Rigidifying the β2-α2 Loop in the Mouse Prion Protein Slows down Formation of Misfolded Oligomers

Area of Science:

• Neuroscience
• Biochemistry
• Structural Biology

Background:

• Transmissible Spongiform Encephalopathies are fatal neurodegenerative diseases.
• Prion protein (PrP^C) misfolding into PrP^Sc causes disease.
• A species barrier limits interspecies prion transmission.

Purpose of the Study:

• Investigate the impact of elk/deer-specific substitutions in the mouse prion protein's β2-α2 loop.
• Determine how these substitutions affect protein dynamics and misfolding pathways.
• Elucidate the role of the β2-α2 loop in prion protein aggregation.

Main Methods:

• Native state hydrogen-deuterium exchange mass spectrometry.
• Analysis of prion protein dynamics and misfolding pathways.
• Introduction of specific amino acid substitutions (169 Ser to Asn, 173 Asn to Thr) into mouse PrP.

Main Results:

• Substitutions at positions 169 and 173 rigidified the β2-α2 loop.
• Stabilization extended to the α3 helix, strengthening inter-segment interactions.
• Increased energy difference between native and partially unfolded forms (PUFs).
• Reduced accessibility of PUFs slowed down protein misfolding.

Conclusions:

• The β2-α2 loop is a key determinant in prion protein aggregation.
• Structural rigidity in the β2-α2 loop significantly impacts protein dynamics and misfolding.
• These findings offer insights into early events of prion protein conformational conversion.