Date of Award

2017

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Cell Biology, Neurobiology and Anatomy

Abstract

Numerous pathological amyloid proteins spread from cell-to-cell during neurodegenerative disease, facilitating the propagation of cellular pathology and disease progression. Understanding the mechanism by which disease-associated amyloid protein assemblies enter target cells and induce cellular dysfunction is therefore key to understanding the progressive nature of such neurodegenerative proteinopathies. In this study, we utilized an imaging-based assay to monitor the ability of disease-associated amyloid assemblies to induce the rupture of intracellular vesicles following endocytosis, as well as to elucidate the cellular consequences of this damaging mechanism of invasion. We observed that the ability to induce vesicle rupture is a conserved feature of fibrillar amyloid assemblies of alpha-synuclein, tau, and polyglutamine-expanded huntingtin. In the case of alpha-synuclein amyloid assemblies, we determined that Serine 129 phosphorylation and strain conformation dictate the potency of endocytic vesicle rupture. We also demonstrated that vesicles ruptured by alpha-synuclein are lysosomes, and that these damaged vesicles are targeted to the autophagic degradation pathway. We observed that vesicles ruptured by alpha-synuclein can accumulate and fuse into large, intracellular structures resembling Lewy bodies in vitro, and showed that the same markers of vesicle rupture surround Lewy bodies in brain sections from PD patients. These data underscore the importance of this conserved endocytic vesicle rupture event as a damaging mechanism of cellular invasion by amyloid assemblies of multiple neurodegenerative disease-associated proteins, and suggest that proteinaceous inclusions such as Lewy bodies form as a consequence of continued fusion of autophagic vesicles in cells unable to degrade ruptured vesicles and their amyloid contents.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.

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