NR AOYO
AU Safar,J.G.
TI Protease-sensitive conformers of disease-causing prion protein (PrPsc): Detection and role in pathogenesis
QU International Conference - Prion diseases: from basic research to intervention concepts - TSE-Forum, 08.10.-10.10.2003, Gasteig, München - Oral sessions OS-32
PT Konferenz-Vortrag
AB The discovery that brain fractions enriched for prion infectivity contain a protein isoform (rPrPsc) that is resistant to limited proteolytic digestion dramatically changed prion research. N-terminal truncation of rPrPsc produced a protease-resistant fragment denoted PrP 27-30 that is readily detected by Western blotting, ELISA or immunohistochemistry. With the development of the conformation-dependent immunoassay (CDI), detection of full-length rPrPsc as well as previously unrecognized protease-sensitive (s) forms of PrPsc became possible (Safar, Wille et al. 1998). Using the CDI, we are able to discriminate between PrPsc molecules from different prion strains propagating in natural hosts, in transgenic mice, or in Syrian hamsters. Because the CDI quantifies PrP isoforms by following antibody binding to both the native (N) and denatured (D) forms of PrP, it may be performed independently of proteolytic treatments. Consequently, the CDI can detect potentially large in vivo concentrations of sPrPsc molecules and is now capable of measuring bovine and human PrPsc with a sensitivity similar to that determined by endpoint titrations in transgenic mice (Safar, Scott et al. 2002). sPrPsc accumulates along with rPrPsc throughout the asymptomatic stage of prion infection. In hamster brains, sPrPsc was detected much earlier than rPrPsc and the level of accumulated sPrPsc in different prion strains directly correlated with the incubation time. Combined with the time course of prion infection in Syrian hamsters, Tg(MHu2M) and Tg(SHaPrP) mice, these results argue that differences in incubation times among strains may arise from distinct rates of PrPsc clearance rather than from different rates of PrPsc formation. This suggests that accelerating clearance may be an important strategy in treating prion diseases and warrants the revision of the definition of an infectious unit with respect to the number of PrPsc molecules. Clearly, the conformation of sPrPsc, its position within the reaction coordinates of PrPc -> PrPsc conversion, and its role in the pathogenesis of prion infection require further investigation. The results converging from independent experimental approaches support the proposal that distinct PrPsc conformers encipher the biological properties of prion strains.
AD Jiri G. Safar, Institute for Neurodegenerative Diseases, University of California, San Francisco, USA; Department of Neurology, University of California, San Francisco, USA
SP englisch
PO Deutschland