Validation of a novel tau clearance mechanism.

除了细胞外β-淀粉样蛋白(Aβ)斑块沉积外，阿尔茨海默病(AD)在病理上也是 以细胞内相互作用为特征的，即异常过度磷酸化的堆积和聚集 微管相关蛋白MAPT/tau形成神经纤维缠结(NFT)，导致功能丧失 神经元。尽管Aβ斑块在启动AD发病机制中起着关键作用，但认知能力下降的严重程度 与新皮质NFT的负担最相关。因此，促进积聚牛磺酸的清除 代表了一种很有希望的治疗策略，这取决于对 疾病进展过程中病理性tau物种退化的机制。我们的 最终目标是阐明诸如阿尔茨海默病等肌萎缩侧索硬化症如何启动和 取得进展，并开发有效的治疗方法来治疗紧张症。据报道，tau可以 被自噬-溶酶体或泛素-蛋白酶体系统降解。牛磺酸的降解与 它的各种翻译后修饰，包括磷酸化、乙酰化和泛素化。我们的 初步研究表明，tau在正常小鼠脑组织中被线性泛素链修饰，这是 在紧张症小鼠模型中显著降低。Tau的线性泛素化促进tau的清除 以一种自噬依赖的方式。我们进一步发现，氧化应激可以增加脱泛素酶OTULIN 通过促进其磷酸化的活性，这两者在AD的脑组织中都显著增加 病人。抑制Otulin可防止病理性tau的聚集并减弱其 直肠结肠炎小鼠模型的细胞毒性。因此，我们假设线性泛素化促进了tau。 降解，被脱泛素酶OTULIN抑制；氧化应激激活OTULIN，导致 增加tau聚集和神经毒性。奥图林的药理抑制作用可能减轻直肠痉挛 通过加强tau聚集体的清除而取得进展。为了检验这一点，我们提出了三个具体目标 假设。AIM1将确定线性泛素化在调节tau积累和神经元中的作用 毒性，并探讨自噬-溶酶体机制。AIM2将研究氧化应激介导的 用系统生物学方法研究OTULIN诱导的肌萎缩侧索硬化症机制。目标3将测试一种新的 新型OTULIN抑制剂促进tau清除及减轻tau细胞毒性的实验研究 模特们。我们的研究将通过提供：1)调节tau聚集的新机制而产生强大的影响 和蛋白毒性；2)氧化应激和tau线性泛素化之间的新的机制联系；3)潜在的 缓解紧张症和认知衰退的治疗方法，最终使AD患者受益。

Besides extracellular β-amyloid (Aβ) plaques deposition, Alzheimer’s disease (AD) is pathologically characterized by intracellular tauopathy that accumulation and aggregation of abnormally hyperphosphorylated microtubule-associated protein MAPT/tau form neurofibrillary tangle (NFT), resulting in loss of functional neurons. Although Aβ plaques play a key role in initiating AD pathogenesis, the severity of cognitive decline correlates best with the burden of neocortical NFTs. Therefore, promoting the clearance of accumulated tau represents a promising therapeutic strategy for tauopathy patients, which depends on a better understanding of the mechanisms underlying the degradation of pathological tau species during disease progression. Our ultimate goal is to elucidate the complex mechanisms underlying how tauopathies, such as AD, initiate and progress, and to develop effective therapeutic approaches to treat tauopathies. It is reported that tau can be degraded by autophagy-lysosomal or ubiquitin-proteasomal systems. Tau degradation is closely associated with its various post-translational modifications, including phosphorylation, acetylation, and ubiquitination. Our preliminary studies indicate that tau is modified by linear ubiquitin chains in normal mouse brain tissues, which were substantially decreased in tauopathy mouse models. Linear ubiquitination of tau promotes tau clearance in an autophagy-dependent manner. We further found that oxidative stress can increase deubiquitinase OTULIN activity by promoting its phosphorylation, which both are substantially increased in the brain tissues from AD patients. Inhibition of OTULIN prevented the accumulation of pathological tau species and attenuated its cytotoxicity in a tauopathy mouse model. Therefore, we hypothesize that linear ubiquitination promotes tau degradation, which is inhibited by deubiquitinase OTULIN; oxidative stress activates OTULIN, resulting in increased tau aggregation and neurotoxicity. Pharmacological inhibition of OTULIN may mitigate tauopathy progression by enhancing the clearance of tau aggregates. Three specific aims are proposed to test this hypothesis. Aim1 will determine the role of linear ubiquitination in regulating tau accumulation and neuronal toxicity and investigate the autophagic-lysosomal mechanism. Aim2 will investigate oxidative stress-mediated mechanisms during OTULIN-induced tauopathies using a systems biology approach. Aim 3 will test a newly developed OTULIN inhibitor in promoting tau clearance and mitigating its cellular toxicity in tauopathy animal models. Our studies will have a strong impact by providing: 1) novel mechanisms regulating tau aggregation and proteotoxicity; 2) new mechanistic link between oxidative stress and tau linear ubiquitination; 3) potential therapeutic approaches for mitigating tauopathy and cognitive decline, eventually benefiting AD patients.