BACKGROUND Intracellular accumulation of tau as neurofibrillary tangles (NFTs) is the hallmark of Alzheimer's disease (AD) as well as in other tauopathies. Tau is present not only in the cytoplasm but also in the extracellular space such as cerebrospinal fluid (CSF) and brain interstitial fluid (ISF). Although clearance is one critical parameter leading to such intracellular/extracellular tau accumulation, in vivo turnover of tau has not been well characterized. The current study has attempted to precisely determine in vivo turnover rates of tau utilizing tet-off regulatable mice. In particular, we assessed intracellular tau and extracellular tau, soluble tau, insoluble tau and phosphorylated tau at certain sites utilizing a combination of in vivo microdialysis, biochemical analysis and specific ELISAs recognizing each species. To examine the effect of a tauopathy-associated mutation on tau clearance, half-lives of various tau species were compared between the mice with a FTDP-17 mutation that induces β-sheet formation, ΔK280 mutation (pro-aggregant mice) and control mice with additional β-sheet breaking mutations (anti-aggregant mice). RESULTS Here we report that tau is metabolized at much slower turnover rates in vivo than in cell culture. We found that insoluble tau in pro-aggregant mice had a significantly slower half-life (t1/2 = ~34.2 days) than soluble tau (t1/2 = ~9.7 days). In contrast, soluble tau phosphorylated in the proline rich region was cleared faster than total soluble tau. When comparing pro-aggregant mice to anti-agregant mice, turnover rates of soluble tau species were not significantly different. CONCLUSIONS The current study provides a comprehensive description of in vivo turnover of various tau species present in mice that express human tau. The turnover rate of soluble tau was not significantly altered between pro-aggregant mice and anti-aggregant mice. This suggests that altered conformation by ΔK280 does not have a major impact on clearance pathways for soluble tau. In contrast, different tau species displayed different half-lives. Turnover was significantly delayed for insoluble tau whereas it was accelerated for soluble tau phosphorylated in the proline rich region. These differences in susceptibilities to clearance suggest that aggregation and phosphorylation influences tau clearance which may be important in tau pathogenesis.

中文翻译：

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在tauopathy小鼠模型中tau的体内转换分析。

背景技术作为神经原纤维缠结（NFT）的tau在细胞内的积累是阿尔茨海默氏病（AD）以及其他疾病的标志。Tau不仅存在于细胞质中，而且还存在于诸如脑脊髓液（CSF）和脑间质液（ISF）等细胞外空间中。尽管清除率是导致这种细胞内/细胞外tau积累的一个关键参数，但尚未充分表征tau的体内转换。当前的研究试图利用可调节tet-off的小鼠精确地确定tau的体内周转率。特别是，我们利用体内微透析，生化分析和识别每种物种的特异性ELISA的组合评估了某些部位的细胞内tau和细胞外tau，可溶性tau，不溶性tau和磷酸化tau。为了检查与tauopathy相关的突变对tau清除的影响，比较了具有FTDP-17突变并诱导β-折叠形成的小鼠，ΔK280突变的小鼠（促聚集小鼠）和对照小鼠的各种tau物种的半衰期。具有其他β-折叠破坏突变（抗聚集小鼠）。结果在这里我们报告说，tau在体内的代谢率比细胞培养中的代谢率低得多。我们发现，在促聚集小鼠中不溶性tau的半衰期（t1 / 2 =〜34.2天）比可溶性tau（t1 / 2 =〜9.7天）明显慢。相反，在富含脯氨酸的区域磷酸化的可溶性tau的清除速度比总可溶性tau的清除速度快。当比较促聚集小鼠和抗聚集小鼠时，可溶性tau物种的周转率没有显着差异。结论本研究对表达人tau的小鼠中存在的各种tau物种的体内更新提供了全面的描述。促聚集小鼠和抗聚集小鼠之间可溶性tau的周转率没有显着改变。这表明ΔK280改变的构象对可溶性tau的清除途径没有重大影响。相反，不同的tau物种显示出不同的半衰期。对于不溶性tau，营业额显着延迟，而对于富含脯氨酸的磷酸化的可溶性tau，营业额则明显加速。清除敏感性的这些差异表明聚集和磷酸化影响tau清除，这可能在tau发病机理中很重要。促聚集小鼠和抗聚集小鼠之间可溶性tau的周转率没有显着改变。这表明ΔK280改变的构象对可溶性tau的清除途径没有重大影响。相反，不同的tau物种显示出不同的半衰期。对于不溶性tau，营业额显着延迟，而对于富含脯氨酸的磷酸化的可溶性tau，营业额则明显加速。清除敏感性的这些差异表明聚集和磷酸化会影响tau清除，这可能在tau发病机理中很重要。促聚集小鼠和抗聚集小鼠之间可溶性tau的周转率没有显着改变。这表明ΔK280改变的构象对可溶性tau的清除途径没有重大影响。相反，不同的tau物种显示出不同的半衰期。对于不溶性tau，营业额显着延迟，而对于富含脯氨酸的磷酸化的可溶性tau，营业额则明显加速。清除敏感性的这些差异表明聚集和磷酸化影响tau清除，这可能在tau发病机理中很重要。不同的tau物种显示出不同的半衰期。对于不溶性tau，营业额显着延迟，而对于富含脯氨酸的磷酸化的可溶性tau，营业额则明显加速。清除敏感性的这些差异表明聚集和磷酸化影响tau清除，这可能在tau发病机理中很重要。不同的tau物种显示出不同的半衰期。对于不溶性tau，营业额显着延迟，而对于富含脯氨酸的磷酸化的可溶性tau，营业额则明显加速。清除敏感性的这些差异表明聚集和磷酸化影响tau清除，这可能在tau发病机理中很重要。