Reactive Oxygen Species-mediated β-Cleavage of the Prion Protein in the Cellular Response to Oxidative Stress

Abstract

The cellular prion protein (PrPC) is critical for the development of prion diseases. However, the physiological role of PrPC is less clear, although a role in the cellular resistance to oxidative stress has been proposed. PrPC is cleaved at the end of the copper-binding octapeptide repeats through the action of reactive oxygen species (ROS), a process termed β-cleavage. Here we show that ROS-mediated β-cleavage of cell surface PrPC occurs within minutes and was inhibited by the hydroxyl radical quencher dimethyl sulfoxide and by an antibody against the octapeptide repeats. A construct of PrP lacking the octapeptide repeats, PrPΔoct, failed to undergo ROS-mediated β-cleavage, as did two mutant forms of PrP, PG14 and A116V, associated with human prion diseases. As compared with cells expressing wild type PrP, when challenged with H2O2 and Cu2+, cells expressing PrPΔoct, PG14, or A116V had reduced viability and glutathione peroxidase activity and increased intracellular free radicals. Thus, lack of ROS-mediated β-cleavage of PrP correlated with the sensitivity of the cells to oxidative stress. These data indicate that the β-cleavage of PrPC is an early and critical event in the mechanism by which PrP protects cells against oxidative stress. The cellular prion protein (PrPC) is critical for the development of prion diseases. However, the physiological role of PrPC is less clear, although a role in the cellular resistance to oxidative stress has been proposed. PrPC is cleaved at the end of the copper-binding octapeptide repeats through the action of reactive oxygen species (ROS), a process termed β-cleavage. Here we show that ROS-mediated β-cleavage of cell surface PrPC occurs within minutes and was inhibited by the hydroxyl radical quencher dimethyl sulfoxide and by an antibody against the octapeptide repeats. A construct of PrP lacking the octapeptide repeats, PrPΔoct, failed to undergo ROS-mediated β-cleavage, as did two mutant forms of PrP, PG14 and A116V, associated with human prion diseases. As compared with cells expressing wild type PrP, when challenged with H2O2 and Cu2+, cells expressing PrPΔoct, PG14, or A116V had reduced viability and glutathione peroxidase activity and increased intracellular free radicals. Thus, lack of ROS-mediated β-cleavage of PrP correlated with the sensitivity of the cells to oxidative stress. These data indicate that the β-cleavage of PrPC is an early and critical event in the mechanism by which PrP protects cells against oxidative stress. Prion diseases or transmissible spongiform encephalopathies are a group of neurodegenerative disorders including scrapie in sheep, bovine spongiform encephalopathy in cattle, Creutzfeldt-Jakob disease, and Gerstmann-Sträussler-Scheinker disease in humans (1Prusiner S.B. Proc. Natl. Acad. Sci. U. S. A. 1998; 95: 13363-13383Crossref PubMed Scopus (5099) Google Scholar). In prion diseases, the normal cellular form of the prion protein (PrPC) 4The abbreviations used are:PrPCcellular form of the prion proteinPrPScinfectious, protease resistant form of PrPALLMN-acetyl-Leu-Leu-Met-aldehydeFCSfetal calf serumPBSphosphate-buffered salinePNGase FPeptide:N-glycosidase FROSreactive oxygen specieswtPrPwild type PrPGPIglycosylphosphatidylinositol 4The abbreviations used are:PrPCcellular form of the prion proteinPrPScinfectious, protease resistant form of PrPALLMN-acetyl-Leu-Leu-Met-aldehydeFCSfetal calf serumPBSphosphate-buffered salinePNGase FPeptide:N-glycosidase FROSreactive oxygen specieswtPrPwild type PrPGPIglycosylphosphatidylinositol undergoes a conformational conversion to the β-sheet-rich scrapie isoform (PrPSc) that