Division of Drug Metabolism and Molecular Toxicology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan.
J Steroid Biochem Mol Biol. 2012 Oct;132(1-2):41-7. doi: 10.1016/j.jsbmb.2012.04.008. Epub 2012 May 3.
The intestinal endocrine hormone human fibroblast growth factor 19 (FGF19) is involved in the regulation of not only hepatic bile acid metabolism but also carbohydrate and lipid metabolism. In the present study, bile acid/farnesoid X receptor (FXR) responsiveness in the FGF19 promoter region was investigated by a reporter assay using the human colon carcinoma cell line LS174T. The assay revealed the presence of bile acid/FXR-responsive elements in the 5'-flanking region up to 8.8 kb of FGF19. Deletion analysis indicated that regions from -1866 to -1833, from -1427 to -1353, and from -75 to +262 were involved in FXR responsiveness. Four, four, and two consecutive half-sites of nuclear receptors were observed in the three regions, respectively. An electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) assay revealed FXR/retinoid X receptor α (RXRα) heterodimer binding in these three regions. EMSA and reporter assays using mutated constructs indicated that the nuclear receptor IR1, ER2, and DR8 motifs in the 5'-flanking region were involved in FXR responsiveness of FGF19. Lithocholic acid (LCA) (10 μM), chenodeoxycholic acid (CDCA) (10 μM), or GW4064 (0.1 μM) treatment increased reporter activity in a construct including the three motifs under FXR-expressing conditions whereas LCA and not CDCA or GW4064 treatment increased the reporter activity under pregnane X receptor (PXR)-expressing conditions. These results suggest that FGF19 is transcriptionally activated through multiple FXR-responsive elements in the promoter region.
肠内分泌激素人成纤维细胞生长因子 19（FGF19）不仅参与了肝胆汁酸代谢的调节，还参与了碳水化合物和脂质代谢的调节。在本研究中，通过使用人结肠癌细胞系 LS174T 的报告基因检测，研究了 FGF19 启动子区域中的胆汁酸/法尼醇 X 受体（FXR）反应性。该检测显示，FGF19 的 5'侧翼区域存在胆汁酸/FXR 反应元件，可达 8.8kb。缺失分析表明，-1866 至-1833 区、-1427 至-1353 区和-75 至+262 区参与了 FXR 反应性。在这三个区域中分别观察到四个、四个和两个连续的核受体半位点。电泳迁移率变动分析（EMSA）和染色质免疫沉淀（ChIP）分析显示，在这三个区域中存在 FXR/视黄酸受体α（RXRα）异二聚体结合。使用突变构建体的 EMSA 和报告基因检测表明，5'侧翼区域中的核受体 IR1、ER2 和 DR8 基序参与了 FGF19 的 FXR 反应性。在 FXR 表达条件下，包含这三个基序的构建体中，石胆酸（LCA）（10μM）、鹅脱氧胆酸（CDCA）（10μM）或 GW4064（0.1μM）处理增加了报告基因活性，而 LCA 而不是 CDCA 或 GW4064 处理在 pregnane X 受体（PXR）表达条件下增加了报告基因活性。这些结果表明，FGF19 通过启动子区域中的多个 FXR 反应元件被转录激活。
