The formation of amyloid fibrils is a key characteristic of many neurodegenerative diseases including Alzheimer’s and Parkinson’s diseases. Similarly prion diseases, those associated with the prion protein, are neurodegenerative disorders with characteristic protein aggregates accumulating in the brain of affected individuals. While fibrillar deposits of these disorders have long been associated with end-stage disease pathology, it is currently hypothesized that protein oligomers are the cytotoxic structural form of these systems. Residues 106-126 of the human prion protein have been found to form both amyloid fibrils, as well as toxic amyloid oligomers and thus provide a suitable model system. This thesis aims to describe the structures of the amyloid fibrils and oligomers formed by PrP(106-126), how they are interrelated as well as interaction with model membranes and cytotoxicity.
Amyloid fibrils of PrP(106-126) contain long, unbranched filaments that contain β-sheet secondary structure and bind the amyloid-indicating dye, thioflavin-T. These fibrils are comprised of parallel β-sheets, stacked in an antiparallel fashion.
The non-fibrillar amyloid oligomers are large, spherical structures that contain β-sheets but do not bind thioflavin-T. It was determined that these oligomers contain parallel β-sheets as well as the same intersheet packing as fibrils of PrP(106-126).
Finally, the interaction of PrP(106-126) with lipid bilayers and cells was examined. Oligomers of PrP(106-126) were shown to affect model membranes; with anionic lipids losing integrity and cholesterol-containing lipid mixtures losing domain structure upon peptide addition. Additionally, amyloid oligomers of PrP(106-126) cause cell death across a number of cell lines as well as rat cerebellar slices.
Overall, these results indicate that the conversion of oligomers to fibrils may be facilitated due to structural similarities between the two. Additionally, the toxicity of PrP(106-126) oligomers may be attributed to a loss of cholesterol domain structure causing subsequent cell death.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:OTU.1807/36061 |
| Date | 13 August 2013 |
| Creators | Walsh, Patrick |
| Contributors | Sharpe, Simon |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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