Exploring the Role Dense Core Vesicle Release in Glial Immunity

总结 神经胶质细胞在保护大脑健康和管理神经元应激和损伤方面发挥着重要作用。 神经退行性变触发了强大的神经胶质免疫反应，包括细胞骨架动力学、神经胶质细胞增殖和神经胶质细胞增殖的变化。 细胞迁移和增加的吞噬活性。及时去除和降解退化的轴突， 神经胶质的神经元碎片在脑中提供神经保护。尽管神经胶质对轴突的反应很重要， 尽管神经元受损，但令人惊讶的是，我们仍然对受损神经元如何引起神经胶质细胞的免疫反应知之甚少。什么 信号是从退化的神经元中释放出来的是什么促使这些伤害线索的释放？最后， 这些讯息是否经由神经胶细胞转译，以进行有效的免疫反应来对抗伤害？ 我们正在使用果蝇Drosophila melanogaster作为一个易处理的模型来研究免疫系统的免疫功能。 存在于体内神经元和神经胶质细胞之间的通信中继。果蝇的神经系统包含 在分子和功能上与脊椎动物神经胶质相似的不同神经胶质亚型。此外， 在成年嗅觉系统和成年翅膀中的轴突切断试验揭示了果蝇轴突经历了一个 经典的沃勒变性（WD）程序，其中包括增加轴突内钙波，轴突 碎片化，随后被吞噬胶质细胞清除。值得注意的是，我们的实验室最近表明轴突 变性触发了反应性成鞘神经胶质中胰岛素样信号传导（ILS）途径的激活， 反过来，增强必要的神经胶质免疫应答，包括免疫基因的转录上调（例如， 吞噬受体德雷珀）和吞噬活性。我们假设，含神经肽的致密 核心囊泡（DCV）从切断的轴突广泛释放以触发局部神经胶质细胞中的免疫应答。 在这里，我们建议使用静态和实时共聚焦成像，转录谱，和新开发的体内 研究神经元和神经胶质之间的神经肽信号传导如何通知神经胶质免疫反应的报告员 神经损伤。具体来说，我们将1）监测DCV动力学和成人切断神经的释放，2）利用 一种新的单转录本标记方法来显示胶质细胞中免疫mRNA转录本的局部翻译 损伤部位的延伸，以及3）确定离散神经胶质亚型之间的神经肽信号传导 确保神经胶质对退化轴突的反应得以正确进行。总之，这些发现将提供 令人兴奋的分子和细胞洞察神经元和神经胶质之间的神经肽信号传导如何控制 急性和慢性退行性疾病的免疫反应。

SUMMARY Glial cells play an essential role in defending brain health and managing neuronal stress and damage. Neurodegeneration triggers robust glial immune responses, including changes in cytoskeletal dynamics, glial cell migration, and increased phagocytic activity. Timely removal and degradation of degenerating axons and neuronal debris by glia confers neuroprotection in the brain. Despite the importance of glial responses to axon injury, we still know surprisingly little about how damaged neurons invoke immune reactions in glial cells. What signals are released from degenerating neurons? What prompts the release of these injury cues? Finally, how are these signals translated by glia to carry out efficient immune responses to damage? We are using the fruit fly Drosophila melanogaster as a tractable model to investigate the immune communication relays that exist between neurons and glial cells in vivo. The fly nervous system contains distinct glial subtypes that are molecularly and functionally similar to vertebrate glia. Moreover, well-established axotomy assays in the adult olfactory system and the adult wing reveal that Drosophila axons undergo a classic Wallerian degeneration (WD) program, which includes increased intra-axonal calcium waves, axon fragmentation, and subsequent clearance by phagocytic glia. Notably, our lab has recently shown that axon degeneration triggers activation of the insulin-like signaling (ILS) pathway in reactive ensheathing glia, which, in turn, elicits essential glial immune responses, including transcriptional upregulation of immune genes (e.g. the engulfment receptor Draper) and phagocytic activity. We hypothesize that neuropeptide-containing dense core vesicles (DCVs) are broadly released from severed axons to trigger immune responses in local glial cells. Here, we propose to use static and live confocal imaging, transcriptional profiling, and newly developed in vivo reporters to investigate how neuropeptide signaling between neurons and glia informs glial immune responses to nerve injury. Specifically, we will 1) monitor DCV dynamics and release in adult severed nerves, 2) utilize novel single transcript labeling methods to visualize local translation of immune mRNA transcripts in glial extensions at sites of injury, and 3) determine how neuropeptide signaling between discrete glial subtypes ensures that glial responses to degenerating axons are properly carried out. Together, these findings will offer exciting molecular and cellular insight into how neuropeptide signaling between neurons and glia govern immune responses in both acute and chronic degenerative conditions.