Cellular prion protein (PrPC) was implicated in amyloid beta (Aβ)-induced toxicity in Alzheimer's disease (AD), but the precise molecular mechanisms involved in this process areunclear. Double transgenic mice were generated by crossing Prnp knockout (KO) with 5xFAD mice, and light-sheet microscopy was used for whole brain tissue analyses. PrPC-overexpressing cells were developed for in vitro studies, and microscopy was used to assess co-localization of proteins of interest. Surface-plasmon resonance (SPR) was used to investigate protein-binding characteristics. In vivo, PrPClevels correlated with reduced lifespan and cognitive and motor function, and its ablation disconnected behavior deficits from Aβ levels. Light-sheet microscopy showed that PrPCinfluenced Aβ-plaque burden but not the distribution of those plaques. Interestingly, caveolin-1 (Cav-1) KO neurons significantly reduced intracellular Aβ-oligomer (Aβo) uptake when compared to wild-type neurons. The findings shed new light on the relevance of intracellular Aβo, suggesting that PrPCand Cav-1 modulate intracellular Aβ levels andthe Aβ-plaque load. PrPC expression adversely affects lifespan and behavior in 5xFAD mice. PrPC increases Aβ1-40 and Aβ1-42 levels and Aβ-plaque load in 5xFAD mice. Cav-1 interacts with both PrPC and Aβ peptides. Knocking out Cav-1 leads to a significant reduction in intracellular Aβ levels.