中文摘要：

目的 探讨凝聚态β淀粉样蛋白25-35片段（Aβ25-35）对胎鼠皮质神经元中性钙蛋白酶-细胞周期依赖性蛋白激酶5（calpain—CDK5）通路的影响及其对tau蛋白的过度磷酸化和骨架稳定性的影响。方法 用荧光酶标仪测定荧光强度来反映calpain活性；用Western—blot和（或）免疫细胞化学检测CDK5的激活蛋白p25／p35的蛋白水平和tau蛋白Thr205／Set404位点磷酸化情况来体现CDK5活性；用电镜技术观察微管结构的变化来显示细胞骨架的改变情况。结果 20μmol／L的凝聚态Aβ25-35作用于皮质神经元12h后，检测反映calpain活性的荧光强度（每微克蛋白荧光强度）高达680．25±37．77，与空白对照组167．25±11．67相比，差异有统计学意义（P〈0．05）；对CDK5有活化作用的p25蛋白水平比空白对照组升高（2．07±0．20）倍，差异也有统计学意义（P〈0．05）；CDK5的作用底物tau蛋白Thr205和Set404位点磷酸化程度也显著增加，分别比空白对照组升高（1．80±0．27）和（1．83±0．14）倍，差异均有统计学意义（P〈0．05）；同时出现神经元微管骨架排列紊乱。结论 凝聚态Aβ25-35通过活化皮质神经元的calpain，使pa5降解p25来激活CDK5，促使tau蛋白过度磷酸化，破坏了微管骨架的稳定性。

英文摘要：

Objective To explore the effect of β-amyloid peptide 25-35 （Aβ25-35）on Calpain/ CDK5-signaling pathway, protein tau hyperphosphorylation and the stability of cyteskeleton in cortical neurons. Methods The fluorescence intensity reflecting the activity of calpain was detected by fluorometer; Western-blot and/or immuno- cytochemical staining was used to detect the level of protein p35/p2.5 and tau phosphorylation at the sites of Thr205 and Set404, which correlated with the activity of CDK5 ; electron microscopy was used to detect cytoskeleton morphology in cortical neurons. Results After exposure to 20 μmol/L of Aβ25-35 for 12 h, the fluorescence intensity reflecting the activity of calpain was higher than that of the controls （ 680.25 ±37.77 vs 167.25 ± 11.67） and there was a significant difference between groups （P 〈 0. 05） ; the level of p2.5, which was proteolyzed from p35, was increased （2. 07 ± 0. 20 fold, P 〈 0. 05）. Meanwhile, the level of tau phosphorylation in the site of Thr205 and Set404 was elevating （1.80±0.27 and 1.83 ±0.14 fold; P 〈 0.05 in each case） and the cytoskeleton was disrupted. Conclusion Aβ25-35 increases the activity of calpain, activates CDK5 by enhancing the level of p2.5 proteolyzed from p35, induces tau hyperphosphorylation and impairs the stability of cytoskeleton in cortical neurons.