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Updated: Aug 15, 2026
Protein Misfolding Cyclic Amplification of Prions
Published on: November 7, 2012
Strain-specific kinetics of prion protein formation in vitro and in vivo
Ellyn R Mulcahy1, Richard A Bessen
1Department of Medical Microbiology and Immunology, Creighton University, Omaha, NE 68178, USA.
Abstract:
The molecular basis of prion strain diversity is proposed to be encoded by distinct conformations of the abnormal scrapie isoform of the prion protein (PrP(Sc)). PrP(Sc) formation for the hyper (HY) and drowsy (DY) strains of the transmissible mink encephalopathy (TME) agent was investigated using the cell-free PrP conversion reaction to determine the role of distinct PrP(Sc) conformations in the rate of in vitro conversion of cellular PrP into protease-resistant PrP. PrP conversion increased at an exponential rate for both TME strains until peak levels were reached at 72-96 h of reaction time. The amount and rate of PrP conversion for HY TME was greater than those for DY TME between 48 h and the peak level of PrP conversion. Between 96 and 120 h, there was a negative rate of PrP conversion; and between 120 and 168 h, the net rate of HY and DY PrP conversion approached zero. These findings suggest that PrP conversion can occur in three distinct stages: an elongation phase, a depolymerization phase, and a steady-state phase. Strain-specific properties between the TME strains were identified only during the elongation phase. The steady-state phase could be disrupted by the addition of PrP(Sc) to, or by sonication of, the cell-free PrP conversion reaction. These treatments resulted in an increase in the amount of PrP conversion that was equal to or greater than that found during the peak level of PrP conversion for both TME strains, indicating that the steady-state phase was in dynamic equilibrium. In a related study, the rate of accumulation of HY and DY PrP(Sc) in hamster brain exhibited a strain-specific pattern that had similarities to the strain-specific PrP conversion reaction during the elongation phase. These results suggest that strain-specific conformations of PrP(Sc) have the ability to influence the rate of additional PrP(Sc) formation from cellular PrP both in vitro and in vivo.
Insights
Distinct prion protein scrapie (PrP(Sc)) conformations influence prion strain diversity. This study reveals strain-specific differences in PrP(Sc) formation rates in vitro and in vivo, highlighting distinct conversion phases.
Area of Science:
- Neuroscience
- Biochemistry
- Molecular Biology
Background:
- Prion diseases are linked to misfolded prion proteins (PrP(Sc)).
- Prion strain diversity is thought to arise from different PrP(Sc) conformations.
- Understanding these conformations is key to understanding disease mechanisms.
Purpose of the Study:
- Investigate the role of distinct PrP(Sc) conformations in prion strain diversity.
- Characterize the in vitro PrP conversion process for hyper (HY) and drowsy (DY) transmissible mink encephalopathy (TME) strains.
- Compare in vitro conversion rates with in vivo PrP(Sc) accumulation in hamster brains.
Main Methods:
- Utilized a cell-free PrP conversion reaction.
- Measured the rate of conversion of cellular PrP to protease-resistant PrP for HY and DY TME strains.
- Monitored PrP(Sc) accumulation in hamster brains for both strains.
Main Results:
- PrP conversion occurred in three distinct phases: elongation, depolymerization, and steady-state.
- Strain-specific differences between HY and DY TME were observed during the elongation phase.
- The steady-state phase was a dynamic equilibrium, disruptible by adding PrP(Sc) or sonication.
- In vivo PrP(Sc) accumulation patterns mirrored the in vitro elongation phase, suggesting strain-specific conformational influence.
Conclusions:
- Strain-specific PrP(Sc) conformations influence the rate of PrP(Sc) formation.
- The cell-free conversion model reveals distinct phases and strain-specific dynamics.
- These findings support the hypothesis that PrP(Sc) conformation encodes prion strain diversity.
