Inhibition of gluconeogenesis through transcriptional activation of EGR1 and DUSP4 by AMP-activated kinase
Inhibition of gluconeogenesis through transcriptional activation of EGR1 and DUSP4 by AMP-activated kinase
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DOI：
10.1074/jbc.m602416200
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发表时间：
2006-09-15
影响因子：
4.8
通讯作者：
Martinez, Robert V.
中科院分区：
文献类型：
--
作者：
Berasi, Stephen P.;Huard, Christine;Martinez, Robert V.
肝脏糖异生增加是导致2型糖尿病患者空腹高血糖的重要因素。低能状态激活细胞内能量感受器AMP激活的激酶(AMPK)。AMP类似物AICAR(5-氨基咪唑-4-甲酰胺核苷)激活AMPK可抑制肝脏糖异生。我们使用转录图谱在肝细胞系中寻找AICAR调节的基因。我们报告了AMPK在AML12、H4IIE和FAO细胞中在mRNA和蛋白质水平上诱导的双特异性磷酸酶Dusp4。AMPK还诱导即时早期转录因子Egr1(早期生长反应1)，这是一种已知的Dusp4转录激活因子，它直接与Dusp4启动子结合在其已知的结合部位。报告基因分析和实时定量聚合酶链式反应均表明，外源DUSP4对葡萄糖-6-磷酸酶(GLC-6-P)和磷酸烯醇式丙酮酸羧酸激酶(PEPCK)启动子活性和表达的抑制程度与AICAR和AMPK相似。相反，使用siRNA去除Egr1或DUSP4不仅部分取消了AICAR对PEPCK表达的抑制，而且对FAO细胞的葡萄糖生产也有重要影响。在FAO细胞中，针对Egr1的小干扰RNA也在AICAR处理后耗尽DUSP4的表达，进一步支持Egr1和DUSP4激活之间的直接联系。P38是cAMP介导的糖异生的已知效应因子，它的表达挽救了DUSP4介导的PEPCK的抑制。这些结果表明，AMPK对肝脏糖异生的抑制可能部分是通过涉及Egr1及其靶点DUSP4的即刻早期基因反应来介导的。
Increased hepatic gluconeogenesis is an important contributor to the fasting hyperglycemia found in Type 2 diabetic patients. Low energy states activate the intracellular energy sensor AMP-activated kinase (AMPK). AMPK activation by the AMP mimetic AICAR (5-aminoimidazole-4-carboxamide riboside) has been shown to inhibit hepatic gluconeogenesis. We used transcriptional profiling to search for AICAR-regulated genes in hepatocyte cell lines. We report that a dual specificity phosphatase, Dusp4, is induced by AMPK in AML12, H4IIE, and Fao cells at both mRNA and protein levels. AMPK also induces the immediate early transcription factor Egr1 (early growth response 1), a known transcriptional activator of Dusp4, and it directly binds the Dusp4 promoter at its known binding site. Both reporter gene assays and real time PCR demonstrate that exogenous DUSP4 inhibits the promoter activity and expression of both glucose-6-phosphatase (Glc-6-P) and phosphoenolpyruvate carboxykinase (Pepck) to an extent similar to both AICAR and constitutively active AMPK. Conversely, depletion of EGR1 or DUSP4 using siRNA not only partially abrogates the inhibition of Pepck expression by AICAR, but also importantly affects glucose production by Fao cells. In Fao cells, small interfering RNA targeted EGR1 also depletes DUSP4 expression following treatment with AICAR, further supporting a direct link between EGR1 and DUSP4 activation. Expression of a constitutively active form of p38, a known effector of cAMP-mediated gluconeogenesis, rescues the DUSP4-mediated repression of PEPCK. These results suggest that the inhibition of hepatic gluconeogenesis by AMPK may, in part, be mediated by an immediate early gene response involving EGR1 and its target, DUSP4.