Neuronal activity can enhance tau release and thus accelerate tauopathies. This activity-dependent tau release can be used to study the progression of tau pathology in Alzheimer's disease (AD), as hyperphosphorylated tau is implicated in AD pathogenesis and related tauopathies. However, our understanding of the mechanisms that regulate activity-dependent tau release from neurons and the role that tau phosphorylation plays in modulating activity-dependent tau release is still rudimentary. In this study, Drosophila neurons in primary culture expressing human tau (hTau) were used to study activity-dependent tau release. We found that hTau release was markedly increased by 50 mM KCl treatment for 1 h. A similar level of release was observed using optogenetic techniques, where genetically targeted neurons were stimulated for 30 min using blue light (470 nm). Our results showed that activity-dependent release of phosphoresistant hTauS11A was reduced when compared with wildtype hTau. In contrast, release of phosphomimetic hTauE14 was increased upon activation. We found that released hTau was phosphorylated in its proline-rich and C-terminal domains using phosphorylation site-specific tau antibodies (e.g., AT8). Fold changes in detectable levels of total or phosphorylated hTau in cell lysates or following immunopurification from conditioned media were consistent with preferential release of phosphorylated hTau after light stimulation. This study establishes an excellent model to investigate the mechanism of activity-dependent hTau release and to better understand the role of phosphorylated tau release in the pathogenesis of AD since it relates to alterations in the early stage of neurodegeneration associated with increased neuronal activity.

中文翻译：

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原代培养物中果蝇神经元磷酸化人 tau 蛋白的活性依赖性释放。

神经元活动可以增强 tau 蛋白的释放，从而加速 tau 蛋白病。这种活性依赖性 tau 释放可用于研究阿尔茨海默病 (AD) 中 tau 病理学的进展，因为过度磷酸化的 tau 与 AD 发病机制和相关 tau 病有关。然而，我们对调节神经元活动依赖性 tau 释放的机制以及 tau 磷酸化在调节活动依赖性 tau 释放中所起的作用的理解仍然很初级。在这项研究中，原代培养物中表达人 tau (hTau) 的果蝇神经元被用来研究活性依赖性 tau 释放。我们发现 50 mM KCl 处理 1 小时后 hTau 释放显着增加。使用光遗传学技术观察到类似水平的释放，其中使用蓝光（470 nm）刺激基因靶向神经元 30 分钟。我们的结果表明，与野生型 hTau 相比，抗磷酸化 hTauS11A 的活性依赖性释放减少。相反，磷酸模拟物 hTauE14 的释放在激活后增加。我们发现使用磷酸化位点特异性 tau 抗体（例如 AT8），释放的 hTau 在其富含脯氨酸和 C 末端的结构域中被磷酸化。细胞裂解物中或条件培养基免疫纯化后总或磷酸化 hTau 的可检测水平的倍数变化与光刺激后磷酸化 hTau 的优先释放一致。这项研究建立了一个很好的模型来研究活性依赖性 hTau 释放的机制，并更好地了解磷酸化 tau 释放在 AD 发病机制中的作用，因为它与神经元活动增加相关的神经变性早期阶段的改变有关。