Lack of cellular prion protein causes Amyloid β accumulation, increased extracellular vesicle abundance, and changes to exosome biogenesis proteins.

Alzheimer's disease (AD) progression is closely linked to the propagation of pathological Amyloid β (Aβ), a process increasingly understood to involve extracellular vesicles (EVs), namely exosomes. The specifics of Aβ packaging into exosomes remain elusive, although evidence suggests an ESCRT (Endosomal Sorting Complex Required for Transport)-independent origin to be responsible in spreading of AD pathogenesis. Intriguingly, PrP, known to influence exosome abundance and bind oligomeric Aβ (oAβ), can be released in exosomes via both ESCRT-dependent and ESCRT-independent pathways, raising questions about its role in oAβ trafficking. Thus, we quantified Aβ levels within EVs, cell medium, and intracellularly, alongside exosome biogenesis-related proteins, following deletion or overexpression of PrP. The same parameters were also evaluated in the presence of specific exosome inhibitors, namely Manumycin A and GW4869. Our results revealed that deletion of PrP increases intracellular Aβ accumulation and amplifies EV abundance, alongside significant changes in cellular levels of exosome biogenesis-related proteins Vps25, Chmp2a, and Rab31. In contrast, cellular expression of PrP did not alter exosomal Aβ levels. This highlights PrP's influence on exosome biogenesis, albeit not in direct Aβ packaging. Additionally, our data confirm the ESCRT-independent exosome release of Aβ and we show a direct reduction in Chmp2a levels upon oAβ challenge. Furthermore, inhibition of opposite exosome biogenesis pathway resulted in opposite cellular PrP levels. In conclusion, our findings highlight the intricate relationship between PrP, exosome biogenesis, and Aβ release. Specifically, they underscore PrP's critical role in modulating exosome-associated proteins, EV abundance, and cellular Aβ levels, thereby reinforcing its involvement in AD pathogenesis.