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Intermolecular crosslinking of abnormal prion protein is efficiently induced by a primuline-sensitized photoreaction

Teruya, Kenta, Nishizawa, Keiko, Oguma, Ayumi, Sakasegawa, Yuji, Kitamoto, Tetsuyuki, Doh-ura, Katsumi
Biochimica et biophysica acta 2019 v.1863 no.2 pp. 384-394
PrPSc proteins, amino acids, antibodies, brain, crosslinking, fluorescent dyes, formic acid, hydrophobicity, luciferin, photochemical reactions, photosensitivity, prion diseases, screening, ultraviolet radiation, urea
In prion diseases, infectious pathogenic particles that are composed of abnormal prion proteins (PrPSc) accumulate in the brain. PrPSc is biochemically characterized by its protease-resistance core (PrPres), but its structural features have not been fully elucidated. Here, we report that primuline, a fluorescent dye with photosensitization activity, dramatically enhances UV-irradiation-induced SDS-resistant PrPSc/res oligomer formation that can be detected by immunoblot analysis of prion-infected materials. This oligomer formation occurs specifically with PrPSc/res but not with normal prion protein, and it was demonstrated using purified PrPSc/res as well as unpurified materials. The oligomer formation proceeded in both primuline-dose- and UV irradiation time-dependent manners. Treatment with urea or formic acid did not break oligomers into monomers. Neither did the presence of aromatic amino acids modify oligomer formation. Analysis with a panel of anti-prion protein antibodies showed that the antibodies against the N-terminal region of PrPres were less reactive in the dimer than the monomer. These findings suggest that the primuline-sensitized photoreaction enhances intermolecular crosslinking of PrPSc/res molecules at a hydrophobic area of the N-terminal region of PrPres. In the screening of other compounds, photoreactive compounds such as luciferin exhibited a similar but lower activity with respect to oligomer formation than primuline. The enhanced photoreaction with these compounds will be useful for evaluating the structural features of PrPSc/res, especially the interactions between PrPSc/res molecules.