AMPK调节骨骼肌细胞GLUT4基因表达的机制研究

Mechanism of AMPK Regulating GLUT4 Gene Expression in Skeletal Muscle Cells

腺苷酸活化蛋白激酶(AMPK)能调节运动/肌肉收缩所引起的骨骼肌细胞葡萄糖转运蛋白4(GLUT4)基因的表达,但至今它的调节机制不清。研究显示在非运动刺激引起的细胞信号事件中由组蛋白去乙酰化酶(HDACs)以及组蛋白乙酰化酶(HATs)控制的组蛋白乙酰化状态是调节基因表达的重要机制,所以我们假设AMPK信号途径是通过征用HDACs中的HDAC5(在骨骼肌细胞内高表达)来实现对运动/肌肉收缩引起的GLUT4基因表达控制。细胞分为正常浓度葡萄糖对照组(NGLU组)、正常浓度AICAR组(NGLU+AICAR组)、高浓度对照组(HGLU组)、高浓度AICAR组(HGLU+AICAR组)。用5 mmol/L和20 mmol/L葡萄糖浓度培养骨骼肌细胞后,NGLU+AICAR组和HGLU+AICAR组与肌肉收缩模拟信号刺激5-氨基-4-甲酰胺咪唑核糖核苷酸(AICAR)孵育。AICAR能激活NGLU组骨骼肌细胞AMPKα2、减少骨骼肌细胞核HDAC5蛋白、促使HDAC5与骨骼肌细胞加强因子(MEF2)蛋白分离和上调GLUT4基因的表达;相反,高浓度葡萄糖延迟由AICAR引起的AMPKα2磷酸化、AMPKα2向细胞核转入、HDAC5向细胞核转出和GLUT4基因的表达。实验结果说明在不同葡萄糖浓度下的骨骼肌细胞GLUT4基因表达变化都对应着上游AMPK蛋白和下游HDAC5蛋白的变化,AMPK可能是征用转录抑制子HDAC5来调节MEF2的活性而达到控制肌肉收缩所引起的GLUT4基因表达。

AMP-activated protein kinase, AMPK, is responsible for regulation of exercise-induced GLUT4 gene expression in skeletal muscle. But the molecular mechanisms for this regulation and key protein in this signaling pathway are obscure. There has been growing recognition that histone acetylation probably represents a central mechanism for regulation of gene transcription, and recent studies showed that numerous gene expressions are regulated by nudec^naal histone acetylation, which is modulated through histone acetyltmnsferases （HATs） and histone deacetylases （HDACs）. So we have a hypothesis that the AMPK regulates GLUT4 gene through recruiting HDACs. Skeletal muscle cells cultured with normal（5mmol/L） and high（20mmol/L） glucose concentration were incubated with AICAR, and then total and nuclear AMPKa2, HDAC5 protein and GLUT4 mRNA were measured. The results show that the AICAR activated AMPKa2, reduced nuclear HDACS,and increased GLUT4 mRNA in skdetal muscle cells; in contrast, the effect evoked by AICAR was blunted in cultured skdetal muscle cells with high glucose. Therefore, the changes of GLUT4 gene expression under different glucose concentration are clcsely related to the changes of AMPKa2. and HDAC5 protein in skdetal muscle cells. This result demonstrates that HDAC5 plays an important role in regulating GLUT4 gene transcription by AMPK signaling pathway skeletal muscle cells.