Open AccessIsolation of a Defective Prion Mutant from Natural Scrapie
Author(s) -
Ilaria Vanni,
Sergio Migliore,
Gian Mario Cosseddu,
Michele Angelo Di Bari,
Laura Pirisinu,
Claudia D’Agostino,
Geraldina Riccardi,
Umberto Agrimi,
Romolo no
Publication year - 2016
Publication title -
plos pathogens
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.719
H-Index - 206
eISSN - 1553-7374
pISSN - 1553-7366
DOI - 10.1371/journal.ppat.1006016
Subject(s) - scrapie , mutant , biology , in vitro , population , mutation , transmissible spongiform encephalopathy , prion protein , bank vole , virology , microbiology and biotechnology , genetics , gene , medicine , demography , disease , pathology , sociology
It is widely known that prion strains can mutate in response to modification of the replication environment and we have recently reported that prion mutations can occur in vitro during amplification of vole-adapted prions by Protein Misfolding Cyclic Amplification on bank vole substrate (bvPMCA). Here we exploited the high efficiency of prion replication by bvPMCA to study the in vitro propagation of natural scrapie isolates. Although in vitro vole-adapted PrP Sc conformers were usually similar to the sheep counterpart, we repeatedly isolated a PrP Sc mutant exclusively when starting from extremely diluted seeds of a single sheep isolate. The mutant and faithful PrP Sc conformers showed to be efficiently autocatalytic in vitro and were characterized by different PrP protease resistant cores, spanning aa ∼155–231 and ∼80–231 respectively, and by different conformational stabilities. The two conformers could thus be seen as different bona fide PrP Sc types, putatively accounting for prion populations with different biological properties. Indeed, once inoculated in bank vole the faithful conformer was competent for in vivo replication while the mutant was unable to infect voles, de facto behaving like a defective prion mutant. Overall, our findings confirm that prions can adapt and evolve in the new replication environments and that the starting population size can affect their evolutionary landscape, at least in vitro . Furthermore, we report the first example of “authentic” defective prion mutant, composed of brain-derived PrP C and originating from a natural scrapie isolate. Our results clearly indicate that the defective mutant lacks of some structural characteristics, that presumably involve the central region ∼90–155, critical for infectivity but not for in vitro replication. Finally, we propose a molecular mechanism able to account for the discordant in vitro and in vivo behavior, suggesting possible new paths for investigating the molecular bases of prion infectivity.