is partially resistant to protease digestion. Although PrPC is critical for the development of prion disease through its conversion into PrPSc (2Bueler H. Aguzzi A. Sailer A. Greiner R.A. Autenried P. Aguet M. Weissmann C. Cell. 1993; 73: 1339-1347Abstract Full Text PDF PubMed Scopus (1802) Google Scholar, 3Prusiner S.B. Groth D. Serban A. Koehler R. Foster D. Torchia M. Burton D. Yang S.L. DeArmond S.J. Proc. Natl. Acad. Sci. U. S. A. 1993; 90: 10608-10612Crossref PubMed Scopus (416) Google Scholar), the physiological role of PrPC is less clear, and thus it is uncertain whether prion diseases are, in part, due to the loss of a normal neuro-protective function of PrPC (4Hetz C. Maundrell K. Soto C. Trends Mol. Med. 2003; 9: 237-243Abstract Full Text Full Text PDF PubMed Scopus (68) Google Scholar). In the brains of animals at the terminal stage of illness, there is a marked decrease of PrPC, supporting the hypothesis that loss of function of PrPC may play a role in the pathogenesis of prion diseases (5Yokoyama T. Kimura K.M. Ushiki Y. Yamada S. Morooka A. Nakashiba T. Sassa T. Itohara S. J. Biol. Chem. 2001; 276: 11265-11271Abstract Full Text Full Text PDF PubMed Scopus (104) Google Scholar). cellular form of the prion protein infectious, protease resistant form of PrP N-acetyl-Leu-Leu-Met-aldehyde fetal calf serum phosphate-buffered saline Peptide:N-glycosidase F reactive oxygen species wild type PrP glycosylphosphatidylinositol cellular form of the prion protein infectious, protease resistant form of PrP N-acetyl-Leu-Leu-Met-aldehyde fetal calf serum phosphate-buffered saline Peptide:N-glycosidase F reactive oxygen species wild type PrP glycosylphosphatidylinositol Among the neuroprotective functions of PrPC are roles in copper homeostasis and the cellular resistance to oxidative stress (6Vassallo N. Herms J. J. Neurochem. 2003; 86: 538-544Crossref PubMed Scopus (175) Google Scholar, 7Roucou X. Gains M. LeBlanc A.C. J. Neurosci. Res. 2004; 75: 153-161Crossref PubMed Scopus (145) Google Scholar). PrPC binds Cu2+ ions, primarily within the N-terminal octapeptide repeats (8Brown D.R. Qin K. Herms J.W. Madlung A. Manson J. Strome R. Fraser P.E. Kruck T. von Bohlen A. Schulz-Schaeffer W. Giese A. Westaway D. Kretzschmar H. Nature. 1997; 390: 684-687Crossref PubMed Scopus (37) Google Scholar, 9Miura T. Hori-i A. Mototani H. Takeuchi H. Biochemistry. 1999; 38: 11560-11569Crossref PubMed Scopus (248) Google Scholar, 10Viles J.H. Cohen F.E. Prusiner S.B. Goodin D.B. Wright P.E. Dyson H.J. Proc. Natl. Acad. Sci. U. S. A. 1999; 96: 2042-2047Crossref PubMed Scopus (506) Google Scholar), undergoes endocytosis upon exposure of cells to Cu2+ (11Pauly P.C. Harris D.A. J. Biol. Chem. 1998; 273: 33107-33110Abstract Full Text Full Text PDF PubMed Scopus (539) Google Scholar, 12Perera W.S.S. Hooper N.M. Curr. Biol. 2001; 11: 519-523Abstract Full Text Full Text PDF PubMed Scopus (209) Google Scholar), and modulates neuronal Cu2+ content (13Brown D.R. J. Neurochem. 2003; 87: 377-385Crossref PubMed Scopus (45) Google Scholar), implicating PrPC in cellular copper metabolism. Cells deficient in PrPC are less viable in culture compared with cells expressing wild-type PrP (wtPrP) and are more susceptible to oxidative damage and toxicity caused by reactive oxygen species (ROS) (14Brown D.R. Schulz-Schaeffer W.J. Schmidt B. Kretzschmar H.A. Exp. Neurol. 1997; 146: 104-112Crossref PubMed Scopus (390) Google Scholar, 15Kuwahara C. Takeuchi A.M. Nishimura T. Haraguchi K. Kubosaki A. Matsumoto Y. Saeki K. Yokoyama T. Itohara S. Onodera T. Nature. 1999; 400: 225-226Crossref PubMed Scopus (373) Google Scholar, 16White A.R. Collins S.J. Maher F. Jobling M.F. Stewart L.R. Thyer J.M. Beyreuther K. Masters C.L. Cappai R. Am. J. Pathol. 