title: Antagonist- and inverse agonist-driven interactions of the vitamin D receptor and the constitutive androstane receptor with corepressor protein.
abstract: Ligand-dependent signal transduction by nuclear receptors (NRs) includes dynamic exchanges of coactivator (CoA) and corepressor (CoR) proteins. Here we focused on the structural determinants of the antagonist- and inverse agonist-enhanced interaction of the endocrine NR vitamin D receptor (VDR) and the adopted orphan NR constitutive androstane receptor (CAR) from two species with the CoR NR corepressor. We found that the pure VDR antagonist ZK168281 and the human CAR inverse agonist clotrimazole are both effective inhibitors of the CoA interaction of their respective receptors, whereas ZK168281 resembled more the mouse CAR inverse agonist androstanol in its ability to recruit CoR proteins. Molecular dynamics simulations resulted in comparable models for the CoR receptor interaction domain peptide bound to VDR/antagonist or CAR/inverse agonist complexes. A salt bridge between the CoR and a conserved lysine in helix 4 of the NR is central to this interaction, but also helix 12 was stabilized by direct contacts with residues of the CoR. Fixation of helix 12 in the antagonistic/inverse agonistic conformation prevents an energetically unfavorable free floatation of the C terminus. The comparable molecular mechanisms that explain the similar functional profile of antagonist and inverse agonists are likely to be extended from VDR and CAR to other members of the NR superfamily and may lead to the design of even more effective ligands.
authors.affiliation: Department of Biochemistry, University of Kuopio, P.O. Box 1627, FIN-70211 Kuopio, Finland.
authors.forename: Harri
authors.initials: H
authors.lastname: Lempiäinen
authors.forename: Ferdinand
authors.initials: F
authors.lastname: Molnár
authors.forename: Manuel
authors.initials: M
authors.lastname: Macias Gonzalez
authors.forename: Mikael
authors.initials: M
authors.lastname: Peräkylä
authors.forename: Carsten
authors.initials: C
authors.lastname: Carlberg
mesh_terms: D000595:Amino Acid Sequence; D000732:Androstanols / Q000737:chemistry / Q000494:pharmacology; D000818:Animals; D002117:Calcitriol / Q000031:analogs & derivatives / Q000737:chemistry / Q000494:pharmacology; D002478:Cells, Cultured; D003022:Clotrimazole / Q000737:chemistry / Q000494:pharmacology; D003198:Computer Simulation; D000090702:Constitutive Androstane Receptor; D019281:Dimerization; D005786:Gene Expression Regulation; D006801:Humans; D008024:Ligands; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism*; D056971:Nuclear Receptor Co-Repressor 1; D025941:Protein Interaction Mapping; D017433:Protein Structure, Secondary; D018167:Receptors, Calcitriol / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000819:agonists* / Q000737:chemistry / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism*; D047488:Retinoid X Receptors / Q000378:metabolism; D013329:Structure-Activity Relationship; D014157:Transcription Factors / Q000819:agonists* / Q000737:chemistry / Q000378:metabolism*
chemical_list: D000732:Androstanols; D000090702:Constitutive Androstane Receptor; D008024:Ligands; C539127:NCOR1 protein, human; C539128:Ncor1 protein, mouse; D009687:Nuclear Proteins; D056971:Nuclear Receptor Co-Repressor 1; D018167:Receptors, Calcitriol; D018160:Receptors, Cytoplasmic and Nuclear; D012097:Repressor Proteins; D047488:Retinoid X Receptors; D014157:Transcription Factors; C417690:ZK 168281; C000658:androstan-3-ol; D002117:Calcitriol; D003022:Clotrimazole