New Drosophila models to uncover the intrinsic and extrinsic factors mediating the toxicity of the human prion protein
Misfolded conformations of the prion protein (PrP) are responsible for devastating neurological disorders in humans and mammals. An unresolved problem is unraveling the mechanisms governing PrP conformational dynamics, misfolding, and the cellular mechanism leading to neurodegeneration. The variable susceptibility of mammals to prion diseases can be exploited to understand the conformational dynamics of PrP. Here we present a new fly model expressing human PrP with robust phenotypes in brain neurons and the eye. Using comparable attP2 insertions, we demonstrate the heightened toxicity of human PrP compared to that of mouse and hamster PrP along with a specific interaction with the amyloid-beta peptide. Using this new highly toxic new model, we started to uncover the intrinsic (sequence / structure) and extrinsic (interactions) factors regulating PrP toxicity. As extrinsic factors, we describe the importance of the PERK - ATF4 branch of the unfolded protein response as a key cellular mechanism mediating the toxicity of human PrP. For intrinsic factors, we introduced point mutations in human PrP (N159D, D167S, N174S) that were partially protective, revealing its high propensity to misfold into toxic conformations.