Phosphorylation of the neuronal microtubule-associated Tau protein plays a critical role in the aggregation process leading to the formation of insoluble intraneuronal fibrils within Alzheimer’s disease (AD) brains. In recent years, other post-translational modifications (PTMs) have been highlighted in the regulation of Tau (dys)functions. Among these PTMs, the O-β-linked N-acetylglucosaminylation (O-GlcNAcylation) modulates Tau phosphorylation and aggregation. We here focus on the role of the PHF-1 phospho-epitope of Tau C-terminal domain that is hyperphosphorylated in AD (at pS396/pS404) and encompasses S400 as the major O-GlcNAc site of Tau while two additional O-GlcNAc sites were found in the extreme C-terminus at S412 and S413. Using high resolution NMR spectroscopy, we showed that the O-GlcNAc glycosylation reduces phosphorylation of PHF-1 epitope by GSK3β alone or after priming by CDK2/cyclin A. Furthermore, investigations of the impact of PTMs on local conformation performed in small peptides highlight the role of S404 phosphorylation in inducing helical propensity in the region downstream pS404 that is exacerbated by other phosphorylations of PHF-1 epitope at S396 and S400, or O-GlcNAcylation of S400. Finally, the role of phosphorylation and O-GlcNAcylation of PHF-1 epitope was probed in in-vitro fibrillization assays in which O-GlcNAcylation slows down the rate of fibrillar assembly while GSK3β phosphorylation stimulates aggregation counteracting the effect of glycosylation.

中文翻译：

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Tau蛋白PHF-1表位的磷酸化和O-GlcNAcylation诱导C端的局部构象变化并调节Tau自组装成纤维状聚集体

神经元微管相关Tau蛋白的磷酸化在聚集过程中起关键作用，聚集过程导致阿尔茨海默氏病（AD）脑内形成不溶性神经内神经原纤维。近年来，其他翻译后修饰（PTM）在Tau（功能障碍）功能的调节中得到了强调。在这些PTM中，O-β联结的N-乙酰基葡萄糖酰胺化（O-GlcNAcylation）调节Tau磷酸化和聚集。我们在此集中讨论Tau C末端结构域的PHF-1磷酸表位在AD中的高磷酸化作用（在pS396 / pS404），包括S400作为Tau的主要O-GlcNAc位点，而另外两个O-GlcNAc位点在S412和S413的极端C端被发现。使用高分辨率NMR光谱，我们表明O-GlcNAc糖基化可单独或通过CDK2 / cyclin A引发后通过GSK3β降低PHF-1表位的磷酸化。此外，对PTM对小肽中局部构象影响的研究强调了S404磷酸化在诱导中的作用在S396和S400处PHF-1表位的其他磷酸化或S400的O-GlcNA酰化加剧了pS404下游区域的螺旋倾向。最后，在体外原纤维化测定中探索了PHF-1表位的磷酸化和O-GlcNAcy的作用，其中O-GlcNAcylation减慢了原纤维组装的速度，而GSK3β磷酸化刺激了聚集，抵消了糖基化的作用。对PTM对小肽的局部构象的影响的研究表明，S404磷酸化在诱导pS404下游区域螺旋倾向中的作用，这一点在S396和S400处的PHF-1表位的其他磷酸化或S400的O-GlcNAcylation加剧了。最后，在体外原纤维化测定中探索了PHF-1表位的磷酸化和O-GlcNAcy的作用，其中O-GlcNAcylation减慢了原纤维组装的速度，而GSK3β磷酸化刺激了聚集，抵消了糖基化的作用。对PTM对小肽的局部构象的影响的研究表明，S404磷酸化在诱导pS404下游区域螺旋倾向中的作用，这一点在S396和S400处的PHF-1表位的其他磷酸化或S400的O-GlcNAcylation加剧了。最后，在体外原纤维化测定中探索了PHF-1表位的磷酸化和O-GlcNAcy的作用，其中O-GlcNAcylation减慢了原纤维组装的速度，而GSK3β磷酸化刺激了聚集，抵消了糖基化的作用。