1999; 155: 1723-1730Abstract Full Text Full Text PDF PubMed Scopus (174) Google Scholar, 17Zeng F. Watt N.T. Walmsley A.R. Hooper N.M. J. Neurochem. 2003; 84: 480-490Crossref PubMed Scopus (67) Google Scholar), implicating PrPC in the cellular response to oxidative stress. However, the mechanism by which PrPC mediates this protective effect is not known. PrPC is a glycosylphosphatidylinositol (GPI)-anchored glycoprotein that undergoes a variety of proteolytic processing events. The protein can be cleaved at amino acids 110 and 111 to produce a 17-kDa C-terminal fragment C1 and a corresponding N-terminal fragment N1 (18Pan K.-M. Stahl N. Prusiner S.B. Protein Sci. 1992; 1: 1343-1352Crossref PubMed Scopus (172) Google Scholar, 19Shyng S.-L. Huber M.T. Harris D.A. J. Biol. Chem. 1993; 268: 15922-15928Abstract Full Text PDF PubMed Google Scholar, 20Chen S.G. Teplow D.B. Parchi P. Teller J.K. P. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, A. R. P. B. F. B. F. Am. J. Pathol. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar). processing has been to as A. F. K. Onodera T. Y. S. Biol. Cell. 2004; 96: PubMed Scopus Google and may be by and of the and B. P. Y. D. B. J. F. J. Biol. Chem. 2001; 276: Full Text Full Text PDF PubMed Scopus Google Scholar). PrPC can be cleaved within or to the octapeptide repeats to a C-terminal fragment and the corresponding N-terminal fragment (18Pan K.-M. Stahl N. Prusiner S.B. Protein Sci. 1992; 1: 1343-1352Crossref PubMed Scopus (172) Google Scholar, A. R. P. B. F. B. F. Am. J. Pathol. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar, A. D.R. Serban D. Prusiner S.B. Mol. Biol. Cell. 1992; PubMed Scopus Google Scholar). event to be by A. N. C. D. S. J. Biol. Chem. 2001; 276: Full Text Full Text PDF PubMed Scopus Google and has been termed β-cleavage A. F. K. Onodera T. Y. S. Biol. Cell. 2004; 96: PubMed Scopus Google Scholar). In we that PrPC is the cell surface by a that has to the of the protein Watt N.T. Hooper N.M. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). the role of proteolytic and of the is critical to a of the functions of PrP and may the role of the protein in prion diseases. However, the role of the β-cleavage in the function of PrPC has not been In the we show that PrP in the human cell undergoes and β-cleavage and that β-cleavage is increased upon exposure of the cells to occurs at the cell and can be inhibited by a free radical show that β-cleavage not in a mutant of PrP that the octapeptide repeats in two of PrP and lack of β-cleavage of the PrP with the sensitivity of cells to that this event may be of the mechanism by which PrPC protects cells against oxidative stress. and of PrPΔoct, and PG14 in has been W.S.S. Hooper N.M. Curr. Biol. 2001; 11: 519-523Abstract Full Text Full Text PDF PubMed Scopus (209) Google Scholar). A116V was the with the The construct was by cells and by and cell by as A.R. F. Hooper N.M. J. 2001; PubMed Scopus (67) Google Scholar). was to the cells as in the of fetal calf serum to a of and for the Cu2+ to the cells had the was with with the for the of exposure in Cells into phosphate-buffered saline by at for and in with protease The protein content of was in a with bovine serum as a PubMed Scopus Google Scholar). and at with with to the and for at in the or of and H2O2 in with to and for with protein The protein was by for at and the was at with Protein was to and for The by at for and with The was in for by and cells for at in the or of as a PrP at the cell surface was by with as W.S.S. Hooper N.M. Curr. Biol. 2001; 11: 519-523Abstract Full Text Full Text PDF PubMed Scopus (209) Google Scholar). and with F for at as A.R. F. Hooper N.M. J. 2001; PubMed Scopus (67) Google Scholar). with of or by through