PDF(Pubmed)
Abstract：
Abnormal accumulation of misfolded and hyperphosphorylated tau protein in brain is the defining feature of several neurodegenerative diseases called tauopathies, including Alzheimer\'s disease (AD). In AD, this pathological change is reflected by highly specific cerebrospinal fluid (CSF) tau biomarkers, including both phosphorylated and non-phosphorylated variants. Interestingly, despite tau pathology being at the core of all tauopathies, CSF tau biomarkers remain unchanged in certain tauopathies, e.g., progressive supranuclear palsy (PSP), Pick\'s disease (PiD), and corticobasal neurodegeneration (CBD). To better understand commonalities and differences between tauopathies, we report a multiplex assay combining immunoprecipitation and high-resolution mass spectrometry capable of detecting and quantifying peptides from different tau protein isoforms as well as non-phosphorylated and phosphorylated peptides, including those carrying multiple phosphorylations. We investigated the tau proteoforms in soluble and insoluble fractions of brain tissue from subjects with autopsy-confirmed tauopathies, including sporadic AD (n = 10), PSP (n = 11), PiD (n = 10), and CBD (n = 10), and controls (n = 10). Our results demonstrate that non-phosphorylated tau profiles differ across tauopathies, generally showing high abundance of microtubule-binding region (MTBR)-containing peptides in insoluble protein fractions compared with controls; the AD group showed 12-72 times higher levels of MTBR-containing aggregates. Quantification of tau isoforms showed the 3R being more abundant in PiD and the 4R isoform being more abundant in CBD and PSP in the insoluble fraction. Twenty-three different phosphorylated peptides were quantified. Most phosphorylated peptides were measurable in all investigated tauopathies. All phosphorylated peptides were significantly increased in AD insoluble fraction. However, doubly and triply phosphorylated peptides were significantly increased in AD even in the soluble fraction. Results were replicated using a validation cohort comprising AD (n = 10), CBD (n = 10), and controls (n = 10). Our study demonstrates that abnormal levels of phosphorylation and aggregation do indeed occur in non-AD tauopathies, however, both appear pronouncedly increased in AD, becoming a distinctive characteristic of AD pathology.
摘要：
大脑中错误折叠和过度磷酸化的tau蛋白的异常积累是几种神经退行性疾病的定义特征，称为tau蛋白病，包括阿尔茨海默病（AD）。在AD中,这种病理变化反映了高度特异性的脑脊液（CSF）tau生物标志物，包括磷酸化和非磷酸化变体。有趣的是,尽管tau病理学是所有tau蛋白病的核心，CSFtau生物标志物在某些tau蛋白病变中保持不变，例如，进行性核上性麻痹（PSP），皮克病（PiD），和皮质基底神经变性（CBD）。为了更好地理解tau蛋白病之间的共性和差异，我们报告了一种结合免疫沉淀和高分辨率质谱的多重测定，能够检测和定量来自不同tau蛋白亚型的肽以及非磷酸化和磷酸化肽，包括那些携带多重磷酸化的。我们研究了尸检证实为tau蛋白病的受试者的脑组织可溶性和不溶性部分中的tau蛋白形式，包括零星的AD（n=10），PSP（n=11），PiD（n=10），和CBD（n=10），和控制（n=10）。我们的结果表明，非磷酸化tau谱在tau蛋白病变中有所不同，与对照组相比，通常在不溶性蛋白质部分中显示出高丰度的含微管结合区（MTBR）的肽；AD组显示出12-72倍的含MTBR的聚集体水平。tau同种型的定量显示3R在PiD中更丰富,并且4R同种型在不溶性部分中的CBD和PSP中更丰富。对23种不同的磷酸化肽进行定量。大多数磷酸化肽在所有研究的tau蛋白病中均可测量。所有磷酸化肽在AD不溶部分中显著增加。然而,即使在可溶性部分中，AD中的双重和三重磷酸化肽也显着增加。使用包含AD（n=10）的验证队列复制结果，CBD（n=10），和控制（n=10）。我们的研究表明，磷酸化和聚集的异常水平确实发生在非ADtau蛋白病变中，然而,两者都在AD中明显增加，成为AD病理学的一个显著特征。
