Correlative cryo-soft X-ray tomography reveals defective lysosomes in amyloid-β oligomer treated hippocampal neurons

Protein misfolding is common to neurodegenerative diseases (NDs) including Alzheimer’s disease (AD), which is characterized by self-assembly and accumulation of Amyloid-beta in the brain. Furthermore, impaired proteostatic mechanisms have been implicated in NDs. Lysosomes are a critical component of the proteostasis network required to degrade and recycle material from outside and within the cell. Using a model of AD neurodegeneration where toxic amyloid beta oligomers are applied exogenously to primary hippocampal neurons, we have previously established that oligomers are endocytosed and trafficked to lysosomes where they accumulate and prevent further endocytosis. Here, we use pioneering correlative cryo-structured illumination microscopy and cryo-soft X-ray tomography imaging techniques to reconstruct 3D cellular architecture in the native state. We demonstrate that lysosomes in oligomer treated neurons are less X-ray dense suggesting they contain less carbon-rich material than untreated cells. Furthermore, we observe an increase in carbon dense lipid vesicles in oligomer treated cells. This work provides unprecedented and critical visual information on the changes to neuronal architecture inflicted by amyloid beta oligomers using advanced methods in structural cell biology.