FUNDC1在运动诱导骨骼肌线粒体自噬中的调控机制研究

Mitochondrion is the center of organism energy regulation. The difference of mitochondrial mass is highly related to the function of the skeletal muscle. When the level of injury goes beyond the restore ability, the mitophagy will start in order to selectively clean those that can’t be restored, leading to control the mitochondrial mass, which has big significance on maintaining its number and function. Thus, it has applied importance to explore the function of the mitophagy happened in skeletal muscle. FUNDC1 is a kind of protein found recently that functioned in the mitophagy, whose level can be controlled by several irritable factors. From research done before, it is also controlled by AMPK, which is the “switch” of energy metabolism. That may be the potential target of the mitophagy happened in skeletal muscle induced by exercise. Our project intends to observe the form and function of the mitochondria and the expression of autophagy-related factors of the rats in experiments both in vivo and in vitro, and to explore whether the change of energy metabolism in skeletal muscle caused by exercise can cause the change of AMPK level and to control the phosphorylation of factors such as ULK1 and FUNDC1, leading to the adjustment of the mitophagy in skeletal muscle of rats, thus providing theory bases to have better understanding of the functional adjustment of the mitochondrion in skeletal muscle during exercise.

作为是机体能量代谢的调控中心，线粒体质量的变化与骨骼肌机能关系密切。当线粒体损伤程度超过其修复能力时，线粒体自噬启动以选择性地清除受损线粒体，控制线粒体质量，对线粒体数量与功能的维持具有重要作用。因此，探讨骨骼肌线粒体自噬中的调控机制具有重要的现实意义。FUNDC1是近期发现的线粒体自噬受体蛋白，受多种应激因素调节。前期研究表明，能量代谢“开关”AMPK可调节FUNDC1，成为运动应激诱导骨骼肌线粒体自噬的潜在靶点。本项目拟通过在体和离体实验观察大鼠在不同运动中的骨骼肌线粒体形态、功能及自噬相关因子的表达，探讨运动导致骨骼肌能量代谢变化，改变AMPK水平的同时，是否可调控下游ULK1、FUNDC1等因子，从而对大鼠骨骼肌线粒体自噬产生调节，为进一步了解运动过程中骨骼肌线粒体功能调节提供理论依据。

线粒体自噬与线粒体生物合成、线粒体修复、线粒体动态变化共同参与线粒体质量控制，对线粒体数量与功能的维持具有重要作用。FUNDC1是近期发现的线粒体自噬受体蛋白，鉴于其已明确的功能及调控信号，其在运动诱导的骨骼肌线粒体自噬中发挥重要作用。本研究主要探讨了有氧运动中FUNDC1介导的通路对骨骼肌线粒体自噬的影响及调控机制。主要的研究成果有：1、运动后骨骼肌线粒体发生了明显的结构及功能改变，4周运动组线粒体自噬蛋白表达、线粒体生物合成和线粒体功能分别高于2周相同强度运动组；大强度运动组较同时程中等强度运动组自噬程度升高，线粒体合成和线粒体数量降低，大强度运动可能造成线粒体功能受损；运动诱导AMPKα及其磷酸化表达增加，上调ULK1，进而磷酸化外膜蛋白FUNDC1，连接LC3诱导自噬。2、AMPK激活剂AICAR与运动均可诱导AMPKα蛋白的表达，上调ULK1，增加自噬水平，且表现出时相性特点，即即刻表达水平最高，随后降低。3、电脉冲刺激后骨骼肌C2C12细胞中线粒功能、生物合成指标发生明显改变，自噬相关蛋白表达增强；电脉冲刺激后AMPKα、p-AMPKα（Thr172）、ULK1、FUNDC1、LC3等自噬相关蛋白的表达增加，说明电脉冲刺激能够激活AMPK-ULK1通路诱导线粒体自噬的发生；电脉冲刺激后抑制AMPK-ULK1通路可以引起FUNDC1蛋白表达下降，说明FUNDC1在电脉冲刺激诱导的线粒体自噬中起到连接蛋白作用。4、间歇性禁食和热量限制可通过AMPK-ULK1途径激活适度骨骼肌自噬。5、中等强度耐力运动可通过BNIP3途径诱导线粒体自噬，而大强度耐力运动对线粒体自噬的诱导可能通过其他途径。这些研究为了解骨骼肌线粒体功能调节提供了理论依据；为明确FUNDC1在运动诱导骨骼肌线粒体自噬中的调控机制提供了科学依据。