ARS | Publication request: PK-sensitive PrPSc is infectious and shares basic structural features with PK-resistant PrPSc

Submitted to: PLoS Pathogens
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 10, 2012
Publication Date: March 1, 2012
Repository URL: http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1002547
Citation: Sajnani, G., Silva, C.J., Ramos, A., Pastrana, M.A., Onisko, B.C., Erickson-Beltran, M.L., Antaki, E.M., Sigurdson, C.J., Carter, J.M., Requena, J.R. 2012. PK-sensitive PrPSc is infectious and shares basic structural features with PK-resistant PrPSc. PLoS Pathogens. 8(3):e1002547. doi:10.1371/journal.ppat.1002547.

Interpretive Summary: Prion diseases are protein misfolding disorders. Different strains of prions are known to have variable resistance to digestion by the enzyme proteinase K (PK). Yet all prion strains are composed of relatively PK-sensitive and PK-resistant forms. We separated these PK-sensitive and the PK-resistant forms into separate fractions. Both fractions are infectious, but have different properties. We found that the brain damage associated with the PK-sensitive and PK-resistant fractions was identical, suggesting that they were the same strain. The biochemical differences between the PK-resistant and PK-sensitive fractions are due to different sized particles that share common structural properties. Furthermore, the comparison of the PK-sensitive and PK-resistant fractions of two hamster strains, 263K and Drowsy, showed strain-dependent differences in the ratios of the PK-sensitive to the PK-resistant forms of prions.

Technical Abstract: One of the main characteristics of the transmissible isoform of the prion protein (PrPSc) is its partial resistance to proteinase K (PK) digestion. Diagnosis of prion disease typically relies upon immunodetection of PK-digested PrPSc following Western blot or ELISA. More recently, researchers determined that there is a sizeable fraction of PrPSc that is sensitive to PK hydrolysis (sPrPSc). Our group has previously reported a method to isolate this fraction by centrifugation and showed that it has protein misfolding cyclic amplification (PMCA) converting activity. We compared the infectivity of the sPrPSc versus the PK-resistant (rPrPSc) fractions of PrPSc and analyzed the biochemical characteristics of these fractions under conditions of limited proteolysis. Our results show that sPrPSc and rPrPSc fractions have comparable degrees of infectivity and that although they contain different sized multimers, these multimers share similar structural properties. Furthermore, the PK-sensitive fractions of two hamster strains, 263K and Drowsy (Dy), showed strain-dependent differences in the ratios of the sPrPSc to the rPrPSc forms of PrPSc. Although the sPrPSc and rPrPSc fractions have different resistance to PK-digestion, sediment differently, and have a different distribution of multimers, they share a common structure and phenotype.