Mitochondrial transport and energy metabolism in synaptic transmission and nerve degeneration and regeneration

突触传递和神经变性与再生中的线粒体运输和能量代谢

• 批准号: 10263029
• 负责人: Zu-hang Sheng
• 金额: $ 335.54万
• 依托单位: NATIONAL INSTITUTE OF NEUROLOGICAL DISORDERS AND STROKE
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10263029
• 关键词: ATP Synthesis Pathway; Accounting; Actins; Action Potentials; Acute; Acute Brain Injuries; Address; Adult; Alzheimer' s Disease; Amyotrophic Lateral Sclerosis; Area; Autophagocytosis; Axon; Bioenergetics; Biology; Brain Ischemia; Cells; Cellular Metabolic Process; Chronic; Chronic stress; Communication; Consumption; Corticospinal Tracts; Coupling; Creatine; Cytoskeleton; Diffusion; Distal; Electrophysiology (science); Energy Metabolism; Energy Supply; Energy-Generating Resources; Ensure; Equilibrium; Estrogen receptor positive; Event; F-Actin; Face; Failure; Foundations; Functional disorder; Generations; Genes; Growth; Growth Cones; Hereditary Spastic Paraplegia; Impairment; Indiana; Injury; Interruption; Investigation; Knowledge; Lead; Maintenance; Mediating; Metabolic; Metabolism; Mitochondria; Modeling; Morphology; Motor; Mus; Natural regeneration; Nature; Nerve Degeneration; Nerve Regeneration; Neurodegenerative Disorders; Neuroglia; Neurologic; Neurons; Neurosurgical Procedures; Parkinson Disease; Pathologic; Pathology; Pathway interactions; Phase; Phenotype; Phosphorylation; Physiological; Play; Positioning Attribute; Power Plants; Presynaptic Terminals; Proteins; Quality Control; Recovery; Recovery of Function; Recycling; Regulation; Reporting; Research; Role; Signal Pathway; Signal Transduction; Solid; Spinal Cord Lesions; Spinal cord injury; Stress; Structure; Synapses; Synaptic Potentials; Synaptic Transmission; Synaptic Vesicles; Synaptic plasticity; Testing; The Sun; Training; Universities; Vesicle; Work; aged; axon injury; axon regeneration; base; building materials; cell motility; central nervous system injury; frontier; functional restoration; genetic manipulation; insight; meetings; mitochondrial dysfunction; mitochondrial metabolism; myosin VI; nervous system disorder; neuronal cell body; parkin gene/protein; presynaptic; recruit; regenerative; response; stressor; synaptic depression; syntaphilin; trafficking; ubiquitin ligase

Accomplishment 1. Reveal an energy signaling that controls presynaptic mitochondrial maintenance and sustains synaptic efficacy (Li et al., Nature Metabolism in press) Mitochondria are essential for maintaining effective synaptic transmission by generating cellular energy and sequestering presynaptic Ca2+. ATP consumption supports synapse assembly, drives action and synaptic potentials, and fuels synaptic vesicle refilling, trafficking and recycling, thus sustaining synaptic transmission. ATP has a limited diffusion capacity in extended long axons, and therefore presynaptic mitochondria are ideally suited to support such a high metabolic demand. A brief interruption in local ATP synthesis or the loss of presynaptic mitochondria compromises synaptic transmission. 