In vitro conversion and seeded fibrillization of posttranslationally modified prion protein

Abstract

AbstractThe conversion of the cellular isoform of the prion protein (PrPC) into the pathologic isoform (PrPSc) is the key event in prion diseases. To study the conversion process, anin vitrosystem based on varying the concentration of low amounts of sodium dodecyl sulfate (SDS) has been employed. In the present study, the conversion of full-length PrPCisolated from Chinese hamster ovary cells (CHO-PrPC) was examined. CHO-PrPCharbors native, posttranslational modifications, including the GPI anchor and two N-linked glyco-sylation sites. The properties of CHO-PrPCwere compared with those of full-length and N-terminally truncated recombinant PrP. As shown earlier with recombinant PrP (recPrP90-231), transition from a soluble α-helical state as known for native PrPCinto an aggregated, β-sheet-rich PrPSc-like state could be induced by dilution of SDS. The aggregated state is partially proteinase K (PK)-resistant, exhibiting a cleavage site similar to that found with PrPSc. Compared to recPrP (90-231), fibril formation with CHO-PrPCrequires lower SDS concentrations (0.0075%), and can be drastically accelerated by seeding with PrPScpurified from brain homogenates of terminally sick hamsters. Our results show that recPrP 90-231 and CHO-PrPC behave qualitatively similar but quantitatively different. Thein vivosituation can be simulated closer with CHO-PrPCbecause the specific PK cleave site could be shown and the seed-assisted fibrillization was much more efficient.