A structural explanation of the effects of dissociated glucocorticoids on glucocorticoid receptor transactivation.
There is a therapeutic need for glucocorticoid receptor (GR) ligands that distinguish between the transrepression and transactivation activity of the GR, the later thought to be responsible for side effects. These ligands are known as "dissociated glucocorticoids" (dGCs). The first published dGCs, RU24782 (9α-fluoro-11β-hydroxy-16α-methylpregna-21-thiomethyl-1,4-diene-3,20-dione) and RU24858 (9α-fluoro-11β-hydroxy-16α-methylpregna-21-cyanide-1,4-diene-3,20-dione), do not have the 17α-hydroxyl group that characterizes dexamethasone (Dex; 9α-fluoro-11β,17α,21-trihydroxy-16α-methylpregna-1,4-diene-3,20-dione), and they differ from one another by having C21-thiomethyl and C21-cyanide moieties, respectively. Our aim was therefore to establish the structural basis of their activity. Both RU24782 and RU24858 induced a transactivation activity highly dependent on the GR expression level but always lower than dexamethasone. They also display less ability than dexamethasone to trigger steroid receptor coactivator 1 (SRC-1) recruitment and histone H3 acetylation. Docking studies, validated by mutagenesis experiments, revealed that dGCs are not anchored by Gln642, in contrast to Dex, which is hydrogen bonded to this residue via its 17α-hydroxyl group. This contact is essential for SRC-1 recruitment and subsequent dexamethasone-induced GR transactivation, but not transrepression. The ability of dGCs to make contacts with Ile747, for both RU24858 and RU24782 and with Asn564 for RU24858 are not strong enough to maintain GR in a conformation able to efficiently recruit SRC-1, unless SRC-1 is overexpressed. Overall, our findings provide some structural guidelines for the synthesis of potential new dissociated glucocorticoids with a better therapeutic ratio.
Institut National de la Santé et de la Recherche Médicale U837, Institut de Recherche pour le Cancer de Lille, Lille, France (X.D., S.T., B.M., D.H., P.F., T.I.); Institut National de la Santé et de la Recherche Médicale U773, Centre de Recherche Biomédicale Bichat-Beaujon, CRB3 (J.F., M.F., M.-E.R.-O.); and Université Paris 7- Denis Diderot, site Bichat, Paris, France (J.F., M.F., M.-E.R.-O.).
Xavier
X
Dezitter
Jérôme
J
Fagart
Solenne
S
Taront
Michel
M
Fay
Bernadette
B
Masselot
Dominique
D
Hétuin
Pierre
P
Formstecher
Marie-Edith
ME
Rafestin-Oblin
Thierry
T
Idziorek
D021581:Active Transport, Cell Nucleus; D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D003907:Dexamethasone / Q000494:pharmacology; D005938:Glucocorticoids / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D056920:Nuclear Receptor Coactivator 1 / Q000502:physiology; D011401:Promoter Regions, Genetic; D011487:Protein Conformation; D011965:Receptors, Glucocorticoid / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics; D015533:Transcriptional Activation / Q000187:drug effects*
D005938:Glucocorticoids; D011965:Receptors, Glucocorticoid; C404226:TSC22D3 protein, human; D014157:Transcription Factors; D003907:Dexamethasone; D056920:Nuclear Receptor Coactivator 1