Dual Mechanisms for Shedding of the Cellular Prion Protein

• Published in: The Journal of biological chemistry Vol. 279; no. 12; pp. 11170 - 11178
• Main Authors: Parkin, Edward T., Watt, Nicole T., Turner, Anthony J., Hooper, Nigel M.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 19.03.2004; American Society for Biochemistry and Molecular Biology
• Subjects: Cell Line, Tumor; Electrophoresis, Polyacrylamide Gel; Filipin - metabolism; Glycosylphosphatidylinositols - metabolism; Humans; Phosphatidylinositol Diacylglycerol-Lyase - metabolism; PrPC Proteins - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M312105200

The cellular prion protein (PrPC) is essential for the pathogenesis and transmission of prion diseases. Whereas the majority of PrPC is bound to the cell membrane via a glycosylphosphatidylinositol (GPI) anchor, a secreted form of the protein has been identified. Here we show that PrPC can be shed into the medium of human neuroblastoma SH-SY5Y cells by both protease- and phospholipase-mediated mechanisms. The constitutive shedding of PrPC was inhibited by a range of hydroxamate-based zinc metalloprotease inhibitors in a manner identical to the α-secretase-mediated shedding of the amyloid precursor protein, indicating a proteolytic shedding mechanism. Like amyloid precursor protein, this zinc metalloprotease-mediated shedding of PrPC could be stimulated by phorbol myristate acetate and by copper ions. The lipid raft-disrupting agents filipin and methyl-β-cyclodextrin promoted the shedding of PrPC via a distinct mechanism that was not inhibited by hydroxamate-based inhibitors. Filipin-mediated shedding of PrPC 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 PrPC can occur via both secretase-like proteolytic cleavage of the protein and phospholipase cleavage of the GPI anchor moiety.