The role of prion strain diversity in the development of successful therapeutic treatments

Effect of host and strain factors on α-synuclein prion pathogenesis

Prion diseases are a group of neurodegenerative disorders caused by misfolding of proteins into pathogenic conformations that self-template to spread disease. Although this mechanism is largely associated with the prion protein (PrP) in classical prion diseases, a growing literature indicates that other proteins, including α-synuclein, rely on a similar disease mechanism. Notably, α-synuclein misfolds into distinct conformations, or strains, that cause discrete clinical disorders including multiple system atrophy (MSA) and Parkinson's disease (PD). Because the recognized similarities between PrP and α-synuclein are increasing, this review article draws from research on PrP to identify the host and strain factors that impact disease pathogenesis, predominantly in rodent models, and focuses on key considerations for future research on α-synuclein prions.

Amyloid-type Protein Aggregation and Prion-like Properties of Amyloids

This review will focus on the process of amyloid-type protein aggregation. Amyloid fibrils are an important hallmark of protein misfolding diseases and therefore have been investigated for decades. Only recently, however, atomic or near-atomic resolution structures have been elucidated from various in vitro and ex vivo obtained fibrils. In parallel, the process of fibril formation has been studied in vitro under highly artificial but comparatively reproducible conditions. The review starts with a summary of what is known and speculated from artificial in vitro amyloid-type protein aggregation experiments. A partially hypothetic fibril selection model will be described that may be suitable to explain why amyloid fibrils look the way they do, in particular, why at least all so far reported high resolution cryo-electron microscopy obtained fibril structures are in register, parallel, cross-β-sheet fibrils that mostly consist of two protofilaments twisted around each other. An intrinsic feature of the model is the prion-like nature of all amyloid assemblies. Transferring the model from the in vitro point of view to the in vivo situation is not straightforward, highly hypothetic, and leaves many open questions that need to be addressed in the future.