Aging is considered a high risk factor for Alzheimer's disease (AD), which is one of the most prevalent neurodegenerative disorders in the elderly population. The major pathologic feature of AD is senile plaques mainly containing amyloid-β (Aβ) components. However, little direct evidence has shown aging in association with Aβ. Here we show that the protein-protein interaction of amyloid precursor protein (APP) and β -site amyloid cleavage enzyme 1 (BACE1) is enhanced by the fluorescence resonance energy transfer (FRET) assay during the aging process, and the APP-BACE1 complex accumulates in the endosome in the IMR-90 fibroblast (NHF) cellular aging models. Moreover, enhanced Aβ is observed in aged cells, rat brain homogenates and human serum. Interestingly, addition of the dominant-negative mutant of Rab5, a small G-protein Rab5 involved in the endocytic process, inhibits the aging-related APP-BACE1 interaction and Aβ production, suggesting that endocytosis contributes to AD progression.

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