Unité de virologie et immunologie moléculaires, Équipe infections à prions, Inra, 78352 Jouy-en-Josas, France, Institut Pasteur, Unité de génétique moléculaire des bunyavirus, département de virologie, 75015 Paris, France
Prion diseases are neurodegenerative disorders causing spongiform encephalopthies in mammals. They have the peculiarity of being transmissible and have led to epidemics such as Kuru in human, scrapie in sheep, chronic wasting disease in cervids and mad cow in bovine. This latter has been transmitted to human where it has induced a variant form of the human Creutzfeldt-Jakob disease. Amyloïd deposits of a misfolded protein (PrP
Sc) due to the conformational change of the host encoded cellular prion protein (PrP
C) are features of these diseases. The prion hypothesis has proposed PrP
Sc to be the infectious agent. Recent arguments in favor of this hypothesis will be reviewed. The puzzling prion strain phenomenon leading to different pathologies and the nature of the infectious particle will also be questioned. The Prion concept, in addition to apply to diseases, has allowed a better understanding of some epigenetics transmissions in fungi. Principle of this concept suggests that different protein conformations may carry and propagate various information opening the way to new investigations on amyloïdosis and their potential to be transmitted. Several examples of Prion-like phenomena not systematically associated with diseases but related to functional amyloïds, sustain a conceptual novelty in biology that will be discussed.