to a The was by for with and with or and with was peroxidase an activity of was in glutathione and The N-acetyl-Leu-Leu-Met-aldehyde in or was at or was as of the a with at and at The data and to The of cell surface PrPC was by cells with antibody for at Cells in in the or of for at Cells with in for and in with for and cells a and data the The corresponding to the of the of by in culture in this was with with H2O2 or a the cells in at for and the cell with the the of was a and in to the cell in of and of intracellular free was exposure of the cells to H2O2 or in for as F. Watt N.T. Walmsley A.R. Hooper N.M. J. Neurochem. 2003; 84: 480-490Crossref PubMed Scopus (67) Google Scholar). peroxidase activity was and glutathione at upon the of of as F. Watt N.T. Walmsley A.R. Hooper N.M. J. Neurochem. 2003; 84: 480-490Crossref PubMed Scopus (67) Google Scholar). to of in cell intracellular radical and glutathione peroxidase activity in the cells expressing the mutant are compared against PrPC in Cells to and proteolytic processing of PrPC the (wtPrP) in the human cell was that in the protein the of the of the of PrP and of the C-terminal to which an within the octapeptide repeats, as PrP the C1 in the cell which the of PrP and the fragment of not the C1 the by this antibody S.G. Teplow D.B. Parchi P. Teller J.K. P. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, A. R. P. B. F. B. F. Am. J. Pathol. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar). which an in the C-terminal of the protein PrP, and the C1 fragment of Although the C1 fragment was at a of as PrP, the fragment was at a These data indicate that in cells PrPC is to and to C1 and as for cell and in S.-L. Huber M.T. Harris D.A. J. Biol. Chem. 1993; 268: 15922-15928Abstract Full Text PDF PubMed Google Scholar, 20Chen S.G. Teplow D.B. Parchi P. Teller J.K. P. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, A. R. P. B. F. B. F. Am. J. Pathol. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar, A. F. K. Onodera T. Y. S. Biol. Cell. 2004; 96: PubMed Scopus Google Scholar). of PrPC Cells to there is to that β-cleavage of PrPC is by A. N. C. D. S. J. Biol. Chem. 2001; 276: Full Text Full Text PDF PubMed Scopus Google Scholar), we the effect of H2O2 and Cu2+ the of the fragment the cell to caused an in the of A and due to the of of the serum the C. Takeuchi A.M. Nishimura T. Haraguchi K. Kubosaki A. Matsumoto Y. Saeki K. Yokoyama T. Itohara S. Onodera T. Nature. 1999; 400: 225-226Crossref PubMed Scopus (373) Google Scholar). In the of H2O2 and Cu2+, there was a in the of that in the cells within A and In to the in the of PrP and the C1 fragment and with the of serum or upon of the cells with H2O2 and These indicate that increased the of β-cleavage had effect that β-cleavage of PrPC is a ROS-mediated the effect of the hydroxyl radical quencher was cells expressing in in the of there was a in the of A and with β-cleavage a ROS-mediated of is by the hydroxyl radical cells expressing to of for in of with F with antibody or an antibody by and as for the fragment ROS-mediated of PrPC at the whether cell surface PrPC was to ROS-mediated β-cleavage, cells expressing to with H2O2 and Cu2+ of PrP with antibody PrP and by with was in the cell although of PrP However, an in the of fragment was of the cells in for and this was increased upon of the cells with H2O2 and Cu2+, that is PrPC at the cell The for the ROS-mediated of whether ROS-mediated β-cleavage of PrPC the octapeptide repeats, we the proteolytic processing of that the copper-binding octapeptide W.S.S. Hooper N.M. Curr. Biol. 2001; 11: 519-523Abstract Full Text Full Text PDF PubMed Scopus (209) Google cells expressing to with and failed to PrPΔoct, this mutant the for this antibody was by and Although antibody the C1 fragment in cells expressing PrPΔoct, antibody the These data indicate that the octapeptide repeats are for PrPC to undergo β-cleavage. ROS-mediated in of the proteolytic processing of two of PG14 an of the octapeptide and is associated with human prion disease P. D. H. