The cholesterol ester cycle regulates signalling complexes and synapse damage caused by amyloid-β

Abstract

Cholesterol is required for the formation and function of some signalling platforms. In synaptosomes amyloid-β (Aβ) oligomers, the causative agent in Alzheimer's disease, bind to cellular prion proteins (PrPC) resulting in increased cholesterol concentrations, translocation of cytoplasmic phospholipase A2 (cPLA2) to lipid rafts and activation of cPLA2. The formation of Aβ:PrPC complexes was controlled by the cholesterol ester cycle. Aβ activated cholesterol ester hydrolases which released cholesterol from stores of cholesterol esters and stabilised Aβ:PrPC complexes resulting in activated cPLA2. Conversely, cholesterol esterification reduced cholesterol concentrations causing the dispersal of Aβ:PrPC complexes. In cultured neurons the cholesterol ester cycle regulated Aβ-induced synapse damage; cholesterol ester hydrolase inhibitors protected neurons while inhibition of cholesterol esterification significantly increased Aβ-induced synapse damage. An understanding of the molecular mechanisms involved in the dispersal of signalling complexes is important as a failure to deactivate signalling pathways can lead to pathology. This study demonstrates that esterification of cholesterol is a key factor in the dispersal of Aβ-induced signalling platforms involved in the activation of cPLA2 and synapse degeneration.