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.
BACKGROUND
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.


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 hGRαV575G 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, hGRαV575G displayed significantly enhanced (∼80%) ability to transrepress the nuclear factor-κΒ signaling pathway. Finally, the mutant receptor hGRαV575G 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 hGRαV575G 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.
Division of Endocrinology, Metabolism, and Diabetes (N.C.N., M.L.R., A.S., G.P.C., E.C.), First Department of Pediatrics, University of Athens Medical School, "Aghia Sophia" Children's Hospital, and Divisions of Endocrinology and Metabolism (N.C.N., M.L.R., A.S., G.P.C., E.C.) and Hematology (E.K.), Clinical Research Center, Biomedical Research Foundation of the Academy of Athens, Athens 11527, Greece; Unit on Molecular Hormone Action (T.K.), Program in Reproductive and Adult Endocrinology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, and Bioinformatics and Computational Biosciences Branch (D.E.H.), Office of Cyber Infrastructure and Computational Biology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892; and Department of Medicine (G.B.), University of Auckland, 1142 Auckland, New Zealand.
Nicolas C
NC
Nicolaides
Michael L
ML
Roberts
Tomoshige
T
Kino
Geoffrey
G
Braatvedt
Darrell E
DE
Hurt
Eleni
E
Katsantoni
Amalia
A
Sertedaki
George P
GP
Chrousos
Evangelia
E
Charmandari
D000328:Adult; D000368:Aged; D001665:Binding Sites / Q000235:genetics; D005260:Female; D006801:Humans; D007030:Hypothalamo-Hypophyseal System / Q000378:metabolism*; D008297:Male; D008661:Metabolism, Inborn Errors / Q000235:genetics* / Q000378:metabolism; D008875:Middle Aged; D010913:Pituitary-Adrenal System / Q000378:metabolism*; D017354:Point Mutation; D011965:Receptors, Glucocorticoid / Q000172:deficiency* / Q000235:genetics* / Q000378:metabolism
D011965:Receptors, Glucocorticoid