Prion protein structure is affected by pH‐dependent interaction with membranes: A study in a model system

Abstract

Interaction of full length recombinant hamster prion protein with liposomes mimicking lipid rafts or non-raft membrane regions was studied by circular dichroism, chemical cross-linking and sucrose gradient ultracentrifugation. At pH 7.0, the protein bound palmitoyloleoylphosphatidylcholine/ cholesterol/sphingomyelin/monosialoganglioside GM1 (GM1) ganglioside liposomes but not palmitoyloleoylphosphatidylcholine alone (bound/free = 0.33 and 0.01, respectively), maintaining the native a-helical structure and monomeric form. At pH 5.0, though still binding to quaternary mixtures, in particular GM1, the protein bound also to palmitoyloleoylphosphatidylcholine (bound/free 0.35) becoming unfolded and oligomeric. The pH-dependent interaction with raft or non-raft membranes might have implication in vivo, by stabilizing or destabilizing the protein.

Anionic Phospholipid Interactions of the Prion Protein N Terminus Are Minimally Perturbing and Not Driven Solely by the Octapeptide Repeat Domain

“…No binding affinity was observed in relation to POPC, the dominant lipid in non-DRM membrane segments, with a consistent and significant pH-dependent association found with POPS. This contrasts with full-length hamster PrP, which was shown to be capable of binding to POPC at pH 5, suggesting there may be differing species affinities for specific phospholipids perhaps most easily appreciated for the restricted regions of the prion protein (31). Anionic lipids such as POPS and POPG are expressed in low quantities compared with bulk phospholipids such as POPC.…”

“…The difference in the required number of lipid molecules was particularly noticeable for two peptides: PrP(23-110)⌬51-89, 10 for POPC/POPG compared with 20 for POPC/POPS; and PrP(50 - Experiments were performed at room temperature in either 50 mM sodium acetate, 100 mM NaF, pH 5, or 20 mM phosphate, 100 mM NaCl, pH 7.4. f/f 0 is the ratio of tryptophan fluorescence intensity of the peptide in the presence of LUV to the fluorescence intensity of the peptide in buffer. H favoring studies of the membrane hydrophobic core via the acyl chains, although 31 P studies probe the headgroup region of the lipids.…”

“…For 31 P experiments, the probe was tuned to a frequency of 121.5 MHz and referenced to H 3 PO 4 (0 ppm). To maximize signal/noise, 31 P relaxation experiments were performed under MAS conditions at a spin rate of 4 kHz. The inversion recovery pulse sequence was used to measure the longitudinal relaxation time (T 1 ) with internal delay times 0.01-2.0 s. Transverse relaxation times (T 2 ) were measured using the Hahn spin-echo experiment with internal delay times of 0.2-160 ms.…”

“…31 P Solid-state NMR-Phospholipid headgroups can be probed using 31 P solid-state NMR (40). In particular, the order of the headgroups can be ascertained from broad line 31 P NMR (49), although relaxation measurements give an insight into the rates of motion of the headgroup (50).…”

Structural changes of membrane-anchored native PrP C

“…Both studies concluded that the structure of recPrP, with a synthetic membrane anchor, is identical upon lipid contact to the structure of anchorless PrP in lipid-free solutions. Very recently, it has been reported that the interaction of anchorless recPrP with lipids can evoke a conformational transition (21,22). However, our present approach continuously follows the secondary structural changes of native, fully posttranslationally modified PrP C upon membrane anchoring.…”