Dissociation of Infectivity from Seeding Ability in Prions with Alternate Docking Mechanism

Michael B. Miller, James C. Geoghegan, Surachai Supattapone, David Westaway
2011 PLoS Pathogens  
Previous studies identified two mammalian prion protein (PrP) polybasic domains that bind the disease-associated conformer PrP Sc , suggesting that these domains of cellular prion protein (PrP C ) serve as docking sites for PrP Sc during prion propagation. To examine the role of polybasic domains in the context of full-length PrP C , we used prion proteins lacking one or both polybasic domains expressed from Chinese hamster ovary (CHO) cells as substrates in serial protein misfolding cyclic
more » ... ification (sPMCA) reactions. After ,5 rounds of sPMCA, PrP Sc molecules lacking the central polybasic domain (DC) were formed. Surprisingly, in contrast to wild-type prions, DC-PrP Sc prions could bind to and induce quantitative conversion of all the polybasic domain mutant substrates into PrP Sc molecules. Remarkably, DC-PrP Sc and other polybasic domain PrP Sc molecules displayed diminished or absent biological infectivity relative to wild-type PrP Sc , despite their ability to seed sPMCA reactions of normal mouse brain homogenate. Thus, DC-PrP Sc prions interact with PrP C molecules through a novel interaction mechanism, yielding an expanded substrate range and highly efficient PrP Sc propagation. Furthermore, polybasic domain deficient PrP Sc molecules provide the first example of dissociation between normal brain homogenate sPMCA seeding ability from biological prion infectivity. These results suggest that the propagation of PrP Sc molecules may not depend on a single stereotypic mechanism, but that normal PrP C /PrP Sc interaction through polybasic domains may be required to generate prion infectivity.
doi:10.1371/journal.ppat.1002128 pmid:21779169 pmcid:PMC3136465 fatcat:utucsnl3zngdlhhu32dcjzyh3m