Martinez Elisabeth D, Pattabiraman Nagarajan, Danielsen Mark
Department of Biochemistry and Molecular Biology, Georgetown University School of Medicine, Washington, DC 20057, USA.
Exp Cell Res. 2005 Aug 15;308(2):320-33. doi: 10.1016/j.yexcr.2005.03.040.
The glucocorticoid receptor and the mineralocorticoid receptor are members of the steroid receptor family that exhibit ligand cross-reactivity. Specificity of steroid receptor action is investigated in the present work by the construction and characterization of chimeras between the glucocorticoid receptor and the mineralocorticoid receptor. We used an innovative approach to make novel steroid receptor proteins in vivo that in general, contrary to our expectations, show increased ligand specificity compared to the parental receptors. We describe a receptor that is specific for the potent synthetic glucocorticoid triamcinolone acetonide and does not bind aldosterone. A further set of chimeras has an increased ability to discriminate between ligands, responding potently to mineralocorticoids and only very weakly to synthetic glucocorticoids. A chimera with the fusion site in the hinge highlights the importance of the region between the DNA-binding and the hormone-binding domains since, unlike both the glucocorticoid and mineralocorticoid receptors, it only responds to mineralocorticoids. One chimera has reduced specificity in that it acts as a general corticoid receptor, responding to glucocorticoids and mineralocorticoids with similar potency and efficacy. Our data suggest that regions of the glucocorticoid and mineralocorticoid receptor hormone-binding domains are functionally non-reciprocal. We present transcriptional, hormone-binding, and structure-modeling evidence that suggests that receptor-specific interactions within and across domains mediate aspects of specificity in transcriptional responses to steroids.
糖皮质激素受体和盐皮质激素受体是类固醇受体家族的成员，它们表现出配体交叉反应性。在本研究中，通过构建糖皮质激素受体和盐皮质激素受体之间的嵌合体并对其进行表征，来研究类固醇受体作用的特异性。我们采用了一种创新方法在体内制造新型类固醇受体蛋白，总体而言，与我们的预期相反，这些蛋白与亲本受体相比显示出更高的配体特异性。我们描述了一种对强效合成糖皮质激素曲安奈德有特异性且不结合醛固酮的受体。另一组嵌合体区分配体的能力增强，对盐皮质激素有强烈反应，而对合成糖皮质激素只有非常微弱的反应。一种在铰链区有融合位点的嵌合体突出了DNA结合域和激素结合域之间区域的重要性，因为与糖皮质激素受体和盐皮质激素受体不同，它只对盐皮质激素有反应。一种嵌合体的特异性降低，因为它作为一种通用的皮质激素受体，对糖皮质激素和盐皮质激素的反应具有相似的效力和效果。我们的数据表明，糖皮质激素受体和盐皮质激素受体激素结合域的区域在功能上是不可互换的。我们提供了转录、激素结合和结构建模证据，表明域内和跨域的受体特异性相互作用介导了对类固醇转录反应特异性的各个方面。
