From Aggregation to Inhibition: N-Amination Converts Amyloidogenic Tau Peptides into Soluble Antagonists of Cellular Seeding

The spread of neurofibrillary tangles resulting from tau protein aggregation is a hallmark of Alzheimer’s and related neurodegenerative diseases. Early oligomerization of tau involves conformational reorganization into parallel b-sheet structures and supramolecular assembly into toxic fibrils. Despite the need for selective inhibitors of tau propagation, b-rich protein assemblies are inherently difficult to target with small molecules. Here, we describe a minimalist approach to mimic the aggregation-prone modules within tau. We carried out a backbone residue scan and show that amide N-amination completely abolishes the tendency of these peptides to self-aggregate, rendering them soluble mimics of ordered b-strands from the tau R2 and R3 domains. Several N-amino peptides (NAPs) inhibit disease-associated tau aggregation and prevent fibril formation in vitro. We further demonstrate that NAPs 12 and 13 are effective at blocking the cellular seeding of endogenous tau by interacting with both monomeric or fibrillar forms of extracellular tau. Peptidomimetic 12 is serum stable, non-toxic to neuronal cells, and selectivity inhibits the aggregation of tau over Ab_­42. Structural analysis of our lead NAPs shows considerable conformational constraint imposed by the N-amino groups. The enhanced rigidity and full complement of sidechains thus enables NAPs to recognize tau fibrils. The described backbone N-amination approach provides a rational basis for the mimicry of other aggregation-prone peptides that drive pathogenic protein assembly.