title: Nanoprobing of the effect of Cu(2+) cations on misfolding, interaction and aggregation of amyloid β peptide.
abstract: Misfolding and aggregation of the amyloid β-protein (Aβ) are hallmarks of Alzheimer's disease. Both processes are dependent on the environmental conditions, including the presence of divalent cations, such as Cu(2+). Cu(2+) cations regulate early stages of Aβ aggregation, but the molecular mechanism of Cu(2+) regulation is unknown. In this study we applied single molecule AFM force spectroscopy to elucidate the role of Cu(2+) cations on interpeptide interactions. By immobilizing one of two interacting Aβ42 molecules on a mica surface and tethering the counterpart molecule onto the tip, we were able to probe the interpeptide interactions in the presence and absence of Cu(2+) cations at pH 7.4, 6.8, 6.0, 5.0, and 4.0. The results show that the presence of Cu(2+) cations change the pattern of Aβ interactions for pH values between pH 7.4 and pH 5.0. Under these conditions, Cu(2+) cations induce Aβ42 peptide structural changes resulting in N-termini interactions within the dimers. Cu(2+) cations also stabilize the dimers. No effects of Cu(2+) cations on Aβ-Aβ interactions were observed at pH 4.0, suggesting that peptide protonation changes the peptide-cation interaction. The effect of Cu(2+) cations on later stages of Aβ aggregation was studied by AFM topographic images. The results demonstrate that substoichiometric Cu(2+) cations accelerate the formation of fibrils at pH 7.4 and 5.0, whereas no effect of Cu(2+) cations was observed at pH 4.0. Taken together, the combined AFM force spectroscopy and imaging analyses demonstrate that Cu(2+) cations promote both the initial and the elongation stages of Aβ aggregation, but protein protonation diminishes the effect of Cu(2+).
authors.affiliation: Department of Pharmaceutical Sciences, University of Nebraska Medical Center, 986025 Nebraska Medical Center, Omaha, NE 68198, USA.
authors.forename: Zhengjian
authors.initials: Z
authors.lastname: Lv
authors.forename: Margaret M
authors.initials: MM
authors.lastname: Condron
authors.forename: David B
authors.initials: DB
authors.lastname: Teplow
authors.forename: Yuri L
authors.initials: YL
authors.lastname: Lyubchenko
mesh_terms: D000465:Algorithms; D000538:Aluminum Silicates; D000595:Amino Acid Sequence; D016229:Amyloid beta-Peptides / Q000737:chemistry / Q000187:drug effects*; D002021:Buffers; D002412:Cations / Q000494:pharmacology; D003300:Copper / Q000494:pharmacology*; D003627:Data Interpretation, Statistical; D006801:Humans; D006863:Hydrogen-Ion Concentration; D018625:Microscopy, Atomic Force; D008969:Molecular Sequence Data; D016874:Neurofibrillary Tangles / Q000473:pathology; D010446:Peptide Fragments / Q000737:chemistry; D057165:Proteostasis Deficiencies / Q000473:pathology*
chemical_list: D000538:Aluminum Silicates; D016229:Amyloid beta-Peptides; D002021:Buffers; D002412:Cations; D010446:Peptide Fragments; C075222:amyloid beta-protein (1-42); D003300:Copper; C011934:mica