Neuronal mechanisms controlling number and function of presynaptic mitochondria

描述（由申请人提供）：我们的总体目标是阐明控制线粒体以满足神经末梢能量需求的神经元机制。线粒体积聚在神经末梢内，在那里它们产生神经递质释放和再循环所需的大部分ATP。因此，神经功能依赖于线粒体产生足够的ATP来维持神经递质的释放。类似地，线粒体为突触前Ca 2+稳态提供动力。神经元Ca 2+稳态的失败具有灾难性的后果，并且是许多神经退行性疾病的标志。令人惊讶的是，我们对协调线粒体数量和功能与突触前能量需求的机制知之甚少，但了解这些机制对于了解神经退行性疾病的进展至关重要。我们的中心假设是，神经元机制控制线粒体的数量和功能，以适应突触前的能量需求，这些机制是突触特异性的。我们建议阐明这些机制在肌肉骨骼系统的果蝇幼虫，每个运动神经元终端有一个不同的工作率，我们可以量化使用电生理和Ca 2+成像技术。突触前能量需求的多样性，遗传的易处理性和神经生理学技术的可访问性，使其成为研究控制线粒体以适应突触前能量需求的神经元机制的理想系统。在目标1中，我们将确定线粒体是否以与其工作速率成比例的数量供应给运动神经末梢。3D-EM重建将用于确定线粒体数量。我们还将探讨线粒体数量和功能之间的关系。在目标2中，我们将检验线粒体体积在同一轴突的不同末端水平上受到控制的假设。将在各个末端确定线粒体功能参数，以测试同一轴突上的末端之间的线粒体功能是否可能不同。在目标3中，我们将测试的假设，在整个发展过程中，活动区间距和终扣直径调整的运动神经元的放电率，使突触前的钙离子水平的范围内最有效的刺激线粒体能量代谢在突触前活动。到目前为止，Ca 2+调节是一个沉重的消费者突触前ATP，这在突触前生物能量学原位模型将提供一个重要的背景下，更好地了解早期事件涉及线粒体功能障碍和Ca 2+失调的神经退行性疾病。

DESCRIPTION (provided by applicant): Our overall goal is to elucidate the neuronal mechanisms that control mitochondria to satisfy the energy demands of nerve terminals. Mitochondria accumulate within nerve terminals where they generate most of the ATP required for the release and recycling of neurotransmitters. Neural function, therefore, relies on mitochondria generating sufficient ATP to sustain neurotransmitter release. Similarly, mitochondria power presynaptic Ca2+ homeostasis. A failure in neuronal Ca2+ homeostasis has catastrophic consequences and is a hallmark of many neurodegenerative diseases. Surprisingly, we know very little about the mechanisms that coordinate mitochondrial number and function with presynaptic energy requirements, yet understanding these mechanisms will be critical to understanding the progression of neurodegenerative disease. Our central hypothesis is that neuronal mechanisms control the number and function of mitochondria to accommodate presynaptic energy requirements, and that these mechanisms are synapse specific. We propose to elucidate these mechanisms in the musculoskeletal system of the fruit fly larva, where each motor neuron terminal has a different work rate which we can quantify using electrophysiological and Ca2+-imaging techniques. Diversity in presynaptic energy requirements, genetic tractability and accessibility to neurophysiological techniques, make this an ideal system in which to investigate neuronal mechanisms that control mitochondria to accommodate presynaptic energy requirements. In Aim 1, we will determine whether mitochondria are supplied to motor nerve terminals in numbers that are proportional to their work rate. 3D-EM reconstruction will be used to determine mitochondrial number. We will also probe the relationship between mitochondrial number and function. In Aim 2, we will test the hypothesis that mitochondrial volume is controlled at the level of different terminals on the same axon. Mitochondrial functional parameters will be determined at individual terminals to test whether mitochondrial function may be different between terminals on the same axon. In Aim 3, we will test the hypothesis that, over the course of development, active zone spacing and bouton diameter adjust to the firing rate of the motor neuron to bring presynaptic Ca2+ levels into a range most effective at stimulating mitochondrial energy metabolism during presynaptic activity. In so far as Ca2+ regulation is a heavy consumer of presynaptic ATP, this in situ model of presynaptic bioenergetics will provide an essential context for a better understanding of the early events involving mitochondrial dysfunction and Ca2+ dysregulation in neurodegenerative disease.