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

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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.