Deleterious effects of soluble amyloid-β oligomers on multiple steps of synaptic vesicle trafficking

• Aβ oligomers alter the ratio of recycling to resting vesicle pools.
• They cause multiple defects in presynaptic endocytic recycling.
• The release probability of the RRP is enhanced.
• The PtdIns(4,5)P2 and calpain-CDK5 pathways are involved in the presynaptic dysfunction.

Growing evidence supports a role for soluble amyloid-β oligomer intermediates in the synaptic dysfunction associated with Alzheimer's disease (AD), but the molecular mechanisms underlying this effect remain unclear. We found that acute treatment of cultured rat hippocampal neurons with nanomolar concentrations of Aβ oligomers reduced the recycling pool and increased the resting pool of synaptic vesicles. Endocytosis of synaptic vesicles and the regeneration of fusion-competent vesicles were also severely impaired. Furthermore, the release probability of the readily-releasable pool (RRP) was increased, and recovery of the RRP was delayed. All these effects were prevented by antibody against Aβ. Moreover reduction of the pool size was prevented by inhibiting calpain or CDK5, while the defects in endocytosis were averted by overexpressing phosphatidylinositol-4-phosphate-5-kinase type I-γ, indicating that these two downstream pathways are involved in Aβ oligomers-induced presynaptic dysfunction.