Understanding the key features of the spontaneous formation of bona fde prions through a novel methodology that enables their swift and consistent generation

Abstract

Among transmissible spongiform encephalopathies or prion diseases afecting humans, sporadic forms such as spo‑ radic Creutzfeldt–Jakob disease are the vast majority. Unlike genetic or acquired forms of the disease, these idiopathic forms occur seemingly due to a random event of spontaneous misfolding of the cellular PrP (PrPC) into the patho‑ genic isoform (PrPSc). Currently, the molecular mechanisms that trigger and drive this event, which occurs in approximately one individual per million each year, remain completely unknown. Modelling this phenomenon in experimental settings is highly challenging due to its sporadic and rare occurrence. Previous attempts to model spontaneous prion misfolding in vitro have not been fully successful, as the spontaneous formation of prions is infre‑ quent and stochastic, hindering the systematic study of the phenomenon. In this study, we present the frst method that consistently induces spontaneous misfolding of recombinant PrP into bona fde prions within hours, providing unprecedented possibilities to investigate the mechanisms underlying sporadic prionopathies. By fne‑tuning the Pro‑ tein Misfolding Shaking Amplifcation method, which was initially developed to propagate recombinant prions, we have created a methodology that consistently produces spontaneously misfolded recombinant prions in 100% of the cases. Furthermore, this method gives rise to distinct strains and reveals the critical infuence of charged sur‑ faces in this process.