Identifying critical sites of PrPc-PrPSc interaction in prion-infected cells by dominant-negative inhibition

Abstract

A direct physical interaction of the prion protein isoforms is a key element in prion conversion. Which sites interact first and which parts of PrPc are converted subsequently is presently not known in detail. We hypothesized that structural changes induced by PrPSc interaction occur in more than one interface and subsequently propagate within the PrPC substrate, like epicenters of structural changes. To identify potential interfaces we created a series of systematically-designed mutant PrPs and tested them in prion-infected cells for dominant-negative inhibition (DNI) effects. This showed that mutant PrPs with deletions in the region between first and second á-helix are involved in PrPPrP interaction and conversion of PrPC into PrPSc. Although some PrPs did not reach the plasma membrane, they had access to the locales of prion conversion and PrP Sc recycling using autophagy pathways. Using other series of mutant PrPs we already have identified additional sites which constitute potential interaction interfaces. Our approach has the potential to characterize PrP-PrP interaction sites in the context of prion-infected cells. Besides providing further insights into the molecular mechanisms of prion conversion, this data may help to further elucidate how prion strain diversity is maintained. © 2013 Landes Bioscience.