Polarized Initiation of Varicosity Formation in Central Neuron Mechanosensation

项目摘要 关于微机械应力在调节神经元形态和功能方面的作用知之甚少 极性机械冲击引起的弥漫性轴索损伤表现为特征性的轴索静脉曲张（肿胀 或串珠状），这是创伤性脑损伤（TBI）的显著特征。丰富的轴索静脉曲张 也是阿尔茨海默氏症和帕金森氏症不可逆神经退行性变的关键标志， 硬化症在生理条件下，可以在脑中观察到较低水平的轴突静脉曲张。 虽然轴突静脉曲张深刻地影响动作电位传播和突触传递， 在轴突中由机械应力特异性诱导并在健康和疾病中调节仍然是一个谜。 我们的初步研究已经导致了几个新的发现来阐明这个重要的问题。我们发现 机械应力会诱导无髓鞘轴突中静脉曲张的形成，但不会诱导树突或有髓鞘轴突中静脉曲张的形成 中枢神经元的轴突这个过程出乎意料地迅速和可逆，其中瞬时受体 TRP通道是主要的机械敏感性离子通道。我们进一步确认了一本小说 该通道的结合蛋白，其调节微管（MT）响应于Ca2+内流的解体。 此外，我们观察到在轻度TBI小鼠模型的脑中轴突静脉曲张的快速发展。 基于我们的初步结果，我们提出了一个原始的假设， 优先诱导中枢神经元的轴突静脉曲张，这一过程受到轴突的调节。 内在和外在机制。为了验证这一假设，我们将采用多学科的方法 包括新的微生物力学测定，蛋白质生物化学，电生理记录， ART成像、髓磷脂共培养、敲除小鼠和轻度TBI小鼠模型。我们将确定（目标1）是否 MS离子通道的靶向和活性调节中枢神经元的极化机械感觉，（目的2）如何 MT分解是由轴突内Ca2+增加诱导的，进而导致静脉曲张形成，并且（目的3） 轻度TBI小鼠模型中轴突静脉曲张形成的模式是否受髓鞘调节，MS 通道及其结合蛋白。 这个项目代表了一个未充分探索的研究领域，有许多悬而未决的问题。这项研究意义重大 因为它将提供一种新形式的中枢神经元极性的新机制见解， 机械感觉

PROJECT SUMMARY Little is known about the role of micromechanical stress in regulating neuronal morphological and functional polarity. Diffuse axonal injury caused by mechanical impact displays characteristic axonal varicosities (swelling or beading), which are a prominent feature of traumatic brain injury (TBI). Abundant axonal varicosities are also a key sign for irreversible neurodegeneration in Alzheimer's and Parkinson's diseases, and multiple sclerosis. Under physiological conditions, a lower level of axonal varicosities can be observed in the brain. Although axonal varicosities profoundly affect action potential propagation and synaptic transmission, how they are specifically induced in axons by mechanical stress and regulated in health and disease remains a mystery. Our preliminary studies have led to several novel findings to shed light on this important question. We found that mechanical stress induces varicosity formation in unmyelinated axons, but not in dendrites or myelinated axons of central neurons. This process is unexpectedly rapid and reversible, where a transient receptor potential (TRP) channel acts as the major mechanosensitive (MS) ion channel. We further identified a novel binding protein of this channel, which regulates microtubule (MT) disassembly in response to Ca2+ influx. Moreover, we observed the rapid development of axonal varicosities in the brain of a mouse model of mild TBI. Based on our preliminary results, we propose an original hypothesis that micromechanical stress preferentially induces axonal varicosities in central neurons, and this process is regulated by axonal intrinsic and extrinsic mechanisms. To test this hypothesis, we will use a multidisciplinary approach including novel microbiomechanical assays, protein biochemistry, electrophysiological recording, state-of-the- art imaging, myelin coculture, knockout mice and a mild TBI mouse model. We will determine (Aim 1) whether targeting and activity of MS ion channels regulate polarized mechanosensation in central neurons, (Aim 2) how MT disassembly is induced by intra-axonal Ca2+ increase and in turn leads to varicosity formation, and (Aim 3) whether the pattern of axonal varicosity formation in the mild TBI mouse model is regulated by myelin, the MS channel and its binding protein. This project represents an underexplored research field with many open questions. This research is significant because it will provide novel mechanistic insights into a new form of central neuron polarity, polarized mechanosensation.