Conformational heterogeneity and alpha-sheet: Determinants of toxicity in Abeta variants

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Amyloid diseases involve conformational changes and aggregation of normally soluble peptides and proteins. As these proteins change begin to misfold and aggregate they pass through a toxic soluble oligomer stage and then they ultimately form insoluble fibrils. We have spent many years characterizing the early events in this progression, and have observed a common structure form among multiple amyloid-associated peptides and proteins despite distinct primary and tertiary structure. The structure we “discovered”, which we call α-sheet, while rare in normal proteins, has been observed experimentally, and short stretches of α-strand are present in the Protein Data Bank. We embarked on an endeavor to design and evaluate small peptides with complementary structures, also α-sheets, and their ability to inhibit amyloid formation in these systems. These de novo designed peptides inhibit the aggregation of multiple unrelated amyloid systems, indicating that we are targeting a generic structure. When immobilized, these designs also selectively bind the toxic oligomeric forms of these amyloid proteins over the monomers or fibrils. Here we propose to extend these studies by investigating whether α-sheet forms during amyloidogenesis of Abeta variants associated with Alzheimer's disease. The effects of targeting the toxic oligomers with de novo α-sheet designs will then be evaluated in vitro, in neuroblastoma cells, and in different, more biologically relevant systems.