Dexamethasone-induced protein degradation in cultured myotubes is p300/HAT dependent.
Dexamethasone-induced protein degradation in cultured myotubes is p300/HAT dependent.
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DOI：
10.1152/ajpregu.00230.2006
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
Hongmei Yang;Wei Wei-Wei;M. Menconi;P. Hasselgren
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文献类型：
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作者：
Hongmei Yang;Wei Wei-Wei;M. Menconi;P. Hasselgren
脓毒症和其他分解代谢状态下的肌肉蛋白分解至少部分受糖皮质激素的调节。地塞米松处理的肌管是一种常用的肌肉萎缩的体外模型。我们最近报道，用地塞米松处理培养的L6肌管后，核辅因子p300的基因和蛋白表达增加，但尚不清楚糖皮质激素是否上调p300组蛋白乙酰转移酶(HAT)活性，以及p300/HAT活性是否调节糖皮质激素诱导的肌肉蛋白分解。在这里，我们发现用地塞米松处理培养的L6肌管导致核p300/HAT活性增加。用p300 siRNA处理肌管，或用在其HAT活性区域突变的p300表达质粒转染肌细胞，可阻断地塞米松诱导的蛋白质降解增加，支持p300/HAT在糖皮质激素诱导的肌肉蛋白分解中的作用。除HAT活性升高外，地塞米松处理肌管后，组蛋白脱乙酰基酶(HDACs)3和6的核表达和活性均降低。当组蛋白脱乙酰酶抑制剂曲古抑素A处理肌管时，蛋白质降解增加的程度与地塞米松处理的肌管相同。结果表明，糖皮质激素增加了HAT和降低了肌肉中的HDAC活性，这两种变化都有利于超乙酰化。这些结果还提供了证据，地塞米松诱导的培养的肌管蛋白降解至少部分地受到p300/HAT活性的调节。
Muscle proteolysis during sepsis and other catabolic conditions is, at least in part, regulated by glucocorticoids. Dexamethasone-treated myotubes are a commonly used in vitro model of muscle wasting. We reported recently that treatment of cultured L6 myotubes with dexamethasone resulted in increased gene and protein expression of the nuclear cofactor p300 but it is not known whether glucocorticoids upregulate p300 histone acetyl transferase (HAT) activity in muscle and whether p300/HAT activity regulates glucocorticoid-induced muscle proteolysis. Here, we found that treatment of cultured L6 myotubes with dexamethasone resulted in increased nuclear p300/HAT activity. Treatment of myotubes with p300 siRNA or transfection of muscle cells with a plasmid expressing p300 that was mutated in its HAT activity domain blocked the dexamethasone-induced increase in protein degradation, supporting a role of p300/HAT in glucocorticoid-induced muscle proteolysis. In addition to increased HAT activity, treatment of the myotubes with dexamethasone resulted in reduced nuclear expression and activity of histone deacetylases (HDACs) 3 and 6. When myotubes were treated with the HDAC inhibitor trichostatin A, protein degradation increased to the same degree as in dexamethasone-treated myotubes. The results suggest that glucocorticoids increase HAT and decrease HDAC activities in muscle, changes that both favor hyperacetylation. The results also provide evidence that dexamethasone-induced protein degradation in cultured myotubes is, at least in part, regulated by p300/HAT activity.