Charmandari Evangelia, Kino Tomoshige, Ichijo Takamasa, Jubiz William, Mejia Liliana, Zachman Keith, Chrousos George P
Section on Endocrinology, Reproductive Biology and Medicine Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
J Clin Endocrinol Metab. 2007 Oct;92(10):3986-90. doi: 10.1210/jc.2006-2830. Epub 2007 Jul 17.
Generalized glucocorticoid resistance is a rare condition characterized by partial, end-organ insensitivity to glucocorticoids, compensatory elevations in adrenocorticotropic hormone and cortisol secretion, and increased production of adrenal steroids with androgenic and/or mineralocorticoid activity. We have identified a new case of glucocorticoid resistance caused by a novel mutation of the human glucocorticoid receptor (hGR) gene and studied the molecular mechanisms through which the mutant receptor impairs glucocorticoid signal transduction.
We identified a novel, single, heterozygous nucleotide (T --> C) substitution at position 2209 (exon 9alpha) of the hGR gene, which resulted in phenylalanine (F) to leucine (L) substitution at amino acid position 737 within helix 11 of the ligand-binding domain of the protein. Compared with the wild-type receptor, the mutant receptor hGRalphaF737L demonstrated a significant ligand-exposure time-dependent decrease in its ability to transactivate the glucocorticoid-inducible mouse mammary tumor virus promoter in response to dexamethasone and displayed a 2-fold reduction in the affinity for ligand, a 12-fold delay in nuclear translocation, and an abnormal interaction with the glucocorticoid receptor-interacting protein 1 coactivator. The mutant receptor preserved its ability to bind to DNA and exerted a dominant-negative effect on the wild-type hGRalpha only after a short duration of exposure to the ligand.
The mutant receptor hGRalphaF737L causes generalized glucocorticoid resistance because of decreased affinity for the ligand, marked delay in nuclear translocation, and/or abnormal interaction with the glucocorticoid receptor-interacting protein 1 coactivator. These findings confirm the importance of the C terminus of the ligand-binding domain of the receptor in conferring transactivational activity.
全身性糖皮质激素抵抗是一种罕见病症，其特征为对糖皮质激素存在部分终末器官不敏感、促肾上腺皮质激素和皮质醇分泌代偿性升高，以及具有雄激素和/或盐皮质激素活性的肾上腺类固醇生成增加。我们鉴定出一例由人类糖皮质激素受体（hGR）基因新突变导致的糖皮质激素抵抗新病例，并研究了突变受体损害糖皮质激素信号转导的分子机制。
我们在hGR基因的2209位（外显子9α）鉴定出一个新的单杂合核苷酸（T→C）替换，该替换导致蛋白质配体结合域第11螺旋内氨基酸位置737处的苯丙氨酸（F）替换为亮氨酸（L）。与野生型受体相比，突变受体hGRαF737L在响应地塞米松时，其激活糖皮质激素诱导的小鼠乳腺肿瘤病毒启动子的能力表现出显著的配体暴露时间依赖性降低，对配体的亲和力降低2倍，核转位延迟12倍，并且与糖皮质激素受体相互作用蛋白1共激活因子存在异常相互作用。突变受体保留了与DNA结合的能力，并且仅在短时间暴露于配体后才对野生型hGRα发挥显性负效应。
突变受体hGRαF737L由于对配体的亲和力降低、核转位明显延迟和/或与糖皮质激素受体相互作用蛋白1共激活因子的异常相互作用而导致全身性糖皮质激素抵抗。这些发现证实了受体配体结合域C末端在赋予反式激活活性方面的重要性。
