Regenerative and Degenerative Responses to Axonal Injury

对轴突损伤的再生和退行性反应

• 批准号: 9028332
• 负责人: CATHERINE A COLLINS
• 金额: $ 33.39万
• 依托单位: UNIVERSITY OF MICHIGAN AT ANN ARBOR
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-04-01 至 2020-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9028332
• 关键词: Address; Adult; Alzheimer' s Disease; Animals; Apoptosis; Attention; Attenuated; Axon; Biochemistry; Brain; Caenorhabditis elegans; Calcium; Cell Death; Cells; Coin; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Data; Diabetes Mellitus; Disease; Distal; Drosophila genus; Dyes; Enzymes; Event; Future; Genetic; Glaucoma; Goals; Grant; Homeostasis; Homologous Gene; Hour; Imaging Techniques; Individual; Injury; Label; Larva; Life; Link; Literature; Mammals; Mediating; Mediator of activation protein; Methods; Mitochondria; Modeling; Molecular; Mus; Names; Natural regeneration; Nerve Growth Factors; Neuraxis; Neurodegenerative Disorders; Neurons; Neuropathy; Neurotoxins; Outcome; Parkinson Disease; Pathway interactions; Pharmacology; Phosphotransferases; Play; Process; Regenerative response; Regulation; Role; Signal Transduction; Spinal cord injury; Synapses; Testing; Time; Vertebrates; Wallerian Degeneration; Work; axon growth; axon injury; axon regeneration; axonal degeneration; chemotherapy; excitotoxicity; injured; insight; public health relevance; regenerative; repaired; research study; response; trafficking; ubiquitin-protein ligase

 DESCRIPTION (provided by applicant): Functional repair after axonal damage requires disparate responses in the proximal and distal parts of the damaged axon. The proximal axon must initiate new axonal growth, however in many cases this fails to occur, particularly in the adult mammalian CNS. In addition, the distal axonal stump must be cleared out of the way. This occurs via a cell-autonomously initiated axonal fragmentation process termed `Wallerian degeneration'. While this degeneration plays a beneficial role in clearing irreparably damaged axons, the loss of axons is generally a deleterious feature of neuropathies and neurodegenerative diseases. The long term goals of this project are to understand the cellular mechanisms that detect axonal damage and facilitate the dichotomous outcomes of degeneration verses repair. Previous work in the lab, using a Drosophila model, has delineated a conserved molecular pathway that regulates both the regeneration and degeneration of damaged axons. The current grant focuses upon two important components of this pathway: (1) Wnd/DLK, a conserved axonal kinase whose can mediate either regenerative or degenerative responses to axonal injury, hence has been coined a `dual-edged sword', and (2) the NAD+ biosynthetic enzyme, Nmnat [2, 3], whose rapid turnover in distal axons appears to play an important role in initiating degeneration, however the cellular mechanism for Nmnat's protective function(s) is not known. Aim 1 tests a hypothesis, raised by preliminary data, that both Wnd and its DLK homologue in mammals are regulated directly by PKA downstream of cAMP signaling. Because elevated cAMP signaling correlates with successful regeneration in the PNS, this mechanism may yield insight into how pro-regenerative outcomes of Wnd/DLK's activation can be specifically biased. Aim 2 tests a new hypothesis for the protective mechanism in axons, specifically that Nmnat attenuates intracellular Ca2+ influx from ER stores that are triggered by injury, and further links calcium homeostasis to ATP rundown and mitochondrial trafficking in damaged axons. The approaches take advantage of genetic and live imaging techniques in Drosophila larvae which allow for subcellular events (including changes in intracellular Ca2+, ATP, and mitochondrial trafficking) to be manipulated and tracked within injured axons and synapses in live animals. In addition, the project initiates complementary studies in mouse DRG cultures to study axonal regeneration in the context of individual cellular events regulated by DLK. This work is expected to reveal important cellular mechanisms that influence both regenerative and degenerative responses to axonal damage.

 描述（由申请人提供）：轴突损伤后的功能修复需要受损轴突近端和远端部分的不同反应。近端轴突必须启动新的轴突生长，然而在许多情况下，这未能发生，特别是在成年哺乳动物CNS中。此外，远端轴突残端必须清除。这是通过细胞自主启动的轴突断裂过程发生的，称为“沃勒变性”。虽然这种变性在清除不可修复的受损轴突中起有益作用，但轴突的损失通常是神经病变和神经变性疾病的有害特征。 这个项目的长期目标是了解检测轴突损伤的细胞机制，并促进退化与修复的二分结果。以前在实验室的工作，使用果蝇模型，描绘了一个保守的分子途径，调节受损轴突的再生和退化。目前的赠款侧重于这一途径的两个重要组成部分：（1）Wnd/DLK是一种保守的轴突激酶，可以介导轴突损伤的再生或退行性反应，因此被称为“双刃剑”，以及（2）NAD+生物合成酶Nmnat [2，3]，其远端轴突的快速周转似乎在启动变性方面发挥着重要作用，然而，Nmnat保护功能的细胞机制尚不清楚。 目的1测试的假设，提出了初步的数据，即Wnd和它的DLK同源物在哺乳动物中的cAMP信号下游的PKA直接调节。由于升高的cAMP信号传导与PNS中的成功再生相关，因此该机制可以产生对Wnd/DLK激活的促再生结果如何特异性偏向的洞察。目的2测试了轴突保护机制的新假设，特别是Nmnat减弱损伤引发的ER储存的细胞内Ca 2+内流，并进一步将钙稳态与受损轴突中的ATP耗竭和线粒体运输联系起来。这些方法利用果蝇幼虫的遗传和活体成像技术，可以在活体动物的损伤轴突和突触内操纵和跟踪亚细胞事件（包括细胞内Ca 2+、ATP和线粒体运输的变化）。此外，该项目还启动了小鼠DRG培养物的补充研究，以研究DLK调控的个体细胞事件背景下的轴突再生。这项工作有望揭示影响轴突损伤再生和退行性反应的重要细胞机制。