DYNAMICS AND REGULATION OF NUCLEAR RECEPTORS OF LIPID SOLUBLE MOLECULE IDENTIFIED BY USING GFPS

核受体包括糖皮质激素受体(GR)、盐皮质激素受体(MR)、雌激素受体(ER)α和β以及雄激素受体(AR)，是配体依赖的转录因子。随着绿色荧光蛋白(GFP)及其颜色变体的出现，许多核受体的亚细胞分布被发现比以前认为的要动态得多。GFP研究表明，微管不参与GR和MR从细胞质到细胞核的移位，但HSP90和Importin系统至少部分与这种移位密切相关。激素刺激诱导核内受体分布从均匀分布到异质点状图像。在加入皮质酮后30min，GR和MR显示部分共存，60min时几乎完全共存。在核内观察到GR和MR之间的FRET发生。FRAP分析表明，胞质GR是动态的，细胞核GR也是流动的，但其迁移率不同。雌激素处理后，ERα和β在同一细胞中重新定位为离散模式，并定位在同一离散簇处，表明两种ER亚型结合到相同的核部位。在没有配体的情况下，没有观察到ERs的弥散分布和Brg-1的离散分布之间的任何显著关系。在雌二醇存在下，ERα和β的离散染色模式大多与Brg-1重叠，表明大多数ERs簇参与了染色质重塑机制。

Nuclear receptors which include glucocorticoid receptor (GR), mineralocorticoid receptor (MR), estrogen receptor (ER) α and β, and androgen receptor (AR) are ligand-dependent transcriptional factor. With the advent of green fluorescent protein (GFP) and its color variants, the subcellular distribution of many nuclear receptors has been found to be much more dynamic than previously thought. GFP studies showed that microtubules are not involved in the translocation of GR and MR from cytoplasm to nucleus, but that HSP90 and importin system, at least in part, are strongly relevant to this translocation. Hormonal stimulation induced intranuclear receptor distribution from a homogeneous pattern to a heterogeneous dot-like image. GR and MR showed a partial colocalization at 30 min and nearly complete colocalization at 60 min after addition of corticosterone. The occurrence of FRET between GR and MR was observed in the nucleus. FRAP analysis showed that cytoplasmic GR was dynamic and nuclear GR was also mobile, but its mobility was different. Upon estradiol treatment ER α and β in the same cell were relocalized to show discrete pattern, and they were localized at the same discrete cluster, suggesting that both subtypes of Ers were bound to the same nuclear sites. In the absence of the ligand, any significant relationship between the diffuse distribution of Ers and the discrete distribution of Brg-1 was not observed. In the presence of the estradiol, however, the discrete staining pattern of ER α and β were mostly overlapped with Brg-1, indicating that most of the Ers clusters are involved in the chromatin remodeling machinery.