Glycosaminoglycan sulfation determines the biochemical properties of prion protein aggregates

Abstract

Prion diseases are transmissible neurodegenerative disorders associated with the conversion of the cellular prion protein, PrP(C), to a misfolded isoform called PrP(Sc). Although PrP(Sc) is a necessary component of the infectious prion, additional factors, or cofactors, have been shown to contribute to the efficient formation of transmissible PrP(Sc). Glycosaminoglycans (GAGs) are attractive cofactor candidates as they can be found associated with PrP(Sc) deposits, have been shown to enhance PrP misfolding in vitro, are found in the same cellular compartments as PrP(C) and have been shown to be disease modifying in vivo. Here we investigated the effects of the sulfated GAGs, heparin and heparan sulfate (HS), on disease associated misfolding of full-length recombinant PrP. More specifically, the degree of sulfation of these molecules was investigated for its role in modulating the disease-associated characteristics of PrP. Both heparin and HS induced a β-sheet conformation in recombinant PrP that was associated with the formation of aggregated species; however, the biochemical properties of the aggregates formed in the presence of heparin or HS varied in solubility and protease resistance. Furthermore, these properties could be modified by changes in GAG sulfation, indicating that subtle changes in the properties of prion disease cofactors could initiate disease associated misfolding.

Liquid–liquid phase separation of full-length prion protein initiates conformational conversion in vitro

“…Of interest, it has been demonstrated that Aβ-oligomers and DNA-aptamers drive the liquid-solid phase transition of rPrP through the interaction of amino acid residues around 90 to 120 (58,59). Furthermore, both full-length prion protein and prion protein peptide (amino acid, 23-144) could form proteinase-resistant, spherical-ellipsoid aggregates that grow as amyloid fibrils by the addition of detergent or polysaccharides, thus supporting our hypothesis that liquid-solid phase transition is associated with prion diseases (60)(61)(62). However, given that several reports have successfully demonstrated the acquisition of seeding activity from rPrP/PrP C by adding RNA, lipid, and other proteins (63)(64)(65), our results argue that the acquisition of PK resistance of rPrP from LLPS alone is not sufficient for seeding activity.…”

Current structural biology of the heparin interactome

“…In contrast, other works have noted the induction of stable, spherical, non-toxic PrP aggregates by heparin, and found that partially 2-O-, 3-Odesulfated heparin has reduced ability to form fully protease resistant, thioflavin T reactive PrP Sc [55].…”

Heparan Sulfate and Heparin Promote Faithful Prion Replication in Vitro by Binding to Normal and Abnormal Prion Proteins in Protein Misfolding Cyclic Amplification

“…Furthermore, our results showed that the abilities of CSA, CSB, and CSC to stimulate Bac-PrP Sc conversion differed according to prion strains; therefore, this strain-dependent difference in CS ability to promote PrP C conversion to PrP Sc might represent one of the underlying causes of strain-specific differences in neuropathology. The binding of HP and HS has been reported to increase the thermal stability, ␤-sheet structure, or PK resistance of recPrP (12,47,48) and alter the solubility of recPrP (38); these findings suggest that PrP C binding to HS and HP induces a conformational change in PrP C . Therefore, Bac-PrP binding to HP and HS might also induce a conformational change in Bac-PrP and contribute to the conversion of Bac-PrP into Bac-PrP Sc .…”

“…Sulfate Groups on HP Are Critical for Bac-PrP res Amplification-GAG length and degree of sulfation were previously reported to affect the conversion of PrP C or recPrP into PrP Sc (9,10,(35)(36)(37)(38). Therefore, to examine the relative effects of GAG length and sulfation degree on Bac-PrP conversion into Bac-PrP res , we added chemically modified HPs to iPMCA reaction mixtures under nucleic acid-depleted conditions (Fig.…”