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

Abstract

Edited by Paul FraserThe precise mechanism underlying the conversion of normal prion protein ( Sc by using a modified PMCA performed with baculovirusderived recombinant PrP (Bac-PrP) as a substrate. The addition of heparan sulfate (HS) or its analog heparin (HP) restored the conversion efficiency in PMCA that was inhibited through nucleic acid depletion. Moreover, the PMCA products obtained under these conditions were infectious and preserved the properties of the input PrP Sc . These data suggest that HS and HP play the same role as nucleic acids in facilitating faithful replication of prions in PMCA. Furthermore, we showed that HP binds to both Bac-PrP and Bac-PrP Sc through the sulfated groups present on HP and that the N-terminal domain of Bac-PrP Sc might potentially not be involved in the binding to HP. These results suggest that the interaction of GAGs such as HS and HP with PrP C and/or PrP Sc through their sulfate groups is critical for the faithful replication of prions.

Prion protein glycans reduce intracerebral fibril formation and spongiosis in prion disease

“…Why did unglycosylated ME7 prion aggregates assemble as highly stable, large parenchymal plaques? HS serves as an extracellular scaffold (73)(74)(75) and is widely recognized to bind prion aggregates, both in vitro and in vivo (76)(77)(78)(79). In accordance with these observations, we found that HS localizes to parenchymal plaques, but not to diffuse aggregates within the same brain.…”

Strain-Dependent Prion Infection in Mice Expressing Prion Protein with Deletion of Central Residues 91–106

“…Therefore, we investigated whether PrP with a deletion from residues 91 to 104 or PrP∆91–104, could be converted into PrP Sc ∆91–104 after infection with BSE prions but not RML prions. To this end, baculovirus-derived recombinant mouse WT PrP and PrP∆91–104 were produced and subjected to an in vitro PMCA assay with brain homogenates from RML-, BSE- and 22L-infected, terminally ill WT mice in the presence or absence of digitonin and heparin, both of which are known to enhance conversion of PrP C into PrP Sc in PMCA [ 17 , 18 ]. The resulting PMCA products in each round were investigated for PrP Sc and PrP Sc ∆91–104 after digestion with PK in western blotting with T2 anti-PrP antibody, which recognizes residues 132–156 and 212–217 of mouse PrP [ 19 ].…”

“…Thus, it is possible that residues 91–106 may also be involved in the structural stability of PrP C , preventing PrP C from becoming structurally unstable enough to form autonomous aggregates. Heparin has been also reported to enhance the conversion of PrP C into PrP Sc in PMCA [ 18 ]. Heparin binds to residues 23–52, 53–93 and 110–128 of PrP C and to the PK-resistant core of PrP Sc via sulfated groups [ 18 , 24 ].…”

“…Heparin has been also reported to enhance the conversion of PrP C into PrP Sc in PMCA [ 18 ]. Heparin binds to residues 23–52, 53–93 and 110–128 of PrP C and to the PK-resistant core of PrP Sc via sulfated groups [ 18 , 24 ]. A previous study reported that heparin promoted the formation of amyloid fibrils from a human PrP peptide comprised of residues 106–126, indicating that heparin may function as a scaffold for the formation of amyloid fibers from peptides [ 25 ].…”

Correlation of cellular factors and differential scrapie prion permissiveness in ovine microglia

“…SEPP1 encodes for selenoprotein P, a protein which binds heparin and defends against oxidative stress and DNA damage (Burk and Hill, 2005). Heparin is a sulfated glycan previously shown to bind PrP D (Hijazi et al, 2005) and enhance prion conversion (Imamura et al, 2016; Yokoyama et al, 2011); thus, low levels of SEPP1 transcripts may be associated with altered levels of heparin and prion misfolding. Further investigations into the role of selenoprotein P in prion permissiveness are pending.…”