Institute of Reconstructive Neurobiology, University of Bonn and Hertie Foundation, Bonn, Germany.
Am J Pathol. 2013 May;182(5):1769-79. doi: 10.1016/j.ajpath.2013.01.043. Epub 2013 Mar 13.
Alterations in the microtubule (MT)-associated protein, tau, have emerged as a pivotal phenomenon in several neurodegenerative disorders, including frontotemporal dementia and Alzheimer's disease. Although compelling lines of evidence from various experimental models suggest that hyperphosphorylation and conformational changes of tau can cause its aggregation into filaments, the actual tau species and effective mechanisms that conspire to trigger the degeneration of human neurons remain obscure. Herein, we explored whether human embryonic stem cell-derived neural stem cells can be exploited to study consequences of an overexpression of 2N4R tau (two normal N-terminal and four MT-binding domains; n-tau) versus pseudohyperphosphorylated tau (p-tau) directly in human neurons. Given the involvement of tau in MT integrity and cellular homeostasis, we focused on the effects of both tau variants on subcellular transport and neuronal survival. By using inducible lentiviral overexpression, we show that p-tau, but not n-tau, readily leads to an MC-1-positive protein conformation and impaired mitochondrial transport. Although these alterations do not induce cell death under standard culture conditions, p-tau-expressing neurons cultured under non-redox-protected conditions undergo degeneration with formation of axonal varicosities sequestering transported proteins and progressive neuronal cell death. Our data support a causative link between the phosphorylation and conformational state of tau, microtubuli-based transport, and the vulnerability of human neurons to oxidative stress. They further depict human embryonic stem cell-derived neurons as a useful experimental model for studying tau-associated cellular alterations in an authentic human system.
微管（MT）相关蛋白 tau 的改变已成为几种神经退行性疾病的关键现象，包括额颞叶痴呆和阿尔茨海默病。尽管来自各种实验模型的令人信服的证据表明 tau 的过度磷酸化和构象变化会导致其聚集为纤维，但实际的 tau 物种和协同触发人类神经元退化的有效机制仍然不清楚。在这里，我们探讨了人类胚胎干细胞衍生的神经干细胞是否可以用于研究过表达 2N4R tau（两个正常 N 端和四个 MT 结合域；n-tau）与假磷酸化 tau（p-tau）对人类神经元的直接影响。鉴于 tau 参与 MT 完整性和细胞内稳态，我们专注于两种 tau 变体对亚细胞运输和神经元存活的影响。通过使用诱导型慢病毒过表达，我们表明 p-tau，但不是 n-tau，容易导致 MC-1 阳性蛋白构象和线粒体运输受损。尽管在标准培养条件下这些改变不会诱导细胞死亡，但在非氧化还原保护条件下培养的表达 p-tau 的神经元会发生退化，形成轴突膨体，隔离运输蛋白并导致进行性神经元细胞死亡。我们的数据支持 tau 的磷酸化和构象状态、基于微管的运输以及人类神经元对氧化应激易感性之间的因果关系。它们进一步将人类胚胎干细胞衍生的神经元描绘为研究在真实人类系统中与 tau 相关的细胞改变的有用实验模型。
