Laboratory of the Structure and Functions of Muscle Proteins, Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia.
Laboratory of Signal Perception Mechanisms, Institute of Cell Biophysics, FRC PSCBR, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia.
Sci Rep. 2020 Sep 16;10(1):15185. doi: 10.1038/s41598-020-72127-y.
Molecular mechanisms underlying muscle-mass retention during hibernation have been extensively discussed in recent years. This work tested the assumption that protein synthesis hyperactivation during interbout arousal of the long-tailed ground squirrel Urocitellus undulatus should be accompanied by increased calpain-1 activity in striated muscles. Calpain-1 is known to be autolysed and activated in parallel. Western blotting detected increased amounts of autolysed calpain-1 fragments in the heart (1.54-fold, p < 0.05) and m. longissimus dorsi (1.8-fold, p < 0.01) of ground squirrels during interbout arousal. The total protein synthesis rate determined by SUnSET declined 3.67-fold in the heart (p < 0.01) and 2.96-fold in m. longissimus dorsi (p < 0.01) during interbout arousal. The synthesis rates of calpain-1 substrates nebulin and titin in muscles did not differ during interbout arousal from those in active summer animals. A recovery of the volume of m. longissimus dorsi muscle fibres, a trend towards a heart-muscle mass increase and a restoration of the normal titin content (reduced in the muscles during hibernation) were observed. The results indicate that hyperactivation of calpain-1 in striated muscles of long-tailed ground squirrels during interbout arousal is accompanied by predominant synthesis of giant sarcomeric cytoskeleton proteins. These changes may contribute to muscle mass retention during hibernation.
近年来，人们广泛探讨了冬眠过程中肌肉质量维持的分子机制。本研究检验了一个假设，即在长尾巴地松鼠 Urocitellus undulatus 的觉醒间歇期，蛋白质合成的超活化应该伴随着横纹肌中钙蛋白酶-1 活性的增加。众所周知，钙蛋白酶-1 会被自动降解并与之平行激活。Western blot 检测到在觉醒间歇期，地松鼠的心脏（1.54 倍，p<0.05）和背最长肌（1.8 倍，p<0.01）中的自降解钙蛋白酶-1 片段的含量增加。SUnSET 测定的总蛋白合成率在心脏（p<0.01）和背最长肌（p<0.01）中下降了 3.67 倍。肌肉中钙蛋白酶-1 底物 nebulin 和 titin 的合成率在觉醒间歇期与活跃的夏季动物没有差异。观察到背最长肌肌肉纤维体积的恢复、心肌质量增加的趋势以及 titin 含量的正常化（在冬眠期间肌肉中减少）。结果表明，在觉醒间歇期，长尾巴地松鼠的横纹肌中钙蛋白酶-1 的超活化伴随着巨大的肌节细胞骨架蛋白的主要合成。这些变化可能有助于冬眠期间的肌肉质量维持。
