Tauopathies are neurodegenerative disorders characterized by Tau aggregation. Genetic studies on familial cases allowed for the discovery of mutations in the MAPT gene that increase Tau propensity to detach from microtubules and to form insoluble cytoplasmic Tau aggregates. Recently, the rare mutation Q336H has been identified to be associated with Pick’s disease (PiD) and biochemical analyses demonstrated its ability to increase the microtubules (MTs) polymerization, thus revealing an opposite character compared to other Tau mutations studied so far. Here we investigated the biophysical and molecular properties of Tau^Q336H in living cells by the employment of the conformational Tau biosensor CST. We found that this mutation alters Tau conformation on microtubules, stabilizes its binding to tubulin, and is associated with a paradoxical lower level of Tau phosphorylation. Moreover, we found that this mutation impacts the cytoskeletal complexity by increasing the tubulin filament length and the number of branches. However, despite these apparently non-pathological traits, we observed the formation of intracellular inclusions confirming that Q336H leads to aggregation. Our results suggest that the Tau aggregation process might be triggered by molecular mechanisms other than Tau destabilization or post-translational modifications which are likely to be detrimental to neuronal function in vivo.

颅骨病是以Tau聚集为特征的神经退行性疾病。对家族病例的遗传研究允许发现MAPT基因中的突变，这些突变会增加Tau从微管分离的趋势，并形成不溶性胞质Tau聚集体。最近，已鉴定出罕见的Q336H突变与皮克氏病（PiD）相关，生化分析表明其具有增加微管（MTs）聚合的能力，因此与迄今研究的其他Tau突变相比，具有相反的特征。在这里，我们研究了Tau ^Q336H的生物物理和分子特性通过使用构象Tau生物传感器CST在活细胞中表达。我们发现该突变改变了微管上的Tau构象，稳定了其与微管蛋白的结合，并与Tau磷酸化的反常较低水平相关。此外，我们发现该突变通过增加微管蛋白丝的长度和分支数来影响细胞骨架的复杂性。然而，尽管有这些明显的非病理学特征，我们仍观察到细胞内包裹物的形成，这证实了Q336H导致聚集。我们的结果表明，Tau聚集过程可能是由Tau不稳定或翻译后修饰以外的分子机制触发的，这些分子机制可能对神经元功能有害体内。