Liu Wei, Zhao Jingya, Lu Guangxiu
Department of Neurology, Huaihe Hospital of Henan University, Kaifeng 475000, China.
Department of Neurology, Huaihe Hospital of Henan University, Kaifeng 475000, China.
Biochem Biophys Res Commun. 2016 Sep 16;478(2):852-7. doi: 10.1016/j.bbrc.2016.08.037. Epub 2016 Aug 9.
Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by β-amyloid deposits and neurofibrillary tangles consisting of hyperphosphorylated tau protein. Increasing evidence has revealed that microRNAs (miRNAs) are implicated in the pathogenesis of AD. However, the effect of miRNAs on abnormal tau phosphorylation remains largely unclear so far. In this study, we investigated the role of miR-106b in tau phosphorylation and identified a new molecular mechanism of the hyperphosphorylation of tau. The results of qRT-PCR showed that the expression level of miR-106b was decreased, but Fyn was increased in the temporal cortex of AD patients. Overexpression of miR-106b inhibited Aβ1-42-induced tau phosphorylation at Tyr18 in SH-SY5Y cells stably expressing tau (SH-SY5Y/tau), whereas no changes were observed in tau phosphorylation at Ser396/404. Dual-luciferase reporter gene assay validated that Fyn was a direct target gene of miR-106b. In addition, western blot analysis revealed that Fyn protein expression was suppressed when SH-SY5Y cells were transfected with miR-106b mimics. Endogenous Fyn expression was knockdown by transfection with a small interfering RNA specific for Fyn (si-Fyn). The phosphorylation level of tau at Tyr 18 was decreased in the si-Fyn group compared with the negative control group, but the inhibitory effect of si-Fyn on tau phosphorylation was attenuated when miR-106b expression was inhibited. Taken together, these data suggest that miR-106b inhibits Aβ1-42-induced tau phosphorylation at Tyr18 by targeting Fyn. Our findings extend the knowledge about the regulation of tau phosphorylation and the regulatory mechanism of Fyn gene expression.
阿尔茨海默病（AD）是一种进行性神经退行性疾病，其特征为β-淀粉样蛋白沉积和由高度磷酸化的tau蛋白组成的神经原纤维缠结。越来越多的证据表明，微小RNA（miRNA）与AD的发病机制有关。然而，迄今为止，miRNA对tau蛋白异常磷酸化的影响仍不清楚。在本研究中，我们研究了miR-106b在tau蛋白磷酸化中的作用，并确定了tau蛋白过度磷酸化的一种新分子机制。qRT-PCR结果显示，AD患者颞叶皮质中miR-106b的表达水平降低，但Fyn蛋白水平升高。在稳定表达tau蛋白的SH-SY5Y细胞（SH-SY5Y/tau）中，miR-106b的过表达抑制了Aβ1-42诱导的Tyr18位点的tau蛋白磷酸化，而Ser396/404位点的tau蛋白磷酸化未观察到变化。双荧光素酶报告基因检测证实Fyn是miR-106b的直接靶基因。此外，蛋白质印迹分析显示，用miR-106b模拟物转染SH-SY5Y细胞时，Fyn蛋白表达受到抑制。用针对Fyn的小干扰RNA（si-Fyn）转染可敲低内源性Fyn表达。与阴性对照组相比，si-Fyn组Tyr 18位点的tau蛋白磷酸化水平降低，但当miR-106b表达受到抑制时，si-Fyn对tau蛋白磷酸化的抑制作用减弱。综上所述，这些数据表明miR-106b通过靶向Fyn抑制Aβ1-42诱导的Tyr18位点的tau蛋白磷酸化。我们这些发现扩展了关于tau蛋白磷酸化调控以及Fyn基因表达调控机制的认识。