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar, S. T. S. Kretzschmar H. W. Res. Mol. Res. PubMed Scopus Google and A116V, in which PrP to in human is to and is associated with Gerstmann-Sträussler-Scheinker disease P. Torchia M. DeArmond S.J. Prusiner S.B. 1998; PubMed Scopus Google cells expressing the two to with and Although in cells expressing PG14 or A116V, and the C1 there was of the fragment in cell by antibody or exposure of the and upon of the cells expressing PG14 or A116V with H2O2 and Cu2+ for to there was for the of was in cells expressing not These data indicate that in cells expressing two of PrP, although C1 is is not upon exposure of the cells to for the lack of ROS-mediated β-cleavage in cells expressing PG14 or A116V is that the to to the cell surface this processing we W.S.S. Hooper N.M. Curr. Biol. 2001; 11: 519-523Abstract Full Text Full Text PDF PubMed Scopus (209) Google and S. Harris D.A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google by surface and that PG14 is at the cell Although the A116V mutant is at a in the cells the of this mutant at the cell surface as by surface was to that of The cell surface of A116V was by the A116V construct a of cell surface which be by of the cells with which the the protein the the the PG14 are when cells are to Cu2+ W.S.S. Hooper N.M. Curr. Biol. 2001; 11: 519-523Abstract Full Text Full Text PDF PubMed Scopus (209) Google Scholar), we that the lack of β-cleavage may with a in However, when cells expressing A116V to a of Cu2+ to endocytosis of W.S.S. Hooper N.M. Curr. Biol. 2001; 11: 519-523Abstract Full Text Full Text PDF PubMed Scopus (209) Google Scholar), this mutant was Thus, the of the A116V and PG14 to the cell surface not for the lack of ROS-mediated β-cleavage of and to undergo β-cleavage not with a in to ROS-mediated with a and of to whether to undergo ROS-mediated β-cleavage a function of PrPC, we the resistance to oxidative stress of cells expressing PrPΔoct, PG14, and we that cells expressing an increased a reduced of intracellular free and increased glutathione peroxidase activity as compared with cells upon exposure to H2O2 and Cu2+ F. Watt N.T. Walmsley A.R. Hooper N.M. J. Neurochem. 2003; 84: 480-490Crossref PubMed Scopus (67) Google Scholar). The viability of cells expressing the of PrP was by of cell Cells expressing PrPΔoct, PG14, or A116V reduced viability when challenged with H2O2 and Cu2+ as compared with cells expressing of intracellular free radical in the cells was the in to whether cell damage was in the cells expressing the PrP there was a decrease in radical in the cells as compared with the cells expressing PrPΔoct, PG14, or A116V had a of radical to that of the cells peroxidase is a of an in H2O2 upon glutathione The cells had a of glutathione peroxidase activity the the cells expressing PrPΔoct, PG14, or A116V had reduced glutathione peroxidase activity as compared with cells data indicate that cells expressing PrPΔoct, PG14, or A116V, of which undergo ROS-mediated β-cleavage, not against oxidative stress in the that cells expressing the ROS-mediated β-cleavage and the resistance of cells to oxidative we to β-cleavage of and cell viability upon exposure to that antibody which binds to the octapeptide repeats may β-cleavage. Cells expressing in the of antibody or antibody as to exposure to Cu2+ and H2O2 Although the of in cells with its was reduced by A and cells with had a viability when to Cu2+ and H2O2 cells to or antibody that β-cleavage is in the cellular response to oxidative stress. the ROS-mediated of PrPC by it has been that in and a fragment is that is and is through of PrPSc by R. T. R.A. