The Mechanisms Of Amyloidosis And The Design, Synthesis And Evaluation Of Small-Molecule Inhibitors

The misfolding and abnormal aggregation of proteins is usually believed as onemain contributing factor of several amyloid diseases, such as Alzheimer’s disease, type2diabetes and prion diseases. Due to the importance of amyloid fibrillization,investigating the underlying mechanism of amyloid protein aggregation and designingappropriate inhibitors have been considered as a promising approach to advance theclinical treatment of these diseases. However, though lots of efforts have beencontributed to related researches on amyloid proteins, the mechanism of amyloidaggregation is still not fully understood. In this thesis, we investigated the aggregationmechanism of amyloid proteins, and designed inhibitors to block the copper-mediatedamyloid aggregation. These works could provide us further insights in relevant areas.Amylin and prion106-126were selected as the protein models to study theassembly mechanisms. For amylin, we studied the annular structure of amylin onnegatively-charged Tantalum oxide surface through atomic force microscopy andmicrosecond force spectroscopy, based on which we proposed an accumulation modelon how annular aggregation is initiated and developed. We further investigated theimpacts of C-terminus on amylin assembly and found that the difference at C-terminalregion between natural amylin and an amylin variant could result in different assemblypathways and different composition of the aggregates by influencing the hydrophobiccore, conformations, and intra-sheet interactions of peptides. The differences in theassembly processes further characterize the differences in cytotoxicity.For prion106-126, we applied atomic force microscopy to study the aggregation ofprion106-126in different solvents and found that the aggregated prion106-126fibrilscould form highly crowded membrane-like structures, which may occupy the space ofneurons and induce neuron death. Furthermore, we found that HCl and ethanol mightaccelerate prion aggregation and aggravate related negative impacts. Therefore, wepropose that environmental factors may influence the aggregation process of prionprotein. The works on amylin and prion aggregation provides us new clues for furthermechanism studies and drug design.Based on the investigation of amyloid aggregation mechanism, we designed smallmolecule inhibitors to target the copper-mediated amyloid aggregation. The designedinhibitors can chelate Cu(I) from the aberrant copper redox cycle, and thus protect cells against Aβ induced neurotoxicity. Our approach on inhibitor design may lead to analternative strategy for developing therapeutic drugs for Cu-mediated protein diseases.