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The molecular biology of prion propagation
A R Clarke1, G S Jackson, J Collinge
1Medical Research Council Prion Unit, Department of Neurogenetics, Imperial College School of Medicine at St Mary's, London W2 1NY, UK.
Abstract:
Prion diseases such as Creutzfeldt-Jakob disease (CJD) in humans and scrapie and bovine spongiform encephalopathy (BSE) in animals are associated with the accumulation in affected brains of a conformational isomer (PrP(Sc)) of host-derived prion protein (PrP(C)). According to the protein-only hypothesis, PrP(Sc) is the principal or sole component of transmissible prions. The conformational change known to be central to prion propagation, from a predominantly alpha-helical fold to one predominantly comprising beta structure, can now be reproduced in vitro, and the ability of beta-PrP to form fibrillar aggregates provides a plausible molecular mechanism for prion propagation. The existence of multiple prion strains has been difficult to explain in terms of a protein-only infectious agent but recent studies of human prion diseases suggest that strain-specific phenotypes can be encoded by different PrP conformations and glycosylation patterns. The experimental confirmation that a novel form of human prion disease, variant CJD, is caused by the same prion strain as cattle BSE, has highlighted the pressing need to understand the molecular basis of prion propagation and the transmission barriers that limit their passage between mammalian species. These and other advances in the fundamental biology of prion propagation are leading to strategies for the development of rational therapeutics.
Insights
Prion diseases involve abnormal prion protein (PrPSc) accumulation. Research shows different PrPSc structures explain prion strains and transmission, guiding therapeutic development.
Area of Science:
- Neuroscience
- Molecular Biology
- Biochemistry
Background:
- Prion diseases, including Creutzfeldt-Jakob disease (CJD), scrapie, and bovine spongiform encephalopathy (BSE), stem from abnormal prion protein (PrPSc) accumulation in the brain.
- The protein-only hypothesis posits PrPSc as the primary infectious agent, causing a conformational shift from alpha-helical PrPC to beta-sheet-rich PrPSc.
- Prion propagation involves PrPSc inducing conformational changes in normal PrPC, leading to aggregation and disease.
Purpose of the Study:
- To explore the molecular mechanisms underlying prion propagation and strain diversity.
- To understand the transmission barriers between mammalian species for prion diseases.
- To identify potential therapeutic strategies based on the fundamental biology of prions.
Main Methods:
- In vitro reproduction of the conformational change from PrPC to PrPSc.
- Analysis of PrP conformations and glycosylation patterns in human prion diseases.
- Experimental confirmation of prion strain identity between variant CJD and BSE.
Main Results:
- The in vitro conversion of PrPC to PrPSc and subsequent fibrillar aggregation provides a model for prion propagation.
- Evidence suggests that different PrP conformations and glycosylation patterns encode prion strain-specific phenotypes.
- Variant CJD in humans shares the same prion strain as BSE in cattle.
Conclusions:
- Prion strains can be encoded by distinct PrP conformations and glycosylation patterns.
- Understanding prion propagation and transmission barriers is crucial for developing effective therapeutics.
- Advances in prion biology are paving the way for rational therapeutic interventions against prion diseases.