Deletion of beta-strand and alpha-helix secondary structure in normal prion protein inhibits formation of its protease-resistant isoform.
A fundamental event in the pathogenesis of transmissible spongiform encephalopathies (TSE) is the conversion of a normal, proteinase K-sensitive, host-encoded protein, PrP-sen, into its protease-resistant isoform, PrP-res. During the formation of PrP-res, PrP-sen undergoes conformational changes that involve an increase of beta-sheet secondary structure. While previous studies in which PrP-sen deletion mutants were expressed in transgenic mice or scrapie-infected cell cultures have identified regions in PrP-sen that are important in the formation of PrP-res, the exact role of PrP-sen secondary structures in the conformational transition of PrP-sen to PrP-res has not yet been defined. We constructed PrP-sen mutants with deletions of the first beta-strand, the second beta-strand, or the first alpha-helix and tested whether these mutants could be converted to PrP-res in both scrapie-infected neuroblastoma cells (Sc(+)-MNB cells) and a cell-free conversion assay. Removal of the second beta-strand or the first alpha-helix significantly altered both processing and the cellular localization of PrP-sen, while deletion of the first beta-strand had no effect on these events. However, all of the mutants significantly inhibited the formation of PrP-res in Sc(+)-MNB cells and had a greatly reduced ability to form protease-resistant PrP in a cell-free assay system. Thus, our results demonstrate that deletion of the beta-strands and the first alpha-helix of PrP-sen can fundamentally affect PrP-res formation and/or PrP-sen processing.
Vorberg
I
I
Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana 59840, USA.
Chan
K
K
Priola
S A
SA
D000818:Animals; D019286:Endopeptidase K / Q000494:pharmacology*; D051379:Mice; D016297:Mutagenesis, Site-Directed; D011328:Prions / Q000737:chemistry* / Q000378:metabolism; D017433:Protein Structure, Secondary; D014407:Tumor Cells, Cultured
D011328:Prions; D019286:Endopeptidase K