Mitochondrial degrading enzyme, synaptic mitochondrial function in AD mouse model

描述(申请人提供)：线粒体和突触功能障碍是阿尔茨海默病(AD)影响大脑的早期病理特征1-7。最近的研究强调了线粒体Abeta在AD发病机制中的作用。在AD脑和过量表达Abeta的转基因AD小鼠的线粒体中，A逐渐积累。值得注意的是，在AD脑中，线粒体Abeta的积累先于细胞外Abeta的沉积，这与突触丢失以及突触和线粒体损伤的早期发生一致。因此，线粒体Abeta的积聚可能是导致线粒体和神经元扰动的一种起始病理事件。人PREP(HPreP)位于脑线粒体中，是一种新的线粒体Abeta降解酶。我们最近的研究表明，在AD脑内富含Abeta的线粒体和过度表达APP/Abeta的转基因AD小鼠中，hPreP的蛋白分解活性显著降低，这表明hPreP可能通过降解和清除线粒体Abeta而在预防AD的淀粉样病变中发挥重要作用。然而，PREP对淀粉样蛋白病理以及Abeta环境中线粒体和突触变性的影响尚未被披露。在我们的初步研究中，我们观察到TG Mapp小鼠体内PREP活性的增加减少了线粒体和大脑皮层中的Abeta积聚。我们推测，在AD的淀粉样变过程中，PREP蛋白功能受损导致线粒体Abeta的慢性积聚，导致线粒体和突触的变性，因此，PREP对线粒体Abeta的清除可能在AD的病理过程中起重要作用。这项建议的目的是对prep在AD发病机制中的作用有新的认识，重点关注线粒体Abeta的积累/清除、淀粉样蛋白的病理变化、突触线粒体的特性、氧化应激、突触功能、利用新型转基因小鼠模型和在富Abeta环境中改变prep水平和蛋白分解活性的神经元培养[(在GLN替换的锌结合反向基序中神经元prep表达增加、具有催化碱基Glu(78)的不活跃突变prep、缺乏酶活性以及AD类型转基因小鼠中神经元prep的遗传缺陷)。该项目的结果还将支持，PREP可能是一种潜在的治疗药物，可以限制线粒体和大脑淀粉样蛋白的积累，从而阻止AD的进展。

DESCRIPTION (provided by applicant): Mitochondrial and synaptic dysfunction is an early pathological feature of Alzheimer's disease (AD) affected brain1-7. Recent studies have highlighted the role of mitochondrial Abeta in AD pathogenesis. A progressively accumulates in mitochondria of AD brain and transgenic AD mice overexpressing Abeta. Notably, accumulation of mitochondrial Abeta precedes extracellular Abeta deposition in AD brain, which is consistent with the early onset of loss of synapses and synaptic and mitochondrial damage. Thus, accumulation of mitochondrial Abeta may be an initiating pathological event leading to mitochondrial and neuronal perturbation. Human PreP (hPreP) located in brain mitochondria, is a novel mitochondrial Abeta degrading enzyme. Our recent studies indicates that the proteolytic activity of hPreP was significantly reduced in Abeta-rich mitochondria from AD-affected brain and transgenic AD mice overexpressing APP/Abeta, suggesting that hPreP may potentially be of importance in preventing amyloid pathology of AD through its degradation and clearance of mitochondrial Abeta. However, the effects of PreP on amyloid pathology and mitochondrial and synaptic degeneration in Abeta milieu have not yet been disclosed. In our pilot studies, we observed the reduction of Abeta accumulation in mitochondria and cerebral cortex by increased PreP activity in Tg mAPP mice. We hypothesize that impaired function of PreP protease contributes to chronic mitochondrial Abeta accumulation relevant to developing amyloid pathology of AD, leading to mitochondrial and synaptic degeneration, thus, clearance of mitochondrial Abeta by PreP may be of importance in the pathology of AD. The goal of this proposal is to gain new insight into the role of PreP in AD pathogenesis, focusing on mitochondrial Abeta accumulation/clearance, amyloid pathology, synaptic mitochondrial properties, oxidative stress, synaptic function, utilizing a novel genetically manipulated transgenic mouse models and neuronal culture with altered PreP levels and proteolytic activity in Abeta-rich environment [(increased expression of neuronal PreP, inactive mutant PreP with catalytic base Glu(78) in the inverted zinc-binding motif replaced by Gln, lacking enzyme activity, and genetic deficiency of neuronal PreP in AD-type transgenic mice overexpressing Abeta). The outcomes of the project would also support that PreP might be a potential therapeutic agent for limiting mitochondrial and cerebral amyloid accumulation thereby halting AD progression.