Structural polymorphism of amyloid fibrils in cardiac transthyretin amyloidosis revealed by cryo-electron microscopy

Abstract

ATTR amyloidosis is a fatal disease associated with the accumulation of transthyretin (ATTR) fibrils that lead to organ failure and death. Mutations in the TTR gene or aging may accelerate the deposition of variant (ATTRv) or wild-type (ATTRwt) transthyretin, respectively. Although ATTR amyloidosis patients accumulate ATTR fibrils in virtually every organ, the clinical presentation is often unpredictable and variable. Recent studies in cryo-electron microscopy (cryo-EM) have revealed that in tauopathies and synucleinopathies, diseases involving amyloidosis of tau and α-synuclein, respectively, all the patients of the same disease display the same fibril fold, or polymorph. In this study, we use cryo-EM to explore whether fibrils from heart tissue of different patients with cardiac ATTR amyloidosis share a common fold. We determined the molecular structures of fibrils extracted from the hearts of seven patients, including both ATTRv and ATTRwt carriers, at resolutions of 3.0 to 3.7 Å. We found that ATTRv mutations perturb the fibril conformation whereas ATTRwt fibrils share a common structure fold. Our findings suggest that unlike in tauopathies and synucleinopathies, ATTRv fibrils display structural polymorphism driven by each individual and their genotypes. ATTR polymorphism challenges the current paradigm of ″one disease equals one fibril polymorph,″ and questions whether similarly novel conformations occur in other amyloidoses.

Structure-based probe reveals the presence of large transthyretin aggregates in plasma of ATTR amyloidosis patients

“…Other groups have identified non-native transthyretin (NNTTR) species in plasma of neuropathic patients using novel peptides and antibodies that target a specific transthyretin segment 3,4 . These species are different from the large ATTR species that we identified in plasma since the former are only present in neuropathic patients whereas the latter are found in our convenience sampling of both ATTRwt and ATTRv amyloidosis patients with cardiomyopathy or mixed phenotypes 3,4,10 Combined with previous results, our study implies that there may be multiple types of disease-associated transthyretin species in the blood of ATTR amyloidosis patients, including misfolded monomers and high molecular weight insoluble aggregates 3,4,10 (Figures 3,4,5). Our study has uncovered a novel form of ATTR species present in cardiac ATTR amyloidosis patients.…”

“…In previous studies, we determined the amyloid structures of the β-strands F and H in isolation and in ex-vivo ATTR fibrils, using xray microcrystallography and cryo-electron microscopy, respectively [5][6][7][8] . We noted that, in all ATTR fibril structures determined to date, the β-strands F and H adopt the same conformation, similar to that shown in the crystal structure of each peptide in isolation [5][6][7][8] . Capitalizing on the strategy described in Saelices et al, 2015 JBC for the design of peptide aggregation inhibitors, we designed new Transthyretin Aggregation Binders (TABs) that cap the tip of ATTR fibrils by interacting with both β-strands F and H (Figure 1A, Supplemental Table 1).…”

“…One commonality shared among all fibril structures is the presence of β-strands F and H on the exterior of the fibril surface 5 . In previous studies, we showed that strands F and H are critical for transthyretin aggregation in vitro [6][7][8][9] .…”

O-GlcNAc modification forces the formation of an α-Synuclein amyloid-strain with notably diminished seeding activity and pathology

“…Like other amyloid fibrils, α-Syn(gS87) fibrils are also characterized by hydrophobic interfaces, such as the one created by residues Ala53-Ala30-Val55, Ala68-Val69-Val95, Ile88-Ala90-Val76 (Figure 2b, highlighted in yellow and green), but they are comparatively small. Possibly, as a result, α-Syn(gS87) fibrils are not likely to be particularly stable in vitro when compared to other amyloids, as they have a solvation energy of approximately -24.0 kcal/mol (Figure S13) 15,49 .…”

Mapping Cellular Response to Destabilized Transthyretin Reveals Cell- and Amyloidogenic Protein-Specific Signatures

“…As SH-SY5Y and AC16 cells both responded to each TTR in unique ways, attention should be paid to differences between each TTR variant. To this end, recent work has identified several structural differences across different TTR mutants [33][34][35] . Although all TTRs employed in this study were produced via bacteria and thus lack post-translational modifications, said proteins could adopt various conformations when in contact with the extracellular environment of each cell type and thus elicit novel responses.…”