Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark.
J Physiol. 2020 Jul;598(13):2637-2649. doi: 10.1113/JP279780. Epub 2020 May 27.
AMP-activated protein kinase (AMPK)-dependent Raptor Ser792 phosphorylation does not influence mechanistic target of rapamycin complex 1 (mTORC1)-S6K1 activation by intense muscle contraction. α -AMPK activity-deficient mice have lower contraction-stimulated protein synthesis. Increasing glycogen activates mTORC1-S6K1. Normalizing muscle glycogen content rescues reduced protein synthesis in AMPK-deficient mice.
The mechansitic target of rapamycin complex 1 (mTORC1)-S6K1 signalling pathway regulates muscle growth-related protein synthesis and is antagonized by AMP-activated protein kinase (AMPK) in multiple cell types. Resistance exercise stimulates skeletal muscle mTORC1-S6K1 and AMPK signalling and post-contraction protein synthesis. Glycogen inhibits AMPK and has been proposed as a pro-anabolic stimulus. The present study aimed to investigate how muscle mTORC1-S6K1 signalling and protein synthesis respond to resistance exercise-mimicking contraction in the absence of AMPK and with glycogen manipulation. Resistance exercise-mimicking unilateral in situ contraction of musculus quadriceps femoris in anaesthetized wild-type and dominant negative α AMPK kinase dead transgenic (KD-AMPK) mice, measuring muscle mTORC1 and AMPK signalling immediately (0 h) and 4 h post-contraction, and protein-synthesis at 4 h. Muscle glycogen manipulation by 5 day oral gavage of the glycogen phosphorylase inhibitor CP316819 and sucrose (80 g L ) in the drinking water prior to in situ contraction. The mTORC1-S6K1 and AMPK signalling axes were coactivated immediately post-contraction, despite potent AMPK-dependent Ser792 phosphorylation on the mTORC1 subunit raptor. KD-AMPK muscles displayed normal mTORC1-S6K1 activation at 0 h and 4 h post-exercise, although there was impaired contraction-stimulated protein synthesis 4 h post-contraction. Pharmacological/dietary elevation of muscle glycogen content augmented contraction-stimulated mTORC1-S6K1-S6 signalling and rescued the reduced protein synthesis-response in KD-AMPK to wild-type levels. mTORC-S6K1 signalling is not influenced by α -AMPK during or after intense muscle contraction. Elevated glycogen augments mTORC1-S6K1 signalling. α -AMPK-deficient KD-AMPK mice display impaired contraction-induced muscle protein synthesis, which can be rescued by normalizing muscle glycogen content.
AMP 激活的蛋白激酶（AMPK）依赖性雷帕霉素复合物 1（mTORC1）-S6K1 激活的 Raptor Ser792 磷酸化不会影响剧烈肌肉收缩引起的机械靶标 rapamycin 复合物 1（mTORC1）-S6K1。α -AMPK 活性缺乏的小鼠收缩刺激的蛋白质合成较低。增加糖原可激活 mTORC1-S6K1。正常化肌肉糖原含量可挽救 AMPK 缺乏型小鼠中减少的蛋白质合成。
机械靶标 rapamycin 复合物 1（mTORC1）-S6K1 信号通路调节肌肉生长相关蛋白的合成，并在多种细胞类型中被 AMP 激活的蛋白激酶（AMPK）拮抗。阻力运动刺激骨骼肌 mTORC1-S6K1 和 AMPK 信号传导以及收缩后的蛋白质合成。糖原抑制 AMPK，并被提议作为一种促合成代谢刺激物。本研究旨在研究在缺乏 AMPK 和糖原操纵的情况下，肌肉 mTORC1-S6K1 信号传导和蛋白质合成如何对阻力运动模拟收缩做出反应。在麻醉野生型和显性负性α AMPK 激酶失活转基因（KD-AMPK）小鼠的股四头肌肌内原位收缩中模拟阻力运动，测量肌肉 mTORC1 和 AMPK 信号在收缩后立即（0 小时）和 4 小时，以及 4 小时时的蛋白质合成。通过在原位收缩前 5 天口服糖原磷酸化酶抑制剂 CP316819 和蔗糖（80g L ）在饮水中操纵肌肉糖原，糖原含量为 80g L ）在原位收缩前 5 天口服。尽管 mTORC1 亚基雷帕素的 AMPK 依赖性 Ser792 磷酸化很强，但 mTORC1-S6K1 和 AMPK 信号轴在收缩后立即被共同激活。KD-AMPK 肌肉在运动后 0 小时和 4 小时显示正常的 mTORC1-S6K1 激活，尽管在收缩后 4 小时时，收缩刺激的蛋白质合成受损。肌肉糖原含量的药理学/饮食升高增强了收缩刺激的 mTORC1-S6K1-S6 信号传导，并将 KD-AMPK 中的降低的蛋白质合成反应恢复至野生型水平。在剧烈肌肉收缩期间或之后，mTORC-S6K1 信号不受α -AMPK 影响。升高的糖原可增强 mTORC1-S6K1 信号。α -AMPK 缺乏的 KD-AMPK 小鼠显示出受损的收缩诱导的肌肉蛋白质合成，可通过正常化肌肉糖原含量来挽救。
