Data_Sheet_1_Phosphorylation and Dephosphorylation of Tau Protein During Synthetic Torpor.pdf

Tau protein is of primary importance for many physiological processes in neurons, where it affects the dynamics of the microtubule system. When hyperphosphorylated (PP-Tau), Tau monomers detach from microtubules and tend to aggregate firstly in oligomers, and then in neurofibrillary tangles, as it occurs in a group of neurodegenerative disorders named thauopathies. A hypothermia-related accumulation of PP-Tau, which is quickly reversed after the return to normothermia, has been shown to occur in the brain of hibernators during torpor. Since, recently, in our lab, a hypothermic torpor-like condition (synthetic torpor, ST) was pharmacologically induced in the rat, a non-hibernator, the aim of the present work was to assess whether ST can lead to a reversible PP-Tau accumulation in the rat brain. PP-Tau was immunohistochemically assessed by staining for AT8 (phosphorylated Tau) and Tau-1 (non-phosphorylated Tau) in 19 brain structures, which were chosen mostly due to their involvement in the regulation of autonomic and cognitive functions in relation to behavioral states. During ST, AT8 staining was strongly expressed throughout the brain, while Tau-1 staining was reduced compared to control conditions. During the following recovery period, AT8 staining progressively reduced close to zero after 6 h from ST. However, Tau-1 staining remained low even after 38 h from ST. Thus, overall, these results show that ST induced an accumulation of PP-Tau that was, apparently, only partially reversed to normal during the recovery period. While the accumulation of PP-Tau may only depend on the physicochemical characteristics of the enzymes regulating Tau phosphorylation, the reverse process of dephosphorylation should be actively regulated, also in non-hibernators. In conclusion, in this work a reversible and widespread PP-Tau accumulation has been induced through a procedure that leads a non-hibernator to a degree of reversible hypothermia, which is comparable to that observed in hibernators. Therefore, the physiological mechanism involved in this process can sustain an adaptive neuronal response to extreme conditions, which may however lead to neurodegeneration when particular intensities and durations are exceeded.

Tau蛋白（Tau protein）是神经元内多项生理过程的核心调控因子，可直接影响微管系统的动态稳定性。当Tau蛋白发生过度磷酸化修饰后（PP-Tau），其单体将从微管上解离，并首先聚集成寡聚体，随后形成神经原纤维缠结，这一病理过程可见于一类被称为tau蛋白病（thauopathies）的神经退行性疾病。研究表明，在冬眠动物的蛰伏期脑内，会出现与低体温相关的PP-Tau积累，且该现象可在恢复常温后快速逆转。鉴于本研究团队近期在非冬眠动物大鼠体内通过药理学手段构建了低体温蛰伏样状态（合成蛰伏，ST），本研究旨在探究ST是否可诱导大鼠脑内出现可逆性PP-Tau积累。本研究通过免疫组化染色，针对19个脑区的AT8（磷酸化Tau）与Tau-1（非磷酸化Tau）标志物进行PP-Tau水平检测；所选脑区均与行为状态相关的自主神经调控及认知功能调控密切相关。在合成蛰伏期，全脑范围内AT8染色信号显著增强，而Tau-1染色信号则较对照组显著降低。在后续的恢复阶段中，AT8染色信号在合成蛰伏结束后6小时逐步降低至接近基线水平，但即便在合成蛰伏结束后38小时，Tau-1染色信号仍维持在较低水平。综上，本研究结果表明，合成蛰伏可诱导PP-Tau积累，且该积累在恢复阶段仅能部分逆转至正常水平。尽管PP-Tau的积累可能仅取决于调控Tau磷酸化的酶的理化特性，但在非冬眠动物体内，其去磷酸化逆转过程同样需要受到主动调控。综合来看，本研究通过构建可诱导非冬眠动物达到与冬眠动物相当程度的可逆性低体温的实验方案，成功诱导出了广泛性、可逆性的PP-Tau积累。由此可见，该过程所涉及的生理机制可支持神经元对极端环境产生适应性应答，但当刺激强度与持续时间超出阈值时，该过程可能诱发神经退行性病变。