression in MCF-7 cells.
无翅 I 型蛋白（FLII）的人类同源物属于凝溶胶蛋白家族，在 C 端含有一个凝溶胶蛋白样结构域，在 N 端含有一个富含亮氨酸重复序列（LRR）结构域。FLII 通过不同结构域的直接相互作用调节雌激素受体α（ERα）和糖皮质激素受体（GR）介导的转录，提示其在 ERα和 GR 信号通路串扰中可能发挥的作用。在此，我们证明 FLII 在 GR 介导的 ERα靶基因表达抑制中起关键作用。在 FLII 缺失的细胞中，在 ERα靶基因的雌激素反应元件（ERE）位点用 dexamethasone（Dex）处理后，17-β-雌二醇（E2）诱导的 ERα占据率的降低受到显著抑制。FLII 缺失显著抑制了 E2 和 Dex 联合处理时 GR 与 ERE 的结合，表明 FLII 是 GR 在 ERα靶基因的 ERE 位点募集所必需的。此外，Dex 处理显著降低了 ERα诱导的 FLII 向 ERE 位点的募集。在蛋白质结合试验中，GR 抑制了 E2 诱导的 ERα与 FLII 之间的相互作用，提示 GR 干扰了 ERα靶基因处 ERα与 FLII 的结合，导致 ERα和 FLII 从 EREs 释放。综上所述，我们的数据揭示了转录共激活因子 FLII 在 MCF-7 细胞中调节 GR 介导的 ERα靶基因表达抑制的未知机制。
