Interaction of Prion Protein with Small Highly Structured RNAs: Detection and Characterization of PrP-Oligomers

Abstract

Conformational modification of normal prion protein (PrP(c)) to protease-resistant, beta-sheet rich, aggregates (PrP(sc)) is commonly accepted cause for prion diseases. On the other hand, several studies in recent years implicate soluble, protease-sensitive, oligomers of PrP(c) in neuronal damage. Previously, our group has shown that small, highly structured RNAs (shsRNAs), in conjunction with a serum factor, facilitated the conversion of hrPrP to a protease resistant, high molecular weight isoform. In the current study we demonstrate that shsRNAs, in the absence of the serum factor, generate soluble, protease-sensitive, and potentially toxic oligomers of ovrPrP. We have isolated a 500 kD oligomer by size exclusion chromatography of the reaction mixture and identified the accessible epitopes. The soluble PrP-oligomers were present in enhanced amounts in scrapie infected sheep brain and treating extracts of normal sheep brain with shsRNA resulted in oligomerization of endogenous PrP. Isolation, characterization of PrP-oligomers and their possible implication in prion diseases is discussed.

α2-Macroglobulin is a potential facilitator of prion protein transformation

“…Nonetheless, even in the in vitro system using purified a2M, RNA played a role in facilitating changes in structure of complexes of PrP with purified-a2M from crystals to spherulites. RNA also altered antibody recognition of PrP demonstrated by immunoblot and ELISA [25] analyses. RNA was also necessary for the formation of PrPRes at lower a2M concentrations suggesting that in a biological complex environment a2M, RNA and perhaps other molecules interact with PrP and alter its structure.…”

“…An in vitro assay based on inhibition of electron transfer in sub-mitochondrial particles was used to demonstrate the toxicity of oligomers of commercially prepared recombinant sheep PrP formed with RNA. The 500-kDa oligomers showed 3-fold greater inhibition of electron transport than monomer PrP, suggesting possible biological relevance and toxic nature of PrP oligomers formed with RNA [25].…”

Development of oligomeric prion‐protein aggregates in a mouse model of prion disease

“…Due to the avoidance of protease digestion, conformation‐dependant immunoassay (CDI) has been recently developed to detect total PrP Sc , including sPrP Sc 3–7. Other novel methods for the detection of PrP Sc that do not require protease treatment have also been developed, such as sucrose gradient sedimentation and size‐exclusion gel chromatography to detect abnormally aggregated PrP 8, 9, fluorescence‐based conformational biosensor to detect β‐folded conformation of PrP 10, fluorescence correlation spectroscopy to detect prion particles 11 or modified sandwich ELISA to detect PrP oligomers 12.…”

Copper (II) promotes the formation of soluble neurotoxic PrP oligomers in acidic environment

“…Data accumulated over the last few years indicated that soluble oligomers are toxic species that damage the cell in neurodegenerative diseases [Bucciantini et al, 2002, 2004]. Certain non‐amyloidal oligomeric forms of PrP have been demonstrated to be cytotoxic as well [Caughey and Lansbury, 2003; Silveira et al, 2005; Vasan et al, 2006]. The oligomerization of PrP may be a key step in prion pathogenesis, but the details of this process remain unclear.…”