title: Dual mechanisms for shedding of the cellular prion protein.
abstract: The cellular prion protein (PrP(C)) is essential for the pathogenesis and transmission of prion diseases. Whereas the majority of PrP(C) is bound to the cell membrane via a glycosylphosphatidylinositol (GPI) anchor, a secreted form of the protein has been identified. Here we show that PrP(C) can be shed into the medium of human neuroblastoma SH-SY5Y cells by both protease- and phospholipase-mediated mechanisms. The constitutive shedding of PrP(C) was inhibited by a range of hydroxamate-based zinc metalloprotease inhibitors in a manner identical to the alpha-secretase-mediated shedding of the amyloid precursor protein, indicating a proteolytic shedding mechanism. Like amyloid precursor protein, this zinc metalloprotease-mediated shedding of PrP(C) could be stimulated by phorbol myristate acetate and by copper ions. The lipid raft-disrupting agents filipin and methyl-beta-cyclodextrin promoted the shedding of PrP(C) via a distinct mechanism that was not inhibited by hydroxamate-based inhibitors. Filipin-mediated shedding of PrP(C) is likely to occur via phospholipase cleavage of the GPI anchor, since a transmembrane polypeptide-anchored PrP construct was not shed in response to filipin treatment. Collectively, our data indicate that shedding of PrP(C) can occur via both secretase-like proteolytic cleavage of the protein and phospholipase cleavage of the GPI anchor moiety.
authors.affiliation: Proteolysis Research Group, School of Biochemistry and Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom.
authors.forename: Edward T
authors.initials: ET
authors.lastname: Parkin
authors.forename: Nicole T
authors.initials: NT
authors.lastname: Watt
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Turner
authors.forename: Nigel M
authors.initials: NM
authors.lastname: Hooper
mesh_terms: D045744:Cell Line, Tumor; D004591:Electrophoresis, Polyacrylamide Gel; D005372:Filipin / Q000378:metabolism; D017261:Glycosylphosphatidylinositols / Q000378:metabolism; D006801:Humans; D043265:Phosphatidylinositol Diacylglycerol-Lyase / Q000378:metabolism; D018621:PrPC Proteins / Q000378:metabolism*
chemical_list: D017261:Glycosylphosphatidylinositols; D018621:PrPC Proteins; D005372:Filipin; D043265:Phosphatidylinositol Diacylglycerol-Lyase