Mechanisms of mitochondrial biogenesis in skeletal muscle

我的研究计划的长期目标是了解肌肉中线粒体生物发生的分子途径，以适应收缩活动的增加和减少(即运动)。生物发生途径的生理后果是在肌肉内形成一个健康的细胞器池，负责ATP的产生、细胞凋亡、活性氧物种(ROS)的产生，以及细胞器向细胞核发出信号以调节基因表达。我们的NSERC支持的研究计划在过去5年中非常成功地识别了与运动诱导的线粒体周转激活有关的重要蛋白质，以及量化了线粒体动力学，以及运动诱导的肌肉中溶酶体生物发生的惊人规模。这些发现为我们继续关注将运动信号传递到细胞核的新型分子转导系统、导致线粒体对运动做出反应的事件以及使用运动作为诱导刺激的肌肉内细胞器(线粒体-溶酶体-核)通信的动态性质奠定了基础。利用各种成熟的体内和细胞培养方法来产生急性和慢性运动，我们的新目标是调查：1)作为细胞器生物发生和有丝分裂平衡的调节蛋白Nrf2的新功能；2)肌管内线粒体运动的显著变化，以及这些运动与收缩活动诱导的细胞器动力学的关系；3)运动应激对UPRmt的激活、蛋白质进入细胞器的调节和激活转录因子-5(ATF5)在决定线粒体和细胞核之间信号的控制之间的相互作用；4)独特的磷脂在决定慢性肌肉使用和停用所介导的周转过程中的细胞器功能和蛋白质输入的作用。这些过程将使用生化和分子生物学技术，以及评估肌肉和细胞器呼吸和ROS产生的生理分析来评估。这项工作的意义在于，它继续代表着对运动诱导的线粒体生物发生的长期、全面的分析，使用多种方法，从分子到全身水平，评估细胞器组装和通讯的机制，以及它们在哺乳动物肌肉中的功能后果。所获得的结果对细胞器合成的基本机制、我们对氧化代谢的理解以及线粒体在细胞健康、疾病和死亡中的功能具有更广泛的适用性。

The long-term objective of my research program is to understand the molecular pathways of mitochondrial biogenesis in muscle during adaptations to increases and decreases in contractile activity (i.e. exercise). The physiological consequences of the biogenesis pathway is the formation of a healthy organelle pool within muscle, responsible for ATP production, apoptosis, the generation of reactive oxygen species (ROS), and organelle signaling to the nucleus to regulate gene expression. Our NSERC-supported research program over the last 5 years was very successful in identifying important proteins involved in the exercise-induced activation of mitochondrial turnover, as well as quantifying mitochondrial dynamics, and the surprising magnitude of exercise-induced lysosome biogenesis in muscle. These discoveries set the stage for us to continue to focus on novel molecular transducers of exercise signals to the nucleus, the events that lead to mitochondrial adaptations in response to exercise, as well as the dynamic nature of organelle (mitochondrial-lysosome-nucleus) communication within muscle using exercise as an inducing stimulus. Using a variety of well-established in vivo and cell culture approaches to produce acute and chronic exercise, our new Objectives are to investigate: 1) a novel function of the protein Nrf2 as a regulator of the balance between organelle biogenesis and mitophagy; 2) the remarkable changes in mitochondrial motility within myotubes, and the relationship of these movements to organelle dynamics induced by contractile activity; 3) the interaction between the activation of the UPRmt to exercise stress, the regulation of protein import into the organelle, and the control exerted by Activating Transcription Factor-5 (ATF5) in determining signals between mitochondria and the nucleus, and 4) the role of the unique phospholipid cardiolipin in determining organelle function and protein import during turnover mediated by chronic muscle use and disuse. These processes will be evaluated using biochemical and molecular biology techniques, along with physiological analyses to assess muscle and organelle respiration and ROS production. The significance of this work is that it continues to represent a long-term, comprehensive analysis of exercise-induced mitochondrial biogenesis using multiple approaches, from the molecular to whole body level, to evaluate the mechanisms of organelle assembly and communication, as well as their functional consequences in mammalian muscle. The results obtained have wider applicability to the basic mechanisms of organelle synthesis, our understanding of oxidative metabolism, as well as the function of mitochondria in cellular health, disease and death.