Sun, Yuanzi;
(2022)
Single-particle Kinetic Measurements and Structure Characterization of PrP Fibril Elongation Using Super-Resolution Microscopy.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
In prion diseases, benign cellular prion protein (PrPC) is converted to PrPSc, fibrillar assemblies of misfolded PrP, which self-propagate by recruiting PrPC into the growing fibril. Using total internal reflection (TIRF) microscopy, this study analyses elongation kinetics of synthetic and authentic PrP fibrils on a single-particle level to reveal polymorphic fibril populations, featuring structural and dynamic heterogeneity similar to prion strains, which were previously hidden in ensemble measurements. MoPrP 91-231 fibrils elongated along a preferred direction with an intermittent ‘stop-and-go’ pattern. Fibrils fell into three main populations, types I, II and III, which displayed distinct structural and dynamic properties, and elongated by different mechanisms. They maintained their properties even under elongation conditions favouring a different fibril type. Type I and II fibrils incorporated folded or partially folded PrP molecules; type III fibrils recruited unfolded monomers with a pronounced inhibition at high PrP concentration. The elongation of authentic fibrils of two strains, RML and ME7, in the presence of MoPrP 91-231 monomers, were slower than synthetic fibrils under the same condition. RML fibril elongation dynamics displayed heterogeneity as well. The discovery of polymorphic fibril populations of amyloid and prions growing in competition suggests that prions may present as quasi-species of structural isomorphs and that the replication environment may tilt the balance between amyloid species and prion isomorphs. The structures of the heterogeneous fibrils after elongation were measured at an enhanced resolution using transient amyloid binding (TAB) and polarised-TAB super-resolution microscopy, revealing unique structural features associated with each fibril type.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Single-particle Kinetic Measurements and Structure Characterization of PrP Fibril Elongation Using Super-Resolution Microscopy |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2022. Original content in this thesis is licensed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) Licence (https://creativecommons.org/licenses/by/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Institute of Prion Diseases |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10161554 |
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