title: Intracellular accumulation of a 46 kDa species of mouse prion protein as a result of loss of glycosylation in cultured mammalian cells.
abstract: Prion diseases are fatal neurodegenerative disorders characterized by the accumulation of an abnormal isoform (PrPSc) of the normal cellular prion protein (PrPC) in the brain. Reportedly, abnormal N-linked glycosylation patterns in PrPC are associated with disease susceptibility; thus, we compared the glycosylation status of normal and several mutant forms of the murine prion protein (MuPrP) in cultured mammalian cells. Substitution of the N-terminal signal sequence of normal MuPrP with a heterologous signal peptide did not alter glycosylation. When expressed without the C-terminal glycophosphatidylinositol anchor signal, the majority of MuPrP remained intracellular and unglycosylated, and a 46 kDa species (p46) of the unglycosylated PrPC was detected on reducing gels. p46 was also observed when wild-type MuPrP was expressed in the presence of tunicamycin or enzymatically deglycosylated in vitro. A rabbit polyclonal anti-serum raised against dimeric MuPrP cross-reacted with p46 and localized the signal within the Golgi apparatus. We propose that the 46 kDa signal is a dimeric form of MuPrP and in the light of recent studies, it can be argued that a relatively stable, non-glycosylated, cytoplasmic PrPC dimer, produced as a result of compromised glycosylation is an intermediate in initiating conversion of PrPC to PrPSc in sporadic transmissible spongiform encephalopathies.
authors.affiliation: Laboratory of Nucleic Acid Vaccines, Department of Medicine, University of Massachusetts Medical School, 364 Plantation St., Worcester, MA 01605, USA.
authors.forename: Subhabrata
authors.initials: S
authors.lastname: Biswas
authors.forename: Jan P M
authors.initials: JP
authors.lastname: Langeveld
authors.forename: Donald
authors.initials: D
authors.lastname: Tipper
authors.forename: Shan
authors.initials: S
authors.lastname: Lu
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism; D019281:Dimerization; D020022:Genetic Predisposition to Disease; D006031:Glycosylation; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D051379:Mice; D017096:Prion Diseases / Q000378:metabolism; D011328:Prions / Q000096:biosynthesis* / Q000737:chemistry; D017434:Protein Structure, Tertiary
chemical_list: D011328:Prions