Picking Prion Infectivity Apart

Prion disorders such as Creutzfeldt–­Jakob disease and bovine spongiform encephalopathy have long kept researchers guessing about exactly how the diseases’ characteristically misfolded proteins lead to infectivity and toxicity. Research from John Collinge and colleagues at UCL Institute of Neurology, in London, suggests that the infectious refolding of normal proteins into misfolded versions and prion diseases’ neurological toxicity are independent processes (Nature, DOI: 10.1038/nature09768). The researchers note that “prions themselves are not neurotoxic but catalyze the formation of such species.” Working with mouse models, Collinge’s team showed that infectious prion proteins catalyze the increase in concentration of misfolded proteins, but that during this phase no clinically relevant toxicity occurs. Only after the misfolded prion proteins reach a saturation concentration does neurotoxicity initiate. In a commentary about the work, Reed B. Wickner of the U.S.’s National Institute of Diabetes & Digestive & Kidney Diseases notes that this “simple experiment [shows] that the infectious and toxic particles are not the same.” Wickner adds that “this is unexpected and raises issues central to our understanding of prion diseases.”