A Novel Point Mutation of the Human Glucocorticoid Receptor Gene Causes Primary Generalized Glucocorticoid Resistance Through Impaired Interaction With the LXXLL Motif of the p160 Coactivators: Dissociation of the Transactivating and Transreppressive Activities

作者：Nicolaides Nicolas C; Roberts Michael L; Kino Tomoshige; Braatvedt Geoffrey; Hurt Darrell E; Katsantoni Eleni; Sertedaki Amalia; Chrousos George P; Charmandari Evangelia^*

来源：Journal of Clinical Endocrinology & Metabolism, 2014, 99(5): E902-E907.

DOI：10.1210/jc.2013-3005

Context: Primary generalized glucocorticoid resistance is a rare genetic disorder characterized by generalized, partial, target-tissue insensitivity to glucocorticoids. The molecular basis of the condition has been ascribed to inactivating mutations in the human glucocorticoid receptor (hGR) gene.
Objective: The objective of the study was to present three new cases caused by a novel mutation in the hGR gene and to delineate the molecular mechanisms through which the mutant receptor impairs glucocorticoid signal transduction.
Design and Results: The index case (father) and his two daughters presented with increased urinary free cortisol excretion and resistance of the hypothalamic-pituitary-adrenal axis to dexamethasone suppression in the absence of clinical manifestations suggestive of Cushing syndrome. All subjects harbored a novel, heterozygous, point mutation (T -> G) at nucleotide position 1724 of the hGR gene, which resulted in substitution of valine by glycine at amino acid 575 of the receptor. Compared with the wild-type receptor, the hGR alpha V575G demonstrated a significant (33%) reduction in its ability to transactivate the mouse mammary tumor virus promoter in response to dexamethasone, a 50% decrease in its affinity for the ligand, and a 2.5-fold delay in nuclear translocation. Although it did not exert a dominant negative effect on the wild-type receptor and preserved its ability to bind to DNA, hGR alpha V575G displayed significantly enhanced (similar to 80%) ability to transrepress the nuclear factor-kappa B signaling pathway. Finally, the mutant receptor hGR alpha V575G demonstrated impaired interaction with the LXXLL motif of the glucocorticoid receptor-interacting protein 1 coactivator in vitro and in computer-based structural simulation via its defective activation function-2 (AF-2) domain.
Conclusions: The natural mutant receptor hGR alpha V575G causes primary generalized glucocorticoid resistance by affecting multiple steps in the glucocorticoid signaling cascade, including the affinity for the ligand, the time required for nuclear translocation, and the interaction with the glucocorticoid-interacting protein-1 coactivator.

• 出版日期2014-5
• 单位NIH