Estrogen Receptor-Coregulator Functional Interactions

细胞环境是受体-配体复合体激活转录能力的关键决定因素。可以定义ERα转录活性的因素包括辅助激活因子和辅助抑制因子、受体与细胞特异性因子相互作用的相对能力、信号转导途径的变化或用于调节ERα活性的辅助激活因子/辅助抑制因子的变化。本申请中概述的研究将提供有关不同ERpha靶基因的辅激活子和辅抑制子使用的重要信息，并评估细胞信号通路作为配体激活ERpha的贡献者所起的作用。我们计划的研究基于四个关键观察。首先，在选择性雌激素受体调节剂(SERM)是部分激动剂的情况下，共激活剂有助于ERAlpha与4HT连接的转录活性。SMRT和NCoR对4HT的拮抗作用具有重要作用。第三，细胞内信号转导通路影响ERa、辅活化子和辅抑制子的转录活性。最后，细胞内信号通路的改变伴随着细胞对部分激动剂/拮抗剂如4HT的反应的改变。这些观察结果导致了一种假设，即SERM，4HT，调节依赖ERα的生物事件的能力是由辅助激活因子和辅助抑制因子在给定的环境中与ERα功能相互作用的能力所调节的，并且这是由这些分子的表达以及调节它们与受体结合的能力的基因特异性和细胞特异性因子的影响来调节的。这一假说将在以下特定目标中得到验证：1)确定SRC家族共激活子对E2和4HT调节ERα依赖基因表达能力的贡献；2)确定辅阻遏子SMRT和NCoR对E2和4HT调节ERα依赖基因表达能力的贡献；3)确定细胞环境是否影响CBP、SRC家族成员以及辅抑制子SMRT和NCoR在没有激素或在E2或4HT存在的情况下与ERα相互作用的能力；4)确定雌激素依赖和他莫昔芬耐药的乳腺癌细胞之间细胞内信号的变化是否影响这些通路改变ERα与辅活化子或辅抑制子之间相互作用的能力，以及ERα依赖的基因表达。因此，我们的研究将提供有关4-羟色胺以基因或细胞特异性方式调节ERpha活性的能力的机制信息。

Cell environment is a critical determinant of the ability of receptor-ligand complexes to activate transcription. Factors that can define ERalpha transcriptional activity include coactivators and corepressors, the relative ability of receptors to interact with cell-specific factors, changes in signal transduction pathways, or alterations in the coactivators/corepressors utilized to regulate ERalpha activity. The studies outlined in this application will provide important information on coactivator and corepressor usage at various ERalpha target genes, and assess the role of cell signaling pathways as a contributor to ERalpha activation by ligands. Our planned studies are based on four key observations. First, coactivators contribute to the transcriptional activity of ERalpha liganded with 4HT in contexts where this selective estrogen receptor modulator (SERM) is a partial agonist. Second, SMRT and NCoR are important for the antagonistic activity of 4HT. Third, intracellular signal transduction pathways affect the transcriptional activity of ERalpha, coactivators and corepressors. Lastly, alterations in intracellular signaling pathways accompany changes in cellular responses to partial agonists/antagonists such as 4HT. These observations have lead to the hypothesis that the ability of the SERM, 4HT, to regulate ERalpha-dependent biological events is modulated by the ability of coactivators and corepressors to functionally interact with the ERalpha within a given context, and that this is regulated by the expression of these molecules and the influence of gene- specific and cell-specific factors that regulate their ability to bind to receptor. This hypothesis will be tested in the following specific aims: 1) Determine SRC family coactivators' contribution to the ability of E2 and 4HT to regulate ERalpha- dependent gene expression; 2) Determine the contribution of the corepressors, SMRT and NCoR, to the ability of E2 and 4HT to regulate ERalpha-dependent gene expression; 3) Determine whether cellular environments influence the ability of CBP, SRC family members, and the corepressors, SMRT and NCoR, to interact with ERalpha in the absence of hormone or in the presence of E2 or 4HT and 4) Determine whether changes in intracellular signaling between estrogen-dependent and tamoxifen resistant breast cancer cells affect the ability of these pathways to alter interactions between ERalpha and coactivators or corepressors, and ERalpha- dependent gene expression. Our studies will therefore provide mechanistic information on 4HT's ability to modulate ERalpha activity in a gene or cell specific manner.