Regulation of GLUT4 expression in denervated skeletal muscle.
Regulation of GLUT4 expression in denervated skeletal muscle.
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去神经骨骼肌中 GLUT4 表达的调节。
DOI：
10.1152/ajpregu.90651.2008
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
Dohm,GLynis
中科院分区：
文献类型：
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作者：
Jensen,EllisB;Zheng,Donghai;Russell,RobertA;Bassel-Duby,Rhonda;Williams,RSanders;Olson,AnnLouise;Dohm,GLynis
坐骨神经切除导致肌肉葡萄糖转运蛋白4（GLUT 4）表达减少，但对导致这种减少的信号传导事件知之甚少。设计实验以检验以下假设：由于钙/CaMK活性降低而发生失神经肌肉中GLUT 4表达降低，这将导致正常GLUT 4表达所需的转录因子肌细胞增强因子2（MEF 2）和GLUT 4增强因子（GEF）的活化降低。GLUT 4 mRNA在表达组成型活性CaMK亚型IV（CaMKIV）的小鼠中升高，并通过去神经支配降低。去神经支配降低了GEF与启动子的结合和细胞核中GEF的含量，但MEF 2结合或MEF 2蛋白含量没有变化。MEF 2依赖性报告基因的表达在失神经骨骼肌中没有变化。为了确定响应去神经支配的GLUT 4启动子的结构域，表达由不同长度的人GLUT 4启动子驱动的氯霉素乙酰转移酶（CAT）报告基因的转基因小鼠被去神经支配。使用几种不同的启动子/报告基因构建体，我们发现GLUT 4启动子的所有区域都被截短或缺失，除了MEF 2结合结构域和基础启动子。所有评估的GLUT 4启动子/CAT报告基因构建体对去神经支配反应正常。我们的数据使我们得出结论，减少CaMK活性的原因是没有减少GLUT 4含量在失神经肌肉和GLUT 4表达的负控制介导的MEF 2或GEF结合域。这些发现表明，GEF或MEF 2依赖性信号的撤回不太可能是去神经支配对GLUT 4表达影响的主要决定因素。因此，对去神经支配的反应可能由GLUT 4基因的基础启动子中存在的其他元件介导。
Denervation by sciatic nerve resection causes decreased muscle glucose transporter 4 (GLUT4) expression, but little is known about the signaling events that cause this decrease. Experiments were designed to test the hypothesis that decreased GLUT4 expression in denervated muscle occurs because of decreased calcium/CaMK activity, which would then lead to decreased activation of the transcription factors myocyte enhancer factor 2 (MEF2) and GLUT4 enhancer factor (GEF), which are required for normal GLUT4 expression. GLUT4 mRNA was elevated in mice expressing constitutively active CaMK isoform IV (CaMKIV) and decreased by denervation. Denervation decreased GEF binding to the promoter and the content of GEF in the nucleus, but there was no change in either MEF2 binding or MEF2 protein content. Expression of a MEF2-dependent reporter gene did not change in denervated skeletal muscle. To determine the domains of the GLUT4 promoter that respond to denervation, transgenic mice expressing the chloramphenicol acetyl transferase (CAT) reporter gene driven by different lengths of the human GLUT4 promoter were denervated. Using several different promoter/reporter gene constructs, we found that all areas of the GLUT4 promoter were truncated or missing, except for the MEF2 binding domain and the basal promoter. All of the GLUT4 promoter/CAT reporter constructs evaluated responded normally to denervation. Our data lead us to conclude that decreased CaMK activity is not the reason for decreased GLUT4 content in denervated muscle and that negative control of GLUT4 expression is not mediated through the MEF2 or GEF-binding domains. These findings indicate that withdrawal of a GEF- or MEF2-dependent signal is not likely a major determinant of the denervation effect on GLUT4 expression. Thus, the response to denervation may be mediated by other elements present in the basal promoter of the GLUT4 gene.