Cell-surface prion protein interacts with glycosaminoglycans Available to Purchase

We used ELISA and flow cytometry to study the binding of prion protein PrP to glycosaminoglycans (GAGs). We found that recombinant human PrP (rPrP) binds GAGs including chondroitin sulphate A, chondroitin sulphate B, hyaluronic acid, and heparin. rPrP binding to GAGs occurs via the N-terminus, a region known to bind divalent cations. Additionally, rPrP binding to GAGs is enhanced in the presence of Cu²⁺ and Zn²⁺, but not Ca²⁺ and Mn²⁺. rPrP binds heparin strongest, and the binding is inhibited by certain heparin analogues, including heparin disaccharide and sulphate-containing monosaccharides, but not by acetylated heparin. Full-length normal cellular prion protein (PrP^C), but not N-terminally truncated PrP^C species, from human brain bind GAGs in a similar Cu²⁺/Zn²⁺-enhanced fashion. We found that GAGs specifically bind to a synthetic peptide corresponding to amino acid residues 23—35 in the N-terminus of rPrP. We further demonstrated that while both wild-type PrP^C and an octapeptide-repeat-deleted mutant PrP produced by transfected cells bound heparin at the cell surface, the PrP N-terminal deletion mutant and non-transfectant control failed to bind heparin. Binding of heparin to wild-type PrP^C on the cell surface results in a reduction of the level of cell-surface PrP^C. These results provide strong evidence that PrP^C is a surface receptor for GAGs.