The Role of Ubiquitination in Tau Oligomers Pathogenesis

阿尔茨海默病（AD）是最普遍的神经退行性疾病，其对人类造成了难以忍受的社会和经济影响。 全球经济负担。目前的治疗方法未能阻止AD进展，表明需要 新的战略，这是这个项目的重点。神经纤维缠结（NFT）-主要病理标志 在人类AD和相关的tau蛋白病中，当微管相关蛋白tau（MAPT或tau）形成时发生 集料.此外，AD脑中tau聚集体的积累促进认知下降，伴随着 神经元蛋白质稳态失调然而，我们和其他人以前已经表明，较小的可溶性 称为寡聚体的tau聚集体是毒性最大的物质，并且在人AD中先于NFT形成。我们 初步研究表明AD-脑衍生的tau寡聚体（BDTO）表现出独特的翻译后 修饰（PTM），包括特定的泛素连接，这似乎涉及tau聚集， 影响稳定性、以朊病毒样方式传播以及随后的认知能力下降。了解 tau寡聚体逃避蛋白酶体降解的基本特征泛素化模式， 促进其组装、稳定、分泌和繁殖对于开发疾病修饰 治疗AD。 这项提议将检验中心假设，即tau寡聚体独特的单泛素化有助于 逃避神经元泛素-蛋白酶体系统（UPS），并促进其在神经元中的积累， 导致突触功能障碍此外，这些tau寡聚体有助于增加神经元毒性， 分泌和传播朊病毒样tau病理，还通过调节 小胶质细胞和星形胶质细胞活化。在具体目标1中，使用质谱和定点诱变， 我们将定义赖氨酸修饰的机制和功能影响，特别是可逆的单- 泛素化，调节神经元中tau寡聚体的加工、组装和运输。这也将 定义tau寡聚体单泛素化在调节 AD中tau寡聚体组装、分泌和增殖的功效，其将作为潜在的AD 死前生物标志物，并提供靶向病理性tau的关键信息。使用同位素标记， 氨基酸在体外和体内（SILAC）蛋白质组学方法，在具体目标2，我们将定义的机制 单泛素化通过其控制PHF-tau组装和tau寡聚体分泌之间的相互作用， 在初级神经元中传播。此外，用于调节tau-去泛素化和AD的生理学机制也是已知的。 将使用补充方法验证发病机制。在具体目标3中，我们将研究 去泛素化酶Otub 1对神经元中tau寡聚体积累、运输和自我繁殖的影响。

Alzheimer’s disease (AD) is the most prevalent neurodegenerative disorder imposing an unbearable socio- economic burden worldwide. Current therapeutic approaches fail to halt AD progression, indicating the need for new strategies, which is the focus of this project. Neurofibrillary tangles (NFTs)–the major pathological hallmark in human AD and related tauopathies, occurs when microtubule-associated protein tau (MAPT or tau) forms aggregates. Further, accumulation of the tau aggregates in AD brain promotes cognitive decline, accompanied with dysregulated proteostasis in neurons. However, we and others have previously shown that smaller soluble tau-aggregates, called oligomers, are the most toxic species and form prior to NFTs in human AD. Our preliminary studies show that AD-brain-derived tau oligomers (BDTOs) exhibit unique post-translational modifications (PTMs), including specific ubiquitin-linkages, which seem to be involved in tau-aggregation that influence stability, propagation in a prion-like manner and subsequent cognitive decline. Understanding the fundamental signature ubiquitination pattern by which tau oligomers evade proteasomal degradation and promote its assembly, stability, secretion and propagation is important for developing disease-modifying therapies for AD. This proposal will test the central hypothesis that the unique mono-ubiquitination of tau oligomers facilitate to evade the neuronal ubiquitin-proteasome system (UPS), and promote its accumulation in neurons, which causes synaptic dysfunction. Furthermore, these tau oligomers contribute to increased neuronal toxicity, secretion and propagation of a prion-like tau pathology, and also promote neuroinflammation by modulating microglia and astrocytes activation. In specific aim 1, using mass-spectroscopy and site-directed mutagenesis, we will define the mechanism and functional impact of lysine modification, and particularly reversible mono- ubiquitination, in regulating the processing, assembly and trafficking of tau oligomers in neurons. This will also define the biochemical and structural consequences of tau oligomer mono-ubiquitination in modulating the efficacy of tau oligomer assembly, secretion and propagation in AD, which will serve as a potential AD antemortem biomarker, and provide key information for targeting the pathological tau. Using isotope labeling by amino acids in vitro and in vivo (SILAC) proteomics approaches, in specific aim 2, we will define the mechanism by which mono-ubiquitination controls the interplay between PHF-tau assembly and tau oligomers secretion and propagation in primary neurons. Further, physiological mechanisms for regulation of tau-deubiquitination and AD pathogenesis will be verified using complementary approaches. In specific aim 3, we will investigate the role of deubiquitinase Otub1 on tau oligomer accumulation, trafficking and self-propagation in neurons.