Diacylglycerol kinase θ couples farnesoid X receptor-dependent bile acid signalling to Akt activation and glucose homoeostasis in hepatocytes.
Diacylglycerol kinase θ couples farnesoid X receptor-dependent bile acid signalling to Akt activation and glucose homoeostasis in hepatocytes.
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DOI：
10.1042/bj20130609
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发表时间：
2013-09-01
期刊：
影响因子：
--
通讯作者：
Sewer MB
中科院分区：
文献类型：
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作者：
Cai K;Sewer MB
DGKs催化甘油二酯转化为磷脂酸，磷脂酸是mTOR(雷帕霉素的哺乳动物靶标)的正向调节剂。我们发现鹅去氧胆酸和人工合成的法尼醇X受体配体GW4064诱导肝癌细胞和原代人肝细胞DGKθ的基因和蛋白表达。用1.5kB的DGKθ启动子与荧光素酶基因融合的报告基因研究表明，胆汁酸增加了DGKθ的转录活性。推测的FXR结合位点的突变减弱了GW4046提高DGKθ荧光素酶活性的能力。与这一发现一致的是，CHIP(染色质免疫沉淀)分析表明，胆汁酸信号增加了FXR对DGKθ启动子的募集。此外，GW4064可引起细胞内PA浓度的时间依赖性增加。我们还发现，GW4064和PA促进mTOR、Akt和FoxO1(叉头盒O1)的磷酸化，而沉默DGKθ的表达显著抑制了GW4046促进这些PA调节靶标的磷酸化的能力。DGKθ也是胆汁酸依赖的葡萄糖产生减少所必需的。综上所述，我们的结果确定DGKθ是胆汁酸刺激的mTORC2(mTOR复合体2)、AKT途径和葡萄糖稳态调节的关键介质。
DGKs (diacylglycerol kinases) catalyse the conversion of diacylglycerol into PA (phosphatidic acid), a positive modulator of mTOR (mammalian target of rapamycin). We have found that chenodeoxycholic acid and the synthetic FXR (farnesoid X receptor) ligand GW4064 induce the mRNA and protein expression of DGKθ in the HepG2 cell line and in primary human hepatocytes. Reporter gene studies using 1.5 kB of the DGKθ promoter fused to the luciferase gene revealed that bile acids increase DGKθ transcriptional activity. Mutation of putative FXR-binding sites attenuated the ability of GW4046 to increase DGKθ luciferase activity. Consistent with this finding, ChIP (chromatin immunoprecipitation) assays demonstrated that bile acid signalling increased the recruitment of FXR to the DGKθ promoter. Furthermore, GW4064 evoked a time-dependent increase in the cellular concentration of PA. We also found that GW4064 and PA promote the phosphorylation of mTOR, Akt and FoxO1 (forkhead box O1), and that silencing DGKθ expression significantly abrogated the ability of GW4046 to promote the phosphorylation of these PA-regulated targets. DGKθ was also required for bile-acid-dependent decreased glucose production. Taken together, our results establish DGKθ as a key mediator of bile-acid-stimulated modulation of mTORC2 (mTOR complex 2), the Akt pathway and glucose homoeostasis.