Lipid rafts are primary mediators of amyloid oxidative attack on plasma membrane

Increasing evidence indicates that cell surfaces are early interaction sites for A beta-derived diffusible ligands (ADDLs) and neurons in Alzheimer's disease (AD) pathogenesis. Our previous data showed significant oxidative damage at the plasma membrane in fibroblasts from familial AD patients with enhanced A beta production. Here, we report that lipid rafts, ordered membrane microdomains, are chronic mediators of A beta-induced lipid peroxidation in SH-SY5Y human neuroblastoma cells overexpressing amyloid precursor protein (APPwt) and APPV717G genes and in fibroblasts bearing the APPV717I gene mutation. Confocal microscope analysis showed that A beta-oxidised rafts recruit more ADDLs than corresponding domains in control cells, triggering a further increase in membrane lipid peroxidation and loss of membrane integrity. Moreover, amyloid pickup at the oxidative-damaged domains was prevented by enhanced cholesterol levels, anti-ganglioside (GM1) antibodies, the B subunit of cholera toxin and lipid raft structure alteration. An enhanced structural rigidity of the detergent-resistant domains, isolated from APPwt and APPV717G cells and exposed to ADDLs, indicates a specific perturbation of raft physicochemical features in cells facing increased amyloid assembly at the membrane surface. These data identify lipid rafts as key mediators of oxidative damage as a result of their ability to recruit aggregates to the cell surface.