Activity-dependent signaling in aging skeletal muscle

衰老骨骼肌中的活动依赖性信号传导

• 批准号: 6989263
• 负责人: Roger A. Fielding
• 金额: $ 7.36万
• 依托单位: TUFTS UNIVERSITY BOSTON
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-09-01 至 2007-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6989263
• 关键词: aging; binding sites; biological signal transduction; electrostimulus; enzyme activity; exercise; genetic translation; laboratory rat; messenger RNA; muscle contraction; muscle hypertrophy; muscle proteins; phosphatidylinositol 3 kinase; phosphorylation; posttranscriptional RNA processing; protein biosynthesis; ribosomal proteins; sarcopenia; serine threonine protein kinase; striated muscles

DESCRIPTION (provided by applicant): The age-related loss of skeletal muscle mass is associated with well-characterized functional limitations and physical disability. Although resistance training attenuates age-related muscle loss, the cellular processes that initiate muscle hypertrophy and the extent to which they are preserved with age are not well understood. The 70-kDa S6 protein kinase (p70S6K) is a downstream target of the protein kinase B/mammalian target of rapamycin (Akt/mTOR) pathway that has been implicated in the regulation of muscle size during overload and disuse atrophy. This and other kinases of the Akt/mTOR pathway affect protein translation by regulating translational inhibitors such as glycogen synthase kinase 3 (GSK-3), phosphorylating key ribosomal proteins, and influencing the availability of eukaryotic initiation factors (elF's). We propose to test the hypotheses that 1) aging is associated with a reduced activation of the Akt/mTOR pathway 2) the reduced phosphorylation of p70S6K and mTOR results in a decreased number of elF4E-elF4G complexes and a reduction in muscle protein synthesis, and 3) chronic contractile activity results in blunted muscle hypertrophy in older animals due to a reduced activation of the Akt/mTOR pathway. We propose to use electrical stimulation to simulate acute resistance exercise in young and old rat hindlimbs, and surgical ablation of synergistic muscles to model the effects of chronic contractile activity. Specifically, we will 1) characterize Akt/mTOR signaling after a single bout of resistance exercise at young age, 2) assess the effects of resistance exercise on the number of capped mRNA binding sites (elF4E-elF4G) available for protein translation at young age, 3) compare the activation of Akt/mTOR, formation of elF4E-elF4G complexes, and protein synthesis of young, middle aged, and old rats in response to acute contractile activity, 4) compare the activation of Akt/mTOR, formation of elF4E-elF4G, and protein synthesis of young, middle aged, and old rats in response to chronic ablation of synergistic muscles. Muscle samples at several time points will be analyzed for p70S6K, Akt, mTOR, 4EBP1, and GSK-3 phosphorylation, elF4E-elF4G complexes, and skeletal muscle protein synthesis. We believe that the identification of molecular dysregulation in the Akt/mTOR pathway associated with age-related muscle atrophy will establish the groundwork for studies aimed at correcting these deficiencies and improving the efficacy of resistance training and other therapeutic interventions in the elderly.

描述（由申请人提供）：与年龄相关的骨骼肌质量损失与明显的功能限制和身体残疾有关。尽管阻力训练可以减轻与年龄相关的肌肉损失，但引发肌肉肥大的细胞过程以及它们随年龄增长而保留的程度尚不清楚。 70-kDa S6 蛋白激酶 (p70S6K) 是蛋白激酶 B/哺乳动物雷帕霉素靶点 (Akt/mTOR) 通路的下游靶点，该通路参与超负荷和废用性萎缩期间肌肉大小的调节。 Akt/mTOR 途径的该激酶和其他激酶通过调节翻译抑制剂（例如糖原合酶激酶 3 (GSK-3)）、磷酸化关键核糖体蛋白以及影响真核起始因子 (elF) 的可用性来影响蛋白质翻译。我们建议测试以下假设：1) 衰老与 Akt/mTOR 通路激活减少有关 2) p70S6K 和 mTOR 磷酸化减少导致 elF4E-elF4G 复合物数量减少和肌肉蛋白合成减少，以及3) 由于 Akt/mTOR 通路激活减少，慢性收缩活动导致老年动物肌肉肥大减弱。我们建议使用电刺激来模拟年轻和年老大鼠后肢的急性阻力运动，并通过外科手术消融协同肌肉来模拟慢性收缩活动的影响。具体来说，我们将 1) 在年轻时进行一次抗阻运动后表征 Akt/mTOR 信号传导，2) 评估抗阻运动对年轻时可用于蛋白质翻译的加帽 mRNA 结合位点 (elF4E-elF4G) 数量的影响, 3) 比较年轻、中年和老年大鼠响应急性收缩活动的 Akt/mTOR 激活、elF4E-elF4G 复合物的形成和蛋白质合成, 4) 比较年轻、中年和老年大鼠响应协同肌慢性消融的 Akt/mTOR 激活、elF4E-elF4G 形成以及蛋白质合成。将分析几个时间点的肌肉样本的 p70S6K、Akt、mTOR、4EBP1 和 GSK-3 磷酸化、elF4E-elF4G 复合物和骨骼肌蛋白合成。我们相信，鉴定与年龄相关的肌肉萎缩相关的 Akt/mTOR 通路中的分子失调将为旨在纠正这些缺陷并提高老年人阻力训练和其他治疗干预措施的效果的研究奠定基础。