Unexpected Function of Inflammasomes in Axon Pruning: Focus on NLRP1

炎症小体在轴突修剪中的意外功能：聚焦 NLRP1

• 批准号: 10156766
• 负责人: Mohanish P Deshmukh
• 金额: $ 163.79万
• 依托单位: UNIV OF NORTH CAROLINA CHAPEL HILL
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-02-01 至 2024-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10156766
• 关键词: APP-PS1; Adult; Alzheimer' s Disease; Alzheimer' s disease model; Alzheimer' s disease pathology; Amyloid beta-Protein; Apoptosis; Axon; Behavioral; Biochemical; CASP1 gene; CASP3 gene; CASP6 gene; CASP9 gene; Caspase; Cells; Cleaved cell; Complex; Defect; Dendrites; Development; Event; Excision; Goals; Immune; Immune system; In Vitro; Infection; Inflammasome; Interleukin-1 beta; Interleukin-18; JUN gene; Knockout Mice; Link; MAPK8 gene; Mediating; Microfluidics; Modeling; Molecular; Multiprotein Complexes; N-terminal; Nerve Growth Factors; Nervous system structure; Neurodegenerative Disorders; Neurons; Pathogenesis; Pathogenicity; Pathologic; Pathway interactions; Physiological; Play; Proteins; Research; Role; Signal Transduction; Site; Stimulus; Synapses; Therapeutic; apoptotic protease-activating factor 1; axonal degeneration; base; cytokine; deprivation; experimental study; extracellular; in vivo; mouse model; mutant; neuron loss; neuronal cell body; novel; pathogen; pathogen exposure; protein complex; receptor; response; sensor

Project Summary/Abstract Neurons are capable of activating pathways that induce either the degeneration of the entire cell by apoptosis or to selectively degenerate only the axons. Physiological axon-specific degeneration, known as axon pruning, is important as it allows neurons to remove excessive or misguided axons and permit plasticity in neuronal connections. Aberrant pruning is observed in several neurodegenerative diseases, including Alzheimer’s Disease (AD). However, exactly how neurons activate this pathway to degenerate axons in physiological or pathological situations of AD is unclear. We have investigated the apoptosis and axon pruning pathways in a microfluidic chamber-based model utilizing sympathetic neurons. Upon nerve growth factor (NGF) deprivation, these neurons can induce either apoptosis (when NGF is deprived from both soma and axon compartments) or axon pruning (when NGF is deprived from only the axon compartment). Our research has identified substantial overlap but also distinct differences between the apoptosis and axon pruning pathways. For example, while caspase-9 (Casp9) and caspase-3 (Casp3) are required for both pathways, their activation is dependent on the apoptosome during apoptosis but is surprisingly independent of the apoptosome during axon pruning. While investigating the mechanism by which caspases are activated during pruning, we unexpectedly found that the inflammasome pathway plays an important function in axon pruning. Inflammasomes have been studied primarily in immune cells in the context of pathogen signaling. These are multi-protein complexes formed in response to pathogenic or danger stimuli, which result in activation of the proinflammatory caspase, caspase-1 (Casp1). Strikingly, we found that Casp1 and NLRP1 (a key component of a particular inflammasome) are both essential for axon pruning. These results are surprising as axon pruning does not involve pathogen exposure. In this proposal, we will identify the specific inflammasome pathway components that are critical for axon pruning and conduct mechanistic experiments to define this novel function of NLRP1 in neurons. In Aim 1, we will define the specific inflammasome proteins that are essential for axon pruning, and determine where they act in the known pruning pathway. In Aim 2, we will define the role of IL-1β/IL-18 in axon pruning. Our focus in Aim 3 will be to conduct mechanistic experiments to examine how NLRP1 is activated in the context of axon pruning. Importantly, in Aim 4 we will focus on AD and investigate whether the pathological degeneration of synapses and axons in AD are mediated by NLRP1. We will examine this in a microfluidic model of Aβ-induced axon degeneration in vitro as well as in a mouse model of AD in vivo where we will examine if NLRP1 deficiency reduces AD pathology and behavioral defects. This project opens an exciting new avenue of research into this unexpected function of the NLRP1 inflammasome in neurons.

项目总结/摘要 神经元能够激活诱导整个细胞变性的途径， 凋亡或选择性地仅使轴突退化。生理性轴突特异性变性，称为轴突 修剪是重要的，因为它允许神经元去除过多或误导的轴突，并允许可塑性， 神经元连接在几种神经退行性疾病中观察到异常修剪，包括 阿尔茨海默病（AD）。然而，神经元究竟是如何激活这条通路，使轴突退化的， AD的生理或病理情况尚不清楚。 我们在微流控室模型中研究了细胞凋亡和轴突修剪途径 利用交感神经元。在神经生长因子（NGF）剥夺后，这些神经元可以诱导 细胞凋亡（当从索马和轴突区室剥夺NGF时）或轴突修剪（当从轴突区室剥夺NGF时）。 仅从轴突隔室剥夺）。我们的研究发现了大量的重叠， 细胞凋亡和轴突修剪途径之间的差异。例如，虽然胱天蛋白酶-9（Casp9）和 caspase-3（Casp3）是两种途径所必需的，它们的激活依赖于细胞周期中的溶酶体。 在轴突修剪过程中，细胞凋亡但令人惊讶地独立于轴突体。 在研究半胱天冬酶在修剪过程中被激活的机制时，我们意外地发现， 炎性小体通路在轴突修剪中起重要作用。炎性小体已经被 主要在免疫细胞中研究病原体信号传导。这些是多蛋白复合物 响应致病或危险刺激而形成，其导致促炎性半胱天冬酶的激活， 半胱天冬酶-1（Casp1）。令人惊讶的是，我们发现Casp1和NLRP 1（一种特定的 炎性小体）都是轴突修剪所必需的。这些结果是令人惊讶的，因为轴突修剪并不 涉及病原体暴露。在这个建议中，我们将确定特定的炎性体通路组件 这对轴突修剪至关重要，并进行机械实验来定义NLRP 1的这种新功能 在神经元中。在目标1中，我们将定义轴突修剪所必需的特定炎性体蛋白， 并确定它们在已知修剪途径中的作用。在目标2中，我们将定义IL-1 β/IL-18在 在轴突修剪中。我们在目标3中的重点将是进行机械实验，以研究NLRP 1是如何 在轴突修剪的情况下被激活。重要的是，在目标4中，我们将重点关注AD，并研究 AD中突触和轴突的病理性变性由NLRP 1介导。我们将在一个 体外A β诱导轴突变性的微流体模型以及体内AD小鼠模型， 我们将检验NLRP 1缺陷是否减少AD病理和行为缺陷。此项目将打开一个 令人兴奋的新途径研究NLRP 1炎性小体在神经元中的这种意想不到的功能。