title: Prion protein "gamma-cleavage": characterizing a novel endoproteolytic processing event.
abstract: The cellular prion protein (PrP(C)) is a ubiquitously expressed protein of currently unresolved but potentially diverse function. Of putative relevance to normal biological activity, PrP(C) is recognized to undergo both α- and β-endoproteolysis, producing the cleavage fragment pairs N1/C1 and N2/C2, respectively. Experimental evidence suggests the likelihood that these processing events serve differing cellular needs. Through the engineering of a C-terminal c-myc tag onto murine PrP(C), as well as the selective use of a far-C-terminal anti-PrP antibody, we have identified a new PrP(C) fragment, nominally 'C3', and elaborating existing nomenclature, 'γ-cleavage' as the responsible proteolysis. Our studies indicate that this novel γ-cleavage event can occur during transit through the secretory pathway after exiting the endoplasmic reticulum, and after PrP(C) has reached the cell surface, by a matrix metalloprotease. We found that C3 is GPI-anchored like other C-terminal and full length PrP(C) species, though it does not localize primarily at the cell surface, and is preferentially cleaved from an unglycosylated substrate. Importantly, we observed that C3 exists in diverse cell types as well as mouse and human brain tissue, and of possible pathogenic significance, γ-cleavage may increase in human prion diseases. Given the likely relevance of PrP(C) processing to both its normal function, and susceptibility to prion disease, the potential importance of this previously underappreciated and overlooked cleavage event warrants further consideration.
authors: Department of Medicine, RMH, The University of Melbourne, Parkville, VIC, 3010, Australia.
authors: Victoria
authors: http://orcid.org/0000-0003-2936-6308
authors: V
authors: Lewis
authors: Department of Pathology, The University of Melbourne, Parkville, VIC, 3010, Australia.
authors: Vanessa A
authors: VA
authors: Johanssen
authors: Department of Pathology, The University of Melbourne, Parkville, VIC, 3010, Australia.
authors: Peter J
authors: PJ
authors: Crouch
authors: Department of Medicine, RMH, The University of Melbourne, Parkville, VIC, 3010, Australia.|The Australian National Creutzfeldt-Jakob Disease Registry, The University of Melbourne, Parkville, VIC, 3010, Australia.
authors: Genevieve M
authors: GM
authors: Klug
authors: Institute of Brain, Behaviour and Mental Health, Faculty of Medical and Human Sciences, The University of Manchester, Manchester, M13 9PT, UK.
authors: Nigel M
authors: NM
authors: Hooper
authors: Department of Medicine, RMH, The University of Melbourne, Parkville, VIC, 3010, Australia. stevenjc@unimelb.edu.au.|The Australian National Creutzfeldt-Jakob Disease Registry, The University of Melbourne, Parkville, VIC, 3010, Australia. stevenjc@unimelb.edu.au.
authors: Steven J
authors: SJ
authors: Collins
mesh_terms: D000818:Animals; D002460:Cell Line; D006801:Humans; D020782:Matrix Metalloproteinases / Q000378:metabolism / Q000502:physiology; D051379:Mice; D010446:Peptide Fragments / Q000032:analysis / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D018621:PrPC Proteins / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D017096:Prion Diseases / Q000378:metabolism; D017510:Protein Folding; D011499:Protein Processing, Post-Translational; D059748:Proteolysis
chemical_list: D010446:Peptide Fragments; D018621:PrPC Proteins; D020782:Matrix Metalloproteinases
keywords: Endoproteolysis; Prion protein; Protein cleavage; Protein processing