title: Molecular determinants of steroid inhibition for the mouse constitutive androstane receptor.
abstract: The constitutive androstane receptor (CAR) regulates drug and steroid metabolism through binding to cytochrome P450 2B, 2C, and 3A gene enhancers. Uniquely among nuclear receptors, mouse CAR (mCAR) can be suppressed by androstenol and activated by structurally diverse drugs, pesticides, and environmental pollutants. To gain insight into presently ill-defined structural requirements of mCAR ligands, we employed a mCAR inhibition assay in mammalian HEK293 cells to create a QSAR model that could well predict the inhibition by three unknown steroids. Two novel mCAR inhibitors were thus identified. Yeast two-hybrid assays indicated that steroids inhibit mCAR primarily by promoting association of mCAR with the corepressor NCoR, with only minor contribution from other mechanisms. Analysis of chimeric and mutant mCAR constructs suggested that androstenol sensitivity is controlled by residues between amino acids 201-263 (helices 5-7) and it does not depend on the residue 350 within helix 12, as previously suggested.
authors.affiliation: Department of Pharmaceutics, University of Kuopio, P.O.Box 1627, FIN-70211 Kuopio, Finland.
authors.forename: Johanna
authors.initials: J
authors.lastname: Jyrkkärinne
authors.forename: Janne
authors.initials: J
authors.lastname: Mäkinen
authors.forename: Jukka
authors.initials: J
authors.lastname: Gynther
authors.forename: Heidi
authors.initials: H
authors.lastname: Savolainen
authors.forename: Antti
authors.initials: A
authors.lastname: Poso
authors.forename: Paavo
authors.initials: P
authors.lastname: Honkakoski
mesh_terms: D000818:Animals; D002460:Cell Line; D000090702:Constitutive Androstane Receptor; D051548:Histone Acetyltransferases; D006801:Humans; D051379:Mice; D008958:Models, Molecular; D009154:Mutation; D009687:Nuclear Proteins / Q000737:chemistry; D056971:Nuclear Receptor Co-Repressor 1; D056920:Nuclear Receptor Coactivator 1; D017433:Protein Structure, Secondary; D021281:Quantitative Structure-Activity Relationship; D018160:Receptors, Cytoplasmic and Nuclear / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics; D012097:Repressor Proteins / Q000737:chemistry; D013256:Steroids / Q000737:chemistry* / Q000494:pharmacology; D014157:Transcription Factors / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics; D020798:Two-Hybrid System Techniques; D015003:Yeasts / Q000187:drug effects / Q000378:metabolism
chemical_list: D000090702:Constitutive Androstane Receptor; C539127:NCOR1 protein, human; C539128:Ncor1 protein, mouse; D009687:Nuclear Proteins; D056971:Nuclear Receptor Co-Repressor 1; D018160:Receptors, Cytoplasmic and Nuclear; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D013256:Steroids; D014157:Transcription Factors; D051548:Histone Acetyltransferases; C538859:NCOA1 protein, human; C538861:Ncoa1 protein, mouse; D056920:Nuclear Receptor Coactivator 1