Inhibition of cholesterol recycling impairs cellular PrPSc propagation

Abstract

The infectious agent in prion diseases consists of an aberrantly folded isoform of the cellular prion protein (PrPc), termed PrP Sc, which accumulates in brains of affected individuals. Studies on prion-infected cultured cells indicate that cellular cholesterol homeostasis influences PrPSc propagation. Here, we demonstrate that the cellular PrPSc content decreases upon accumulation of cholesterol in late endosomes, as induced by NPC-1 knock-down or treatment with U18666A. PrP c trafficking, lipid raft association, and membrane turnover are not significantly altered by such treatments. Cellular PrPSc formation is not impaired, suggesting that PrPSc degradation is increased by intracellular cholesterol accumulation. Interestingly, PrPSc propagation in U18666A-treated cells was partially restored by overexpression of rab 9, which causes redistribution of cholesterol and possibly of PrP Sc to the trans-Golgi network. Surprisingly, rab 9 overexpression itself reduced cellular PrPSc content, indicating that PrP Sc production is highly sensitive to alterations in dynamics of vesicle trafficking.