Reactive Oxygen Species-mediated β-Cleavage of the Prion Protein in the Cellular Response to Oxidative Stress*

Abstract

The cellular prion protein (PrP^C) is critical for the development of prion diseases. However, the physiological role of PrP^C is less clear, although a role in the cellular resistance to oxidative stress has been proposed. PrP^C is cleaved at the end of the copper-binding octapeptide repeats through the action of reactive oxygen species (ROS), a process termed β-cleavage. Here we show that ROS-mediated β-cleavage of cell surface PrP^C occurs within minutes and was inhibited by the hydroxyl radical quencher dimethyl sulfoxide and by an antibody against the octapeptide repeats. A construct of PrP lacking the octapeptide repeats, PrPΔoct, failed to undergo ROS-mediated β-cleavage, as did two mutant forms of PrP, PG14 and A116V, associated with human prion diseases. As compared with cells expressing wild type PrP, when challenged with H₂O₂ and Cu²⁺, cells expressing PrPΔoct, PG14, or A116V had reduced viability and glutathione peroxidase activity and increased intracellular free radicals. Thus, lack of ROS-mediated β-cleavage of PrP correlated with the sensitivity of the cells to oxidative stress. These data indicate that the β-cleavage of PrP^C is an early and critical event in the mechanism by which PrP protects cells against oxidative stress.