Coactivator peptides have a differential stabilizing effect on the binding of estrogens and antiestrogens with the estrogen receptor.
Coactivator peptides have a differential stabilizing effect on the binding of estrogens and antiestrogens with the estrogen receptor.
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DOI：
10.1210/mend.13.11.0373
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发表时间：
1999-11
影响因子：
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通讯作者：
Arvin C. Gee;K. Carlson;Paolo G. V. Martini;B. Katzenellenbogen;J. Katzenellenbogen
中科院分区：
文献类型：
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作者：
Arvin C. Gee;K. Carlson;Paolo G. V. Martini;B. Katzenellenbogen;J. Katzenellenbogen
雌激素在刺激由雌激素受体（ER）介导的基因转录中的有效性似乎取决于ER与辅激活蛋白的相互作用。当雌激素受体与雌激素激动剂结合时，这些辅激活因子与雌激素受体结合，而当雌激素受体与雌激素拮抗剂结合时，这些辅激活因子与雌激素受体结合。因为雌激素激动剂是已知的，以诱导在ER的构象，稳定辅激活剂结合，我们问是否辅激活剂结合到ER引起的激动剂配体结合的相互稳定。我们使用ER的荧光配体四氢屈酮来监测配体从ER α和ER β解离的速率，并观察这一过程如何受到p160类共激活因子类固醇受体共激活因子-1（SRC-1）的影响。我们使用了对应于SRC-1中第二个核受体盒LXXLL基序的15个氨基酸的肽（NR-2肽），其已知与ER配体结合结构域相互作用，具有LXXAL序列的突变肽（NR-2A肽），以及SRC-1的203个氨基酸的片段，称为核受体结构域（SRC 1-NRD），其体现了该蛋白质的所有三个内部NR盒。NR-2肽和SRC 1-NRD片段都显着减缓激动剂配体四氢屈酮、雌二醇和己烯雌酚的解离速率，使ER激动剂复合物的半衰期增加高达50至60倍。SRC 1-NRD在延迟配体解离方面具有比NR-2肽高得多的效力;它在30 nM时最有效，并且它似乎以每个ER二聚体一个SRC 1-NRD的化学计量结合。肽对拮抗剂配体的解离速率几乎没有影响。与这些结果一致，我们发现，通过转染编码SRC-1的表达质粒来增加细胞中SRC-1的浓度，在雌激素应答报告基因转录测定中导致雌二醇的效力增加17倍。因此，存在对受体-共激活因子相互作用的多因素控制，其强度由配体的激动剂与拮抗剂性质和激动剂配体的特定结构以及受体亚型和NR盒序列决定。共激活剂对ER-激动剂配体复合物的稳定作用在确定细胞中雌激素激动剂的效力中可能是重要的，并且也可能是某些合成雌激素的组织选择性药理学的基础。
The effectiveness of estrogens in stimulating gene transcription mediated by the estrogen receptor (ER) appears to depend on ER interactions with coactivator proteins. These coactivators bind to ER when it is liganded with an estrogen agonist, but not when it is liganded with an estrogen antagonist. Because estrogen agonists are known to induce a conformation in ER that stabilizes coactivator binding, we asked whether coactivator binding to ER causes a reciprocal stabilization of agonist ligand binding. We used a fluorescent ligand for ER, tetrahydrochrysene-ketone, to monitor the rates of ligand dissociation from ERalpha and ERbeta, and to see how this process is affected by the p160-class coactivator, steroid receptor coactivator-1 (SRC-1). We used a 15-amino acid peptide corresponding to the second nuclear receptor box LXXLL motif in SRC-1 (NR-2 peptide), which is known to interact with the ER ligand-binding domain, a mutant peptide with an LXXAL sequence (NR-2A peptide), and a 203-amino acid fragment of SRC-1, termed the nuclear receptor domain (SRC1-NRD), embodying all three of the internal NR boxes of this protein. Both the NR-2 peptide and the SRC1-NRD fragment markedly slow the rate of dissociation of the agonist ligands tetrahydrochrysene-ketone, estradiol, and diethylstilbestrol, increasing the half-life of the ER-agonist complex by up to 50- to 60-fold. The SRC1-NRD has much higher potency in retarding ligand dissociation than does the NR-2 peptide; it is maximally effective at 30 nM, and it appears to bind with the stoichiometry of one SRC1-NRD per ER dimer. The peptides had little effect on the dissociation rate of antagonist ligands. Consistent with these results, we find that increasing the concentration of SRC-1 in cells by transfection of an expression plasmid encoding SRC-1 causes a 17-fold increase in the potency of estradiol in an estrogen-responsive reporter gene transcription assay. Thus, there is multifactorial control over receptor-coactivator interaction, its strength being determined by the agonist vs. antagonist nature of the ligand and the particular structure of the agonist ligand, and by the receptor subtype and the NR box sequence. The stabilizing effect of coactivator on ER-agonist ligand complexes may be important in determining the potency of estrogen agonists in a cell and may also underlie the tissue-selective pharmacology of certain synthetic estrogens.