Regulation of the mouse organic solute transporter α-β, Ostα-Ostβ, by bile acids
Regulation of the mouse organic solute transporter α-β, Ostα-Ostβ, by bile acids
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DOI：
10.1152/ajpgi.00479.2005
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发表时间：
2006-05-01
影响因子：
4.5
通讯作者：
Dawson, PA
中科院分区：
文献类型：
--
作者：
Frankenberg, T;Rao, A;Dawson, PA
研究了胆汁酸调节小鼠肠道有机溶质转运蛋白α-β（Ost α-Ost β）表达的机制。Ost α-Ost β mRNA的表达在喂食胆酸的小鼠的盲肠和近端结肠中以及在鹅去氧胆酸盐处理的小鼠CT26结肠腺癌细胞中增加。序列分析显示，小鼠Ost α和Ost β启动子中法尼醇X受体（FXR）和肝受体同源物-1（LRH-1）的潜在顺式作用元件，以及含有Ost α和Ost β 5 '侧翼序列的报告基因构建体受胆汁酸正调控。显性负性FXR的表达、用干扰小RNA（siRNA）减少FXR或潜在FXR元件的突变降低了Ost α和Ost β启动子活性，并消除了鹅去氧结肠酸的诱导作用。胆汁酸对Ost α和Ost β启动子的负调控是通过LRH-1元件介导的。Ost α和Ost β启动子活性通过LRH-1的共表达而增加，通过SHP的共表达而降低。潜在的LRH-1元件的突变和siRNA介导的LRH-1表达的减少降低了基础启动子活性。正如启动子分析所预测的那样，回肠Ost α和Ost β mRNA表达在给予FXR激动剂GW 4064的野生型小鼠中增加，而在FXR缺失小鼠中减少。免疫印迹分析显示，Ost α和Ost β肠蛋白表达与mRNA表达相关。小鼠Ost α和Ost β启动子是不寻常的，因为它们含有功能性FXR和LRH元件，它们分别介导胆汁酸的正反馈和负反馈调节。虽然正调控途径似乎是占主导地位的，这种安排提供了一种机制，精细滴定Ost α-Ost β表达的胆汁酸流量。
The mechanisms responsible for bile acid regulation of mouse intestinal organic solute transporter alpha-beta (Ost alpha-Ost beta) expression were investigated. Expression of Ost alpha-Ost beta mRNA was increased in cecum and proximal colon of cholic acid-fed mice and in chenodeoxycholate-treated mouse CT26 colon adenocarcinoma cells. Sequence analysis revealed potential cis-acting elements for farnesoid X receptor (FXR) and liver receptor homolog-1 (LRH-1) in the mouse Ost alpha and Ost beta promoters and reporter constructs containing Ost alpha and Ost beta 5'-flanking sequences were positively regulated by bile acids. Expression of a dominant-negative FXR, reduction of FXR with interfering small RNA (ssiRNA), or mutation of the potential FXR elements decreased Ost alpha and Ost beta promoter activity and abolished the induction by chenodeoxycolic acid. Negative regulation of the Ost alpha and Ost beta promoters by bile acids was mediated through LRH-1 elements. Ost alpha and Ost beta promoter activities were increased by coexpression of LRH-1 and decreased by coexpression of SHP. Mutation of the potential LRH-1 elements and siRNA-mediated reduction of LRH-1 expression decreased basal promoter activity. As predicted from the promoter analyses, ileal Ost alpha and Ost beta mRNA expressions were increased in wild-type mice administered the FXR agonist GW4064 and decreased in FXR-null mice. Immunoblotting analysis revealed that Ost alpha and Ost beta intestinal protein expressions correlated with mRNA expression. The mouse Ost alpha and Ost beta promoters are unusual in that they contain functional FXR and LRH elements, which mediate, respectively, positive and negative feedback regulation by bile acids. Although the positive regulatory pathway appears to be dominant, this arrangement provides a mechanism to finely titrate Ost alpha-Ost beta expression to the bile acid flux.