Glial regulation of neuronal physiology in response to local injury

神经系统的局部损伤可导致神经生理学的深远改变，即使在远离损伤部位的未损伤神经元中也是如此。令人惊讶的是，正是这些未损伤神经元的生理变化，而不是损伤神经元本身的损伤，导致了神经损伤后与周围神经病变相关的慢性疼痛。这些变化也在创伤性脑损伤后未损伤的神经元中被观察到，并且已经假设未损伤神经元的生理变化可能是局灶性脑损伤导致的广泛认知变化的原因。尽管它们参与了这些重要的过程，但损伤信号在神经系统中传播的机制尚不清楚。我们最近开发了一种模型，在该模型中，单个神经内的神经元可以被稀疏标记，并且在轴切术后确定单个损伤和未损伤的神经元。使用果蝇翅膀前神经的轴突切开术模型，我们发现神经内未受伤的神经元轴突运输停滞，并且在对感觉刺激的反应中表现出活性降低。有趣的是，我们发现这些效应需要神经胶质信号传导，这表明神经胶质作为受伤和未受伤神经元之间的介质来驱动生理变化。这一建议将集中于理解神经胶质细胞如何感知神经元受伤，以及这些细胞如何以及为什么改变周围神经元的生理机能。在Aim 1中，我将评估哪种类型的损伤胶质细胞识别为足以调节神经元生理，并将测试这些信号通路是否与受损轴突变性所需的信号通路不同。我们已经确定，神经胶质细胞需要德雷珀受体来感知损伤。在Aim 2中，我将对Draper受体进行结构功能分析，以确定受体激活的下游信号传递需要哪些功能域，并测试相关的信号分子是否需要用于未损伤神经元信号的胶质调节。在Aim 3中，我将通过阻断未损伤神经元信号和评估神经生理学和神经内存活的长期恢复来确定为什么胶质细胞可能在未损伤神经元中引起这些变化。总之，这些研究将深入了解损伤信号在神经系统中传播的机制，并确定导致这一未知但重要现象的细胞和分子途径。这些机制可以在治疗上有针对性地维持神经胶质细胞在损伤后清除轴突碎片的有益反应，但防止导致未损伤神经元生理有害变化的信号传导。这将是一种全新的治疗损伤后神经性疼痛和认知功能障碍的方法。此外，进行这项工作将使我能够发展新的技术技能和智力方法，我将需要使用果蝇来解决我自己实验室中的基本神经生物学问题。在这个奖学金中提出的额外培训活动也将提高我的定量和分析能力，提高我的工作沟通能力，并参与指导，为我成为一名成功的独立调查员做好准备。

Localized damage to the nervous system can lead to far-reaching alterations in neurophysiology, even in uninjured neurons distant from the site of injury. Surprisingly, it is these changes in the physiology of uninjured neurons, rather than damage to injured neurons themselves, that is responsible for the chronic pain associated with peripheral neuropathy after nerve injury. These changes have also been observed in uninjured neurons following traumatic brain injury, and it has been posited that physiological changes in uninjured neurons could be responsible for the widespread cognitive changes that result from even focal brain injuries. Despite their involvement in these important processes, the mechanisms by which injury signals spread across the nervous system are poorly defined. We have recently developed a model in which neurons within a single nerve can be sparsely labeled and individual injured and uninjured neurons definitively identified after axotomy. Using this model of axotomy in the anterior nerve of the Drosophila wing, we found that uninjured neurons within the nerve undergo stalling of axon transport and exhibit reduced activity in response to sensory stimuli. Interestingly, we found that these effects require glial signaling, demonstrating that glia act as mediators between injured and uninjured neurons to drive changes in physiology. This proposal will focus on understanding how glia sense that neurons have been injured, and how and why these cells then change the physiology of surrounding neurons. In Aim 1, I will assess what type of injury glia recognize as sufficient to modulate neuronal physiology and will test whether these signaling pathways are distinct from those required for injured axon degeneration. We have already identified that the Draper receptor is required in glia to sense injury. In Aim 2, I will perform a structure function analysis of the Draper receptor to determine which functional domains are required for signaling downstream of receptor activation and test whether the associated signaling molecules are required for glial modulation of uninjured neuron signaling. In Aim 3, I will determine why glia might cause these change in uninjured neurons by blocking uninjured neuron signaling and assessing long-term recovery of neuronal physiology and survival within the nerve. Together, these studies will provide insight into the mechanisms by which injury signals spread across the nervous system and identify the cellular and molecular pathways responsible for this unknown but important phenomenon. These mechanisms could then be targeted therapeutically to maintain beneficial responses of glia in clearing axonal debris after injury, but prevent signaling that leads to detrimental changes in uninjured neuronal physiology. This would be a completely novel approach to targeting neuropathic pain and cognitive dysfunction after injury. In addition, performing this work will allow me to develop the new technical skills and intellectual approaches I will need to use Drosophila to address fundamental neurobiological questions in my own laboratory. The additional training activities proposed in this fellowship will also enhance my quantitative and analytical skills, improve my ability to communicate my work, and engage in mentorship, preparing me for success as an independent investigator.