Inhibition of phospholipase A2 increased the removal of the prion derived peptide PrP82-146 from cultured neurons

The prion diseases are characterised by the formation of the disease-associated isoform of the prion protein (PrPSc) and the production of disease-related peptides. The prion derived peptide PrP82-146 bound readily to cortical neurons and was found within detergent resistant membranes that are commonly called lipid rafts. It was not found within lysosomes and the slow degradation of PrP82-146 resulted in a half-life of approximately 5 days. In cortical neurons pre-treated with phospholipase A2 (PLA2) inhibitors (AACOCF3 or MAFP) less PrP82-146 entered lipid rafts, more PrP82-146 was found within lysosomes and the half-life of PrP82-146 was reduced to 24 h. Similarly, pre-treatment of neurons with platelet-activating factor (PAF) receptor antagonists (Hexa-PAF and ginkgolide B) increased the entry of PrP82-146 into lysosomes and reduced its half-life. Furthermore, the addition of PAF reversed the effects of PLA2 inhibitors on PrP82-146 trafficking. PAF controlled the amount of cholesterol in cell membranes and the effects of PAF receptor antagonists on the trafficking of PrP82-146 were reversed by the addition of cholesterol. We conclude that activation of PLA2 and the production of PAF control a cholesterol-sensitive pathway that affects the cellular localisation and hence the fate of PrP82-146 in neurons.

Research highlights► Neurotoxic prion derived peptides accumulate in lipid rafts and traffic within neurons via an intracellular pathway that mostly avoids the lysosomes. ► In neurons treated with phospholipase A2 or platelet-activating factor antagonists the neurotoxic peptides are rerouted into lysosmes and are rapidly cleared from cells. ► Platelet-activating factor controlled the amount of cholesterol in cell membranes and hence the formation and function of lipid rafts. ► We conclude that activation of phospholipase A2 and the production of platelet-activating factor control a cholesterol-sensitive pathway that affects the cellular localisation and hence the fate of the neurotoxic peptide PrP82-146 in neurons.