An Arrayed Genome-Wide Perturbation Screen Identifies the Ribonucleoprotein hnRNP K As Rate-Limiting for Prion Propagation
A defining characteristic of mammalian prions is their capacity for self-sustained propagation. Theoretical considerations and experimental evidence suggest that prion propagation is modulated by cell-autonomous and non-autonomous modifiers. Using a novel quantitative phospholipase protection assay (QUIPPER) for high-throughput prion measurements, we performed an arrayed genome-wide RNA interference (RNAi) screen aimed at detecting modifiers of prion propagation. We exposed prion-infected cells in high-density microplates to 35364 ternary pools of 52746 siRNAs targeting 17582 genes representing the mouse protein-coding transcriptome. We identified 1191 modulators of prion propagation. While 1151 of these modified the expression of both the pathological prion protein, PrPSc, and its cellular counterpart PrPC, 40 genes affected selectively PrPSc. Of the latter, 20 genes augmented prion production when suppressed. A prominent limiter of prion propagation was the heterogeneous nuclear ribonucleoprotein Hnrnpk. Psammaplysene A (PSA), which binds Hnrnpk, reduced prion levels in cultured cells and protected them from cytotoxicity. PSA also reduced prion levels in infected cerebellar organotypic slices and alleviated locomotor deficits in prion-infected Drosophila melanogaster expressing ovine PrPC. Hence, genome-wide QUIPPER-based perturbations can discover actionable cellular pathways involved in prion propagation. Finally, the unexpected identification of a prioncontrolling ribonucleoprotein suggests a role for RNA in the generation of infectious prions.