Biophysical study of lipid rafts and their role in amyloid fibril formation

淀粉样原纤维是由蛋白质组成的不溶性分子聚集体。尽管形成淀粉样蛋白的天然结构不同，但它们形成相似的淀粉样蛋白原纤维，而不管它们起源于哪种蛋白质。斑块（原纤维的集合）形成的分子机制以及这一过程启动的原因目前尚不清楚。尽管纤维斑块的形成与体内的生物膜有关，但大多数关于纤维形成的研究都是在溶液阶段进行的，其中只考虑了“蛋白质”模型。脂筏存在于细胞膜中，是细胞组织的一个重要方面，也是细胞与周围环境交流的中心。因此，脂筏可能在淀粉样蛋白原纤维的形成机制和原纤维与细胞的相互作用中起重要作用。本研究将探讨脂筏的性质和功能，并阐明其在淀粉样蛋白纤维形成的分子机制、能量学和动力学中的作用。由于它们的尺寸很小（纳米级），解决这些问题是一项艰巨的任务，需要高度先进的显微技术。通过原子力显微镜、新型频率调制开尔文探针力显微镜和原子力光谱学，将研究导致淀粉样蛋白纤维形成的单个肽分子之间的相互作用以及肽与脂质膜的相互作用。随着周围环境（包括脂质组成、胆固醇或抑制剂的存在）的改变，原子尺度上的相互作用力将被研究。这些新方法将使脂筏的性质与它们与纤维形成蛋白质和聚集体的相互作用有关。本研究的结果将为在脂质模板存在下淀粉样蛋白纤维形成的基本机制以及小的中间毒性聚集体在模型膜上的作用提供分子水平的见解。这一知识对于开发更复杂的淀粉样蛋白纤维形成模型和膜异质性在这一过程中的作用至关重要，并将有助于促进淀粉样蛋白相关疾病治疗方法的发展。

Amyloid fibrils are insoluble molecular aggregates composed of proteins. Despite of the differences in native structures of amyloid forming proteins, they form similar amyloid fibrils irrespective of the protein from which they originate. The molecular mechanism of the formation of plaques (which are collections of fibrils), and the reason for initiation of this process, are currently unknown. Although fibril plaque formation is associated with biological membranes in vivo, most of research on fibrillogenesis has been performed in a solution phase, in which "only protein" model is considered. Lipid rafts, which are present in cell membrane, are a major aspect of cell organization and central to the communication of cells with their environs. Therefore lipid rafts may play an important role in the mechanism of amyloid fibril formation and the interaction of fibrils with the cell. The proposed research will investigate the nature and functions of lipid rafts and elucidating their role in the molecular mechanism, energetics, and kinetics of amyloid fibril formation. Because of their small (nanometer) size, solving these problems is a demanding undertaking requiring highly advanced microscopic techniques. The interaction between single peptide molecules that results in amyloid fibril formation and interaction of peptides with the lipid membrane will be investigated by atomic force microscopy, novel frequency modulation Kelvin probe force microscopy and atomic force spectroscopy. Forces of interaction at an atomic scale will be studied as the surrounding environment (including lipid composition, the presence of cholesterol or inhibitors) is modified. These new approaches will allow the nature of lipid rafts to be related to their interaction with fibril forming proteins and aggregates. The outcome of this study will provide molecular level insight into the fundamental mechanisms of amyloid fibril formation in the presence of lipid templates, and action of small intermediate toxic aggregates on model membranes. This knowledge is essential to develop a more sophisticated model for amyloid fibril formation and the role of membrane heterogeneity in this process and will help to facilitate the development of therapies for amyloid-related diseases.