Interaction of alpha-synuclein with nanoscale systems that mimic synaptic vesicles

Alpha-synuclein is a naturally abundant neuronal protein that has been implicated in the development of several neurodegenerative conditions including, most prominently, Parkinson’s disease. While alpha-synuclein is believed to play a role in neurotransmission and synaptic vesicle trafficking in healthy individuals, its abnormal misfolding and incorporation into protein aggregates known as Lewy bodies has become a pathogenic hallmark of Parkinson’s disease and other synucleinopathies. The work presented in this dissertation aims to expand the current understanding of alpha-synuclein’s native function as well as its role in disease states by using gold nanoparticles as a platform to study alpha-synuclein/membrane interactions. In Chapter 1, the history of alpha-synuclein and its connection to neurodegeneration will be discussed in more detail. Background on the use of nanoparticles as a platform to study protein behaviors will also be provided, as well as an overview of the advantageous properties of gold nanoparticles and their application toward previous studies investigating alpha-synuclein. Finally, insights are given into approaches for the functionalization of inorganic nanoparticles with membrane mimicking surface chemistries. The work described in Chapter 2 presents a systematic investigation into the impact of membrane surface curvature on alpha-synuclein binding behavior. A series of simple, surfactant-based synaptic vesicle mimics were developed through surface functionalization of spherical gold nanoparticles ranging in size from approximately 10-100 nm in diameter. Adsorption of alpha-synuclein to these synaptic vesicle mimics is found to impact accessibility of certain regions to protease digestion, exposing the aggregation prone NAC region of the protein. Furthermore, in contrast with previous studies, dynamic light scattering titrations reveal similar binding affinities of three alpha-synuclein variants (i.e., wildtype, A30P, and E46K) toward surfactant-coated gold nanoparticles of all sizes. Finally, in Chapter 3, the impact of membrane mechanical properties on alpha-synuclein binding behavior is explored. A library of more complex, biologically relevant lipid-based synaptic vesicle mimics is synthesized comprising a range of malleable phospholipid vesicles and rigid lipid-coated gold nanoparticles of two distinct sizes. In this system, the binding affinity of alpha-synuclein toward small lipid vesicles and lipid-coated gold nanoparticles without cholesterol is found to be lower than their respective malleable and rigid counterparts. Additionally, the orientation of alpha-synuclein on the surface of rigid synaptic vesicle mimics appears to be dependent upon protein-to-particle incubation ratio.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Chemistry

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2023

Author dc:creator

• McClain, Sophia M

Contributors dc:contributor

• Murphy, Catherine
• Mirica, Liviu
• Chan, Jefferson
• Girolami, Gregory

• Gold Nanoparticles
• Alpha-synuclein
• Synaptic Vesicles
• Membrane Mimics
• Limited Proteolysis

Statement dc:rights

• Copyright 2023 Sophia McClain

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/121219

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F121219