Intraneuronal Abeta accumulation: mechanism of pathogenesis

描述(由申请人提供)：尽管有多条证据表明β-淀粉样多肽与阿尔茨海默病的发病机制有关，但β-淀粉样蛋白参与其中的分子机制仍不清楚。突触功能障碍是阿尔茨海默病的早期事件，越来越多的证据表明，神经元内β-淀粉样蛋白的异常积聚是突触功能障碍的关键。具体地说，描述了一种三重转基因小鼠，其中涉及记忆的生理变化随着神经元内β-淀粉样蛋白积累的开始而改变，并在斑块和缠结之前改变。利用免疫金电子显微镜，我们报道了在发生年龄相关的β-淀粉样变性的转基因APR突变小鼠中，β-淀粉样蛋白的积聚，特别是在远端突起和突触间隔的晚期内体小泡中，这有时与与退变一致的亚细胞形态变化有关。在随后的研究中，我们证明了β-淀粉样蛋白寡聚化开始于突触和突触间隔内，并与神经退行性变一致相关。此外，我们通过Western印迹、免疫荧光显微镜和免疫电子显微镜发现，淀粉样前体蛋白(APR)突变转基因小鼠的神经元随着培养时间的延长，与体内观察到的脑亚细胞β-淀粉样蛋白积聚和阿尔茨海默病样突触变化平行。我们假设，神经元内β-淀粉样蛋白积聚通过损害神经元中的多囊小体分类和泛素蛋白酶体系统而导致突触功能障碍。我们建议在培养的突变型APR转基因神经元中进行研究，以阐明导致突触功能障碍的生物学机制。我们的结果表明，突变的APR转基因神经元的内吞作用、突触前和突触后的差异蛋白以及泛素蛋白酶体系统都发生了变化。更好地了解β-淀粉样蛋白参与突触功能障碍和阿尔茨海默病发病机制的机制，对于设计更有效的阿尔茨海默病治疗方法可能是重要的。

DESCRIPTION (provided by applicant): Although multiple lines of evidence link beta-amyloid peptides to the pathogenesis of Alzheimer's disease, the molecular mechanism whereby beta-amyloid is involved remains unknown. Synaptic dysfunction is an early event in Alzheimer's disease and increasing evidence indicates that the aberrant accumulation of beta- amyloid within neurons is critical for synaptic dysfunction. Specifically, a triple transgenic mouse was described in which physiological alterations implicated in memory were altered with the onset of intraneuronal beta-amyloid accumulation and prior to plaques and tangles. Employing immuno-gold electron microscopy, we reported in transgenic mutant APR mice that develop age-related beta-amyloidosis the accumulation of beta-amyloid especially in late endosomal vesicles of distal processes and synaptic compartments, which at times were associated with subcellular morphological alterations consistent with degeneration. In a subsequent study, we demonstrated that beta-amyloid oligomerization begins within processes and synaptic compartments and is consistently linked with neurodegeneration. Moreover, we found by Western blot, immunofluorescence microscopy and immuno-electron microscopy that neurons from amyloid precursor protein (APR) mutant transgenic mice with time in culture paralleled the subcellular beta- amyloid accumulation and Alzheimer's disease-like synaptic alterations observed in brain in vivo. We hypothesize that intraneuronal beta-amyloid accumulation induces synaptic dysfunction by impairing multivesicular body sorting and the ubiquitin proteasome system in neurons. We propose studies in mutant APR transgenic neurons in culture to elucidate the biological mechanism leading to synaptic dysfunction. Our results indicate that mutant APR transgenic neurons have alterations in endocytosis, differential pre- and post-synaptic proteins and the ubiquitin proteasome system. A better understanding of the mechanism whereby beta-amyloid is involved in synaptic dysfunction and Alzheimer's disease pathogenesis may be important for devising more effective treatments for Alzheimer's disease.