PHOSPHATIDIC ACID VESICLES INDUCE THE FORMATION OF HIGHLY THERMOSTABLE AGGREGATES OF PRION PROTEIN

INTRODUCTION: Conversion of the cellular prion protein (PrP^C) to prion scrapie (PrP^Sc) is the central event in the onset of prion diseases. DNA, RNA, and lipids may act as cofactors in this conversion, modulating infectivity and toxicity. In previous work, we showed that phosphatidic acid (PA) vesicles interact with murine recombinant PrP (recPrP), inducing its aggregation in the absence of any other biomolecules. OBJECTIVE: We aimed to analyze and characterize the structural conversion of PrP mediated by PA, to a better understanding of PrP conversion upon interaction with this phospholipid. METHODS: Spectroscopic techniques were employed at various temperatures to analyze fibril formation and stability. Two PrP constructs were used to understand the importance of the N- and C-termini in PrP-PA-induced conversion. RESULTS AND DISCUSSION: PA induces the formation of PrP amyloid aggregates of both constructs, suggesting that recPrP conversion induced by this phospholipid is independent of the N-terminal region. Thermal stability experiments indicate that the fibrillization process passes through the formation of an intermediate with a highly thermostable β-sheet secondary structure. The formation of this intermediate may be a key step in the fibrillization induced by PA vesicles. PA-mediated aggregation is most favorable at the lowest temperature evaluated, where the vesicles’ bilayers exhibit greater rigidity compared to those at higher temperatures. CONCLUSION: Our results suggest that PA induces N-terminal independent aggregation of recPrP, forming highly thermostable intermediate structures. PrP fibrillization is dependent on the PA membrane structure. These findings highlight the potential of PA as a model system for studying the early steps of prion aggregation.