title: Structural basis of digoxin that antagonizes RORgamma t receptor activity and suppresses Th17 cell differentiation and interleukin (IL)-17 production.
abstract: The retinoic acid-related orphan nuclear receptor γt (RORγt)/RORγ2 is well known as a master regulator of interleukin 17 (IL-17)-producing helper T (Th17) cell development. To develop a therapeutic agent against Th17-mediated autoimmune diseases, we screened chemical compounds and successfully found that digoxin inhibited IL-17 production. Further studies revealed that digoxin bound to the ligand binding domain of RORγt and suppressed Th17 differentiation without affecting Th1 differentiation. To better understand the structural basis for the inhibitory activity of digoxin, we determined the crystal structure of the RORγt ligand-binding domain in complex with digoxin at 2.2 Å resolution. The structure reveals that digoxin binds to the ligand-binding pocket protruding between helices H3 and H11 from the pocket. In addition, digoxin disrupts the key interaction important for the agonistic activity, resulting in preventing the positioning of helix H12 in the active conformation, thus antagonizing coactivator interaction. Functional studies demonstrated that digoxin inhibited RORγt activity and decreased IL-17 production but not RORα activity. Digoxin inhibited IL-17 production in CD4(+) T cells from experimental autoimmune encephalomyelitis mice. Our data indicates that RORγt is a promising therapeutic target for Th17-derived autoimmune diseases and our structural data will help to design novel RORγt antagonists.
authors: Oncology Research Laboratories, R&D Division, Daiichi Sankyo Co., Ltd., Tokyo 134-8630, Japan.
authors: Saori
authors: S
authors: Fujita-Sato
authors: Shuichiro
authors: S
authors: Ito
authors: Takashi
authors: T
authors: Isobe
authors: Takao
authors: T
authors: Ohyama
authors: Kenji
authors: K
authors: Wakabayashi
authors: Kaoru
authors: K
authors: Morishita
authors: Osamu
authors: O
authors: Ando
authors: Fujio
authors: F
authors: Isono
mesh_terms: D000818:Animals; D001327:Autoimmune Diseases / Q000188:drug therapy; D015496:CD4-Positive T-Lymphocytes; D002454:Cell Differentiation / Q000187:drug effects; D018360:Crystallography, X-Ray; D004077:Digoxin / Q000737:chemistry* / Q000494:pharmacology; D004681:Encephalomyelitis, Autoimmune, Experimental; D020381:Interleukin-17 / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D051379:Mice; D015394:Molecular Structure; D057132:Nuclear Receptor Subfamily 1, Group F, Member 3 / Q000037:antagonists & inhibitors*; D058504:Th17 Cells / Q000166:cytology / Q000187:drug effects*
chemical_list: D020381:Interleukin-17; D057132:Nuclear Receptor Subfamily 1, Group F, Member 3; D004077:Digoxin