Quaternary Structure of Pathological Prion Protein as a Determining Factor of Strain-Specific Prion Replication Dynamics

Abstract

Prions are proteinaceous infectious agents responsible for fatal neurodegenerative diseases in animals and humans. They are essentially composed of PrPSc, an aggregated, misfolded conformer of the ubiquitously expressed host-encoded prion protein (PrPC). Stable variations in PrPSc conformation are assumed to encode the phenotypically tangible prion strains diversity. However the direct contribution of PrPSc quaternary structure to the strain biological information remains mostly unknown. Applying a sedimentation velocity fractionation technique to a panel of ovine prion strains, classified as fast and slow according to their incubation time in ovine PrP transgenic mice, has previously led to the observation that the relationship between prion infectivity and PrPSc quaternary structure was not univocal. For the fast strains specifically, infectivity sedimented slowly and segregated from the bulk of proteinase-K resistant PrPSc. To carefully separate the respective contributions of size and density to this hydrodynamic behavior, we performed sedimentation at the equilibrium and varied the solubilization conditions. The density profile of prion infectivity and proteinase-K resistant PrPSc tended to overlap whatever the strain, fast or slow, leaving only size as the main responsible factor for the specific velocity properties of the fast strain most infectious component. We further show that this velocity-isolable population of discrete assemblies perfectly resists limited proteolysis and that its templating activity, as assessed by protein misfolding cyclic amplification outcompetes by several orders of magnitude that of the bulk of larger size PrPSc aggregates. Together, the tight correlation between small size, conversion efficiency and duration of disease establishes PrPSc quaternary structure as a determining factor of prion replication dynamics. For certain strains, a subset of PrP assemblies appears to be the best template for prion replication. This has important implications for fundamental studies on prions.

Analysis of Conformational Stability of Abnormal Prion Protein Aggregates across the Spectrum of Creutzfeldt-Jakob Disease Prions

“…For example, it is largely believed that the heterogeneity in the fragment profile of proteinase K (PK)-digested PrP Sc , which distinguishes at least some of the known prion strains, is the direct consequence of PrP Sc aggregates having distinct conformations (17)(18)(19)(20)(21). Similarly, sedimentation profiles and protease sensitivity have been used as indirect markers of PrP Sc structure and have shown a correlation with strain-specific transmission properties (22)(23)(24)(25)(26)(27). More recently, studies with rodent-adapted, cloned prion strains demonstrated that also the conformational stability of PrP Sc , measured indirectly either by inducing a progressive denaturation of the protein with the chaotropic salt guanidine hydrochloride (GdnHCl) or by exposing the protein to increasing temperatures in the presence of sodium dodecyl sulfate (SDS), may vary among different strains (28)(29)(30).…”

The Volumetric Diversity of Misfolded Prion Protein Oligomers Revealed by Pressure Dissociation

“…Little is known about the changes in hydration properties and intrinsic packing that directly affect the volume of the system during the native to oligomer transition. However, knowledge of the volumetric properties of PrP assemblies is crucial because they might govern strain-specific prion replication dynamics (15) and also because they might dictate the gains in biological functions, such as binding to other molecules and cytotoxicity (10,11).…”

“…It has been hypothesized that hydrodynamic/volumetric properties could be a key factor in strain-specific prion replication dynamics (15). Consistent with this finding, PrP misfolding, which exhibits a strong pressure dependence, affects its hydration and packing (16 -21), two properties that directly alter the volume of the system.…”

Transmission des lésions amyloïdes de la maladie d’Alzheimer : apports des modèles animaux

“…(Aguzzi et al 2007), et par conséquent des phénotypes cliniques différents (Colby & Prusiner, 2011). De nos jours, le support moléculaire de ces souches reste encore mal compris mais pourrait reposer sur des profils d'agrégation (distribution des tailles d'agrégats) de PrPSc différents (Laferriere et al 2013). Les propriétés de ces souches sont fidèlement conservées à travers plusieurs passages de transmission expérimentale (Morales et al 2007).…”