title: Effect of acidic pH on the stability of α-synuclein dimers.
abstract: Environmental factors, such as acidic pH, facilitate the assembly of α-synuclein (α-Syn) in aggregates, but the impact of pH on the very first step of α-Syn aggregation remains elusive. Recently, we developed a single-molecule approach that enabled us to measure directly the stability of α-Syn dimers. Unlabeled α-Syn monomers were immobilized on a substrate, and fluorophore-labeled monomers were added to the solution to allow them to form dimers with immobilized α-Syn monomers. The dimer lifetimes were measured directly from the fluorescence bursts on the time trajectories. Herein, we applied the single-molecule tethered approach for probing of intermolecular interaction to characterize the effect of acidic pH on the lifetimes of α-Syn dimers. The experiments were performed at pH 5 and 7 for wild-type α-Syn and for two mutants containing familial type mutations E46K and A53T. We demonstrate that a decrease of pH resulted in more than threefold increase in the α-Syn dimers lifetimes with some variability between the α-Syn species. We hypothesize that the stabilization effect is explained by neutralization of residues 96-140 of α-Syn and this electrostatic effect facilitates the association of the two monomers. Given that dimerization is the first step of α-Syn aggregation, we posit that the electrostatic effect thereby contributes to accelerating α-Syn aggregation at acidic pH. © 2016 Wiley Periodicals, Inc. Biopolymers 105: 715-724, 2016.
authors.affiliation: Department of Pharmaceutical Sciences, University of Nebraska Medical Center, 986025 Nebraska Medical Center, Omaha, NE, 68198.
authors.forename: Zhengjian
authors.initials: Z
authors.lastname: Lv
authors.affiliation: Department of Pharmaceutical Sciences, University of Nebraska Medical Center, 986025 Nebraska Medical Center, Omaha, NE, 68198.|Department of Physics, University of Nebraska Omaha, Omaha, NE, 68182.
authors.forename: Alexey V
authors.initials: AV
authors.lastname: Krasnoslobodtsev
authors.affiliation: Department of Pharmaceutical Sciences, University of Nebraska Medical Center, 986025 Nebraska Medical Center, Omaha, NE, 68198.
authors.forename: Yuliang
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN, 47907-2091.
authors.forename: Daniel
authors.initials: D
authors.lastname: Ysselstein
authors.affiliation: Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN, 47907-2091.
authors.forename: Jean Christophe
authors.initials: JC
authors.lastname: Rochet
authors.affiliation: Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY and the Weill Cornell Medical College, Rockefeller University, Memorial Sloan-Kettering Cancer Center Tri-Institutional Training Program in Chemical Biology, New York, NY.
authors.forename: Scott C
authors.initials: SC
authors.lastname: Blanchard
authors.affiliation: Department of Pharmaceutical Sciences, University of Nebraska Medical Center, 986025 Nebraska Medical Center, Omaha, NE, 68198.
authors.forename: Yuri L
authors.initials: YL
authors.lastname: Lyubchenko
mesh_terms: D019943:Amino Acid Substitution; D006801:Humans; D006863:Hydrogen-Ion Concentration; D020125:Mutation, Missense; D066329:Protein Aggregates; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D055672:Static Electricity; D051844:alpha-Synuclein / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D066329:Protein Aggregates; C497604:SNCA protein, human; D051844:alpha-Synuclein
keywords: alpha-synuclein protein; amyloid aggregation; interprotein interactions; protein self-assembly; single molecule fluorescence