PrPSc typing by N-terminal sequencing and mass spectrometry

The heterogeneity of the clinicopathological phenotype in human prion diseases is associated with the presence of the different forms of the abnormal prion protein, PrP^Sc. We have previously shown that PrP^Sc in FFI and a subtype of familial CJD linked to the D178N mutation can be distinguished by their difference in gel mobility following proteinase K (PK) treatment. To further characterize the structural difference of PrP^Sc in familial prion diseases, N-terminal sequencing and mass spectrometry were used to identify the protease cleavage sites in PrP^Sc extracted from affected brains. We found that the main PK cleavage sites of PrP^Sc are located at residue 97 in FFI, and residue 82 in both CJD¹⁷⁸ and a GSS subtype linked to the P102L mutation. The differential accessibility to protease in the native PrP^Sc suggests that PrP^Sc exist as distinct conformers in different disease states.