Oligomerization Alters Binding Affinity Between Amyloid Beta and a Modulator of Peptide Aggregation

Publication year: 2017
Authors: Hilt S. 1, Rojalin T. 2, 3, Viitala T. 3, Koivuniemi A.3, Bunker A. 3, Wachsmann-Hogiu S. 2, 4, Kálai T. 5, Hideg K. 5, Yliperttula M. 3, 6, Voss J. C. 1

1 - Department of Biochemistry & Molecular Medicine, University of California, Davis, CA 95616, USA
2 - Department of Pathology and Laboratory Medicine, and Center for Biophotonics, University of California Davis, USA
3 - Centre for Drug Research, Division of Pharmaceutical Biosciences, University of Helsinki, Finland
4 - Intellectual Ventures / Global Good, Bellevue, WA, USA
5 - Institute of Organic and Medicinal Chemistry, University of Pécs, H-7624 Pécs, Szigeti st. 12. Pécs, Hungary
6 - Department of Pharmaceutical Sciences, University of Padova, Italy

Published in: The Journal of Physical Chemistry C, 2017, Vol. 121 (43), p. 23974–23987
doi: 10.1021/acs.jpcc.7b06164

The soluble oligomeric form of the amyloid beta (Aβ) peptide is the major causative agent in the molecular pathogenesis of Alzheimer’s disease (AD). We have previously developed a pyrroline-nitroxyl fluorene compound (SLF) that blocks the toxicity of Aβ. Here we introduce the multiparametric surface plasmon resonance (MP-SPR) approach to quantify SLF binding and its effect on the self-association of the peptide via a label-free, real-time approach. Kinetic analysis of SLF binding to Aβ and measurements of layer thickness alterations inform on the mechanism underlying the ability of SLF to inhibit Aβ toxicity and its progression toward larger oligomeric assemblies. Depending on the oligomeric state of Aβ, distinct binding affinities for SLF are revealed. The Aβ monomer and dimer uniquely possess subnanomolar affinity for SLF via a nonspecific mode of binding. SLF binding is weaker in oligomeric Aβ, which displays an affinity for SLF on the order of 100 μM. To complement these experiments we carried out molecular docking and molecular dynamics simulations to explore how SLF interacts with the Aβ peptide. The MP-SPR results together with in silico modeling provide affinity data for the SLF-Aβ interaction and allow us to develop a new general method for examining protein aggregation.

MP-SPR keywords: Alzheimer’s disease, amyloid beta, amyloid beta aggregation, binding kinetics, layer thickness, MBP-thiol SAM, molecular docking, molecular dynamics simulations, peptide, reduced aggregation, small molecules, spin-labeled fluorene