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

淀粉样纤维是由蛋白质组成的不可溶的分子聚集体。尽管淀粉样蛋白形成蛋白的天然结构不同，但它们形成的淀粉样原纤维相似，无论它们来自哪种蛋白质。斑块(原纤维的集合)形成的分子机制，以及这一过程的启动原因，目前尚不清楚。虽然在体内纤维斑块的形成与生物膜有关，但大多数关于纤维形成的研究都是在溶液相进行的，其中考虑了“唯一的蛋白质”模型。脂筏存在于细胞膜中，是细胞组织的主要方面，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纤维形成和纤维与细胞相互作用的机制中发挥重要作用。这项拟议的研究将调查脂筏的性质和功能，并阐明它们在淀粉样原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)，解决这些问题是一项要求非常高的任务，需要非常先进的显微技术。原子力显微镜、新型调频开尔文探针力显微镜和原子力光谱将研究导致淀粉样原纤维形成的单肽分子之间的相互作用以及多肽与脂膜的相互作用。随着周围环境(包括脂质成分、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。这些新方法将允许脂筏的性质与其与形成纤维的蛋白质和聚集体的相互作用有关。这项研究的结果将在分子水平上深入了解在脂质模板存在的情况下淀粉样原纤维形成的基本机制，以及小的中等毒性聚集体对模型膜的作用。这些知识对于开发更复杂的淀粉样原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的治疗方法的发展。

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.