Stages and conformations of the Tau repeat domain during aggregation and its effect on neuronal toxicity.
Stages and conformations of the Tau repeat domain during aggregation and its effect on neuronal toxicity.
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DOI：
10.1074/jbc.m114.554725
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发表时间：
2014-07-18
期刊：
影响因子：
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通讯作者：
Mandelkow E
中科院分区：
文献类型：
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作者：
Kumar S;Tepper K;Kaniyappan S;Biernat J;Wegmann S;Mandelkow EM;Müller DJ;Mandelkow E
背景：Tau寡聚体被认为在阿尔茨海默病中起关键作用。结果：Tau重复结构域的寡聚体不引起总神经元毒性，但降低棘密度。结论：来自细胞外Tau寡聚体的突触毒性是局部的，没有活力的总体丧失。重要性：细胞外Tau寡聚体不太可能解释Tau介导的神经变性，但可能通过脊柱减少引起功能障碍。一些神经退行性疾病的特征在于Tau蛋白的聚集和翻译后修饰。其“重复结构域”（TauRD）主要负责聚集性质，并且寡聚体形式被认为主导Tau的毒性作用。在这里，我们使用几种互补的成像和光谱方法研究了该结构域在β倾向和假磷酸化的不同状态下寡聚和聚集过程中的构象转变。尽管重复结构域通常比全长Tau更容易聚集，但其聚集通过KXGS基序处的磷酸化或假磷酸化而大大减慢，伴随着延长的寡聚化阶段。用TauRD的前聚集体变体观察到类似的效果。寡聚体在前聚集体突变体TauRDΔK280的情况下变得最明显，如通过原子力显微镜监测的，以及Alexa标记的Tau的荧光寿命（时间相关单光子计数（TCSPC）），与其在小鼠模型中的显著毒性一致。在细胞模型或原代神经元中，TauRD或TauRDΔK280的寡聚体或原纤维均不具有毒性作用，如分别用乳酸脱氢酶和3-（4，5-二甲基噻唑-2-基）-2，5-二苯基四唑溴化物进行的测定所示。然而，前聚集体TauRDΔK280的寡聚体特异性地引起分化的神经元中的棘密度的损失，表明局部限制的功能损害。
Background: Tau oligomers are thought to play key roles in Alzheimer disease. Results: Oligomers of the Tau repeat domain do not cause gross neuronal toxicity but decrease spine density. Conclusion: Synaptic toxicity from extracellular Tau oligomers is local, without general loss of viability. Significance: Extracellular Tau oligomers are not likely to explain Tau-mediated neurodegeneration but may cause functional impairment by spine reduction. Several neurodegenerative diseases are characterized by the aggregation and posttranslational modifications of Tau protein. Its “repeat domain” (TauRD) is mainly responsible for the aggregation properties, and oligomeric forms are thought to dominate the toxic effects of Tau. Here we investigated the conformational transitions of this domain during oligomerization and aggregation in different states of β-propensity and pseudo-phosphorylation, using several complementary imaging and spectroscopic methods. Although the repeat domain generally aggregates more readily than full-length Tau, its aggregation was greatly slowed down by phosphorylation or pseudo-phosphorylation at the KXGS motifs, concomitant with an extended phase of oligomerization. Analogous effects were observed with pro-aggregant variants of TauRD. Oligomers became most evident in the case of the pro-aggregant mutant TauRDΔK280, as monitored by atomic force microscopy, and the fluorescence lifetime of Alexa-labeled Tau (time-correlated single photon counting (TCSPC)), consistent with its pronounced toxicity in mouse models. In cell models or primary neurons, neither oligomers nor fibrils of TauRD or TauRDΔK280 had a toxic effect, as seen by assays with lactate dehydrogenase and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, respectively. However, oligomers of pro-aggregant TauRDΔK280 specifically caused a loss of spine density in differentiated neurons, indicating a locally restricted impairment of function.