33% of presynaptic terminals retain mitochondria, and as such sustained synaptic activity is restricted within mitochondria-containing synapses. However, mechanisms recruiting and retaining presynaptic mitochondria in sensing synaptic ATP levels remain elusive. We specifically address two fundamental questions: (1) does increased energy consumption during intensive synaptic activity lead to presynaptic energy deficits? (2) how are mitochondria recruited to presynaptic terminals as a response to reduced energy availability? Our hypothesis is that axonal mitochondria are recruited to and anchored at presynaptic terminals through a motor-driven switch from MT-based trafficking to actin-based anchoring and that such mitochondrial capture is regulated by an energetic signaling cascade during intensive synaptic activity. Investigation into the energy-sensitive regulation of presynaptic mitochondrial maintenance is an important emerging frontier. Addressing these questions is also relevant to a range of neurological disorders associated with energy deficits, and synaptic dysfunction. Our study reveals a mechanistic crosstalk between energy sensing and mitochondrial anchoring that sustains synaptic efficacy by maintaining presynaptic metabolism. Sustained synaptic activity induces presynaptic energy deficits, a phenotype that could be rescued by recruiting mitochondria through an AMPK-PAK energy signaling pathway. Axonal mitochondria are captured at presynaptic terminals via an interplay between myosin VI (myo6) and SNPH. Synaptic activity induces AMPK activation within axonal compartments and AMPK-PAK signaling mediates myo6 phosphorylation, which drives mitochondrial recruitment and anchoring on presynaptic F-actin. This pathway maintains presynaptic ATP supply as a response to energy stress during intensive synaptic activity. Disrupting this signaling crosstalk triggers local energy deficits and Ca2+i buildup, leading to impaired synaptic efficacy during trains of stimulation, and reduced recovery from synaptic depression after prolonged synaptic activity. Our study reveals an energy-sensitive regulation of presynaptic mitochondrial positioning, thus fine-tuning short-term synaptic plasticity and maintaining prolonged synaptic efficacy. Accomplishment 2. Elucidate mechanisms recovering stressed mitochondria by regulating ER-mitochondrial contacts (Puri et al., Nature Communications 2019; Puri et al., Autophagy 2020 ) Chronic mitochondrial stress associates with major neurodegenerative diseases. Recovering stressed mitochondria and thus energy maintenance constitutes a critical step of mitochondrial quality control in early stages of neurodegeneration. While Parkin-mediated mitophagy is a key cellular pathway to eliminate damaged mitochondria in non-neuronal cells, our previous studies showed that mitophagy is observed only in a small portion of mature neurons and occurs much more slowly than in non-neuronal cells (Cai et al., Current Biology 2012; Lin and Cheng et al., Neuron 2017). These findings argue for unique neuronal mechanisms that recover stressed mitochondrial and energy supply. In order to support this assumption, we reveal that neurons