Misfolded amyloid-β-42 impairs the endosomal-lysosomal pathway

Misfolding and aggregation of proteins is strongly linked to several neurodegenerative diseases, but how such species bring about their cytotoxic actions remains poorly understood. Here we used specifically-designed optical reporter probes and live fluorescence imaging in primary hippocampal neurons to characterise the mechanism by which prefibrillar, oligomeric forms of the Alzheimer's-associated peptide, A beta 42, exert their detrimental effects. We used a pH-sensitive reporter, A beta 42-CypHer, to track A beta internalisation in real-time, demonstrating that oligomers are rapidly taken up into cells in a dynamin-dependent manner, and trafficked via the endo-lysosomal pathway resulting in accumulation in lysosomes. In contrast, a non-assembling variant of A beta 42 (vA beta 42) assayed in the same way is not internalised. Tracking ovalbumin uptake into cells using CypHer or Alexa Fluor tags shows that preincubation with A beta 42 disrupts protein uptake. Our results identify a potential mechanism by which amyloidogenic aggregates impair cellular function through disruption of the endosomal-lysosomal pathway.