Department of Neurology, Washington University School of Medicine, St. Louis, MO, 63110, USA.
Hope Center for Neurological Disorders, Washington University, Campus Box 8111, 660 S. Euclid Avenue, St. Louis, MO, 63110, USA.
Mol Neurodegener. 2019 Oct 22;14(1):38. doi: 10.1186/s13024-019-0340-6.
The accumulation of pathological tau is the main component of neurofibrillary tangles and other tau aggregates in several neurodegenerative diseases, referred to as tauopathies. Recently, immunotherapeutic approaches targeting tau have been demonstrated to be beneficial in decreasing tauopathy in animal models. We previously found that passive immunotherapy with anti-tau antibody to human tau or expression of an anti-tau secreted single-chain variable fragment (scFv) in the central nervous system of a mouse model of tauopathy decreased but did not remove all tau-associated pathology. Although these and other studies demonstrate that conventional immunotherapeutic approaches targeting tau can influence tau pathogenesis, the majority of pathological tau remains in the cytosol of cells, not typically accessible to an extracellular antibody. Therefore, we reasoned targeting intracellular tau might be more efficacious in preventing or decreasing tauopathy.
By utilizing our anti-tau scFv, we generated anti-tau intrabodies for the expression in the cytosol of neurons. To enhance the degradation capacity of conventional intrabodies, we engineered chimeric anti-tau intrabodies fused to ubiquitin harboring distinct mutations that shuttle intracellular tau for either the proteasome or lysosomal mediated degradation. To evaluate the efficacy in delaying or eliminating tauopathy, we expressed our tau degrading intrabodies or controls in human tau transgenic mice by adeno-associated virus prior to overt tau pathology and after tau deposition.
Our results demonstrate, the expression of chimeric anti-tau intrabodies significantly reduce tau protein levels in primary neuronal cultures expression human tau relative to a non-modified anti-tau intrabody. We found the expression of engineered tau-degrading intrabodies destined for proteasomal-mediated degradation are more effective in delaying or eliminating tauopathy than a conventional intrabody in aged human tau transgenic mice.
This study, harnesses the strength of intrabodies that are amendable for targeting specific domains or modifications with the cell-intrinsic mechanisms that regulate protein degradation providing a new immunotherapeutic approach with potentially improved efficacy.
病理性 tau 的积累是几种神经退行性疾病中神经纤维缠结和其他 tau 聚集物的主要成分，这些疾病被称为 tau 病。最近，靶向 tau 的免疫治疗方法已被证明在减少动物模型中的 tau 病方面是有益的。我们之前发现，tau 病小鼠模型中被动免疫治疗用抗 tau 抗体或表达抗 tau 的分泌单链可变片段（scFv）可减少但不能去除所有与 tau 相关的病理学。尽管这些和其他研究表明，靶向 tau 的常规免疫治疗方法可以影响 tau 的发病机制，但大多数病理性 tau 仍存在于细胞的细胞质中，通常无法被细胞外抗体接触。因此，我们推断靶向细胞内 tau 可能更有效地预防或减少 tau 病。
我们利用我们的抗 tau scFv，在神经元的细胞质中表达了抗 tau 内抗体。为了增强常规内抗体的降解能力，我们设计了融合了具有不同突变的泛素的嵌合抗 tau 内抗体，这些突变可将细胞内 tau 穿梭到蛋白酶体或溶酶体介导的降解途径中。为了评估延迟或消除 tau 病的疗效，我们在明显的 tau 病发生前和 tau 沉积后，通过腺相关病毒在人 tau 转基因小鼠中表达我们的 tau 降解内抗体或对照物。
我们的结果表明，与非修饰的抗 tau 内抗体相比，在表达人 tau 的原代神经元培养物中，嵌合抗 tau 内抗体的表达显著降低 tau 蛋白水平。我们发现，与传统内抗体相比，靶向蛋白酶体介导降解的工程化 tau 降解内抗体的表达更有效地延迟或消除老年人类 tau 转基因小鼠中的 tau 病。
这项研究利用了内抗体的优势，它可以针对特定的结构域或修饰，并利用细胞内调节蛋白降解的机制，为免疫治疗提供了一种新的潜在更有效的方法。
