Cryo-EM structures of prion protein filaments from Gerstmann–Sträussler–Scheinker disease

Abstract

Prion protein (PrP) aggregation and formation of PrP amyloid (APrP) are central events in the pathogenesis of prion diseases. In the dominantly inherited prion protein amyloidosis known as Gerstmann–Sträussler–Scheinker (GSS) disease, plaques made of PrP amyloid are present throughout the brain. The c.593t > c mutation in the prion protein gene (PRNP) results in a phenylalanine to serine amino acid substitution at PrP residue 198 (F198S) and causes the most severe amyloidosis among GSS variants. It has been shown that neurodegeneration in this disease is associated with the presence of extracellular APrP plaques and neuronal intracytoplasmic Tau inclusions, that have been shown to contain paired helical filaments identical to those found in Alzheimer disease. Using cryogenic electron microscopy (cryo-EM), we determined for the first time the structures of filaments of human APrP, isolated post-mortem from the brain of two symptomatic PRNP F198S mutation carriers. We report that in GSS (F198S) APrP filaments are composed of dimeric, trimeric and tetrameric left-handed protofilaments with their protomers sharing a common protein fold. The protomers in the cross-β spines consist of 62 amino acids and span from glycine 80 to phenylalanine 141, adopting a previously unseen spiral fold with a thicker outer layer and a thinner inner layer. Each protomer comprises nine short β-strands, with the β1 and β8 strands, as well as the β4 and β9 strands, forming a steric zipper. The data obtained by cryo-EM provide insights into the structural complexity of the PrP filament in a dominantly inherited human PrP amyloidosis. The novel findings highlight the urgency of extending our knowledge of the filaments' structures that may underlie distinct clinical and pathologic phenotypes of human neurodegenerative diseases.

Cryo-EM of prion strains from the same genotype of host identifies conformational determinants

“…Our a22L structure allows us to provide high-resolution structural evidence for the long-proposed hypothesis that prion strains from a given type of host differ in conformation (9–13). This structure also adds to the short list of brain-derived pathological prions (5-7, 25-27) and PrP amyloids (28) that have PIRIBS-based fibril architectures, as we had predicted some years ago based on our observations of PIRIBS backbones in PrP Sc -seeded synthetic PrP fibrils (38). The highly infectious prion structures also share several key structural motifs, but the conformational details of these motifs vary between strains, even when the fibrils are assembled from monomers of the same PrP amino acid sequence.…”

“…Although non-fibrillar or sub-fibrillar ultrastructures can accompany amyloid fibrils in infectious brain-derived preparations of prions, all of the high-resolution structures reported to date (n=5, including a22L described herein) are fibrils with PIRIBS architectures (5–7, 25–27). A much less, if at all, infectious human GSS F198S-associated brain-derived PrP amyloid structure also has a PIRIBS architecture, but with a much smaller order core spanning residues 80-141 (62 residues) (28). As noted above, the much larger cores (132-138 residues) of the highly infectious prion structures extend nearly to the C-terminus and share several structural motifs; these include an N-proximal steric zipper, N, middle, and disulfide β-arches, and a central, and often staggered interface between N-and C-terminal lobes (5–7, 25–27).…”

Conformation-Dependent Influences of Hydrophobic Amino Acids in Two In-Register Parallel β-Sheet Amyloids, an α-Synuclein Amyloid and a Local Structural Model of PrPSc

“…The authors reasoned that the delay of age at onset seen in heterozygous GSS(F198S) patients might be due to the inefficient aggregation of the endogenous M129 PrP because the bulky side chain of M129 does not fit the narrow space of the core. 23 It is intriguing that every PrP Sc whose structure was identified thus far has a Greek-key motif in the same region. This could imply the significance of a U-shaped loop in this region for PrP C –PrP Sc conversion.…”

“… 21 , 22 In 2022, Hallinan et al reported cryo-EM structures of human PrP Sc isolated from the brains of patients with Gerstmann–Sträussler–Scheinker syndrome (GSS) associated with F198S mutation. 23 …”

Evidence of Orientation-Dependent Early States of Prion Protein Misfolded Structures from Single Molecule Force Spectroscopy

“…The structural conversion of the α-helical folded cellular prion protein (PrP C ) into its pathological form, PrP Sc , causes TSE [ 11 ]. The very recently solved cryo-electron microscopy (EM) near-atomic structures of infectious, brain-derived PrP Sc fibrils unveiled a continuum of β-strand serpentine threading of the protein C-terminal domain and following studies have confirmed that the PrP Sc amyloids feature parallel in-register β-strand stack folding [ 12 , 13 , 14 , 15 , 16 , 17 ]. However, the conformational conversion of PrP C into PrP Sc appears as a multi-step process whose molecular mechanisms still remain unclear and are extremely difficult to probe at the single-molecule level.…”