A new mechanism for transmissible prion diseases

Area of Science:

• Neuroscience
• Biochemistry
• Molecular Biology

Background:

• Prion diseases are linked to the misfolding of prion protein (PrP) into a β-sheet-rich state (PrP(Sc)).
• The established mechanism suggests PrP(Sc) acts as a template to convert normal PrP (PrP(C)) into the pathogenic form.
• Understanding the initial triggers and alternative conversion pathways is crucial for prion disease research.

Purpose of the Study:

• To investigate whether in vitro-generated amyloid structures, distinct from PrP(Sc), can induce prion disease.
• To explore novel mechanisms of prion disease pathogenesis beyond the canonical PrP(Sc) templating model.
• To identify early misfolded PrP species involved in disease initiation.

Main Methods:

• Preparation of three distinct recombinant Syrian hamster PrP (rPrP) amyloid states in vitro.
• Inoculation of Syrian hamsters with these rPrP amyloid preparations.
• Analysis of PrP conformation, proteinase K resistance, and infectivity using modified protein misfolding cyclic amplification (PMCAb).

Main Results:

• Amyloid fibrils resembling PrP(Sc) did not induce prion disease.
• An alternative amyloid structure, conformationally different from PrP(Sc), initiated a transmissible prion disease.
• An atypical proteinase K-resistant PrP (PrPres) form emerged during a silent stage, preceding authentic PrP(Sc), and appeared to be the initial misfolded product.

Conclusions:

• Non-prion, structurally distinct amyloids can act as seeds to initiate transmissible prion diseases.
• A novel pathogenic mechanism exists where atypical PrPres may precede and give rise to PrP(Sc).
• This finding broadens the understanding of prion disease etiology and has implications for other neurodegenerative disorders.