Role of dMiro Signaling for Axonal Transport of Mitochondria

描述(申请人提供)：线粒体对有氧呼吸、钙稳态调节、细胞凋亡、衰老和癌症至关重要。线粒体在细胞内的分布对生理应激和细胞活动的变化具有适应性。这种可塑性控制被认为在神经元中尤其重要，因为在突触等能量消耗高的区域，线粒体得到了丰富。尽管线粒体对突触功能具有重要意义，但我们仍然不清楚控制其传递和靶向突触的分子机制。由于线粒体转运异常与线粒体功能异常一样，与各种形式的肌营养不良、心肌病、神经病、截瘫和神经变性有关，因此迫切需要全面的了解。我们以前的工作表明，进化保守的线粒体Rho样GTP酶Miro可能作为线粒体传感器，整合细胞内信号来控制线粒体的长距离运输。具体地说，果蝇Miro(DMiro)功能的丧失阻止了线粒体向轴突和树突的运输，而dMiro功能的获得会导致线粒体在运动神经末梢异常聚集。综上所述，这些结果提示dMiro可能控制轴突的顺行运输和线粒体到突触部位的分布。为了进一步验证这一假设，我们将利用果蝇模型系统，对线粒体运输机制的dMiro和其他蛋白质进行遗传操作。突变对线粒体运输的影响将主要通过GFP标记的线粒体的实时成像在幼虫运动神经元、其轴突和轴突末端进行检测，以解决以下关键问题：Aim 1将解决dMiro是否通过增加微管(MT)加末端或减少负末端定向运输的效率来促进净顺行轴突运输。目的2将确定dMiro的EF-手钙结合结构域在线粒体运输和/或线粒体的细胞内分布中的作用。目的3将测试dMiro可能控制线粒体运输的分子机制。这项拟议的项目有望揭示重要的分子信号机制，这些机制调控线粒体的长距离运输以及它们在突触终末的使用依赖分布。这些信号通路的发现将极大地扩展我们对基本机制的理解，并加速发展新的概念来检测、治疗和/或预防由线粒体运输途径缺陷和/或线粒体功能受损引起的疾病。

DESCRIPTION (provided by applicant): Mitochondria are vital for aerobic respiration, the regulation of Ca2+ homeostasis, apoptosis, aging, and cancer. The intracellular distribution of mitochondria is adaptable to physiological stresses and changes in cellular activity. This plastic control is believed to be especially important in neurons where mitochondria are enriched at regions of intense energy consumption like synapses. Despite the significance of mitochondria for synaptic function, we still do not understand the molecular mechanisms controlling their delivery and targeting to synapses. A comprehensive understanding is urgently needed since abnormal mitochondrial transport, like abnormal mitochondrial function, is associated with various forms of muscular dystrophy, cardiomyopathy, neuropathy, paraplegia, and neurodegeneration. Our previous work suggests that the evolutionary conserved mitochondrial Rho-like GTPase Miro may act as a mitochondrial sensor that integrates intracellular signals to control long-distance transport of mitochondria. Specifically, loss of Drosophila Miro (dMiro) function prevents mitochondrial transport into axons and dendrites while gain of dMiro function leads to an abnormal accumulation of mitochondria at motor nerve terminals. Together, these results suggest dMiro may control anterograde axonal transport and the distribution of mitochondria to synaptic sites. To further test this hypothesis, we will take advantage of the model system Drosophila and genetically manipulate dMiro and other proteins of the mitochondrial transport machinery. Mutant effects on mitochondrial transport will be primarily examined in larval motor neurons, their axons and axon terminals by live imaging of GFP-tagged mitochondria to resolve the following key issues: Aim 1 will resolve whether dMiro promotes net-anterograde axonal transport by increasing the efficiency of microtubules (MT) plus end- or decreasing minus end-directed transport. Aim 2 will determine the role of dMiro's EF-hand Ca2+ binding domains for mitochondrial transport and/or the intracellular distribution of mitochondria. Aim 3 will test the molecular mechanisms by which dMiro may control mitochondrial transport. The proposed project is expected to reveal important molecular signaling mechanisms that regulate the long- distance transport of mitochondria and their use-dependent distribution into synaptic terminals. Uncovering these signaling pathways will significantly expand our understanding of basic mechanisms and accelerate the development of new concepts for detecting, treating, and/or preventing disorders that are caused by defective mitochondrial transport pathways and/or impaired mitochondrial function.