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Amyloid aggregates of the HET-s prion protein are infectious
Marie-Lise Maddelein1, Suzana Dos Reis, Stéphane Duvezin-Caubet
1Laboratoire de Génétique Moléculaire des Champignons, Institut de Biochimie et de Génétique Cellulaires, Unité Mixte de Recherche 5095, Centre National de la Recherche Scientifique, Université de Bordeaux 2, France. ML.Maddelein@ibgc.u-bordeaux2.fr
Abstract:
The [Het-s] infectious element of the filamentous fungus Podospora anserina is a prion. We have recently reported that recombinant HET-s protein aggregates in vitro into amyloid fibers. In vivo, the protein aggregates specifically in the [Het-s] prion strains. Here, we show that biolistic introduction of aggregated recombinant HET-s protein into fungal cells induces emergence of the [Het-s] prion with a high frequency. Thus, we demonstrate that prion infectivity can be created de novo, in vitro from recombinant protein in this system. Although the amyloid filaments formed from HET-s could transmit [Het-s] efficiently, neither the soluble form of the protein nor amorphous aggregates would do so. In addition, we have found that (i) [Het-s] infectivity correlates with the ability to convert HET-s to amyloids in vitro, (ii) [Het-s] infectivity is resistant to proteinase K digestion, and (iii) HET-s aggregates formed in vivo in [Het-s] strains have the ability to convert the recombinant protein to aggregates. Together, our data designate the HET-s amyloids as the molecular basis of [Het-s] prion propagation.
Insights
Prion infectivity of the [Het-s] element in Podospora anserina can be created de novo from recombinant HET-s protein aggregates. These amyloid fibers efficiently transmit the prion, demonstrating a molecular basis for prion propagation.
Area of Science:
- Mycology
- Prion Biology
- Molecular Biology
Background:
- The [Het-s] infectious element in Podospora anserina is a prion.
- Recombinant HET-s protein forms amyloid fibers in vitro and aggregates in vivo within [Het-s] strains.
Purpose of the Study:
- To investigate the de novo creation of prion infectivity from recombinant HET-s protein.
- To determine the role of HET-s amyloid aggregates in prion propagation.
Main Methods:
- Biolistic introduction of aggregated recombinant HET-s protein into fungal cells.
- In vitro conversion assays using recombinant HET-s protein.
- Proteinase K digestion assays.
Main Results:
- Aggregated recombinant HET-s protein induced [Het-s] prion emergence de novo with high frequency.
- HET-s amyloid filaments efficiently transmitted [Het-s] prion infectivity.
- Soluble HET-s or amorphous aggregates did not transmit infectivity.
- [Het-s] infectivity correlated with in vitro amyloid conversion ability and was resistant to proteinase K.
Conclusions:
- HET-s amyloids are the molecular basis for [Het-s] prion propagation.
- Prion infectivity can be generated de novo from purified amyloid aggregates.