recover chronically stressed mitochondria through mitochondrial ubiquitin ligase 1 (Mul1) before mitophagy is activated. Mul1 plays a dual-role in regulating mitochondrial morphology and ER-Mitochondria (ER-Mito) contacts. Mul1 deficiency increases Mfn2 activity that triggers the first phasic mitochondrial hyperfusion and also acts as an ER-Mitochondria tethering antagonist. Reduced ER-Mito coupling leads to increased cytoplasmic Ca2+ load that induces the second phasic mitochondrial fragmentation and mitophagy. By regulating mitochondrial morphology and ER-Mito contacts, Mul1-Mfn2 play an early checkpoint role in maintaining mitochondrial integrity and restrains Parkin-mediated mitophagy in neurons. Our study provides mechanistic insights into neuronal mitochondrial maintenance under stress conditions. Identifying this pathway is particularly relevant because chronic mitochondrial dysfunction and altered ER-Mito contacts have been reported in major neurodegenerative diseases including Alzheimers and Parkinsons diseases, amyotrophic lateral sclerosis, and hereditary spastic paraplegia. Accomplishment 3. Promoting CNS regeneration and functional recovery after spinal cord injuries (Han et al., Cell Metabolism 2020) Mature CNS axons typically fail to regenerate after injuries, leading to permanent neurological impairments. The underlying mechanisms accounting for regeneration failure in spinal cord injury (SCI) remain largely unknown. For regeneration, injured axons must reseal their terminals, reconstruct cytoskeleton, synthesize and transport building materials, and assemble axon components; all of these events require high levels of energy consumption. While anchored mitochondria in axons serve as local energy sources, axonal injury is a strong stressor that induces acute mitochondrial damage. Insufficient energy supply when mitochondria are damaged and increased energy consumption during regeneration lead to energy deficits in injured axons. Our previous work revealed SNPH as a static anchor holding axonal mitochondria stationary (Kang et al., Cell 2008). Our hypothesis is that elevation of SNPH expression in adult CNS neurons and reduced mitochondrial transport accelerate a local energy crisis, thus accounting for declined regenerative capacity in CNS neurons. Such a local energy supply may be particularly critical to support regenerative growth when injury occurs to long-projection axons. Therefore, enhancing mitochondrial transport by genetic manipulation would help remove damaged mitochondria and replenish healthy ones in injured axons, thus meeting heightened energy demand during regeneration. To test our hypothesis directly in SCI models, we collaborated with Dr. Xiao-Ming Xus lab at the Department of Neurological Surgery, Indiana University. We had the unique experimental advantage of utilizing three different SCI models to study axonal regeneration in snph-/- mice, in which axonal mitochondrial transport is robustly increased. We demonstrate that snph-/- mice display enhanced corticospinal tract (CST) regeneration passing through a spinal cord lesion, accelerated regrowth of