Alzheimer’s disease: Ablating single master site abolishes tau hyperphosphorylation

Hyper-phosphorylation of the neuronal tau protein is a hallmark of neurodegenerative tauopathies like Alzheimer’s disease. A central unanswered question is why tau becomes progressively hyper-phosphorylated. Here, we show that tau phosphorylation is governed by interdependence - a mechanistic link between initial site-specific and subsequent multi-site phosphorylation. Systematic assessment of site interdependence identified distinct residues (Threonine-50, -69, -181) as master sites that determine propagation of phosphorylation at multiple epitopes. CRISPR point mutation and expression of human tau in Alzheimer’s mice showed that site interdependence governs physiologic and amyloid-associated multi-site phosphorylation and cognitive deficits, respectively. Combined targeting of master sites and p38α, the most central tau kinase linked to interdependence, synergistically ablated hyper-phosphorylation. In summary, our work delineates how complex tau phosphorylation arises to inform therapeutic and biomarker design for tauopathies.

Methods
Raw Immunoblot data for Figure 1. Chemiluninescence signals were imaged on a ChemiDoc MP (Biorad) digital system.

神经元tau蛋白的过度磷酸化是阿尔茨海默病等神经退行性tau蛋白病（tauopathies）的标志性病理特征。目前一个核心未解之谜是tau蛋白为何会逐步发生过度磷酸化。本研究证实，tau蛋白的磷酸化过程受位点相互依赖性调控——即初始位点特异性磷酸化与后续多位点磷酸化之间存在机制性关联。通过系统评估位点间的相互依赖性，我们鉴定出苏氨酸（Threonine）-50、-69、-181作为主控位点，决定了多个表位处磷酸化信号的传播过程。在阿尔茨海默病小鼠模型中开展CRISPR点突变实验以及人源tau蛋白过表达实验表明，位点相互依赖性分别调控生理状态下与淀粉样蛋白相关的多位点磷酸化进程，以及认知功能缺陷表型。联合靶向主控位点以及与该相互依赖性关联最为紧密的核心tau激酶p38α，可协同消除tau蛋白的过度磷酸化现象。综上，本研究阐明了复杂tau蛋白磷酸化的产生机制，可为tau蛋白病的治疗策略开发与生物标志物（biomarker）设计提供理论指导。

方法
图1的原始免疫印迹（Immunoblot）数据。化学发光信号通过ChemiDoc MP（Bio-Rad）数字成像系统完成成像采集。