Cryo-EM of full-length α-synuclein reveals fibril polymorphs with a common structural kernel

Abstract

α-Synuclein (aSyn) fibrillar polymorphs have distinct in vitro and in vivo seeding activities, contributing differently to synucleinopathies. Despite numerous prior attempts, how polymorphic aSyn fibrils differ in atomic structure remains elusive. Here, we present fibril polymorphs from the full-length recombinant human aSyn and their seeding capacity and cytotoxicity in vitro. By cryo-electron microscopy helical reconstruction, we determine the structures of the two predominant species, a rod and a twister, both at 3.7 Å resolution. Our atomic models reveal that both polymorphs share a kernel structure of a bent β-arch, but differ in their inter-protofilament interfaces. Thus, different packing of the same kernel structure gives rise to distinct fibril polymorphs. Analyses of disease-related familial mutations suggest their potential contribution to the pathogenesis of synucleinopathies by altering population distribution of the fibril polymorphs. Drug design targeting amyloid fibrils in neurodegenerative diseases should consider the formation and distribution of concurrent fibril polymorphs.

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.…”

“…Fibrillar a-syn structure and shape Several structures for fibrillar a-syn polymorphs generated under different experimental conditions have been published. Some studies suggest that the fibrils are made of one protofilament while other indicate that they are made of two protofilaments (Tuttle et al 2016;Guerrero-Ferreira et al 2018;Li et al 2018a). At a first glimpse, a-syn has apparently a similar fold within the different structures resembling a Greek key (Fig.…”

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

“…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]. In their study, they were able to identify two such polymorphs in large quantities: the rod and the twister polymorph formed by full-length αS.…”

Computer simulations of protein–membrane systems

“…[343][344][345] So far, two monomeric structures of aSyn (PDB code: 1XQ8, 346 2KKW 347 ) have been solved in sodium dodecyl sulfate (SDS) and sodium lauroyl sarcosine (SLAS) micelles. Recently, using cryoEM, Li et al, 348 solved the structure of aSyn fibril in rod and twister polymorphs (PDB code: 6CU8 348 ) at 3.7 Å resolution. Unlike Aβ and hIAPP, computational studies of aSyn-membrane interactions are limited.…”