The farnesoid X receptor induces fetuin-B gene expression in human hepatocytes

Takeshi Murakami , Robert Walczak , Sandrine Caron , Christian Duhem , Vincent Vidal , Raphaël Darteil , Bart Staels (1)

1 Atherosclerosis

Farnesoid X receptor (FXR), a nuclear receptor activated by bile acids, is a key factor in the regulation of bile acid, lipid and carbohydrate metabolism. The recent development of synthetic FXR agonists and knock-out mouse models has accelerated the discovery of FXR target genes. In this study we identify human Fetuin-B as a novel FXR target gene. Treatment with FXR agonists increased Fetuin-B expression in human primary hepatocytes and in the human hepatoma HepG2 cell line. In contrary, Fetuin-B expression was not responsive to FXR agonist treatment in murine primary hepatocytes. Fetuin-B induction by FXR agonist was abolished upon FXR knockdown by siRNA. In addition to the previously described P1 promoter, we show that the human Fetuin-B gene is also transcribed from an alternative promoter, termed P2. Transcription via the P2 promoter was induced by FXR agonist treatment, whereas P1 promoter activity was not sensitive to FXR agonist treatment. Two putative FXR response elements (IR-1) were identified in the region -1.6kb upstream of the predicted P2 transcriptional start site. Both motifs bound FXR/RXR complexes in vitro and were activated by FXR in transient transfection reporter assays. Mutations in the IR-1 sites abolished FXR/RXR binding and activation. Taken together, these results identify human Fetuin-B as a new FXR target gene in human hepatocytes.

Mots clés: Life Sciences

Takeshi Murakami, Robert Walczak, Sandrine Caron, Christian Duhem, Vincent Vidal, et al.. The farnesoid X receptor induces fetuin-B gene expression in human hepatocytes. Biochemical Journal, 2007, 407 (3), pp.461-469. ⟨10.1042/BJ20070658⟩. ⟨hal-00478806⟩