Studies on the conformational stability and infectivity of abnormal prion protein derived from the Chandler strain

There are prion strains that are distinguishable by incubation periods and distribution of neuropathological lesions after inoculation to experimental animals. Mechanisms that determine the prion strain remain to be elucidated; however, in some cases, biochemical properties of abnormal isoform of prion protein (PrPSc) also differ among prion strains. Thus, it may be possible that prion strains can be classified by biochemical properties of PrPSc. In this study, an extensive discrimination of prion strains was performed by the combination of three biochemical properties of PrPSc i.e., molecular weight, glycoform, and conformational stability against the GdnHCl treatment. A total of 7 prion strains used in this study was classified into 3, 3, or 4 groups by molecular weight, glycoform, or conformational stability of PrPSc, respectively. The combination of the three biochemical properties could distinguish 7 prion strains into 5 groups, suggesting that the profile of biochemical properties of PrPSc is useful for the discrimination of prion strains. During the analysis of conformational stability of PrPSc, it was found that the N-terminal region of PrPSc derived from the Chandler strain is gradually denatured with the increase of GdnHCl concentration. The region from around amino acid (aa) 80 to around aa 140 began to be denatured by the treatment with 1.5 M or higher GdnHCl. Within this, the region between around aa 80 and aa 90 was denatured almost completely by the treatment with 2 M or higher GdnHCl. Furthermore, the region from around aa 90 to around aa 140 denatured completely by the treatment with 3 M or higher GdnHCl. However, compared with PrPSc derived from other prion strains used in this study, the C-terminal region of PrPSc derived from the Chandler strain from around aa 140 showed extremely high resistance to the GdnHCl treatment. This property was conserved in PrPSc obtained from cells persistently infected with the Chandler strain and PrPSc derived from the Chandler strain propagated in mouse with different PrP allotype. In addition, this property was not observed in PrPSc from other prion strains, suggesting that this property is specific to PrPSc of the Chandler strain. Furthermore, the denaturation and removal of the region from around aa 80 to around aa 140 resulted in the significant reduction of infectivity of the Chandler strain. This suggests that the conformation of this region in PrPSc of the Chandler strain is tightly associated with