monoaminergic axons across a transection gap, and increased compensatory sprouting of uninjured CST. Notably, regenerating CST axons form functional synapses, transmit electrophysiological signals, and promote motor functional recovery. Our injury-induced energy crisis model is further supported by the finding that systemic administration of creatine, a bioenergetic compound, facilitates CST regeneration. Thus, our study provides new mechanistic insights into intrinsic regeneration failure in the CNS and suggests that recovering local energy supply by enhancing mitochondrial transport or by boosting cellular energetics is a promising strategy to promote nerve regeneration and functional restoration after CNS injuries.

成就1。揭示能够控制突触前线粒体维持并持续突触功效的能量信号（Li等人，印刷中的自然代谢） 线粒体对于通过产生细胞能量和隔离突触前Ca2+来维持有效的突触传递至关重要。 ATP消耗支持突触组件，驱动动作和突触电位，以及燃料突触囊泡的补充，运输和回收，从而维持突触传播。 ATP在延长的长轴突中的扩散能力有限，因此突触前的线粒体非常适合支持这种高代谢需求。局部ATP合成的短暂中断或突触前线粒体的丧失会损害突触传播。 33％的突触前末端保留了线粒体，因此持续的突触活动受到线粒体突触的限制。然而，在感应突触ATP水平中募集和保留突触前线粒体的机制仍然难以捉摸。我们特别解决了两个基本问题：（1）在强化突触活动期间增加能量消耗会导致突触前能量缺陷吗？ （2）如何将线粒体募集到突触前末端，以响应降低能量可用性？我们的假设是，轴突线粒体是通过从基于MT的运输到基于肌动蛋白的锚定的电动机开关来募集并锚定在突触前末端的，并且这种线粒体捕获在强化突触活动期间受到高能信号级联的调节。对突触前线粒体维持的能量敏感调节的研究是重要的新兴领域。解决这些问题也与与能量缺陷和突触功能障碍有关的一系列神经系统疾病有关。 我们的研究揭示了能量传感与线粒体锚定之间的机械串扰，该锚定通过维持突触前代谢来维持突触功效。持续的突触活性会引起突触前的能量缺陷，该表型可以通过通过AMPK-PAK能量信号通路募集线粒体来挽救。轴突线粒体通过肌球蛋白VI（MyO6）和SNPH之间的相互作用在突触前终端捕获。突触活性在轴突室内诱导AMPK激活，并且AMPK-PAK信号传导介导肌6磷酸化，从而驱动线粒体募集并锚定在突触前F-肌动蛋白上。该途径将突触前的ATP供应作为对强化突触活动期间能量应力的反应。破坏这种信号传导串扰会触发局部能量缺陷和Ca2+I的积累，从而导致刺激列车期间的突触功效受损，并减少了长时间突触活动后突触抑郁症的恢复。我们的研究揭示了对突触前线粒体定位的能量敏感调节，从而微调短期突触可塑性并保持长时间的突触功效。 成就2。阐明通过调节ER线粒体接触来恢复压力线粒体的机制（Puri等，Nature Communications 2019; Puri等人，自噬2020） 慢性线粒体应激与主要神经退行性疾病相关。在神经变性的早期阶段，恢复应力的线粒体和能量维持构成了线粒体质量控制的关键步骤。虽然Parkin介导的线粒体是消除非神经元细胞中线粒体受损的关键细胞途径，但我们先前的研究表明，仅在成熟神经元的一小部分中观察到线粒体，并且比非神经元细胞的速度要慢得多（Cai等人，Cai等，Current Biology，Lin和Cheng 2012; Lin and Cheng et neuron 2017，Neuron 2017）。这些发现主张恢复应力的线粒体和能量供应的独特神经元机制。为了支持这一假设，我们揭示了神经元在激活线粒体之前通过线粒体泛素连接酶1（MUL1）恢复长期应力的线粒体。 MUL1在调节线粒体形态和ER-MITOCHIRA（ER-MITO）触点方面发挥了双重作用。 MUL1缺乏会增加MFN2活性，从而触发第一个阶段性线粒体过度灌注，并且还充当ER-Mitochontria连接拮抗剂。减少的ER-mito偶联导致细胞质Ca2+载荷增加，从而诱导第二个阶段性线粒体碎片和线粒体。通过调节线粒体形态和ER-mito接触，MUL1-MFN2在维持线粒体完整性并限制神经元中的Parkin介导的线粒体方面起着早期检查点的作用。我们的研究提供了在压力条件下对神经元维持神经元维持的机理见解。鉴定该途径特别相关，因为在包括阿尔茨海默氏症和帕金森氏症，肌萎缩性侧面硬化症以及遗传性痉挛性parapastic Paraplegia在内的主要神经退行性疾病中已经报道了慢性线粒体功能障碍和ER-MITO接触改变。 成就3。促进脊髓损伤后CNS再生和功能恢复（Han等人，细胞代谢2020） 成熟的中枢神经系统轴突通常在受伤后无法再生，从而导致永久性神经系统障碍。考虑到脊髓损伤（SCI）再生失败（SCI）的基本机制仍然未知。为了再生，受伤的轴突必须重新密封其末端，重建细胞骨架，合成和运输建筑材料，并组装轴突成分；所有这些事件都需要高水平的能耗。尽管轴突中的线粒体锚定为局部能源，但轴突损伤是诱导急性线粒体损伤的强胁迫。当线粒体受损时能量供应不足并在再生过程中增加能量消耗会导致轴突的能量缺陷。我们以前的工作表明，SNPH是固定轴突线粒体固定的静态锚定（Kang等，Cell 2008）。我们的假设是，成人中枢神经系统神经元中SNPH表达的升高并减少了线粒体转运加速了局部能量危机，因此CNS神经元的再生能力下降。这种局部能源供应对于在长期投射轴突发生伤害时支持再生生长特别重要。因此，通过遗传操作增强线粒体运输将有助于清除损伤的线粒体并补充受伤的轴突中的健康，从而满足再生过程中能量需求的增强。 为了直接在SCI模型中检验我们的假设，我们与印第安纳大学神经外科系的Xiao-Ming Xus Lab博士合作。我们具有利用三种不同的SCI模型来研究SNPH - / - 小鼠中的轴突再生的独特实验优势，其中轴突线粒体转运可稳健地增加。我们证明SNPH - / - 小鼠表现出通过脊髓病变的增强的皮质脊髓段（CST）再生，在横断间隙中加速了单氨基能轴突的加速，并增加了无构型CST的补偿性发芽。值得注意的是，再生CST轴突形成功能突触，传递电生理信号并促进运动功能恢复。我们的伤害引起的能源危机模型得到了以下发现，即肌酸的系统给药促进了CST的再生。因此，我们的研究为中枢神经系统的内在再生失败提供了新的机械见解，并表明，通过增强线粒体转运或增强细胞能量来恢复局部能量供应是一种有希望的策略，是促进CNS损伤后神经再生和功能恢复的策略。