A Novel Point Mutation in Helix 11 of the Ligand-Binding Domain of the Human Glucocorticoid Receptor Gene Causing Generalized Glucocorticoid Resistance
Evangelia Charmandari,
Tomoshige Kino,
Takamasa Ichijo,
William Jubiz,
Liliana Mejia,
Keith Zachman and
George P. Chrousos
Section on Pediatric Endocrinology (E.C., T.K., T.I., K.Z., G.P.C.), Reproductive Biology and Medicine Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892; First Department of Pediatrics (G.P.C.), Athens University Medical School, Athens 11527, Greece; and Centro de Endocrinologia (W.J., L.M.), Metabolismo y Diabetes and Clinica, Fundacion Valle del Lili, Cali, Colombia
Address all correspondence and requests for reprints to: Evangelia Charmandari, M.D., Section on Endocrinology and Metabolism, Foundation for Biomedical Research of the Academy of Athens, 4 Soranou Efessiou, Athens 11527, Greece. E-mail: evangelia.charmandari{at}googlemail.com.
Background: Generalized glucocorticoid resistance is a rarecondition characterized by partial, end-organ insensitivityto glucocorticoids, compensatory elevations in adrenocorticotropichormone and cortisol secretion, and increased production ofadrenal steroids with androgenic and/or mineralocorticoid activity.We have identified a new case of glucocorticoid resistance causedby a novel mutation of the human glucocorticoid receptor (hGR)gene and studied the molecular mechanisms through which themutant receptor impairs glucocorticoid signal transduction.
Methods and Results: We identified a novel, single, heterozygousnucleotide (T C) substitution at position 2209 (exon 9) ofthe hGR gene, which resulted in phenylalanine (F) to leucine(L) substitution at amino acid position 737 within helix 11of the ligand-binding domain of the protein. Compared with thewild-type receptor, the mutant receptor hGRF737L demonstrateda significant ligand-exposure time-dependent decrease in itsability to transactivate the glucocorticoid-inducible mousemammary tumor virus promoter in response to dexamethasone anddisplayed a 2-fold reduction in the affinity for ligand, a 12-folddelay in nuclear translocation, and an abnormal interactionwith the glucocorticoid receptor-interacting protein 1 coactivator.The mutant receptor preserved its ability to bind to DNA andexerted a dominant-negative effect on the wild-type hGR onlyafter a short duration of exposure to the ligand.
Conclusions: The mutant receptor hGRF737L causes generalizedglucocorticoid resistance because of decreased affinity forthe ligand, marked delay in nuclear translocation, and/or abnormalinteraction with the glucocorticoid receptor-interacting protein1 coactivator. These findings confirm the importance of theC terminus of the ligand-binding domain of the receptor in conferringtransactivational activity.
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