부산대학교 도서관

Prions result from a drastic conformational change of the host-encoded cellular prion protein (PrP), leading to the formation of b-sheet-rich, insoluble, and protease-resistant selfreplicating assemblies (PrPSc). The cellular and molecular mechanisms involved in spontaneous prion formation in sporadic and inherited human prion diseases or equivalent animal diseases are poorly understood, in part because cell models of spontaneously forming prions are currently lacking. Here, extending studies on the role of the H2 a-helix C terminus of PrP, we found that deletion of the highly conserved 190HTVTTTT196 segment of ovine PrP led to spontaneous prion formation in the RK13 rabbit kidney cell model. On long-term passage, the mutant cells stably produced proteinase K (PK)-resistant, insoluble, and aggregated assemblies that were infectious for naïve cells expressing either the mutant protein or other PrPs with slightly different deletions in the same area. The electrophoretic pattern of the PK-resistant core of the spontaneous prion (DSpont) contained mainly C-terminal polypeptides akin to C1, the cell-surface anchored C-terminal moiety of PrP generated by natural cellular processing. RK13 cells expressing solely the D190-196 C1 PrP construct, in the absence of the full-length protein, were susceptible to DSpont prions. DSpont infection induced the conversion of the mutated C1 into a PK-resistant and infectious form perpetuating the biochemical characteristics of DSpont prion. In conclusion, this work provides a unique cell-derived system generating spontaneous prions and provides evidence that the 113 C-terminal residues of PrP are sufficient for a self-propagating prion entity. [ABSTRACT FROM AUTHOR]