BACKGROUND Daurian ground squirrels (Spermophilus dauricus) deviate from significant increase of protein catabolism and loss of myofibrillar contents during long period of hibernation inactivity. METHODS Here we use iTRAQ based quantitative analysis to examine proteomic changes in the soleus of squirrels in pre-hibernation, hibernation and post-hibernation states. The total proteolysis rate of soleus was measured by the release of the essential amino acid tyrosine from isolated muscles. Immunofluorescent analysis was used to determine muscle fiber cross-sectional area. Western blot was used for the validation of the quantitative proteomic analysis. RESULTS The proteomic responses to hibernation had a 0.4- to 0.8-fold decrease in the myofibrillar contractile protein levels of myosin-3, myosin-13 and actin, but a 2.1-fold increase in myosin-2 compared to pre-hibernation group. Regulatory proteins such as troponin C and tropomodulin-1 were 1.4-fold up-regulated and 0.7-fold down-regulated, respectively, in hibernation compared to pre-hibernation group. Moreover, 10 proteins with proteolytic function in hibernation, which was less than 14 proteins in the post-hibernation group, were up-regulated relative to the pre-hibernation group. The total proteolysis rates of soleus in hibernation and post-hibernation groups were significantly inhibited as compared with pre-hibernation group. CONCLUSION These findings suggest that the myofibrillar remodeling and partial suppression of myofibrillar proteolysis were likely responsible for preventing skeletal muscle atrophy during prolonged disuse in hibernation. This is the first study where the myofibrillar contents and relevant synthesis and proteolytic proteins in slow soleus was discussed based on proteomic investigation performed on wild Daurian ground squirrels. Our results lay the foundation for further research in preventing disuse-induced skeletal muscle atrophy in mammals.

中文翻译：

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基于 iTRAQ 的蛋白质组学分析，对冬眠达乌尔地松鼠 (Spermophilus dauricus) 的比目鱼肌中肌原纤维含量以及相关合成和蛋白水解蛋白进行分析。


背景达乌尔地松鼠(Spermophilus dauricus)在长期冬眠不活动期间蛋白质分解代谢显着增加并且肌原纤维含量减少。方法在这里，我们使用基于 iTRAQ 的定量分析来检查松鼠比目鱼肌在冬眠前、冬眠和冬眠后状态下的蛋白质组变化。通过从离体肌肉中释放必需氨基酸酪氨酸来测量比目鱼肌的总蛋白水解率。使用免疫荧光分析来确定肌纤维横截面积。蛋白质印迹用于验证定量蛋白质组分析。结果 与冬眠前组相比，冬眠后的蛋白质组学反应中，肌原纤维收缩蛋白肌球蛋白 3、肌球蛋白 13 和肌动蛋白水平降低了 0.4 至 0.8 倍，但肌球蛋白 2 水平增加了 2.1 倍。与冬眠前组相比，冬眠组的肌钙蛋白 C 和原调节蛋白-1 等调节蛋白分别上调 1.4 倍和下调 0.7 倍。此外，冬眠期间具有蛋白水解功能的蛋白质有10个，较冬眠前组的表达量有所上调，而冬眠后组的蛋白质数量少于14个。冬眠组和冬眠后组的比目鱼肌总蛋白水解率较冬眠前组明显受到抑制。结论 这些研究结果表明，肌原纤维重塑和肌原纤维蛋白水解的部分抑制可能是防止冬眠期间长时间不用时骨骼肌萎缩的原因。 这是第一项基于对野生达乌尔地松鼠进行的蛋白质组学研究来讨论慢比目鱼肌中肌原纤维含量以及相关合成和蛋白水解蛋白的研究。我们的结果为预防哺乳动物废用性骨骼肌萎缩的进一步研究奠定了基础。