Browsing by Subject "Cryo-electron microscopy"

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    Amyloid fibril polymorphism in the heart of an ATTR amyloidosis patient with polyneuropathy attributed to the V122Δ variant
    (bioRxiv, 2024-05-10) Ahmed, Yasmin; Nguyen, Binh An; Afrin, Shumaila; Singh, Virender; Evers, Bret; Singh, Preeti; Pedretti, Rose; Wang, Lanie; Bassett, Parker; Fernandez-Ramirez, Maria del Carmen; Pekala, Maja; Kluve-Beckerman, Barbara; Saelices, Lorena; Pathology and Laboratory Medicine, School of Medicine
    ATTR amyloidosis is a phenotypically heterogeneous disease characterized by the pathological deposition of transthyretin in the form of amyloid fibrils into various organs. ATTR amyloidosis may stem from mutations in variant (ATTRv) amyloidosis, or aging in wild-type (ATTRwt) amyloidosis. ATTRwt generally manifests as a cardiomyopathy phenotype, whereas ATTRv may present as polyneuropathy, cardiomyopathy, or mixed, in combination with many other symptoms deriving from secondary organ involvement. Over 130 different mutational variants of transthyretin have been identified, many of them being linked to specific disease symptoms. Yet, the role of these mutations in the differential disease manifestation remains elusive. Using cryo-electron microscopy, here we structurally characterized fibrils from the heart of an ATTRv patient carrying the V122Δ mutation, predominantly associated with polyneuropathy. Our results show that these fibrils are polymorphic, presenting as both single and double filaments. Our study alludes to a structural connection contributing to phenotypic variation in ATTR amyloidosis, as polymorphism in ATTR fibrils may manifest in patients with predominantly polyneuropathic phenotypes.
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    New SNCA mutation and structures of α-synuclein filaments from juvenile-onset synucleinopathy
    (Springer, 2023) Yang, Yang; Garringer, Holly J.; Shi, Yang; Lövestam, Sofia; Peak‑Chew, Sew; Zhang, Xianjun; Kotecha, Abhay; Bacioglu, Mehtap; Koto, Atsuo; Takao, Masaki; Grazia Spillantini, Maria; Ghetti, Bernardino; Vidal, Ruben; Murzin, Alexey G.; Scheres, Sjors H. W.; Goedert, Michel; Pathology and Laboratory Medicine, School of Medicine
    A 21-nucleotide duplication in one allele of SNCA was identified in a previously described disease with abundant α-synuclein inclusions that we now call juvenile-onset synucleinopathy (JOS). This mutation translates into the insertion of MAAAEKT after residue 22 of α-synuclein, resulting in a protein of 147 amino acids. Both wild-type and mutant proteins were present in sarkosyl-insoluble material that was extracted from frontal cortex of the individual with JOS and examined by electron cryo-microscopy. The structures of JOS filaments, comprising either a single protofilament, or a pair of protofilaments, revealed a new α-synuclein fold that differs from the folds of Lewy body diseases and multiple system atrophy (MSA). The JOS fold consists of a compact core, the sequence of which (residues 36–100 of wild-type α-synuclein) is unaffected by the mutation, and two disconnected density islands (A and B) of mixed sequences. There is a non-proteinaceous cofactor bound between the core and island A. The JOS fold resembles the common substructure of MSA Type I and Type II dimeric filaments, with its core segment approximating the C-terminal body of MSA protofilaments B and its islands mimicking the N-terminal arm of MSA protofilaments A. The partial similarity of JOS and MSA folds extends to the locations of their cofactor-binding sites. In vitro assembly of recombinant wild-type α-synuclein, its insertion mutant and their mixture yielded structures that were distinct from those of JOS filaments. Our findings provide insight into a possible mechanism of JOS fibrillation in which mutant α-synuclein of 147 amino acids forms a nucleus with the JOS fold, around which wild-type and mutant proteins assemble during elongation.