Generation of Infectious Prions Amenable to Site-specific Click Chemistry

Prion diseases are a group of fatal neurodegenerative diseases that proceed through the templated conversion of the normal PrPC protein to a self-propagating and infectious form, termed PrPSc. This conversion process is central to disease progression. However, due to difficulties in producing functional PrPSc molecules that can be selectively modified with chemical probes, many aspects of PrPSc biology cannot be directly studied. To overcome this limitation, we substituted p-azido-L-phenylalanine (AzF), a small click chemistry-reactive amino acid, for tryptophan residue 99 of PrPC. W99AzF PrPC substrate can efficiently and faithfully propagate either infectious or non-infectious PrPSc conformers in vitro. Critically, W99AzF PrPSc amyloid fibrils remain amenable to click chemistry by various ligands after the prion conversion process. Through the combination of site-specific substitution, the modularity of click chemistry, and the functional diversity of click labels, a multitude of modified prions can now be produced to ask targeted questions about the biochemical and biological basis of prion infectivity.