Scrapie infectivity, fibrils and low molecular weight protein

Abstract

The development of a short incubation model of scrapie (strain 263K), in golden hamsters has added impetus to the purification of the infectious agent. Our own attempts have been based on methods pioneered by Millson and developed by Prusiner. We present here results indicating that a purification factor of up to 10(4) with respect to protein may now be possible. Fractions from brain with high infectivity had a sedimentation range of 70-300S and contained an abundance of fibrils closely similar to the scrapie-associated fibrils (SAF) discovered by Merz et al.. Material of molecular weight (Mr) 26,000, which is probably protein, appears to be a major constituent of the fibrils. The association between infectivity and fibrils raises two possibilities: the fibrils are an infectious form of the scrapie agent or they are a pathological response to scrapie infection.

In Situ Formation of Protease-resistant Prion Protein in Transmissible Spongiform Encephalopathy-infected Brain Slices

“…Our conclusions are supported by the findings that both PrP-res and TSE infectivity are tightly associated with membrane fractions from TSE-infected brain extracts and not with soluble tissue extracts (48). Furthermore, purified PrP-res is extensively aggregated, insoluble in nondenaturing detergents, and associated with high levels of TSE infectivity (10). These data suggest that if the TSE agent is demonstrated to consist solely of PrP-res, then a PrP-res aggregate or nucleus, but not a monomer, is the infectious form.…”

“…The discovery of scrapie-associated fibrils in the early 1980s (9) paved the way to the identification of a protease-resistant protein (8,10) that was a major component of scrapie-associated fibrils (10) and unique to TSE-infected hosts. This protein, called the scrapie prion protein (PrP Sc ) or protease-resistant PrP (PrP-res) (8), appears to be a conformational isomer of a cellular homologue called PrP C (11).…”

Western blot mapping of disease-specific amyloid in various animal species and humans with transmissible spongiform encephalopathies using a high-yield purification method

“…SAF consist primarily of the disease-specific SAFprotein [also referred to as protease-resistant protein or prion protein, PrP (Bolton et al, 1982;McKinley et al, 1983)] (Diringer et al, 1983a;Barry et al, 1985;DeArmond et al, 1985;Merz et al, 1987;Wiley et al, 1987). This amyloid protein is derived from a highly conserved host-encoded precursor, a cellular glycoprotein (tool.…”

The Neurochemistry of Prion Diseases

“…The PrP found in fractions enriched for Sc infectivity was designated P r P to distinguish it from the normal, constitutively expressed, cellular isoform of PrP, designated PrPc (Oesch et al, 1985). PrP'" is identified by its resistance to protease digestion Prusiner et al, 1982;Diringer et al, 1983), insolubility after detergent extraction (Meyer et al, 1986), accumulation in secondary lysosomes (McKinley et al,199 l), posttranslational synthesis (Borchelt et al, 1990), and enrichment during purification of prion infectivity Gabizon et al, 1988). Limited proteolysis of PrP= removes the Nterminal 67-amino-acid residues to yield PrP 27-30 without loss of infectivity, whereas P r F is completely digested under the same conditions.…”