Understanding Amyloid-Beta Plaque Formation By Monitoring the Redox Activity of Copper at the Active Site

Abstract

Alzheimer’s patients are found to have high concentrations of Amyloid-Beta peptide (Aβ-42), an overexpressed 42 amino acid sequence, along with a high concentration of copper ions in the brain. The Aβ-42 peptide results from the cleavage of a precursor protein (APP) and aggregates to form beta sheets during post-translational modification due to oxidative stress. Free metal ions, particularly Cu2+, initiate this oxidative stress by binding to the 14th Histidine residue in the primary structure of Aβ-42 and undergoing a single electron-transfer reduction to Cu+. This redox activity ultimately generates reactive oxygen species (ROS) through Fenton Decomposition to produce hydroxyl radicals within the brain. ROS initiate the progressive transitive states of Aβ-42 from fibril to oligomer to finally aggregate plaque formation, which causes cellular degeneration. The work presented here specifically focuses on the copper redox activity in the biological pathway leading to Alzheimer’s disease. The redox activity of copper at the active site is monitored and correlated to the degree of Aβ-42 fibrillization and aggregation, which is examined using Atomic Force Microscopy (AFM). Evaluating the copper-mediated toxicity will allow for a better understanding of the electrochemical process that initiates ROS and ultimately leads to Aβ-42 plaque formation.