A novel point mutation in helix 11 of the ligand-binding domain of the human glucocorticoid receptor gene causing generalized glucocorticoid resistance.
BACKGROUND
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.


RESULTS
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.


CONCLUSIONS
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.
Charmandari
Evangelia
E
Section on Endocrinology, Reproductive Biology and Medicine Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA. evangelia.charmandari@googlemail.com
Kino
Tomoshige
T
Ichijo
Takamasa
T
Jubiz
William
W
Mejia
Liliana
L
Zachman
Keith
K
Chrousos
George P
GP
D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D002648:Child; D002522:Chlorocebus aethiops; D004700:Endocrine System Diseases / Q000235:genetics* / Q000378:metabolism; D005938:Glucocorticoids / Q000378:metabolism*; D006801:Humans; D008024:Ligands; D008297:Male; D051958:Nuclear Receptor Coactivator 2 / Q000378:metabolism; D017354:Point Mutation; D017433:Protein Structure, Secondary; D011965:Receptors, Glucocorticoid / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D014162:Transfection
D005938:Glucocorticoids; D008024:Ligands; D051958:Nuclear Receptor Coactivator 2; D011965:Receptors, Glucocorticoid