Department of Veterinary Anatomy, Division of Veterinary Science, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Izumisano, Osaka, 598-8531, Japan.
Department of Anatomy and Neurobiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, 602-8566, Japan.
Histochem Cell Biol. 2021 Sep;156(3):239-251. doi: 10.1007/s00418-021-01998-7. Epub 2021 Jun 15.
Estrogen-related receptor (ERR), a member of the nuclear receptor superfamily, consists of three subtypes (α, β, γ) and has strong homology with estrogen receptor. No endogenous ligands have been identified for ERRs, but they play key roles in metabolic, hormonal, and developmental processes as transcription factors without ligand binding. Although subnuclear dynamics are essential for nuclear events including nuclear receptor-mediated transcriptional regulation, the dynamics of ERRs are poorly understood. Here, we report that ERRs show subcellular kinetic changes in response to diethylstilbestrol (DES), a synthetic estrogen that represses the transactivity of all three ERR subtypes, using live-cell imaging with fluorescent protein labeling. Upon DES treatment, all ERR subtypes formed discrete clusters in the nucleus, with ERRγ also displaying nuclear export. Fluorescence recovery after photobleaching analyses revealed significant reductions in the intranuclear mobility of DES-bound ERRα and ERRβ, and a slight reduction in the intranuclear mobility of DES-bound ERRγ. After DES treatment, colocalization of all ERR subtypes with scaffold attachment factor B1 (SAFB1), a nuclear matrix-associated protein, was observed in dot-like subnuclear clusters, suggesting interactions of the ERRs with the nuclear matrix. Consistently, co-immunoprecipitation analyses confirmed enhanced interactions between ERRs and SAFB1 in the presence of DES. SAFB1 was clarified to repress the transactivity of all ERR subtypes through the ERR-response element. These results demonstrate ligand-dependent cluster formation of ERRs in the nucleus that is closely associated with SAFB1-mediated transrepression. Taken together, the present findings provide a new understanding of the pathophysiology regulated by ERR/SAFB1 signaling pathways and their subcellular dynamics.
雌激素相关受体 (ERR) 是核受体超家族的成员，由三个亚型 (α、β、γ) 组成，与雌激素受体具有很强的同源性。虽然 ERR 没有内源性配体，但作为无配体结合的转录因子，它们在代谢、激素和发育过程中发挥着关键作用。虽然亚核动力学对于包括核受体介导的转录调节在内的核事件至关重要，但 ERR 的动力学仍知之甚少。在这里，我们使用荧光蛋白标记的活细胞成像报告说，ERR 会响应二乙基stilbestrol (DES) 发生亚细胞动力学变化，DES 是一种抑制所有三种 ERR 亚型的反式活性的合成雌激素。在用 DES 处理后，所有 ERR 亚型在核内形成离散的簇，ERRγ 也显示核输出。光漂白后荧光恢复分析显示，与 DES 结合的 ERRα 和 ERRβ 的核内迁移率显著降低，与 DES 结合的 ERRγ 的核内迁移率略有降低。在用 DES 处理后，所有 ERR 亚型与支架附着因子 B1 (SAFB1)（一种核基质相关蛋白）在点状亚核簇中发生共定位，表明 ERR 与核基质相互作用。一致地，共免疫沉淀分析证实了在存在 DES 的情况下 ERR 与 SAFB1 之间的相互作用增强。SAFB1 通过 ERR 反应元件被证实抑制所有 ERR 亚型的反式活性。这些结果表明，ERR 核内的配体依赖性簇形成与 SAFB1 介导的转录抑制密切相关。总之，这些发现提供了对 ERR/SAFB1 信号通路及其亚细胞动力学调节的病理生理学的新认识。
