title: Proteolytic processing of the ovine prion protein in cell cultures.
abstract: The cellular compartment and purpose of the proteolytic processing of the prion protein (PrP) are still under debate. We have studied ovine PrP constructs expressed in four cell lines; murine neuroblastoma cells (N2a), human neuroblastoma cells (SH-SY5Y), dog kidney epithelial cells (MDCK), and human furin-deficient colon cancer cells (LoVo). Cleavage of PrP in LoVo cells indicates that the processing is furin independent. Neither is it reduced by some inhibitors of lysosomal proteinases, proteasomes or zinc-metalloproteinases, but incubation with bafilomycin A1, an inhibitor of vacuolar H+/ATPases, increases the amount of uncleaved PrP in the apical medium of MDCK cells. Mutations affecting the putative cleavage site near amino acid 113 reveal that the cleavage is independent of primary structure at this site. Absence of glycosylphosphatidylinositol anchor and glycan modifications does not influence the proteolytic processing of PrP. Our data indicate that PrP is cleaved during transit to the cell membrane.
authors.affiliation: Department of Molecular Biosciences, University of Oslo, P.O. Box 1041 Blindern, N-0316 Oslo, Norway.
authors.forename: Heidi
authors.initials: H
authors.lastname: Tveit
authors.forename: Christoffer
authors.initials: C
authors.lastname: Lund
authors.forename: Christel M
authors.initials: CM
authors.lastname: Olsen
authors.forename: Cecilie
authors.initials: C
authors.lastname: Ersdal
authors.forename: Kristian
authors.initials: K
authors.lastname: Prydz
authors.forename: Ingrid
authors.initials: I
authors.lastname: Harbitz
authors.forename: Michael A
authors.initials: MA
authors.lastname: Tranulis
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D045744:Cell Line, Tumor; D004285:Dogs; D004791:Enzyme Inhibitors / Q000494:pharmacology; D049452:Green Fluorescent Proteins / Q000235:genetics; D006801:Humans; D018942:Macrolides / Q000494:pharmacology; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011328:Prions / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012756:Sheep / Q000378:metabolism; D025262:Vacuolar Proton-Translocating ATPases / Q000037:antagonists & inhibitors
chemical_list: D004791:Enzyme Inhibitors; D018942:Macrolides; D011328:Prions; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; C040929:bafilomycin A1; D025262:Vacuolar Proton-Translocating ATPases