Role(s) of nucleoli and phosphorylation of ribosomal protein S6 and/or HSP27 in the regulation of muscle mass
Role(s) of nucleoli and phosphorylation of ribosomal protein S6 and/or HSP27 in the regulation of muscle mass
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DOI：
10.1152/ajpcell.00297.2006
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发表时间：
2007-07-01
影响因子：
5.5
通讯作者：
Ohira, Y.
中科院分区：
文献类型：
--
作者：
Kawano, F.;Matsuoka, Y.;Ohira, Y.
在大鼠比目鱼肌中研究了14天的后肢卸载或切除相关的过载（有或没有传入神经阻滞）对纤维横截面积、肌纤维数目、大小和结构域、单个肌细胞核中的核仁数目以及核糖体蛋白S6（S6）和27-kDa热休克蛋白（HSP 27）磷酸化水平的影响。纤维肥大（+24%），与实验前水平相比，与肌核和肌球蛋白结构域（+27%）内的核仁数量增加（从1 - 2增加到3 - 5）相关，是由电刺激消融诱导的。这种现象与磷酸化S6（+ 84%）和HSP 27（+ 28%）水平的增加有关。纤维萎缩（+ 52%），与肌核数量（+ 31%）和结构域大小（+ 28%）减少以及S6（- 98%）和HSP 27（- 63%）磷酸化相关，与肌球蛋白大小（+ 19%）增加和肌球蛋白重链泛素化相关（+33%，P > 0.05），对机械负荷有抑制作用。反应去传入，抑制肌电图水平（-47%），基本上类似于后肢卸载所造成的，虽然幅度较小。去传入相关的反应被阻止，核仁数甚至增加（+ 18%），通过添加去传入消融，即使整合的肌电图水平仍然比对照组低30%。这表明负荷依赖性的核仁数量和/或S6和HSP 27磷酸化的维持或上调在肌肉质量的调节中发挥着重要作用。研究还表明，这种调节不一定与神经活动有关。
Effects of 14 days of hindlimb unloading or synergist ablation-related overloading with or without deafferentation on the fiber cross-sectional area, myonuclear number, size, and domain, the number of nucleoli in a single myonucleus, and the levels in the phosphorylation of the ribosomal protein S6 (S6) and 27-kDa heat shock protein (HSP27) were studied in rat soleus. Hypertrophy of fibers (+24%), associated with increased nucleolar number (from 1 - 2 to 3 - 5) within a myonucleus and myonuclear domain (+ 27%) compared with the preexperimental level, was induced by synergist ablation. Such phenomena were associated with increased levels of phosphorylated S6 (+ 84%) and HSP27 (+ 28%). Fiber atrophy (+ 52%), associated with decreased number (+ 31%) and domain size (+ 28%) of myonuclei and phosphorylation of S6 (- 98%) and HSP27 (- 63%), and with increased myonuclear size (+ 19%) and ubiquitination of myosin heavy chain (+ 33%, P > 0.05), was observed after unloading, which inhibited the mechanical load. Responses to deafferentation, which inhibited electromyogram level (- 47%), were basically similar to those caused by hindlimb unloading, although the magnitudes were minor. The deafferentation-related responses were prevented and nucleolar number was even increased (+ 18%) by addition of synergist ablation, even though the integrated electromyogram level was still 30% less than controls. It is suggested that the load-dependent maintenance or upregulation of the nucleolar number and/or phosphorylation of S6 and HSP27 plays the important role(s) in the regulation of muscle mass. It was also indicated that such regulation was not necessarily associated with the neural activity.