Mechanism of the nerve cell death accompanied with tau protein phosphorylation in tauopathy

神经元缠结（NFT）是阿尔茨海默病（AD）的神经病理学标志，并且异常过度磷酸化的tau蛋白是主要的。NFT的蛋白质组分。过度磷酸化tau蛋白的积累也在其他神经退行性疾病中观察到，包括亚急性硬化性全脑炎（SSPE），并且SSPE是由麻疹RNA病毒感染引起的。多聚肌苷酸-多聚胞苷酸（Poly（I ; C）），人工合成的双链RNA（dsRNA），常被用于制作病毒感染的细胞模型。我们之前报道过，细胞中的tau蛋白磷酸化是由双链RNA通过TLR 3激活来诱导的。在这项研究中，研究了双链RNA对tau的微管聚合和tau的自聚合的影响，因为tau是一种带负电荷的蛋白质，具有与包括肝素在内的古葡糖胺聚糖相似的特征。在结合试验中，聚（I ; C）与 * 组合GST-Staufen Δ tub结合，所述组合GST-Staufen Δ tub是缺乏微管蛋白结合结构域的典型dsRNA结合蛋白或tau蛋白，但不与肌动蛋白或微管蛋白结合。接着，在存在和不存在0.2mg/ml的Poly（I ; C）的情况下检查微管的聚合，并且发现证实了在Poly（I ; C）的存在下微管的聚合显著降低。当tau（1.6mg/ml）和聚（LC）（0.8 mg/ml）混合并在37℃下孵育48小时，电子显微镜研究显示，（直径20- 30 nm）这表明，神经元细胞外的dsRNA通过TLR激活诱导tau蛋白磷酸化，神经元细胞内的dsRNA干扰微管聚合并促进tau蛋白丝的形成。蛋白质.聚肌苷酸-聚胞苷酸（pI-pC），合成的

Neurofibrillary tangles (NFTs) are neuropathological hallmarks of Alzheimer disease (AD) and abnormally hyperphosphorylated tau is the major. protein component of NFTs. Accumulation of hyperphosphorylated tau protein is also observed in other neurodegenerative diseases including subacute sclerosing panencephaltis (SSPE), and SSPE is caused by infection with measles RNA virus. Polyinosinic-polycytidylic acid (Poly(I ; C)), synthetic double stranded RNA (dsRNA), has been often used to make virus-infected cell models. We previously reported that tau protein phosphorylation in cells, was induced by dsRNA through TLR3 activation.In this study effects of dsRNA was examined on microtubule-polymerization by tau and self-polymerization of tau, because tau is a negative-charged protein that has a similar character as gulucosaminoglycans including heparin. In binding assay poly(I ; C) was bound with *combinant GST-Staufen Δ tub which was a typical dsRNA binding protein lacking tubulin-binding domain, or tau protein, but not with actin or tubulin. Next, the polymerization of the microtubule was examined in the presence and absence of 0.2mg/ml of Poly(I ; C), and it was found that confirmed that the polymerization of the microtubule decreased remarkably in the presence of Poly(I ; C). When tau (1.6mg/mi) and Poly(LC) (0.8mg/ml) were mixed and incubated for 48 hours at 37℃, the electron microscopic study showed there were straight fibers (20-3Onm diameter).It was suggested that dsRNA outside of neuronal cells induced tau protein phosphorylation through TLR activation and that dsRNA inside of neuronal cells disturbed the microtubule polymerization and promoted filament formations of tau protein.Polyinosinic-polycytidylic acid (pI-pC), synthetic