The prion protein protease sensitivity, stability and seeding activity in variably protease sensitive prionopathy brain tissue suggests molecular overlaps with sporadic Creutzfeldt-Jakob disease

Abstract

IntroductionVariably protease sensitive prionopathy (VPSPr) is a recently described, sporadic human prion disease that is pathologically and biochemically distinct from the currently recognised sporadic Creutzfeldt-Jakob disease (sCJD) subtypes. The defining biochemical features of the abnormal form of the prion protein (PrPSc) in VPSPr are increased sensitivity to proteolysis and the presence of an N- and C-terminally cleaved ~8 kDa protease resistant PrPSc (PrPres) fragment. The biochemical and neuropathological profile of VPSPr has been proposed to resemble either Gerstmann–Sträussler–Scheinker syndrome (GSS) or familial CJD with the PRNP-V180I mutation. However, in some cases of VPSPr two protease resistant bands have been observed in Western blots that co-migrate with those of type 2 PrPres, suggesting that a proportion of the PrPSc present in VPSPr has properties similar to those of sCJD.ResultsHere, we have used conformation dependent immunoassay to confirm the presence of PrPSc in VPSPr that is more protease sensitive compared with sCJD. However, CDI also shows that a proportion of PrPSc in VPSPr resists PK digestion of its C-terminus, distinguishing it from GSS associated with ~8 kDa PrPres, and showing similarity to sCJD. Intensive investigation of a single VPSPr case with frozen tissue from multiple brain regions shows a broad, region-specific spectrum of protease sensitivity and differential stability of PrPSc in the absence of PK treatment. Finally, using protein misfolding cyclic amplification and real-time quaking induced conversion, we show that VPSPr PrPSc has the potential to seed conversion in vitro and that seeding activity is dispersed through a broad range of aggregate sizes. We further propose that seeding activity is associated with the ~19 and ~23 kDa PrPres rather than the ~8 kDa fragment.ConclusionsTherefore, PrPSc in VPSPr is heterogeneous in terms of protease sensitivity and stability to denaturation with the chaotrope GdnHCl and includes a proportion with similar properties to that found in sCJD.Electronic supplementary materialThe online version of this article (doi:10.1186/s40478-014-0152-4) contains supplementary material, which is available to authorized users.

Proteinase K resistant cores of prions and amyloids

“…Thus, VPSPr can be regarded as a sporadic variant of GSS [25]. Interestingly, VPSPr PrP Sc preparations sometimes show fragments of high molecular mass similar to those observed in CJD type 2 [27,28]. This shows possibility of conversion of GSS-type core into CJD-type.…”

Clinical update of Jakob–Creutzfeldt disease

“…PrP extracted from cortical samples of these patients was sensitive to proteinase K digestion even at very low proteinase K concentrations (1-5 mg/mL) and Western blots showed a ladder of five PrP res fragments ranging from 29 to 6 kDa [53]. The clinicopathological phenotype and sensitivity of PrP res , however, appear to be affected by the codon 129 polymorphism [16,54,61]. These findings indicate that the PrP res fragments from patients with VPSPr have a very different conformation from that observed in sCJD cases.…”

Recent advances in the histo‐molecular pathology of human prion disease

“…However, PK‐resistance is also significantly influenced by the PRNP codon 129 genotype, being lowest in VPSPr‐129VV, highest in 129MM, and intermediate in 129MV. A recent study documented a regional variability of PrP Sc properties in VPSPr involving both PK‐resistance and the presence of a CJD‐like fully glycosylated (ie, comprising the diglycosylated form) PrP Sc form of 19 kDa . Further biochemical similarities with CJD were revealed by in vitro seeding assays, such as protein misfolding cyclic amplification (PMCA) and real time‐quaking induced conversion (RT‐QuIC), which showed striking similarities in the profile of newly converted PrP Sc induced by both sCJDVV2 and VPSPr.…”

“…Further biochemical similarities with CJD were revealed by in vitro seeding assays, such as protein misfolding cyclic amplification (PMCA) and real time‐quaking induced conversion (RT‐QuIC), which showed striking similarities in the profile of newly converted PrP Sc induced by both sCJDVV2 and VPSPr. Indeed, in VPSPr the converted PrP Sc appears mainly determined by the 19 kDa CJD‐like fragment rather than by the GSS‐like ~7 kDa fragment .…”