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  • Title: Characterization of the proapoptotic intracellular mechanisms induced by a toxic conformer of the recombinant human prion protein fragment 90-231.
    Author: Villa V, Corsaro A, Thellung S, Paludi D, Chiovitti K, Venezia V, Nizzari M, Russo C, Schettini G, Aceto A, Florio T.
    Journal: Ann N Y Acad Sci; 2006 Dec; 1090():276-91. PubMed ID: 17384271.
    Abstract:
    Prion diseases comprise a group of fatal neurodegenerative disorders that affect both animals and humans. The transition of the prion protein (PrP) from a mainly alpha-structured isoform (PrPC) to a prevalent beta-sheet-containing protein (PrPSc) is believed to represent a major pathogenetic mechanism in prion diseases. To investigate the linkage between PrP neurotoxicity and its conformation, we used a recombinant prion protein fragment corresponding to the amino acidic sequence 90-231 of human prion protein (hPrP90-231). Using thermal denaturation, we set up an experimental model to induce the process of conversion from PrPC to PrPSc. We report that partial thermal denaturation converts hPrP90-231 into a beta-sheet-rich isoform, displaying a temperature- and time-dependent conversion into oligomeric structures that share some physico-chemical characteristics with brain PrPSc. SH-SY5Y cells were chosen to characterize the potential neurotoxic effect of hPrP90-231 in its different structural conformations. We demonstrated that hPrP90-231 in beta-conformation, but not when alpha-structured, powerfully affected the survival of these cells. hPrP90-231 beta-structured caused DNA fragmentation and a significant increase in caspase-3 proteolytic activity (maximal effects+170%), suggesting the occurrence of apoptotic cell death. Finally, we investigated the involvement of MAP kinases in the regulation of beta-hPrP90-231-dependent apoptosis. We observed that the p38 MAP kinase blocker SB203580 prevented the apoptotic cell death evoked by hPrP90-231, and Western blot analysis revealed that the exposure of the cells to the peptide induced p38 phosphorylation. In conclusion, we demonstrate that the hPrP90-231 elicits proapoptotic activity when in beta-sheet-rich conformation and that this effect is mediated by p38 and caspase-3 activation.
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