Glial regulation of neuronal physiology in response to local injury

神经系统的局部损伤可能会导致神经生理学的深远变化，即使是在远离损伤部位的未受损伤的神经元中也是如此。令人惊讶的是，正是这些未受伤神经元的生理变化，而不是受损神经元本身的损伤，导致了神经损伤后与周围神经病变相关的慢性疼痛。在创伤性脑损伤后未受损伤的神经元中也观察到了这些变化，并假设即使是局灶性脑损伤，未受损伤神经元的生理变化也可能导致广泛的认知变化。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，在这种模型中，单个神经内的神经元可以被稀疏地标记，并在轴突切断后明确地识别单个受损和未受损的神经元。利用果蝇翅膀前神经切断轴突的模型，我们发现神经内未受损伤的神经元经历轴突运输停滞，并表现出对感觉刺激的反应减少的活动。有趣的是，我们发现这些效应需要胶质信号，这表明胶质细胞在受损和未受损神经元之间发挥中介作用，推动生理变化。这项提议将侧重于了解神经胶质细胞如何感觉到神经元受到了损伤，以及这些细胞如何以及为什么会改变周围神经元的生理。在目标1中，我将评估神经胶质细胞识别的足以调节神经元生理学的损伤类型，并测试这些信号通路是否与损伤轴突变性所需的信号通路不同。我们已经确定，在神经胶质细胞中，Draper受体是感知损伤所必需的。在目标2中，我将对Draper受体进行结构功能分析，以确定受体激活下游信号所需的功能结构域，并测试相关信号分子是否需要对未损伤的神经元信号进行神经胶质调控。在目标3中，我将通过阻断未损伤的神经元信号和评估神经生理的长期恢复和神经内的存活来确定为什么胶质细胞可能会导致未损伤神经元的这些变化。总之，这些研究将提供对伤害信号在神经系统中传播的机制的洞察，并确定导致这一未知但重要现象的细胞和分子途径。然后，这些机制可以作为治疗的靶点，以维持神经胶质细胞在损伤后清除轴突碎片的有益反应，但阻止导致未受损伤的神经元生理发生有害变化的信号。这将是一种针对损伤后神经病理性疼痛和认知功能障碍的全新方法。此外，执行这项工作将使我能够发展新的技术技能和智力方法，我将需要在我自己的实验室里使用果蝇来解决基本的神经生物学问题。该奖学金中提议的额外培训活动还将增强我的量化和分析技能，提高我沟通工作的能力，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.