Simulations of membrane-bound diglycosylated human prion protein reveal potential protective mechanisms against misfolding

Prion diseases are associated with the misfolding of the prion protein (PrP) from its normal cellular form (PrPC) to its infectious scrapie form (PrPSc). Posttranslational modifications of PrP in vivo can play an important role in modulating the process of misfolding. To gain more insight into the effects of posttranslational modifications on PrP structure and dynamics and to test the hypothesis that such modifications can interact with the protein, we have performed molecular dynamics simulations of diglycosylated human PrPC bound to a lipid bilayer via a glycophosphatidylinositol anchor. Multiple simulations were performed at three different pH ranges to explore pH effects on structure and dynamics. In contrast to simulations of protein-only PrPC, no large effects were observed upon lowering the pH of the system. The protein tilted toward the membrane surface in all of the simulations and the putative PrPSc oligomerization sites became inaccessible, thereby offering a possible protective mechanism against PrPSc-induced misfolding of PrPC.