AbstractThe assembly of amyloid ß protein (Aß) on ganglioside-enriched microdomains in presynaptic neuronal membranes is involved in the onset of Alzheimer’s disease. We previously found that a highly enriched ganglioside domain generated in a reconstituted lipid bilayer composed of synaptosomal lipids functioned as an Aß-sensitive ganglioside nanocluster (ASIGN) that may induce a spherical Aß assembly. In the present study, the major lipid components of a detergent-resistant membrane microdomain (DRM) fraction of synaptosomes prepared from an aged mouse brain were identified, and we demonstrate that the proportion of Aß-insensitive gangliosides such as GM3 directly affects the Aß assembly in synaptosomal membranes. Liquid chromatography coupled to mass spectrometry analyses indicated that ganglio a-series gangliosides (GM1, GM2, GM3, and GD1a) were abundant in DRM fractions. In addition, the GM3/GM1 ratio and the cholesterol content in the synaptosomal fraction differed from those in the non-synaptosomal fraction, in which GM1 and GM3 are sensitive and insensitive gangliosides, respectively. The highly enriched ganglioside nanocluster was identified by the surface topography of ternary mixed lipid bilayers composed of gangliosides, sphingomyelin, and cholesterol. Our results indicate that the composition of gangliosides is responsible for the characteristics of the nanocluster generated in the presynaptic neuronal membranes.Amyloid ß-protein (Aß) is converted to toxic forms through interactions with the ganglioside in neuronal membranes. The highly ganglioside-enriched microdomain (ganglioside cluster) in neuronal membranes plays a key role in Aß assembly. In the present study, lipid components of synaptosome extracted from mouse aged brain was determined by LC-MS spectroscopy. We demonstrated that ganglioside ratio (GM3 to GM1) and cholesterol content are an important factor for inducing Aß assembly. These results provides important insight into the mechanism of polypeptide assembly on the neuronal membrane in Alzheimer’s disease patients.

中文翻译：

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脂质组合物对小鼠突触体膜中神经节苷脂纳米簇诱导的淀粉样β组装的责任

摘要 淀粉样 ß 蛋白 (Aß) 在突触前神经元膜中富含神经节苷脂的微结构域上的组装与阿尔茨海默病的发病有关。我们之前发现，在由突触体脂质组成的重组脂质双层中产生的高度富集的神经节苷脂结构域作为 Aß 敏感神经节苷脂纳米团簇 (ASIGN)，可诱导球形 Aß 组装。在本研究中，鉴定了从老年小鼠大脑制备的突触体的抗洗涤剂膜微区 (DRM) 部分的主要脂质成分，我们证明 Aß 不敏感神经节苷脂（如 GM3）的比例直接影响 Aß 组装在突触体膜中。液相色谱结合质谱分析表明神经节 a 系列神经节苷脂（GM1、GM2、GM3、和 GD1a) 在 DRM 组分中含量丰富。此外，突触体部分的 GM3/GM1 比率和胆固醇含量与非突触体部分不同，其中 GM1 和 GM3 分别是敏感和不敏感的神经节苷脂。通过由神经节苷脂、鞘磷脂和胆固醇组成的三元混合脂质双层的表面形貌鉴定出高度富集的神经节苷脂纳米团簇。我们的结果表明，神经节苷脂的组成决定了突触前神经元膜中产生的纳米团簇的特征。淀粉样 β 蛋白 (Aß) 通过与神经元膜中的神经节苷脂相互作用而转化为有毒形式。神经元膜中高度富含神经节苷脂的微区（神经节苷脂簇）在 Aß 组装中起着关键作用。在本研究中，从小鼠衰老大脑中提取的突触体的脂质成分是通过 LC-MS 光谱确定的。我们证明神经节苷脂比率（GM3 与 GM1）和胆固醇含量是诱导 Aß 组装的重要因素。这些结果提供了对阿尔茨海默病患者神经元膜上多肽组装机制的重要见解。