FTF and LRH-1, two related but different transcription factors in human Caco-2 cells: their different roles in the regulation of bile acid transport.
The apical sodium dependent bile acid transporter (ASBT) mediates ileal bile acid reabsorption. The transcription factors, liver receptor homologue-1 (LRH-1:mouse) and fetoprotein transcription factor (FTF:human), are presumably orthologues. Bile-acid induced negative feedback regulation of mouse (m) and human (h) ASBT occurs via LRH-1 and RAR/RXR, respectively. hASBT has a potential FTF cis-element, although its functional role is unknown. hASBT and mASBT promoter constructs and an FTF cis-element mutated hASBT (hASBT/FTFmu) were assessed in human Caco-2 cells treated with chenodeoxycholic acid (CDCA) and/or co-transfected with hFTF, mLRH-1, or specific small interfering FTF or LRH-1 RNA (siFTF or siLRH). Basal promoter activity was reduced in hASBT/FTFmu, although bile acid response persisted. hFTF activated hASBT but not mASBT, while mLRH-1 activated mASBT but not hASBT. siFTF reduced hASBT but not mASBT activity; siLRH reduced mASBT but not hASBT activity. siLRH but not siFTF abrogated bile acid responsiveness. Electrophoretic mobility shift assays demonstrated distinct and specific binding of the mLRH-1 or hFTF cis-elements. In conclusion, FTF and LRH-1 are two related but different transcription factors in human Caco-2 cells, suggesting that they may be homologues and not orthologues. FTF is not involved directly in bile acid mediated negative feedback regulation of the ASBT.
Pan
Debra H
DH
Department of Pediatrics, Division of Pediatric Hepatology, Mount Sinai School of Medicine, One Gustave L. Levy Place, Box 1656, New York, NY 10029, USA.
Chen
Frank
F
Neimark
Ezequiel
E
Li
Xiaoping
X
Shneider
Benjamin L
BL
D000595:Amino Acid Sequence; D001647:Bile Acids and Salts / Q000378:metabolism*; D001692:Biological Transport; D015152:Blotting, Northern; D015153:Blotting, Western; D018938:Caco-2 Cells; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D008957:Models, Genetic; D008969:Molecular Sequence Data; D029363:Organic Anion Transporters, Sodium-Dependent / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D050436:Regulatory Elements, Transcriptional / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D027981:Symporters / Q000235:genetics; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D001647:Bile Acids and Salts; D004268:DNA-Binding Proteins; C431936:Nr5a2 protein, mouse; D029363:Organic Anion Transporters, Sodium-Dependent; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D018160:Receptors, Cytoplasmic and Nuclear; D027981:Symporters; D014157:Transcription Factors; C099948:fetoprotein transcription factor; C071908:sodium-bile acid cotransporter; D004247:DNA