Nuclear receptors CAR and PXR cross talk with FOXO1 to regulate genes that encode drug-metabolizing and gluconeogenic enzymes
Nuclear receptors CAR and PXR cross talk with FOXO1 to regulate genes that encode drug-metabolizing and gluconeogenic enzymes
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DOI：
10.1128/mcb.24.18.7931-7940.2004
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发表时间：
2004-09-01
影响因子：
5.3
通讯作者：
Yamamoto, Y
中科院分区：
文献类型：
--
作者：
Kodama, S;Koike, C;Yamamoto, Y
核受体 CAR 和 PXR 激活肝脏基因以响应治疗药物和异生素，从而诱导药物代谢酶，例如细胞色素 P450。胰岛素抑制 FOXO1 表达编码糖异生酶的基因的能力。众所周知，胰岛素会降低药物的诱导作用，而糖异生活性通常会受到某些药物（例如苯巴比妥（PB））治疗的抑制。通过使用药物反应和胰岛素反应增强剂、谷胱甘肽 S-转移酶下拉、RNA 干扰 (RNAi) 和小鼠原代肝细胞进行基于细胞的转染测定，我们检查了核受体和 FOXO1 协调调节两种酶途径的分子机制。 FOXO1被发现是CAR和PXR介导的转录的共激活因子。相比之下，CAR和PXR作为辅阻遏物，在其激活剂存在的情况下下调FOXO1介导的转录，例如分别为1,4-双[2-(3,5-二氯吡啶氧基)]苯(TCPOBOP)和孕烯醇酮16α-甲腈。胰岛素反应性蛋白激酶 Akt 的组成型活性突变体（而非激酶阴性突变体）在细胞检测中有效阻断了 FOXO1 活性。因此，胰岛素可以通过激活 Akt-FOXO1 信号来抑制受体，而药物可以通过激活 CAR 和/或 PXR 来干扰 FOXO1 介导的转录。 TCPOBOP 或 PB 治疗降低了小鼠中磷酸烯醇丙酮酸羧激酶 1 mRNA 的水平，但在 Car(-/-) 小鼠中则没有。我们得出结论，FOXO1 和核受体相互共同调节其靶基因，调节药物代谢和糖异生。
The nuclear receptors CAR and PXR activate hepatic genes in response to therapeutic drugs and xenobiotics, leading to the induction of drug-metabolizing enzymes, such as cytochrome P450. Insulin inhibits the ability of FOXO1 to express genes encoding gluconeogenic enzymes. Induction by drugs is known to be decreased by insulin, whereas gluconeogenic activity is often repressed by treatment with certain drugs, such as phenobarbital (PB). Performing cell-based transfection assays with drug-responsive and insulin-responsive enhancers, glutathione S-transferase pull down, RNA interference (RNAi), and mouse primary hepatocytes, we examined the molecular mechanism by which nuclear receptors and FOXO1 could coordinately regulate both enzyme pathways. FOXO1 was found to be a coactivator to CAR- and PXR-mediated transcription. In contrast, CAR and PXR, acting as corepressors, downregulated FOXO1-mediated transcription in the presence of their activators, such as 1,4-bis[2-(3,5-dichloropyridyloxy)] benzene (TCPOBOP) and pregnenolone 16alpha-carbonitrile, respectively. A constitutively active mutant of the insulin-responsive protein kinase Akt, but not the kinase-negative mutant, effectively blocked FOXO1 activity in cell-based assays. Thus, insulin could repress the receptors by activating the Akt-FOXO1 signal, whereas drugs could interfere with FOXO1-mediated transcription by activating CAR and/or PXR. Treatment with TCPOBOP or PB decreased the levels of phosphoenolpyruvate carboxykinase 1 mRNA in mice but not in Car(-/-) mice. We conclude that FOXO1 and the nuclear receptors reciprocally coregulate their target genes, modulating both drug metabolism and gluconeogenesis.