Accelerated Aβ aggregation in the presence of GM1‐ganglioside‐accumulated synaptosomes of aged apoE4‐knock‐in mouse brain

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Abstract
Aging and apolipoprotein E4 (apoE4) expression are strong risk factors for the development of Alzheimer's disease (AD); however, their pathological roles remain to be clarified. In the process of AD development, the conversion of the nontoxic amyloid β‐protein (Aβ) monomer to its toxic aggregates is a fundamental process. We previously hypothesized that Aβ aggregation is accelerated through the generation of GM1 ganglioside (GM1)‐bound Aβ which acts as a seed for Aβ fibril formation. Here we report that GM1 level in detergent‐resistant membrane microdomains (DRMs) of synaptosomes increased with age and that this increase was significantly pronounced in the apoE4‐ than the apoE3‐knock‐in mouse brain. Furthermore, we show that Aβ aggregation is markedly accelerated in the presence of the synaptosomes of the aged apoE4‐knock‐in mouse brain. These observations suggest that aging and apoE4 expression cooperatively accelerate Aβ aggregation in the brain through an increase in the level of GM1 in neuronal membranes.