Neuronal Apolipoprotein E4 Expression Results in Proteome-Wide Alterations and Compromises Bioenergetic Capacity by Disrupting Mitochondrial Function
Neuronal Apolipoprotein E4 Expression Results in Proteome-Wide Alterations and Compromises Bioenergetic Capacity by Disrupting Mitochondrial Function
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DOI：
10.3233/jad-181184
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发表时间：
2019-01-01
影响因子：
4
通讯作者：
Mahley, Robert W.
中科院分区：
文献类型：
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作者：
Orr, Adam L.;Kim, Chaeyoung;Mahley, Robert W.
载脂蛋白(Apo)E4是阿尔茨海默病(AD)的主要遗传危险因素，在AD发病早期改变线粒体功能和代谢。当受到损伤或应激时，神经元增加载脂蛋白E的合成。由于apoE4与apoE3的结构不同，apoE4经历神经元特异性的蛋白分解，产生进入胞浆的片段，与线粒体相互作用，引起神经毒性。然而，载脂蛋白E4的S对线粒体呼吸代谢的影响还不是很清楚。在这里，我们使用生化分析和蛋白质组学分析来更全面地描述apoE4对稳定表达apoE4或apoE3的Neuro-2a神经细胞的线粒体功能和细胞代谢的影响。在基础状态下，apoE4损伤呼吸，增加糖酵解，但当受到刺激或应激时，apoE4表达的神经元产生ATP以满足能量需求的储备能力比apoE3表达的神经元少50%。ApoE4的表达还降低了NAD(+)/NADH的比值，增加了细胞内活性氧和线粒体钙的水平。全球蛋白质组学分析显示，apoE4细胞的线粒体过程发生了广泛的变化，包括许多呼吸复合体亚基的水平降低，以及复合体V(ATP合成酶)中所有检测到的亚基的严重中断。在apoE4细胞中，与线粒体内质网相关膜、线粒体融合/分裂、线粒体蛋白易位、蛋白酶和线粒体核糖体蛋白相关的蛋白水平也发生了变化。载脂蛋白E4诱导的生物能量缺陷导致了广泛的代谢重联，但尽管有许多细胞适应，表达载脂蛋白E4的神经元仍然容易受到代谢应激的影响。我们的结果为纠正apoE4相关线粒体功能障碍和改变细胞代谢的治疗的潜在分子靶点提供了见解。
Apolipoprotein (apo) E4, the major genetic risk factor for Alzheimer's disease (AD), alters mitochondrial function and metabolism early in AD pathogenesis. When injured or stressed, neurons increase apoE synthesis. Because of its structural difference from apoE3, apoE4 undergoes neuron-specific proteolysis, generating fragments that enter the cytosol, interact with mitochondria, and cause neurotoxicity. However, apoE4's effect on mitochondrial respiration and metabolism is not understood in detail. Here we used biochemical assays and proteomic profiling to more completely characterize the effects of apoE4 on mitochondrial function and cellular metabolism in Neuro-2a neuronal cells stably expressing apoE4 or apoE3. Under basal conditions, apoE4 impaired respiration and increased glycolysis, but when challenged or stressed, apoE4-expressing neurons had 50% less reserve capacity to generate ATP to meet energy requirements than apoE3-expressing neurons. ApoE4 expression also decreased the NAD(+)/NADH ratio and increased the levels of reactive oxygen species and mitochondrial calcium. Global proteomic profiling revealed widespread changes in mitochondrial processes in apoE4 cells, including reduced levels of numerous respiratory complex subunits and major disruptions to all detected subunits in complex V (ATP synthase). Also altered in apoE4 cells were levels of proteins related to mitochondrial endoplasmic reticulum-associated membranes, mitochondrial fusion/fission, mitochondrial protein translocation, proteases, and mitochondrial ribosomal proteins. ApoE4-induced bioenergetic deficits led to extensive metabolic rewiring, but despite numerous cellular adaptations, apoE4-expressing neurons remained vulnerable to metabolic stress. Our results provide insights into potential molecular targets of therapies to correct apoE4-associated mitochondrial dysfunction and altered cellular metabolism.