Abstract

The conversion of soluble prion protein into an insoluble, pathogenic, protease-resistant isoform is a key event in the development of prion diseases. Although the mechanism by which the conversion engenders a pathogenic event is unclear, there is increasing evidence to suggest that this may depend on the function of the prion protein in preventing oxidative damage. Therefore, in this study, we assessed the interrelationship between redox-sensitive cysteine, glycosylation, and prion metabolism. Cells were treated with a thioreductant, dithiothreitol, to assess the effect of the cellular oxidation state on the synthesis of the prion protein. This change in redox balance affected the glycosylation of the prion protein, resulting in the sole production of glycosylated forms. The role of the single disulfide bridge in mediating this effect within the prion protein was confirmed by mutating the cysteine residues involved in its formation. These data suggest that conditions that increase the rate of formation of the disulfide bridge favor formation of the unglycosylated prion protein. Thus, since the presence of glycans on the prion protein is protective against its pathogenic conversion, a change in the redox status of the cell would increase the risk of developing a prion disease by favoring the production of the unglycosylated form.

Highlights

  • Proximity of the glycosylation sites to the disulfide bridge in PrPC led us to consider a possible interrelationship between the two

  • Elimination of the disulfide bridge by mutagenesis of a single cysteine residue resulted in the exclusive synthesis of diglycosylated PrPC, the protein was retained in the ER

  • These findings demonstrate a relationship between PrPC processing and redox balance and suggest a mechanism whereby oxidative stress could play a role in prion disease pathogenesis

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Summary

Introduction

Proximity of the glycosylation sites to the disulfide bridge in PrPC led us to consider a possible interrelationship between the two. Elimination of the disulfide bridge by mutagenesis of a single cysteine residue resulted in the exclusive synthesis of diglycosylated PrPC, the protein was retained in the ER.

Results
Conclusion
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