Insulin induces the expression of the SHARP-2/Stra13/DEC1 gene via a phosphoinositide 3-kinase pathway
Insulin induces the expression of the SHARP-2/Stra13/DEC1 gene via a phosphoinositide 3-kinase pathway
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DOI：
10.1074/jbc.m301597200
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发表时间：
2003-08-15
影响因子：
4.8
通讯作者：
Miyamoto, K
中科院分区：
文献类型：
--
作者：
Yamada, K;Kawata, H;Miyamoto, K
高碳水化合物饮食可调节大鼠肝脏脂肪酸合成酶（FAS）基因的转录。在大鼠FAS基因启动子上发现了一个碳水化合物反应元件（ChoRE）。以ChoRE多拷贝为诱饵，在酵母单杂交系统中筛选大鼠肝脏cDNA文库，克隆ChoRE结合蛋白cDNA。获得了一个编码基本螺旋-环-螺旋蛋白的阳性克隆，即分裂和毛发相关蛋白-2 （SHARP-2）的增强子。Northern blot分析显示，当给正常大鼠喂食高碳水化合物或给糖尿病大鼠注射胰岛素时，夏普-2 mRNA水平升高。在原代培养的大鼠肝细胞中，即使在没有葡萄糖的情况下，胰岛素也能迅速诱导夏普-2 mRNA的积累。SHARP-2 mRNA水平升高的时间过程表明，FAS和l型丙酮酸激酶mRNA的升高紧随其后，SHARP-2 mRNA的初始时间过程与葡萄糖激酶mRNA和磷酸烯醇丙酮酸羧激酶mRNA水平的变化相似。虽然wortmannin、LY294002和放线菌素D阻断了胰岛素对SHARP-2 mRNA水平的升高，但雷帕霉素、stausporine、PD98059、冈田酸和8-溴环AMP对SHARP-2 mRNA水平的升高没有影响。此外，核运行试验显示胰岛素诱导大鼠SHARP-2基因的转录。因此，我们得出结论，胰岛素通过磷酸肌苷3激酶途径诱导大鼠夏普-2基因的转录。
Transcription of the rat fatty acid synthase (FAS) gene in the rat liver can be regulated by feeding a high carbohydrate diet. A carbohydrate response element (ChoRE) located on the rat FAS gene promoter has been identified. Using multiple copies of the ChoRE as the bait in a yeast one-hybrid system, a rat liver cDNA library was screened, and the cDNA of ChoRE-binding proteins was cloned. A positive clone that encodes a basic helix-loop-helix protein, enhancer of split- and hairy-related protein-2 (SHARP-2), was obtained. Northern blot analysis revealed that the levels of SHARP-2 mRNA increase when a high carbohydrate diet is fed to normal rats or when insulin is administered to diabetic rats. In primary cultured rat hepatocytes, insulin rapidly induced an accumulation of SHARP-2 mRNA even in the absence of glucose. A time course for the increase in SHARP-2 mRNA levels indicated that it followed by those of FAS and L-type pyruvate kinase mRNAs and that the initial time course of SHARP-2 mRNA was similar to changes in the levels of glucokinase mRNA and phosphoenolpyruvate carboxykinase mRNA. Although wortmannin, LY294002, and actinomycin D blocked the increase in SHARP-2 mRNA levels by insulin, rapamycin, staurosporine, PD98059, okadaic acid, and 8-bromocyclic AMP had no effect. In addition, nuclear run-on assay revealed that transcription of the rat SHARP-2 gene was induced by insulin. Thus, we conclude that insulin induces the transcription of the rat SHARP-2 gene via a phosphoinositide 3-kinase pathway.