Self-assembly of Mutant Huntingtin Exon-1 Fragments into Large Complex Fibrillar Structures Involves Nucleated Branching
| Autor: | Stephanie Plassmann, Juan Manuel Ramírez-Anguita, Annett Boeddrich, Elsa Sanchez-Garcia, Jana Wolf, Erich E. Wanker, Kenny Bravo-Rodriguez, Nadine U. Strempel, Antonio Z. Politi, Anne Ast, Konrad Klockmeier, Katharina Baum, Alexander Buntru, Anne S. Wagner, Christian Haenig, Lydia Brusendorf |
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| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: |
Models
Molecular Amyloid Cancer Research Huntingtin Nucleation macromolecular substances Microscopy Atomic Force 010402 general chemistry Branching (polymer chemistry) Fibril 01 natural sciences Protein Structure Secondary law.invention Protein Aggregates 03 medical and health sciences law Humans 030304 developmental biology Huntingtin Protein 0303 health sciences Cell-Free System Chemistry Fibrillogenesis Exons Small molecule 0104 chemical sciences Microscopy Electron Mutation Biophysics Self-assembly Electron microscope Peptides Function and Dysfunction of the Nervous System Biologie |
| Popis: | Huntingtin (HTT) fragments with extended polyglutamine (polyQ) tracts self-assemble into amyloid-like fibrillar aggregates. Elucidating the fibril formation mechanism is critical for understanding Huntington’s disease pathology and for developing novel therapeutic strategies. Here, we performed systematic experimental and theoretical studies to examine the self-assembly of an aggregation-prone N-terminal HTT exon-1 fragment with 49 glutamines (Ex1Q49). Using high resolution imaging techniques such as electron microscopy and atomic force microscopy, we show that Ex1Q49 fragments in cell-free assays spontaneously convert into large, highly complex bundles of amyloid fibrils with multiple ends and fibril branching points. Furthermore, we present experimental evidence that two nucleation mechanisms control spontaneous Ex1Q49 fibrillogenesis: (1) a relatively slow primary fibril-independent nucleation process, which involves the spontaneous formation of aggregation-competent fibrillary structures, and (2) a fast secondary fibril-dependent nucleation process, which involves nucleated branching and promotes the rapid assembly of highly complex fibril bundles with multiple ends. The proposed aggregation mechanism is supported by studies with the small molecule O4, which perturbs early events in the aggregation cascade and delays Ex1Q49 fibril assembly, comprehensive mathematical and computational modelling studies, and seeding experiments with small, preformed fibrillar Ex1Q49 aggregates that promote the assembly of amyloid fibrils. Together, our results suggest that nucleated branchingin vitroplays a critical role in the formation of complex fibrillar HTT exon-1 aggregates with multiple ends. |
| Databáze: | OpenAIRE |
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