Intraneuronal Abeta accumulation: mechanism of pathogenesis

描述（由申请人提供）：尽管多种证据将β -淀粉样蛋白肽与阿尔茨海默病的发病机制联系起来，但β -淀粉样蛋白所涉及的分子机制仍然未知。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累是突触功能障碍的关键。具体来说，研究人员描述了一只三重转基因小鼠，其中涉及记忆的生理改变随着神经元内β -淀粉样蛋白积累的开始而发生改变，并先于斑块和缠结。利用免疫金电子显微镜，我们报道了在转基因突变APR小鼠中发生与年龄相关的β -淀粉样变性，特别是在远端突和突触室的内体囊泡晚期β -淀粉样蛋白的积累，这有时与与变性一致的亚细胞形态改变有关。在随后的研究中，我们证明β -淀粉样蛋白寡聚化始于过程和突触室，并始终与神经变性有关。此外，我们通过Western blot、免疫荧光显微镜和免疫电子显微镜发现，淀粉样蛋白前体蛋白（APR）突变转基因小鼠的神经元随着培养时间的推移，在体内观察到亚细胞β -淀粉样蛋白积累和阿尔茨海默病样突触改变。我们假设神经元内的β -淀粉样蛋白积累通过损害神经元中的多泡体分选和泛素蛋白酶体系统而诱导突触功能障碍。我们建议在培养的APR基因突变神经元中进行研究，以阐明导致突触功能障碍的生物学机制。我们的研究结果表明，突变APR转基因神经元在胞吞作用、突触前和突触后差异蛋白和泛素蛋白酶体系统方面发生了改变。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，可能对设计更有效的阿尔茨海默病治疗方法很重要。

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.