N-Amination Converts Amyloidogenic Tau Peptides into Soluble Antagonists of Cellular Seeding

Abstract

The spread of neurofibrillary tangles composed of tau protein aggregates is a hallmark of Alzheimer’s and related neurodegenerative diseases. Early oligomerization of tau involves conformational reorganization into parallel β-sheet structures and supramolecular assembly into toxic fibrils. Despite the need for selective inhibitors of tau propagation, β-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 β-strands from the tau R2 and R3 domains. Several N-amino peptides (NAPs) inhibit tau 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 monomeric or fibrillar forms of extracellular tau. Peptidomimetic 12 is serum stable, non-toxic to neuronal cells, and selectivity inhibits the fibrilization of tau over Aβ42. Structural analysis of our lead NAPs shows considerable conformational constraint imposed by the N-amino groups. The described backbone N-amination approach provides a rational basis for the mimicry of other aggregation-prone peptides that drive pathogenic protein assembly.

Backbone N-Amination Promotes the Folding of β-Hairpin Peptides via a Network of Hydrogen Bonds

“…Promising results have already been reported from using peptides containing N-aminated residues to inhibit the fibrilization of Aβ 42 and tau protein. 13 , 14 N-Aminated residues in peptides also have the potential to act as inhibitors of β-strand mediated protein–protein interactions, and the MD simulations reported here reveal an important understanding that contributes to the design of these systems.…”

“…Promising results have already been reported from using peptides containing N-aminated residues to inhibit the fibrilization of Aβ 42 and tau protein. 13,14 N-Aminated residues in peptides also have the potential to act as inhibitors of β-strand mediated protein−protein interactions, and the MD simulations reported here reveal an important understanding that contributes to the design of these systems. GROMOS molecular topology building blocks for ornithine and for the N-aminated Tyr, Val, Glu, Lys, and Leu (ZIP)…”

“…In these studies, a diaminated peptide, with N-amination at residues 3 and 5, was shown to be an effective inhibitor of the fibrilization of Aβ 42 . Furthermore, N-aminated peptides from aggregation-prone sequences from the R2 and R3 domains of tau protein have also been shown to block tau fibrilization and seeding . Another study of the possibilities of using N-aminated residues in peptide-based drug candidates has shown that N-aminated analogues of gramicidin-S have enhanced broad-spectrum microbial activity …”

“…Furthermore, N-aminated peptides from aggregationprone sequences from the R2 and R3 domains of tau protein have also been shown to block tau fibrilization and seeding. 14 Another study of the possibilities of using N-aminated residues in peptide-based drug candidates has shown that N-aminated analogues of gramicidin-S have enhanced broad-spectrum microbial activity. 15 To support the development of further applications of Naminated peptidomimetics, one must develop a firm understanding of the conformational properties of peptides containing N-aminated residues.…”

Protein condensation diseases: therapeutic opportunities

“…or inhibit post-translational modifications that regulate the condensed states, such as those that stabilise the droplet state 120 , or promote formation of prion-like states 121 . Inhibitors of the dual-specificity kinase DYRK3 for example can prevent stress-granule dissolution 23 .…”