Introduction of a Fluorescent Probe to Amyloid‐β to Reveal Kinetic Insights into Its Interactions with Copper(II)

Abstract

The kinetics of the interactions between amyloid‐β (Aβ) and metal ions are crucial to understanding the physiological and pathological roles of Aβ in the normal brain and in Alzheimer’s disease. Using the quenching of a fluorescent probe by Cu2+, the mechanism of Aβ/Cu2+ interactions in physiologically relevant conditions has been elucidated. Cu2+ binds to Aβ at a near diffusion‐limited rate, initially forming component I. The switching between component I and II occurs on the second timescale, with a significant energy barrier. Component I is much more reactive towards Cu2+ ligands and likely responsible for initial Aβ dimer formation. Clioquinol (CQ) is shown to sequester Cu2+ more effectively than other tested ligands. These findings have implications for the potential roles of Aβ in regulating neurotransmission, and for the screening of small molecules targeting Aβ–metal interactions.

Acetylation Rather than H50Q Mutation Impacts the Kinetics of Cu(II) Binding to α‐Synuclein

“…Here we report the effects of the H50Q mutation and N‐terminal acetylation on Cu 2+ binding to αSyn from kinetic perspective. Highly sensitive fluorescent probe was used to detect fast reaction kinetics as reported previously [29–31] . We have found that His50 in αSyn is not involved in high‐affinity Cu 2+ binding, whereas N‐terminal acetylation reduces the Cu 2+ binding affinity of αSyn by approximately four orders of magnitude.…”

“…Kinetic techniques have been employed recently in several studies to give insights into IDP‐Cu 2+ interactions [28–31] . In brain, the existence of labile Cu 2+ released in synaptic cleft during neuronal excitation is transient.…”

Multifunctionality of Acidulated Serum Albumin on Inhibiting Zn2+-Mediated Amyloid β-Protein Fibrillogenesis and Cytotoxicity

“…4 Aβ encounters metal ions during synaptic transmission and it has been proved as a crucial step in the amyloid cascade. 5 It has been found that under physiological conditions, Zn 2+ not only rapidly induced Aβ oligomerization but also significantly enhanced the toxicity of Aβ species. 6,7 Although many studies have investigated the involvement of Zn 2+ in Aβ aggregation, the molecular mechanisms of Zn 2+ −Aβ interactions are still not clearly elucidated.…”

Impact of a Single Point Mutation on the Antimicrobial and Fibrillogenic Properties of Cryptides from Human Apolipoprotein B

“…HDPs often cause the death of microorganisms by interacting with the lipid bilayer and then determining membrane disruption in a specific, but not receptor-mediated, process [ 15 , 66 ]; several models have been proposed to describe this process of membrane permeabilization. In recent years, it has been also demonstrated that several HDPs have the ability to form β-sheet-rich amyloid-like fibrillar structures, what has led to postulate the existence of two seemingly unrelated classes of polypeptides, HDPs and fibril-forming (amyloidogenic) antimicrobial peptides, that share common mechanisms of cytotoxicity based on membrane disruption [ 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 ]. The deposits known as amyloids exhibit a characteristic cross-β structure that allows them to exert toxic effects by forming ion channels in bacterial cell membranes, thus causing membrane depolarization, energy drainage, and in some cases apoptosis [ 60 ].…”

“…Obtained results did not highlight significant differences, since, in the case of both ApoB-derived peptides, a surface interaction with lipid head groups coupled with a lipid segregation process has been demonstrated, while both peptides are not able to destabilize the hydrophobic core of the bilayer ( Figure 3 ). It has been reported that the formation of lipid domains in membranes can have a deep impact on the biological activity of the cells [ 74 ], such as an alteration of the diffusion rates of lipids and membrane proteins and an interference with membrane physiological curvature, with a consequent negative impact on key processes, such as cell division [ 14 ]. In the present manuscript, circular dichroism analyses reveal conformation shifts from a random-coil structure to a structural ensemble comprising significant β-sheet conformation, in the case of both peptides upon incubation with LPS or LTA ( Figure 4 c,d, Tables S3 and S4 ).…”