Identification of the functional domain of glucocorticoid receptor involved in RU486 antagonism.
Mifepristone, also known as RU486, is a potent glucocorticoid receptor (GR) antagonist that inhibits GR-mediated transactivation. As an alternative to existing antidepressants, RU486 has been shown to rapidly reverse psychotic depression, most likely by blocking GR. Although a number of studies have demonstrated RU486-induced GR antagonism, the precise mechanism of action still remains unclear. To identify the GR domain involved in RU486-induced suppression, GR transactivation and nuclear translocation were examined using cells transfected with human GR (hGR), Guyanese squirrel monkey GR (gsmGR), and GR chimeras into COS-1 cells. RU486 showed a much more potent suppressive effect in gsmGR-expressing cells versus hGR-expressing cells, without significant cortisol- or RU486-induced changes in nuclear translocation. A GR chimera containing the gsmGR AF1 domain (amino acids 132-428) showed a marked decrease in luciferase activity, suggesting that this domain plays an important role in RU486-induced GR antagonism. Furthermore, fluorescence recovery after photobleaching (FRAP) analysis indicated that, in the presence of RU486, gsmGR AF1 domain contributes to GR mobility in living COS-1 cells. Taken together, these results demonstrate, for the first time, that the antagonistic effects of RU486 on GR transactivation involve a specific GR domain.
Lee
Mi-Sook
MS
Division of Bio-Imaging, Chuncheon Center, Korea Basic Science Institute, Chuncheon 200-701, Republic of Korea.
Choi
Hoon-Sung
HS
Kwon
Seung-Hae
SH
Morita
Kyoji
K
Her
Song
S
D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D019943:Amino Acid Substitution; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D036681:Fluorescence Recovery After Photobleaching; D006727:Hormone Antagonists / Q000494:pharmacology*; D006801:Humans; D015735:Mifepristone / Q000494:pharmacology*; D017434:Protein Structure, Tertiary; D011965:Receptors, Glucocorticoid / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics; D012453:Saimiri; D015533:Transcriptional Activation / Q000187:drug effects
D006727:Hormone Antagonists; D011965:Receptors, Glucocorticoid; D011993:Recombinant Fusion Proteins; D015735:Mifepristone