Is Parkinson's disease a prion disease?

The accumulation of a specific protein in aggregated form is a common phenomenon in human neurodegenerative diseases. In Parkinson's disease, this protein is alpha-synuclein which is a neuronal protein of 143 amino acids. With a monomeric conformation in solution, it also has a natural capacity to aggregate into amyloid structures (dimers, oligomers, fibrils and Lewy bodies or neurites). It therefore fulfils the characteristics of a prion protein (different conformations, seeding and spreading). In vitro and in vivo experimental evidence in transgenic and wild animals indicates a prion-like propagation of Parkinson's disease. The sequential and predictive distribution of a-synuclein demonstrated by Braak et al. and its correlation with non-motor signs are consistent with the prion-like progression. Although the triggering factor causing the misfolding and aggregation of the target protein is unknown, Parkinson's disease is a highly relevant model for the study of these mechanisms and also to test specific treatments targeting the assemblies of alpha-synuclein and propagation from pre-motor phase of the disease. Despite this prion-like progression, there is currently no argument indicating a risk of human transmission of Parkinson's disease. (C) 2015 Elsevier Masson SAS. All rights reserved.