Controlling the Oligomerization State of Aβ-Derived Peptides with Light

Abstract

A key challenge in studying the biological and biophysical properties of amyloid-forming peptides is that they assemble to form heterogeneous mixtures of soluble oligomers and insoluble fibrils. Photolabile protecting groups have emerged as tools to control the properties of biomolecules with light. Blocking intermolecular hydrogen bonds that stabilize amyloid oligomers provides a general strategy to control the biological and biophysical properties of amyloid-forming peptides. In this paper we describe the design, synthesis, and characterization of macrocyclic β-hairpin peptides that are derived from amyloidogenic peptides and contain the N-2-nitrobenzyl photolabile protecting group. Each peptide contains two heptapeptide segments from Aβ or Aβ constrained into β-hairpins. The N-2-nitrobenzyl group is appended to the amide backbone of Gly to disrupt the oligomerization of the peptides by disrupting intermolecular hydrogen bonds. X-ray crystallography reveals that N-2-nitrobenzyl groups can either block assembly into discrete oligomers or permit formation of trimers, hexamers, and dodecamers. Photolysis of the N-2-nitrobenzyl groups with long-wave UV light unmasks the amide backbone and alters the assembly and the biological properties of the macrocyclic β-hairpin peptides. SDS-PAGE studies show that removing the N-2-nitrobenzyl groups alters the assembly of the peptides. MTT conversion and LDH release assays show that decaging the peptides induces cytotoxicity. Circular dichroism studies and dye leakage assays with liposomes reveal that decaging modulates interactions of the peptides with lipid bilayers. Collectively, these studies demonstrate that incorporating N-2-nitrobenzyl groups into macrocyclic β-hairpin peptides provides a new strategy to probe the structures and the biological properties of amyloid oligomers.

Repurposing Triphenylmethane Dyes to Bind to Trimers Derived from Aβ

“…We prepared these trimer 2 homologues using the same procedures our laboratory has previously used to prepare other crosslinked trimers. 31,55…”

Visualizing and trapping transient oligomers in amyloid assembly pathways

“…In combination with methods such as NMR, kinetic modelling, and cell toxicity assays, these samples can provide insights into the role, disease-relevance, and structure of particular oligomeric populations, and validate potential routes for the treatment of amyloid diseases. There are now several examples where the stabilization (or destabilization) of specific species has reduced heterogeneity sufficiently to facilitate detailed structural studies using X-ray crystallography, thereby providing high-resolution insights into these potential therapeutic targets [ [27] , [28] , [29] , [30] ].…”

Light-induced modulation of DNA recognition by the Rad4/XPC damage sensor protein

“…3,4 Such lightinduced chemical/structural conversions have emerged as useful tools to control the properties and hence probe the functions of biomolecules harboring the photoconvertible groups, as light can be easily applied to biological systems in vitro or in vivo to trigger specific events. [5][6][7][8][9] Photoconvertible modifications in small molecules, [10][11][12] oligonucleotides, 13 peptides, 14,15 and proteins (mostly enzymes) [16][17][18][19] have also been used to control and monitor a wide variety of biological outcomes including gene expression, enzyme activity, oligomerization states, cellular localization and immune responses.…”