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). In the fragment in the cells in the was whether the the of and of the cells with in to a in the of However, this was due to the free radical effect of the of and and in did not the of the that in or inhibited the activity of against a Thus, the failed to the ROS-mediated β-cleavage of PrPC in the and the fragment was to digestion. PrPC is to a variety of proteolytic that may its However, the role of and the function of the to be In the we show for the that the ROS-mediated β-cleavage of PrPC occurs at the cell the octapeptide within PrPC, and is in two forms of PrP associated with prion we show that this to undergo ROS-mediated β-cleavage with an increased sensitivity of cells to oxidative the that β-cleavage may be a critical in the mechanism PrPC protects cells against oxidative stress. Although the β-cleavage of PrPC at the C-terminal end of the octapeptide repeats, has been by (18Pan K.-M. Stahl N. Prusiner S.B. Protein Sci. 1992; 1: 1343-1352Crossref PubMed Scopus (172) Google Scholar, A. R. P. B. F. B. F. Am. J. Pathol. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar, A. D.R. Serban D. Prusiner S.B. Mol. Biol. Cell. 1992; PubMed Scopus Google Scholar), the mechanism of this A. N. C. D. S. J. Biol. Chem. 2001; 276: Full Text Full Text PDF PubMed Scopus Google that it was ROS-mediated and These that PrP in β-cleavage upon exposure to of H2O2 in the of this to a more in by that exposure of cells expressing PrPC to of H2O2 and β-cleavage, as by the of the C-terminal fragment has been that PrPC is in the cellular response mechanism to oxidative as a of D.R. Trends Neurosci. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar, S. Res. Res. 38: PubMed Scopus Google Scholar). Although it has been that β-cleavage of PrP A. N. C. D. S. J. Biol. Chem. 2001; 276: Full Text Full Text PDF PubMed Scopus Google Scholar), it has not been whether the β-cleavage of PrPC may be in the mechanism by which cells to oxidative stress. that PrPC undergoes β-cleavage upon exposure of cells to and that lack of β-cleavage with an increased sensitivity to oxidative stress the that this processing event is an early in the cellular response to oxidative stress. it has been that in and in scrapie a fragment is that is and is through of PrPSc by R. T. R.A. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). The of PrPC in the cells was not by a was with the of R. T. R.A. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google that in cells and the fragment is not Thus, it that PrPC is to ROS-mediated β-cleavage, which the fragment that is PrPSc is cleaved by to produce a fragment that is is that the conformational PrPC to PrPSc a for that is not in the copper the of as the hydroxyl radical although not a is an of oxidative stress in A.R. Collins S.J. Maher F. Jobling M.F. Stewart L.R. Thyer J.M. Beyreuther K. Masters C.L. Cappai R. Am. J. Pathol. 1999; 155: 1723-1730Abstract Full Text Full Text PDF PubMed Scopus (174) Google Scholar). the is the Cu2+ are in the octapeptide repeats of PrPC, the can that may at in the in K. S.G. J. Biol. Chem. Full Text PDF PubMed Google Scholar). The critical of in the β-cleavage of PrPC is by the effect of the hydroxyl radical The of the Cu2+ at the octapeptide repeats of PrPC to the ROS-mediated β-cleavage is by the lack of ROS-mediated of PrPΔoct, which the octapeptide repeats and has Cu2+ in this of the Although Cu2+ of the octapeptide repeats been N. A.R. J. Proc. Natl. Acad. Sci. U. S. A. 2001; PubMed Scopus Google Scholar, K. Yang Y. P. Westaway D. