Progress towards structural understanding of infectious sheep PrP-amyloid

Area of Science:

• Neurobiology
• Structural Biology
• Biochemistry

Background:

• The structural basis of prion protein (PrP) amyloid infectivity remains largely unknown.
• Existing models of PrP amyloid are based on low-resolution data.
• High-resolution structural differences between infectious and non-infectious PrP amyloid are critical for understanding neurodegenerative diseases.

Purpose of the Study:

• To establish protocols for preparing infectious full-length recombinant PrP amyloid suitable for high-resolution structural analysis.
• To link biological and structural data of infectious PrP amyloid.
• To provide a foundation for future high-resolution characterization of PrP amyloid.

Main Methods:

• Spontaneous fibrillation and seeded fibril growth from brain extract for sample preparation.
• Bioassays for infectivity assessment.
• Atomic force microscopy and solid-state Nuclear Magnetic Resonance (NMR) spectroscopy for structural analysis.

Main Results:

• Developed protocols for generating NMR-sufficient amounts of infectious recombinant PrP amyloid.
• Identified a semi-mobile N-terminus, an α-helical region (residues ~115-155), and a β-sheet core (C-terminal to ~155) in infectious PrP amyloid.
• Observed that brain-seeded samples may differ in segment flexibility rather than overall secondary structure arrangement.

Conclusions:

• The study provides essential protocols for high-resolution structural characterization of infectious PrP amyloid.
• The findings challenge existing models of PrP amyloid structure.
• This work paves the way for detailed structural comparisons of infectious and non-infectious PrP amyloid states.