Mechanism and function of retrograde mitochondrial transport in axons

项目摘要 线粒体是细胞功能和生物体生存所必需的。这些细胞器以它们的 生产三磷酸腺苷，大多数真核细胞的主要能源货币。鲜为人知的是过多的 这些细胞器具有的其他功能包括产生信号分子、调节细胞凋亡 信号级联作用，既是钙的汇，也是铁的主要储存和利用场所。 牢房。为了服务于这些不同的功能，线粒体必须在所有细胞中适当地定位；然而，这 细胞器在神经元中尤其重要。神经元高度新陈代谢活跃，电极化， 可能具有巨大的体积，这使得对线粒体种群的调控特别具有挑战性。 可能是由于该细胞对新陈代谢的高要求，精确控制线粒体的定位和 维持线粒体的健康对神经元的生存至关重要。线粒体定位异常， 健康和功能与包括阿尔茨海默病在内的许多神经退行性疾病有关。在……里面 阿尔茨海默病、线粒体钙负荷缺陷和与内质网接触都有 已经被注意到了。此外，早期患者的高级神经成像显示线粒体存在缺陷。 功能，使理解线粒体功能如何在神经元中维持至关重要 了解疾病生物学。虽然在过去的几十年里，人们对 在神经元线粒体生物学方面，我们仍然没有透彻地了解种群是如何 线粒体在神经元的长寿过程中得以维持。顺行运输对带来健康至关重要 细胞器从细胞体进入可从细胞体延伸一米的长轴突。 人类。相反，逆行运输将老化或受损的细胞器移向细胞体。一次 受损的细胞器到达细胞体，一些细胞器进行靶向降解。其中大部分人的命运 细胞器和健康线粒体的来源尚未确定。我们已经开发出一种体内系统 来解决这些在该领域长期存在的问题。使用斑马鱼神经元，我们可以成像线粒体 在一个完全完整的神经回路中定位、健康和体内运输。我们已经开发出转基因品系， 基因工具和成像方法，以单独标记线粒体以跟踪它们并跟踪它们的生命周期 以及神经元的生物发生。这将使我们能够确定健康的线粒体的来源 维持神经元种群(目标1)。独立地，我们设计了一种策略来定义 细胞器逆行运输所特有的运动-线粒体附着机制 (目标2)。总之，拟议中的实验将提供对线粒体如何及其原因的机械性洞察 向逆行方向移动，同时也定义了健康细胞器的来源 神经元中线粒体数量的维持。所获得的知识将增强我们对 细胞的基本生物学，可重新用于潜在的治疗干预。

Project Summary Mitochondria are essential for cellular function and organism viability. These organelles are well known for their production of ATP, the primary energy currency of most eukaryotic cells. Less well known are the plethora of other functions these organelles have including production of signaling molecules, regulation of apoptotic signaling cascades, serving as a calcium sink, and also being the primary storage and utilization site of iron in the cell. To serve these diverse functions, mitochondria must be properly localized in all cells; however, this organelle is particularly critical in neurons. Neurons are highly metabolically active, electrically polarized, and can have an enormous volume making regulation of the mitochondrial population particularly challenging. Likely due to the high metabolic demands of this cell, precise control of mitochondrial localization and maintenance of mitochondrial health are essential for neuronal survival. Abnormal mitochondrial localization, health, and function have been linked to many neurodegenerative diseases including Alzheimer’s disease. In Alzheimer’s, defects in mitochondrial calcium load and contacts with the endoplasmic reticulum have both been noted. Additionally, advanced neuroimaging of early-stage patients revealed defects in mitochondrial function, making understanding how mitochondrial function is maintained in neurons paramount to understanding disease biology. While the last several decades have revealed fascinating insights into mitochondrial biology in neurons, we still do not have a thorough understanding of how the population of mitochondria is maintained over the long life of the neuron. Anterograde transport is critical for bringing healthy organelles from the cell body into the long axonal process which can extend a meter from the cell body in humans. Conversely, retrograde transport moves aged or damaged organelles towards to cell body. Once damaged organelles reach the cell body, some undergo targeted degradation. The fate of the bulk of these organelles and the source of healthy mitochondria has not been defined. We have developed an in vivo system to address these long-standing questions in the field. Using zebrafish neurons, we can image mitochondrial localization, health, and transport in vivo in a fully intact neural circuit. We have developed transgenic lines, genetic tools, and imaging approaches to individually label mitochondria to track them and follow their lifetime and biogenesis in neurons. This will allow us to determine the source of healthy mitochondria necessary for maintenance of the population in neurons (Aim 1). Independently, we designed a strategy to define the mechanism of motor-mitochondria attachment specifically necessary for retrograde transport of the organelle (Aim 2). Together, the proposed experiments will provide mechanistic insight into how and why mitochondria move in the retrograde direction while also defining the source of healthy organelles necessary for maintenance of the mitochondrial population in neurons. The knowledge gained will enhance our insight into the basic biology of the cell that can be repurposed for potential therapeutic interventions.