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, Prusiner S.B. J. Biochemistry. 2003; PubMed Scopus Google Scholar), the Cu2+ at not to be in the ROS-mediated of PrPC, as by the lack of of PrPΔoct, which Cu2+ data indicate that ROS-mediated β-cleavage of PrPC may be the in a of cellular that the cell to a response to increased oxidative stress. with this is the that cells expressing increased viability and glutathione peroxidase activity and reduced intracellular free when to as compared with cells and that protective to are not in the cells expressing PrPΔoct, which to undergo β-cleavage due to the lack of the octapeptide repeats or in cells expressing when β-cleavage is by the of antibody to the octapeptide repeats. it that PG14 A116V was to ROS-mediated β-cleavage. As in the and W.S.S. Hooper N.M. Curr. Biol. 2001; 11: 519-523Abstract Full Text Full Text PDF PubMed Scopus (209) Google Scholar, S. Harris D.A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar), this is not due to a of of PrP to the cell ROS-mediated β-cleavage it is not to an to undergo endocytosis as with PG14 and W.S.S. Hooper N.M. Curr. Biol. 2001; 11: 519-523Abstract Full Text Full Text PDF PubMed Scopus (209) Google Scholar), A116V was upon of the cells with PG14, which an of the octapeptide be to be more susceptible to ROS-mediated this is not the and the octapeptide through the of an S. Harris D.A. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar, R. B. A. P. B. Harris D.A. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar), may ROS-mediated β-cleavage. In the of A116V, a the of β-cleavage has a effect is not is that this the of the and thus ROS-mediated β-cleavage In this it is to that of and to the of this into the of H. J. Prusiner S.B. D.A. J. Mol. Biol. PubMed Scopus Google Scholar). The of the not to which of the proteolytic or ROS-mediated β-cleavage of PrPC is for the The fragment may as a to D.R. Trends Neurosci. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar). In of this is the that of the N-terminal PrP the to R. N. K. S. T. S. S. J. Biol. Chem. 2003; Full Text Full Text PDF PubMed Scopus (45) Google and that cells expressing a construct of PrP in which the is to the through an are in resistance to oxidative stress F. Watt N.T. Walmsley A.R. Hooper N.M. J. Neurochem. 2003; 84: 480-490Crossref PubMed Scopus (67) Google Scholar). it has been that the fragment is in the cellular response to oxidative stress and of S. Res. Res. 38: PubMed Scopus Google and that the protective function of is by to C1 A. F. K. Onodera T. Y. S. Biol. Cell. 2004; 96: PubMed Scopus Google Scholar). Thus, there is a the and C1 However, data against a although PrPΔoct, PG14, and A116V failed to produce of C1 to by we the that the and of PrPC are proteolytic to the and of the protein N.M. Curr. Med. Chem. 9: PubMed Scopus Google Scholar). The that ROS-mediated β-cleavage of PrPC is in the two PG14 and A116V to the that prion diseases are, in part, due to the loss of a normal function of PrPC (4Hetz C. Maundrell K. Soto C. Trends Mol. Med. 2003; 9: 237-243Abstract Full Text Full Text PDF PubMed Scopus (68) Google Scholar). the of cells expressing the PG14 and A116V to a protective response against oxidative stress be is that oxidative stress is in prion diseases M. T. C. H. PubMed Scopus Google Scholar, Res. 1999; PubMed Scopus Google Scholar, J. 1998; 96: PubMed Scopus Google Scholar). upon conversion to PrPC is to be to ROS-mediated β-cleavage as part, the of the cellular mechanism to against oxidative stress. In of prion disease due to in PrP, as in PG14 and A116V, that ROS-mediated β-cleavage of PrPC, the normal cellular response to oxidative stress is and this in may to the