Thermostability as a highly dependent prion strain feature

Alba Marín-Moreno,Juan Carlos Espinosa,Vincent Béringue,Juan María Torres,Mohammed Moudjou,Patricia Aguilar-Calvo

doi:10.1038/s41598-019-47781-6

Abstract

Prion diseases are caused by the conversion of physiological PrPC into the pathogenic misfolded protein PrPSc, conferring new properties to PrPSc that vary upon prion strains. In this work, we analyze the thermostability of three prion strains (BSE, RML and 22L) that were heated at 98 °C for 2 hours. PrPSc resistance to proteinase K (PrPres), residual infectivity by mouse bioassay and in vitro templating activity by protein misfolding cyclic amplification (PMCA) were studied. Heated strains showed a huge loss of PrPres and a radically different infectivity loss: RML was the most thermolabile strain (6 to 7 log10 infectivity loss), followed by 22L (5 log10) while BSE was the most thermostable strain with low or null infectivity reduction showing a clear dissociation between PrPres and infectivity. These results indicate that thermostability is a strain-specific feature, measurable by PMCA and mouse bioassay, and a great tool to distinguish prion strains.

Highlights

Prion diseases are fatal neurodegenerative diseases that affect numerous mammal species and include kuru, Creutzfeldt-Jakob disease (CJD), fatal familial insomnia (FFI) and Gerstmann-Sträussler-Scheinker disease (GSS) in humans, scrapie in sheep and goats, bovine spongiform encephalopathy (BSE) in cattle and chronic wasting disease (CWD) in cervids[1]
This suggests that highly neuroinvasive prion strains may be conformationally unstable in denaturing conditions and efficiently form diffuse, non-fibrillar PrP aggregates in the central nervous system (CNS), which produces a rapid progression to terminal disease in mice
In the same line of results, Western blot (WB) analysis of the heated samples showed lower amounts of detectable PrPSc resistance to proteinase K (PrPres) than their respective non-heated counterparts (Fig. 1B)

Summary

Introduction

Prion diseases are fatal neurodegenerative diseases that affect numerous mammal species and include kuru, Creutzfeldt-Jakob disease (CJD), fatal familial insomnia (FFI) and Gerstmann-Sträussler-Scheinker disease (GSS) in humans, scrapie in sheep and goats, bovine spongiform encephalopathy (BSE) in cattle and chronic wasting disease (CWD) in cervids[1]. PrPC conversion into PrPSc is a post-translational process where both isoforms share an identical amino acid sequence but differ in their conformation This conformational change confers distinct physicochemical properties such as greater tendency to aggregate, greater insolubility in non-ionic detergents, partial resistance to protease digestion and high resistance to heat and chemical sterilization[3,4,5,6,7]. These properties vary upon prion agents which may result in distinctive prion disease phenotypes including incubation times, clinical signs, histopathological lesions and PrPSc deposition patterns in the brain.

Methods

Results

Conclusion