Amyloid fibril structure of α-synuclein determined by cryo-electron microscopy

Abstract

α-Synuclein (α-syn) amyloid fibrils are the major component of Lewy bodies, which are the pathological hallmark of Parkinson's disease (PD) and other synucleinopathies. High-resolution structure of α-syn fibril is important for understanding its assembly and pathological mechanism. Here, we determined a fibril structure of full-length α-syn (1-140) at the resolution of 3.07 Å by cryo-electron microscopy (cryo-EM). The fibrils are cytotoxic, and transmissible to induce endogenous α-syn aggregation in primary neurons. Based on the reconstructed cryo-EM density map, we were able to unambiguously build the fibril structure comprising residues 37-99. The α-syn amyloid fibril structure shows two protofilaments intertwining along an approximate 2 screw axis into a left-handed helix. Each protofilament features a Greek key-like topology. Remarkably, five out of the six early-onset PD familial mutations are located at the dimer interface of the fibril (H50Q, G51D, and A53T/E) or involved in the stabilization of the protofilament (E46K). Furthermore, these PD mutations lead to the formation of fibrils with polymorphic structures distinct from that of the wild-type. Our study provides molecular insight into the fibrillar assembly of α-syn at the atomic level and sheds light on the molecular pathogenesis caused by familial PD mutations of α-syn.

Pre-structured hydrophobic peptide β-strands: A universal amyloid trap?

“…Salveson et al showed that this hairpin region of αS was capable of forming higher order structures that display high levels of toxicity to neuronal cells, further supporting the hypothesis that the soluble oligomer conformation of amyloidogenic peptides is the more toxic [32]. The latest cryo-EM studies of the protofilament state of αS have also pinpointed this region as the interface between αS protofilament dimers [25,26]. And finally, the importance of this region within αS can be seen in the point mutations within the SNCA gene that have been linked to autosomal dominant forms of Parkinson's disease.…”

“…An investigation of the protofilament structure adopted by αS (1-121) has proposed that this truncated form of αS forms 8 distinct β-strands that are broken up by glycine residues [25]. Li et al on the other hand have used cryo-EM to study the protofilament state of full length αS and their results indicate that αS protofilaments adopt 7 distinct β-strands [26]. A third study done by Jiang and co-workers argues that αS protofilaments are polymorphic and therefore capable of forming different structures [27].…”

Segmental 13C‐Labeling and Raman Microspectroscopy of α‐Synuclein Amyloid Formation

“…[12] We also observe a large shift of the amide-III band (1230 cm −1 for 12 C) in the ligated-α-syn spectrum, suggesting this vibrational mode is strongly influenced by the N-terminal region polypeptide backbone. Interestingly, we see very little perturbation of the C-H deformation stretch (1450 cm −1 ) of ligated-α-syn.…”

“…Early time points are shown in the insets for clarity owing to large differences in intensity scales. B) Comparison of 13 C-amide-I,12 C-amide-I, CÀH deformation (left axis), and ThT emission intensity (right axis) as afunction of aggregation time for the two independent aggregation reactions shown in (A). The changes in the Raman peaks have been normalizedf or comparison.…”

α‐synuclein oligomers and fibrils: a spectrum of species, a spectrum of toxicities

“…Structure of the different fibrillar polymorphs αSN forms. The structures of fibrillar αSN obtained by solid‐state NMR [pdb ID# 2n0a (Tuttle et al )] or Cryo‐Electron Microscopy [PDB id# 6cu7 (Li et al ), 6h6b (Guerrero‐Ferreira et al 2018), 6flt (Guerrero‐Ferreira et al 2018), 6a6b (Li et al ), and 6cu8 (Li et al )] are represented with their respective pdb identity. The amino acid residues located to the N‐terminal side of residue 60 are colored in gray.…”