NR AWBQ
AU Bate,C.; Williams,A.
TI Role of glycosylphosphatidylinositol anchors in the neurotoxicity of prions
QU International Conference - Prion 2006: Strategies, advances and trends towards protection of society - 3.10.-6.10.2006, Torino, Italy, Lingotto Conference Centre - Poster sessions PA-06
PT Konferenz-Poster
AB There is increasing interest in the mechanisms by which the formation of PrPsc leads to neuronal dysfunction and ultimately neuronal death. While the changes in protein structure between PrPc and PrPsc have been extensively reported, one consequence of the conversion of PrPc to the PrPsc has been largely ignored; self-aggregation of PrPsc results in the clustering of glycosylphosphatidylinositol (GPI) anchors in lipid rafts that are enriched in signalling molecules. In this study we demonstrate that the addition of GPI anchors isolated from PrPc or PrPsc, but not GPI anchors isolated from other proteins, to cultured neurones mimics some of the effects of PrPsc. We previously identified phospholipase A2 as a key enzyme in the process by which prions damage/kill some neurones. Here we report that phospholipase A2 was activated by GPIs isolated from PrPc / PrPsc. Immunoprecipitation studies showed that cytoplasmic phospholipase A2 was associated with PrPsc in ScGT1 cells, but not with PrPc in GT1 cells and that phospholipase A2 activity was higher in infected than uninfected cells. The addition of these GPIs to neurones also caused synapse damage (reduced cellular synaptophysin content) and activated caspase-3, a marker of apoptosis. These activities of GPIs were lost following digestion with phosphatidylinositol (PI)specific phospholipase C, the removal of acyl chains, the cleavage of the PI-glycan linkage, or following incubation with a monoclonal antibody that recognised PI. In competition assays, pretreatment of neurones with the GPI analogue, glucosamine-PI reduced phospholipase A2 activation in response to PrPsc and rendered neurones resistant to the otherwise toxic effects of HuPrP82-146 or PrPsc preparations. This neuroprotective effect was selective as glucosamine-PI treated neurons remained susceptible to the toxicity of arachidonic acid or platelet activating factor. We propose that PrPsc causes neuronal damage as a consequence of the clustering of specific GPI anchors at high concentrations within lipid raft membranes enriched with signalling molecules. More specifically aggregated GPIs activate phospholipase A2 as an early event in prion-induced neurodegeneration.
AD Department of Pathology and Infectious Diseases, Royal Veterinary College, North Mymms, London, UK. E-mail: cbate@rvc.ac.uk
SP englisch
PO Italien