Myology Laboratory, Institute of Biomedical Problems, Russian Academy of Sciences , Moscow , Russia.
Am J Physiol Endocrinol Metab. 2019 Jan 1;316(1):E86-E95. doi: 10.1152/ajpendo.00261.2018. Epub 2018 Nov 20.
The aim of the study was to 1) measure time-course alternations in the rate of protein synthesis (PS) and phosphorylation status of the key anabolic markers, and 2) find out the role of stretch-activated ion channels (SACs) in the activation of anabolic signaling in the rat soleus during an acute reloading following disuse atrophy. Wistar rats were subjected to 14-day hindlimb suspension (HS) followed by 6, 12, and 24 h of reloading. To examine the role of SAC in the reloading-induced activation of anabolic signaling, the rats were treated with gadolinium (Gd), a SAC blocker. The content of signaling proteins was determined by Western blot. c-Myc mRNA expression was assessed by RT-PCR. After 24-h reloading, the PS rate was elevated by 44% versus control. After 6-h reloading, the p-70-kDa ribosomal protein S6 kinase (p70S6k) and translation initiation factor 4E-binding protein 1 (4E-BP1) did not differ from control; however, 12-h reloading resulted in an upregulation of both p70s6k and 4E-BP1 phosphorylation versus control. The phosphorylation of AKT (Ser473) and glycogen synthase kinase-3β (Ser9) was reduced after HS and then completely restored by 12-h reloading. c-Myc was significantly upregulated during the entire reloading. Gd treatment during reloading (12 h) prevented a full phosphorylation of p70S6k, rpS6, 4E-BP1, as well as PS activation. The results of the study suggest that 1) enhanced PS during the acute recovery from HS may be associated with the activation of ribosome biogenesis as well as mammalian target of rapamycin complex 1 (mTORC1)-dependent signaling pathways, and 2) functional SACs are necessary for complete activation of mTORC1 signaling in rat soleus during acute recovery from HS.
1）测定蛋白质合成（PS）速率的时程变化和关键合成代谢标记物的磷酸化状态，2）探究在废用性萎缩后急性再负荷期间，牵张激活离子通道（SAC）在大鼠比目鱼肌中合成代谢信号激活中的作用。Wistar 大鼠接受 14 天的后肢悬吊（HS），随后进行 6、12 和 24 小时的再负荷。为了研究 SAC 在再负荷诱导的合成代谢信号激活中的作用，大鼠用 SAC 阻断剂钆（Gd）处理。通过 Western blot 测定信号蛋白含量。通过 RT-PCR 评估 c-Myc mRNA 表达。再负荷 24 小时后，PS 速率比对照升高 44%。再负荷 6 小时后，p-70-核糖体蛋白 S6 激酶（p70S6k）和翻译起始因子 4E 结合蛋白 1（4E-BP1）与对照无差异；然而，12 小时再负荷导致 p70S6k 和 4E-BP1 磷酸化均上调，与对照相比。AKT（Ser473）和糖原合成酶激酶-3β（Ser9）的磷酸化在 HS 后降低，然后在 12 小时再负荷时完全恢复。c-Myc 在整个再负荷过程中显著上调。再负荷（12 小时）期间用 Gd 处理可阻止 p70S6k、rpS6、4E-BP1 的完全磷酸化以及 PS 的激活。研究结果表明：1）HS 后急性恢复期间 PS 的增强可能与核糖体生物发生的激活以及雷帕霉素靶蛋白复合物 1（mTORC1）依赖性信号通路有关，2）功能性 SACs 是大鼠比目鱼肌在急性 HS 恢复期间完全激活 mTORC1 信号所必需的。
