Misfolded Amyloid β-42 induced impairment of the endo-lysosomal pathway revealed by real-time optical monitoring

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 Alzheimers-associated peptide, Abeta, exert their detrimental effects. We used a pH-sensitive reporter, Abeta42-CypHer, to track Abeta 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 Abeta42 (vAbeta42) assayed in the same way is not internalised. Tracking ovalbumin uptake into cells using CypHer or Alexa Fluor tags shows that preincubation with Abeta42 significantly disrupts protein uptake. Our results identify a potential mechanism by which amyloidogenic aggregates directly impair cellular function through disruption of the endosomal-lysosomal pathway.