1. Expression of Mutant or Cytosolic PrP in Transgenic Mice and Cells Is Not Associated with Endoplasmic Reticulum Stress or Proteasome Dysfunction
- Author
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Sara Dossena, Anna Garofoli, Ada De Luigi, Antonio Migheli, Gianluigi Forloni, Elena Quaglio, Mario Salmona, Roberto Chiesa, Roberto Sitia, Luigina Tagliavacca, Elena Restelli, Daniele Imperiale, Quaglio, E, Restelli, E, Garofoli, A, Dossena, S, DE LUIGI, A, Tagliavacca, L, Imperiale, D, Migheli, A, Salmona, M, Sitia, Roberto, Forloni, G, and Chiesa, R.
- Subjects
PRION ,Mutant ,lcsh:Medicine ,Endoplasmic Reticulum ,PC12 Cells ,Prion Diseases ,Mice ,ENDOPLSAMIC RETICULUM ,Cytosol ,Molecular Cell Biology ,Neurobiology of Disease and Regeneration ,PROTEASOME ,lcsh:Science ,Endoplasmic Reticulum Chaperone BiP ,Cells, Cultured ,Cellular Stress Responses ,Neurons ,Multidisciplinary ,Cell Death ,UNFOLDED PROTEIN RESPONSE ,Neurodegenerative Diseases ,Infectious Diseases ,Neurology ,Medicine ,Research Article ,Genetically modified mouse ,Proteasome Endopeptidase Complex ,Prions ,Transgene ,Green Fluorescent Proteins ,Mice, Transgenic ,Biology ,Animals ,Humans ,Secretory pathway ,Endoplasmic reticulum ,lcsh:R ,Molecular biology ,Rats ,Mice, Inbred C57BL ,Proteasome ,Protein Biosynthesis ,Mutation ,Mice, Inbred CBA ,Unfolded protein response ,lcsh:Q ,Peptides ,Neuroscience - Abstract
The cellular pathways activated by mutant prion protein (PrP) in genetic prion diseases, ultimately leading to neuronal dysfunction and degeneration, are not known. Several mutant PrPs misfold in the early secretory pathway and reside longer in the endoplasmic reticulum (ER) possibly stimulating ER stress-related pathogenic mechanisms. To investigate whether mutant PrP induced maladaptive responses, we checked key elements of the unfolded protein response (UPR) in transgenic mice, primary neurons and transfected cells expressing two different mutant PrPs. Because ER stress favors the formation of untranslocated PrP that might aggregate in the cytosol and impair proteasome function, we also measured the activity of the ubiquitin proteasome system (UPS). Molecular, biochemical and immunohistochemical analyses found no increase in the expression of UPR-regulated genes, such as Grp78/Bip, CHOP/GADD153, or ER stress-dependent splicing of the mRNA encoding the X-box-binding protein 1. No alterations in UPS activity were detected in mutant mouse brains and primary neurons using the Ub(G76V)-GFP reporter and a new fluorogenic peptide for monitoring proteasomal proteolytic activity in vivo. Finally, there was no loss of proteasome function in neurons in which endogenous PrP was forced to accumulate in the cytosol by inhibiting cotranslational translocation. These results indicate that neither ER stress, nor perturbation of proteasome activity plays a major pathogenic role in prion diseases.
- Published
- 2011