Lipid rafts are primary mediators of amyloid oxidative attack on plasma membrane
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Increasing evidence indicates that cell surfaces are early interaction sites for Aβ-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 Aβ production. Here, we report that lipid rafts, ordered membrane microdomains, are chronic mediators of Aβ-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 Aβ-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.
KeywordsAβ42-GM1 colocalisation Membrane lipid peroxidation Lipid raft cholesterol Amyloid precursor protein Alzheimer’s disease fibroblasts Alzheimer’s disease Beta-amyloid Gene expression Cholesterol
The authors would like to thank Daniel Wright for the critical reading of the manuscript. This study has been supported by grants from the Italian MIUR (PRIN project no. 2008R25HBW_002), from the Fondazione Cassa di Risparmio di Pistoia e Pescia (project no. 2009.0202) and Fondazione San Paolo (Alzheimer).
All authors declare the absence of any actual or potential conflicts of interest including any financial, personal or other relationships with other people or organisations within 2 years of beginning the work submitted that could inappropriately influence (bias) their work. All data contained in the manuscript being submitted have not been previously published, have not been submitted elsewhere and will not be submitted elsewhere while under consideration at Journal of Molecular Medicine. All authors have reviewed the contents of the manuscript being submitted, approve of its contents and validate the accuracy of the data.
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