Relation between the expression of prion protein and the cellular response to oxidative stress: a biological and proteomic approach

Several functions have been attributed to the cellular prion protein, PrPc, amongst which its anti-oxidant role has rapidly been gaining interest in the recent years. We and others have previously shown, that PrPc expressing cells, of neuroblastoma or epithelial origin, seem to exhibit a higher overall viability towards paraquat toxicity than cells expressing basal or low levels of the protein. Although several studies propose a protective mechanism that involves PrPc dependent activation of the superoxide dismutase (SOD) enzymatic machinery or an activation of its own intrinsic antioxidant function, others argue against this SOD-like role. Our objective was to investigate, at a biological and proteomic level, by which potential mechanism PrPc could protect neuroblastoma cells against paraquat induced oxidative damage.Using a biological aproach, we firstly evaluated the status of the Cu/Zn-SOD enzyme in Human neuroblastoma cells expressing different forms of PrPc following their exposure to paraquat. Next, we performed a proteomic study to investigate by which other potential mechanism(s), PrPc could protect the cell against paraquat induced oxidative stress. Our proteomic approach made use of an optimised two-dimensional liquid chromatography system, the ProteomeLab PF-2D, and reverse phase chromatography coupled with lava purple stained SDS-PAGE, both interfaced with tandem mass spectrometry.An interesting aspect of our study has been the development of an original immunoproteomic technique called immuno-PF2D-MS/MS, coupling classical immunological methods to a two-dimensional liquid chromatography proteomic tool interfaced with tandem mass spectrometry. We have proposed this technique for antigenic and serological characterization that have important implications in the study of biomarkers. Another important aspect of our study has been the detection of several candidates that could participate in PrPc-mediated protection against paraquat induced oxidative stress. Although, it was out of our scope to investigate each of these candidates in the present study, it presents an interesting perspective for future studies. We have, however, shown the implication of one such candidate: PARP-1. Complimentary tests will be necessary in the future to confirm the actual interaction of this candidate with PrPc.