Characteristics of prion protein (PrP(Sc)) in the brains of hamsters inoculated serially with a mouse-passaged scrapie strain

Genesis of mammalian prions: from non-infectious amyloid fibrils to a transmissible prion disease

The transmissible agent of prion disease consists of a prion protein in its abnormal, β-sheet rich state (PrP^Sc), which is capable of replicating itself according to the template-assisted mechanism. This mechanism postulates that the folding pattern of a newly recruited polypeptide chain accurately reproduces that of a PrP^Sc template. Here we report that authentic PrP^Sc and transmissible prion disease can be generated de novo in wild type animals by recombinant PrP (rPrP) amyloid fibrils, which are structurally different from PrP^Sc and lack any detectable PrP^Sc particles. When induced by rPrP fibrils, a long silent stage that involved two serial passages preceded development of the clinical disease. Once emerged, the prion disease was characterized by unique clinical, neuropathological, and biochemical features. The long silent stage to the disease was accompanied by significant transformation in neuropathological properties and biochemical features of the proteinase K-resistant PrP material (PrPres) before authentic PrP^Sc evolved. The current work illustrates that transmissible prion diseases can be induced by PrP structures different from that of authentic PrP^Sc and suggests that a new mechanism different from the classical templating exists. This new mechanism designated as “deformed templating” postulates that a change in the PrP folding pattern from the one present in rPrP fibrils to an alternative specific for PrP^Sc can occur. The current work provides important new insight into the mechanisms underlying genesis of the transmissible protein states and has numerous implications for understanding the etiology of neurodegenerative diseases.

The transmissible agent of prion disease consists of a prion protein in its abnormal conformation (PrP^Sc), which replicates itself according to the template-assisted mechanism. This mechanism postulates that the folding pattern of a newly recruited polypeptide chain accurately reproduces that of a PrP^Sc. The current study reports that infectious prions and transmissible prion disease can be triggered in wild type animals by amyloid fibrils produced from recombinant prion prtotein, which are structurally different from PrP^Sc and lacks any detectable PrP^Sc particles. This work introduces a new hypothesis that transmissible prion diseases can be induced by prion protein structures different from that of authentic PrP^Sc and suggests that a new mechanism for triggering PrP^Sc formation different from the classical templating exists. The current work provides important new insight into the mechanisms underlying genesis and evolution of the transmissible states of the prion protein and has numerous implications for understanding the etiology of prion and other neurodegenerative diseases.

Both host prion protein 131-188 subregion and prion strain characteristics regulate glycoform of PrP Sc

Prion proteins (PrPs) contain 2 N-linked glycosylation sites and are present in cells in 3 different forms. An abnormal isoform of prion protein (PrP(Sc)) has different glycoform patterns for different prion strains. However, the molecular basis of the strain-specific glycoform variability in prions has remained elusive. To understand the molecular basis of these glycoform differences, we analyzed PrP(Sc) in 2 lines of transgenic mice (MHM2 and MH2M with PrP null background) that expressed a chimeric PrP. Our result indicated that PrP 131-188 (substitutions at I139M, Y155N, and S170N) contributed to both PrP(C) and PrP(Sc) glycoform ratios. Furthermore, the PrP(Sc) glycoform pattern within these transgenic mice showed a subtle difference depending on the inoculated prion. This study indicated that the PrP(Sc) glycoform ratio was influenced by both host PrP(C) and the prion strain.