Reconstitution of prion infectivity from solubilized protease-resistant PrP and nonprotein components of prion rods

The scrapie isoform of the prion protein, PrPSc, is the only identified com ponent of the infectious prion, an agent causing neurodegenerative diseases such as Creutzfeldt-Jakob disease and bovine spongiform encephalopathy, Fo llowing proteolysis, PrPSc is trimmed to a fragment designated PrP 27-30, B oth PrPSc and PrP 27-30 molecules tend to aggregate and precipitate as amyl oid rods when membranes from prion-infected brain are extracted with deterg ents. Although prion rods mere also shown to contain lipids and sugar polym ers, no physiological role has yet been attributed, to these molecules. In this work, we show that prion infectivity can be reconstituted by combining Me2SO-solubilized PrP 27-30, which at best contained low prion infectivity , with nonprotein components of prion rods (heavy fraction after deproteina tion, originating from a scrapie-infected hamster brain), which did not pre sent any infectivity. Whereas heparanase digestion of the heavy fraction af ter deproteination (originating from a scrapie-infected hamster brain), bef ore its combination with solubilized PrP 27-30, considerably reduced the re constitution of infectivity, preliminary results suggest that infectivity c an be greatly increased by combining nonaggregated protease-resistant PrP w ith heparan sulfate, a known component of amyloid plaques in the brain. We submit that whereas PrP 27-30 is probably the obligatory template for the c onversion of Pr-Pc to PrPSc, sulfated sugar polymers may play an important role in the pathogenesis of prion diseases.