State Key Laboratory of Medical Neurobiology & Institutes of Brain Science, Shanghai Medical College, Fudan University, Shanghai, China.
Department of Neurology, Renji Hospital, School of Medicine, Shanghai Jiaotong University, Shanghai, China.
Exp Cell Res. 2018 Sep 1;370(1):103-115. doi: 10.1016/j.yexcr.2018.06.010. Epub 2018 Jun 13.
Tau pathology in Alzheimer's disease (AD) includes hyperphosphorylation and truncation of tau. Phosphorylation at S422 is found to suppress truncation of tau at D421 that leading to the generation of ΔTau. However, the interrelation between hyperphosphorylation and generation of ΔTau in AD remains elusive. In current study, staurosporine (Stau) induced ΔTau generation by caspases in SH-SY5Y cells with tau overexpression was found to be accompanied by a dramatic dephosphorylation at S422 and the epitope of the diagnostic antibody AT8 (S199 + S202 + T205), but a moderate dephosphorylation of PHF1 (S396 + S404) epitope. Therefore, to explore the effect of AT8 epitope on tau truncation, the residues in AT8 epitope were mutated to produce "pseudo-phosphorylated" (AT8E) or "pseudo-unphosphorylated" (AT8A) tau constructs. With Stau treatment, the generation of ΔTau from tau-AT8E was significantly attenuated comparing with that from tau-AT8A, which was S422-independent in that addition of S422A mutation still preserved this effect. Interestingly, this modulatory effect was able to be reversed by addition of PHF1E mutation. Moreover, treating the crude tau extracts with recombinant caspase-3 in vitro, also showed that ΔTau level was suppressed by AT8E, and potentiated by AT8E + PHF1E. The results primarily revealed the modulating effects of phosphorylation on ΔTau generation which may have potential implications in tau pathological processes and therapeutic intervention.
阿尔茨海默病（AD）中的 Tau 病理学包括 Tau 的过度磷酸化和截断。在 S422 处发现的磷酸化可抑制 Tau 在 D421 处的截断，从而导致 ΔTau 的产生。然而，AD 中 Tau 的过度磷酸化和 ΔTau 的产生之间的相互关系仍然难以捉摸。在当前的研究中，发现 staurosporine (Stau) 通过 caspase 在过度表达 Tau 的 SH-SY5Y 细胞中诱导 ΔTau 的产生，同时伴随着 S422 处和诊断抗体 AT8 的表位（S199+S202+T205）的显著去磷酸化，但 PHF1（S396+S404）表位的中度去磷酸化。因此，为了探讨 AT8 表位对 Tau 截断的影响，将 AT8 表位中的残基突变为产生“假磷酸化”（AT8E）或“假非磷酸化”（AT8A）Tau 构建体。用 Stau 处理后，与 Tau-AT8A 相比，Tau-AT8E 产生的 ΔTau 明显减少，这与 S422 无关，因为添加 S422A 突变仍保留了这种作用。有趣的是，这种调节作用可以通过添加 PHF1E 突变来逆转。此外，在体外用重组 caspase-3 处理粗 Tau 提取物也表明，ΔTau 水平被 AT8E 抑制，而 AT8E+PHF1E 增强。这些结果主要揭示了磷酸化对 Tau 生成的调节作用，这可能对 Tau 的病理过程和治疗干预具有潜在意义。
