Bolster Douglas R, Kubica Neil, Crozier Stephen J, Williamson David L, Farrell Peter A, Kimball Scot R, Jefferson Leonard S
The Pennsylvania State University College of Medicine, Department of Cellular and Molecular Physiology, Hershey, PA 17033, USA.
J Physiol. 2003 Nov 15;553(Pt 1):213-20. doi: 10.1113/jphysiol.2003.047019. Epub 2003 Aug 22.
The purpose of the present investigation was to determine whether mammalian target of rapamycin (mTOR)-mediated signalling and some key regulatory proteins of translation initiation are altered in skeletal muscle during the immediate phase of recovery following acute resistance exercise. Rats were operantly conditioned to reach an illuminated bar located high on a Plexiglass cage, such that the animals completed concentric and eccentric contractions involving the hindlimb musculature. Gastrocnemius muscle was extracted immediately after acute exercise and 5, 10, 15, 30 and 60 min of recovery. Phosphorylation of protein kinase B (PKB) on Ser-473 peaked at 10 min of recovery (282% of control, P < 0.05) with no significant changes noted for mTOR phosphorylation on Ser-2448. Eukaryotic initiation factor (eIF) 4E-binding protein-1 (4E-BP1) and S6 kinase-1 (S6K1), both downstream effectors of mTOR, were altered during recovery as well. 4E-BP1 phosphorylation was significantly elevated at 10 min (292%, P < 0.01) of recovery. S6K1 phosphorylation on Thr-389 demonstrated a trend for peak activation at 10 min following exercise (336%, P = 0.06) with ribosomal protein S6 phosphorylation being maximally activated at 15 min of recovery (647%, P < 0.05). Components of the eIF4F complex were enhanced during recovery as eIF4E association with eIF4G peaked at 10 min (292%, P < 0.05). Events regulating the binding of initiator methionyl-tRNA to the 40S ribosomal subunit were assessed through eIF2B activity and eIF2 alpha phosphorylation on Ser-51. No differences were noted with either eIF2B or eIF2 alpha. Collectively, these results provide strong evidence that mTOR-mediating signalling is transiently upregulated during the immediate period following resistance exercise and this response may constitute the most proximal growth response of the cell.
本研究的目的是确定在急性抗阻运动后的即刻恢复阶段，哺乳动物雷帕霉素靶蛋白（mTOR）介导的信号传导以及一些翻译起始的关键调节蛋白在骨骼肌中是否发生改变。对大鼠进行操作性条件训练，使其够到位于有机玻璃笼高处的发光杆，这样动物就完成了涉及后肢肌肉组织的向心和离心收缩。急性运动后以及恢复5、10、15、30和60分钟后，立即提取腓肠肌。蛋白激酶B（PKB）在Ser-473位点的磷酸化在恢复10分钟时达到峰值（为对照的282%，P<0.05），而mTOR在Ser-2448位点的磷酸化未观察到显著变化。mTOR的两个下游效应分子，真核起始因子（eIF）4E结合蛋白-1（4E-BP1）和S6激酶-1（S6K1）在恢复过程中也发生了改变。4E-BP1的磷酸化在恢复10分钟时显著升高（292%，P<0.01）。S6K1在Thr-389位点的磷酸化在运动后10分钟呈现出峰值激活趋势（336%，P=0.06），核糖体蛋白S6的磷酸化在恢复15分钟时被最大程度激活（647%，P<0.05）。在恢复过程中，eIF4F复合物的成分增加，因为eIF4E与eIF4G的结合在10分钟时达到峰值（292%，P<0.05）。通过eIF2B活性和eIF2α在Ser-51位点的磷酸化来评估调节起始甲硫氨酰-tRNA与40S核糖体亚基结合的事件。eIF2B或eIF2α均未观察到差异。总体而言，这些结果提供了有力证据，表明在抗阻运动后的即刻期间，mTOR介导的信号传导被短暂上调，并且这种反应可能构成细胞最直接的生长反应。
