中文摘要：

背景：神经细丝的磷酸化程度与阿尔茨海默病的发生密切相关，载脂蛋白E4是阿尔茨海默病公认的易患因子，但载脂蛋白E4对神经元细胞内神经细丝磷酸化的影响及机制尚不十分清楚。研究显示在阿尔茨海默病患者脑组织和体外培养的神经元细胞中，载脂蛋白E4蛋白C末端的272～299位氨基酸残基可被水解截去，产生truncated-apoE4片段，且与阿尔茨海默病的特征性病理改变神经纤维缠结中的磷酸化神经细丝相互作用。 目的：在细胞水平观察truncated-ApoE4过度表达对培养的神经元中神经细丝磷酸化的影响。 设计：非随机对照实验观察。 单位：华中科技大学同济医学院基础医学院生物化学与分子生物学系。 材料：实验于2005／12在华中科技大学同济医学院生物化学与分子生物学实验室完成。小鼠成神经瘤贴壁生长细胞株N2a由许华熙博士提供。 方法：构建pEGFP-T-apoE4真核表达重组体，采用脂质体介导的方法分别将pEGFP-c3、pEGFP-apoE4和pEGFP-T-apoE4瞬时转染小鼠成神经瘤细胞株（N2a），24～48h后，免疫印迹技术检测神经细丝的磷酸化状态，测定糖原合酶激酶3、细胞周期依赖性蛋白激酶5（CDK5）的活性。 主要观察指标：神经细丝的磷酸化程度及糖原合酶激酶3、细胞周期依赖性蛋白激酶5的酶活性。 结果：转染组细胞内磷酸化神经细丝含量显著增多，糖原合酶激酶3酶活性显著增加，以pEGFP-T-apoE4转染组最为显著（P〈0．05），细胞周期依赖性蛋白激酶5酶活性与对照组相比差异无显著性意义（P〉0.05）。结论：Truncated-ApoE4过度表达可通过激活糖原合酶激酶3而非细胞周期依赖性蛋白激酶5引起成神经瘤细胞株（N2a）细胞中神经细丝过度磷酸化，提示truncated-ApoE4可能参与了阿尔茨海默病的病理过程。

英文摘要：

BACKGROUND： The degree of neurofilament （NF） phosphorylation is closely correlated with the occurrence of Alzbeimer disease （AD）, and apolipoprotein E4 （apoE4） is a generally acknowledged liability factor for AD, but the effect and mechanism of apoE4 on the NF phosphorylation in neurons are not very clear. It has been reported that in the neurons cultured in vitro and in brain tissue of AD patients, the amino acid residues of apoE4 protein C terminal （272-299） could be truncated by hydrolysis, and produce truncated-apoE4 fragment. The latter interacts with the NF phosphorylation in neurofibrillary tangles （NFTs）, which are the characteristic pathological changes of AD. OBJECTIVE： To observe the effect of truncated-apoE4 overexpression on the NF phosphorylation in the cultured neurons. DESIGN： A non-randomized controlled observation. SETTING： Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tongji Medical College, Huazhong University of Science and Technology, MATERIALS： The experiment was carried out in the Laboratory of Biochemistry and Molecular Biology, Tongji Medical College, Huazhong University of Science and Technology in December 2005. The mice neuroma cell strain N2a was provided by Dr. Xu. METHODS： The truncated-apoE4（△272-299） cDNA was subcloned into pEGFP-c3 to form pEGFP-T-apoE4 recombinant. Then pEGFP-c3, pEGFP-apoE4 and pEGFP-T-apoE4 were transfected into N2a cells by lipofectamine2000 respectively. NF phosphorylation was detected by Western blot assay. The activities of glycogen synthase kinase-3 （GSK-3） and cyclin-dependent kinase 5（CDK-5） were measured. MAIN OUTCOME MEASURES： The degree of NF phosphorylation and the activities of GSK-3 and CDK-5 were mainly observed. RESULTS： In the transfected groups, the contents of phosphorylated NF were significantly increased, the GSK-3 activities were significantly increased, which were the most significant in the pEGFP-T-apoE4 transfected group （P 〈 0.05?