Mitochondrial degrading enzyme, synaptic mitochondrial function in AD mouse model

描述（由申请人提供）：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β在AD发病中的作用。A在阿尔茨海默病脑和过度表达β的转基因阿尔茨海默病小鼠的线粒体中逐渐积累。值得注意的是，在AD大脑中，线粒体Abeta的积累先于细胞外Abeta的沉积，这与突触丢失和突触和线粒体损伤的早期发作是一致的。因此，线粒体β的积累可能是导致线粒体和神经元扰动的初始病理事件。Human PreP （hPreP）位于脑线粒体中，是一种新型的线粒体β降解酶。我们最近的研究表明，hPreP在AD受影响的大脑和过表达APP/Abeta的转基因AD小鼠中富含Abeta的线粒体中的蛋白水解活性显著降低，这表明hPreP可能通过降解和清除线粒体Abeta在预防AD淀粉样蛋白病理中发挥重要作用。然而，PreP对β环境中淀粉样蛋白病理、线粒体和突触变性的影响尚未披露。在我们的前期研究中，我们观察到通过增加Tg mAPP小鼠的PreP活性，线粒体和大脑皮层中β积累的减少。我们假设PreP蛋白酶的功能受损导致了与AD淀粉样蛋白病理发生相关的线粒体慢性Abeta积累，导致线粒体和突触变性，因此，PreP清除线粒体Abeta可能在AD病理中起重要作用。本课题的目标是获得关于PreP在AD发病机制中的作用的新见解，重点关注线粒体Abeta积累/清除、淀粉样蛋白病理、突触线粒体特性、氧化应激、突触功能，利用一种新的转基因小鼠模型和在富含Abeta的环境中改变PreP水平和蛋白水解活性的神经元培养[（增加神经元PreP的表达），失活突变体PreP，催化基Glu（78）在倒转锌结合基序中被Gln取代，缺乏酶活性，并且在过表达Abeta的ad型转基因小鼠中缺乏神经元PreP)。该项目的结果也将支持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.