title: Ligand-dependent regulation of the activity of the orphan nuclear receptor, small heterodimer partner (SHP), in the repression of bile acid biosynthetic CYP7A1 and CYP8B1 genes.
abstract: Small heterodimer partner (SHP) plays important roles in diverse biological processes by directly interacting with transcription factors and inhibiting their activities. SHP has been designated an orphan nuclear receptor, but whether its activity can be modulated by ligands has been a long-standing question. Recently, retinoid-related molecules, including 4-[3-(1-adamantyl)-4-hydroxyphenyl]-3-chlorocinnamic acid (3Cl-AHPC), were shown to bind to SHP and enhance apoptosis. We have examined whether 3Cl-AHPC acts as an agonist and increases SHP activity in the repression of bile acid biosynthetic CYP7A1 and CYP8B1 genes and delineated the underlying mechanisms. Contrary to this expectation, micromolar concentrations of 3Cl-AHPC increased CYP7A1 expression but indirectly via p38 kinase signaling. Nanomolar concentrations, however, repressed CYP7A1 expression and decreased bile acid levels in HepG2 cells, and little repression was observed when SHP was down-regulated by small hairpin RNA. Mechanistic studies revealed that 3Cl-AHPC bound to SHP, increased the interaction of SHP with liver receptor homologue (LRH)-1, a hepatic activator for CYP7A1 and CYP8B1 genes, and with repressive cofactors, Brahma, mammalian Sin3a, and histone deacetylase-1, and, subsequently, increased the occupancy of SHP and these cofactors at the promoters. Mutation of Leu-100, predicted to contact 3Cl-AHPC within the SHP ligand binding pocket by molecular modeling, severely impaired the increased interaction with LRH-1, and repression of LRH-1 activity mediated by 3Cl-AHPC. 3Cl-AHPC repressed SHP metabolic target genes in a gene-specific manner in human primary hepatocytes and HepG2 cells. These data suggest that SHP may act as a ligand-regulated receptor in metabolic pathways. Modulation of SHP activity by synthetic ligands may be a useful therapeutic strategy.
authors.affiliation: Department of Molecular and Integrative Physiology, University of Illinois, Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Ji
authors.initials: J
authors.lastname: Miao
authors.forename: Sung-E
authors.initials: SE
authors.lastname: Choi
authors.forename: Sun Mi
authors.initials: SM
authors.lastname: Seok
authors.forename: Linda
authors.initials: L
authors.lastname: Yang
authors.forename: William J
authors.initials: WJ
authors.lastname: Zuercher
authors.forename: Yong
authors.initials: Y
authors.lastname: Xu
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Willson
authors.forename: H Eric
authors.initials: HE
authors.lastname: Xu
authors.forename: Jongsook Kim
authors.initials: JK
authors.lastname: Kemper
mesh_terms: D000218:Adamantane / Q000031:analogs & derivatives / Q000494:pharmacology; D020816:Amino Acid Motifs; D000818:Animals; D001647:Bile Acids and Salts / Q000096:biosynthesis*; D001665:Binding Sites / Q000235:genetics; D002460:Cell Line; D002790:Cholesterol 7-alpha-Hydroxylase / Q000235:genetics* / Q000378:metabolism; D047369:Chromatin Immunoprecipitation; D002934:Cinnamates / Q000494:pharmacology; D017930:Genes, Reporter; D056284:Histone Deacetylase 1 / Q000378:metabolism; D006801:Humans; D007930:Leucine / Q000737:chemistry; D049409:Luciferases, Firefly / Q000096:biosynthesis / Q000235:genetics; D051379:Mice; D008958:Models, Molecular; D020125:Mutation, Missense; D011485:Protein Binding; D018160:Receptors, Cytoplasmic and Nuclear / Q000819:agonists / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013253:Steroid 12-alpha-Hydroxylase / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: C480030:4-(3-(1-adamantyl)-4-hydroxyphenyl)-3-chlorocinnamic acid; D001647:Bile Acids and Salts; D002934:Cinnamates; C431936:Nr5a2 protein, mouse; D018160:Receptors, Cytoplasmic and Nuclear; C499503:Smarca2 protein, mouse; D014157:Transcription Factors; C099713:nuclear receptor subfamily 0, group B, member 2; D049409:Luciferases, Firefly; D002790:Cholesterol 7-alpha-Hydroxylase; C502772:Cyp7a1 protein, mouse; D013253:Steroid 12-alpha-Hydroxylase; C484389:Hdac1 protein, mouse; D056284:Histone Deacetylase 1; D007930:Leucine; D000218:Adamantane