Abstract

Prions, the infectious pathogens of prion diseases are thought to arise by template-assisted conversion of the cellular prion protein, but the underpinning cellular mechanism of this pathogenic process remains unknown. While a growing body of data suggests that self-templating assemblies of protein aggregates are the basis of many, if not all neurodegenerative diseases, such “prion-like” mechanisms are ill-defined, which underscores the importance to better define common pathogenic mechanisms. We provide first evidence of how prions replicate in neuronal cells and propose, in collaboration with Sharon Tooze, an expert in protein secretion from the Francis Crick Institute, a comprehensive work plan to gain further evidence in support of our preliminary data. Our results suggest that aggregates of disease-associated PrP (PrPd) segregate into the protein secretory pathway and reach the plasma membrane, where they convert PrPc to full-length (FL-) PrPd. Formation of long rod-like FL-PrPd fibrils, detected by anti-PrP antibodies against FL-PrP, can be blocked by lowering cellular cholesterol and stimulated by dissipation of the vesicular pH gradient, a treatment that concomitantly led to an increase in prion release. Owing to evidence that neuropeptides and prohormones are sorted into the regulated secretory pathway by virtue of protein aggregation, we will address the important questions whether (i) prions are sorted into the secretory pathway by default and (ii) whether the cellular environment of vesicle biogenesis favours misfolding of aggregation-prone proteins. This project contributes to a better characterisation of seeded aggregation and may provide guiding principles to characterise prion-like mechanisms.