The N-Terminal Polybasic Region of Prion Protein Is Crucial in Prion Pathogenesis Independently of the Octapeptide Repeat Region
Conformational conversion of the cellular isoform of prion protein, designated PrPC, into the abnormally folded, amyloidogenic isoform, PrPSc, is an essential pathogenic event in prion diseases. However, the exact conversion mechanism remains largely unknown. Lines of evidence indicate that the N-terminal domain, which includes the N-terminal, positively charged polybasic region and the octapeptide repeat (OR) region, is important for PrPC to convert into PrPSc after infection with prions. To further gain insights into the role of the polybasic region and the OR region in prion pathogenesis, we generated two different transgenic mice, designated Tg(PrP3K3A)/Prnp0/0 and Tg(PrP3K3A∆OR)/Prnp0/0 mice, which express PrPC with lysine residues at codons 23, 24, and 27 in the polybasic region mutated with or without a deletion of the OR region on the Prnp0/0 background, respectively, and intracerebrally inoculated them with RML and 22L prions. We show that Tg(PrP3K3A)/Prnp0/0 mice were highly resistant to the prions, indicating that lysine residues at 23, 24, and 27 could be important for the polybasic region to support prion infection. Tg(PrP3K3A∆OR)/Prnp0/0 mice also had reduced susceptibility to RML and 22L prions equivalent to Tg(PrP3K3A)/Prnp0/0 mice. The pre-OR region, including the polybasic region, of PrP3K3A∆OR, but not PrP3K3A, was unusually converted to a protease-resistant structure during conversion to PrPSc3K3A∆OR. These results suggest that, while the OR region could affect the conformation of the polybasic region during conversion of PrPC into PrPSc, the polybasic region could play a crucial role in prion pathogenesis independently of the OR region.
KeywordsPrion Prion protein Polybasic region Octapeptide repeat Transgenic mice Neurodegeneration
We thank Dr. Stanley B. Prusiner for providing Zrch I Prnp0/0 mice.
SS designed the experiments. NRD and HM performed prion infection. HH performed pathological experiments. NRD, HH, JC, and KU performed biochemical experiments. KM performed an epitope mapping. HM, HW, and GK produced Tg mice. SS wrote the paper. All authors revised and approved the final manuscript.
This work was supported in part by JSPS KAKENHI 26293212 and 19H03548, MEXT KAKENHI 15H01560, and 17H05701 to SS.
Compliance with Ethical Standards
All experiments were performed in accordance with The Guiding Principle for Animal Care and Experimentation of the University of Occupational and Environmental Health and Tokushima University and with Japanese Law for Animal Welfare and Care. The Ethics Committees of Animal Care and Experimentation of the University of Occupational and Environmental Health and Tokushima University approved this study (approval number AE08-013, T28-100). All efforts were made to minimize animal suffering and to reduce the number of animals used.
Conflict of Interest
The authors declare that they have no conflicts of interest.
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