1,25-dihydroxyvitamin D3 and its receptor inhibit the chenodeoxycholic acid-dependent transactivation by farnesoid X receptor.
Farnesoid X receptor (FXR), the receptor for bile acids, including chenodeoxycholic acid (CDCA), is a member of the nuclear receptor superfamily, which also includes the receptors for retinoic acid, vitamin D (D3), thyroid hormone, thiazolidinedione and 22(R)-hydroxycholesterol. Here, we have evaluated the effects of a series of ligands and their receptors on the promoter activity induced by CDCA/FXR. The kidney cell line, CV1, was cotransfected with FXR-expression plasmid and the luciferase-based reporter gene that has a thymidine kinase promoter fused to the canonical FXR-responsive element or the natural promoter for the small heterodimer partner (SHP), bile salt export pump (BSEP), and ileum bile acid (I-BABP) gene. D3 and its receptor (VDR) inhibited the transactivation of all four reporter constructs that are enhanced by CDCA/FXR. The effect of D3 on the expression of the BSEP and SHP genes in HepG2 cells and that of the I-BABP gene in Caco-2 cells were confirmed by reverse transcription (RT)-PCR. Deletion analysis of VDR revealed that its ligand-binding domain (LBD) is responsible for the repression and the DNA-binding domain (DBD) is dispensable. Specific interaction between FXR and VDR was detected with the in vitro pull-down assay using chimeric FXR or VDR fused to glutathione-S-transferase.
Honjo
Yumiko
Y
Second Division, Department of Internal Medicine, Hamamatsu University School of Medicine, 1-20-1 Handayama, Hamamatsu, Shizuoka 431-3192, Japan.
Sasaki
Shigekazu
S
Kobayashi
Yoshimasa
Y
Misawa
Hiroko
H
Nakamura
Hirotoshi
H
D000074020:ATP Binding Cassette Transporter, Subfamily B, Member 11; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002117:Calcitriol / Q000378:metabolism / Q000494:pharmacology*; D002460:Cell Line; D002635:Chenodeoxycholic Acid / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004926:Escherichia coli; D050556:Fatty Acid-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005768:Gastrointestinal Hormones; D017353:Gene Deletion; D006801:Humans; D008099:Liver / Q000378:metabolism*; D010957:Plasmids; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051381:Rats; D018167:Receptors, Calcitriol / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection / Q000379:methods; D000099150:Receptor, Farnesoid X-Activated
D000074020:ATP Binding Cassette Transporter, Subfamily B, Member 11; D018528:ATP-Binding Cassette Transporters; D002117:Calcitriol; D002635:Chenodeoxycholic Acid; D004268:DNA-Binding Proteins; D050556:Fatty Acid-Binding Proteins; D005768:Gastrointestinal Hormones; D018167:Receptors, Calcitriol; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors; D000099150:Receptor, Farnesoid X-Activated; C093491:ABCB11 protein, human; C057275:fatty acid-binding protein 6