Non-glycosylphosphatidylinositol (GPI)-anchored recombinant prion protein with dominant-negative mutation inhibits PrPSc replication in vitro

Dominant-negative mouse prion protein (PrP) with a lysine mutation at codon 218 (Q218K) is known to inhibit prion replication. In order to gain further mechanistic insight into such dominant negative inhibition, non-glycosylphosphatidylinositol (GPI)-anchored recombinant PrP with Q218K (rPrP-Q218K) was investigated. When applied into scrapie-infected mouse neuroblastoma (ScN2a) cells, rPrP-Q218K but not wild-type rPrP (rPrP-WT) exclusively inhibited abnormal protease-resistant pathogenic isoform (PrPSc) replication without reducing the viability of the cells. It was even more efficient than quinacrine, which has already been prescribed for sporadic Creutzfeldt-Jakob disease (CJD) patients; 50% effective concentration (EC50) = 0.20 μM, 99% effective concentration (EC99) = 0.86 μM vs. EC50 = 0.45 μM, EC99 = 1.5 μM. Besides, no apparent cell damage was observed at the concentration of up to 4.3 μM (100 μg/ml). In combination treatment with 0.43 μM (10 μg/ml) of rPrP-Q218K, EC99 of quinacrine was decreased fr...