A C-terminal Membrane Anchor Affects the Interactions of Prion Proteins with Lipid Membranes

Background: Membrane attachment of PrP via a GPI anchor is critical for conversion into PrPSc. Results: Semisynthetic membrane-anchored PrP variants are generated and analyzed in different lipid environments. Conclusion: A membrane anchor drastically changes PrP interactions with membranes and enables pore formation. Significance: Membrane-induced conformational changes and pore formation of PrP play a role in the conversion into PrPSc and its toxic effects. Membrane attachment via a C-terminal glycosylphosphatidylinositol anchor is critical for conversion of PrPC into pathogenic PrPSc. Therefore the effects of the anchor on PrP structure and function need to be deciphered. Three PrP variants, including full-length PrP (residues 23-231, FL_PrP), N-terminally truncated PrP (residues 90-231, T_PrP), and PrP missing its central hydrophobic region (105-125, CR_PrP), were equipped with a C-terminal membrane anchor via a semisynthesis strategy. Analyses of the interactions of lipidated PrPs with phospholipid membranes demonstrated that C-terminal membrane attachment induces a different binding mode of PrP to membranes, distinct from that of non-lipidated PrPs, and influences the biochemical and conformational properties of PrPs. Additionally, fluorescence-based assays indicated pore formation by lipidated CR_PrP, a variant that is known to be highly neurotoxic in transgenic mice. This finding was supported by using patch clamp electrophysiological measurements of cultured cells. These results provide new evidence for the role of the membrane anchor in PrP-lipid interactions, highlighting the importance of the N-terminal and the central hydrophobic domain in these interactions.