Authors: Ahmed Abdallah, Ping Wang, Juergen A. Richt and Srinand Sreevatsan

Ahmed Abdallah

Department of Veterinary Population Medicine; University of Minnesota; St. Paul, MN USA

Ping Wang

Department of Veterinary Population Medicine; University of Minnesota; St. Paul, MN USA

Juergen A. Richt

College of Veterinary Medicine; Kansas State University; Manhattan, KS USA

Srinand Sreevatsan

Corresponding author: sreev001@umn.edu
Department of Veterinary Population Medicine; University of Minnesota; St. Paul, MN USA; Department of Veterinary Biomedical Sciences; University of Minnesota; St. Paul, MN USA

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Abstract:

A point mutation in Prnp that converts tyrosine (Y) at position 145 into a stop codon leading to a truncated prion molecule as found in an inherited transmissible spongiform encephalopathy (TSE), Gertsmann-Sträussler-Scheincker syndrome, suggests that the N-terminus of the molecule (spanning amino acids 23–144) likely plays a critical role in prion misfolding as well as in protein-protein interactions. We hypothesized that Y145Stop molecule represents an unstable part of the prion protein that is prone to spontaneous misfolding. Utilizing protein misfolding cyclic amplification (PMCA) we show that the recombinant polypeptide corresponding to the Y145Stop of sheep and deer PRNP can be in vitro converted to PK-resistant PrP^Sc in presence or absence of preexisting prions. In contrast, recombinant protein full-length PrP^C did not show a propensity for spontaneous conformational conversion to protease resistant isoforms. Further, we show that seeded or spontaneously misfolded Y145Stop molecules can efficiently convert purified mammalian PrP^C into protease resistant isoforms. These results establish that the N-terminus of PrP^C molecule corresponding to residues 23–144 plays a role in seeding and misfolding of mammalian prions.