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）影响脑的早期病理学特征1 -7。最近的研究强调了线粒体Abeta在AD发病机制中的作用。A在AD脑和过表达A β的转基因AD小鼠的线粒体中进行性积累。值得注意的是，AD脑中线粒体Abeta的积累先于细胞外Abeta沉积，这与突触损失以及突触和线粒体损伤的早期发作一致。因此，线粒体Abeta的积累可能是导致线粒体和神经元扰动的起始病理事件。人PreP（human PreP，hPreP）是一种位于脑线粒体内的新型线粒体Abeta降解酶。我们最近的研究表明，hPreP的蛋白水解活性显着降低，在富含A β的线粒体从AD影响的大脑和过表达APP/A β的转基因AD小鼠，这表明hPreP可能是重要的，通过其降解和清除线粒体A β在预防AD的淀粉样病变。然而，尚未公开PreP对Abeta环境中淀粉样蛋白病理学和线粒体及突触变性的影响。在我们的初步研究中，我们观察到在Tg mAPP小鼠中通过增加PreP活性来减少线粒体和大脑皮层中的Abeta积累。我们假设PreP蛋白酶功能受损导致与AD淀粉样病变相关的慢性线粒体Abeta积聚，导致线粒体和突触变性，因此，PreP对线粒体Abeta的清除可能在AD的病理学中具有重要意义。本提案的目标是获得对PreP在AD发病机制中的作用的新见解，重点是线粒体Abeta积累/清除，淀粉样蛋白病理学，突触线粒体特性，氧化应激，突触功能，利用新的遗传操纵的转基因小鼠模型和在富含Abeta的环境中具有改变的PreP水平和蛋白水解活性的神经元培养物[（神经元PreP的表达增加，在反向锌结合基序中催化碱基Glu（78）被Gln取代的失活突变体PreP，缺乏酶活性，以及过表达Abeta的AD型转基因小鼠中神经元PreP的遗传缺陷）。该项目的结果也将支持PreP可能是限制线粒体和大脑淀粉样蛋白积累从而阻止AD进展的潜在治疗剂。

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.