Isolating Tyrosine-Derived Crosslinks in Alpha-Synuclein and The Consequences of Cu(II) and Fe(III) Competitive Binding to the Parkinson’s Protein

Author

Sheridan E. Messier, Virginia Commonwealth UniversityFollow

DOI

https://doi.org/10.25772/44TV-PT31

Author ORCID Identifier

https://orcid.org/0009-0009-1050-3940

Defense Date

2024

Document Type

Thesis

Degree Name

Master of Science

Department

Chemistry

First Advisor

Dr. Heather R. Lucas

Abstract

Parkinson’s Disease (PD) is the world’s second most common neurodegenerative movement disorder. The substantia nigra from PD patients have revealed proteinaceous inclusions termed Lewy Bodies (LBs) primarily composed of a-Synuclein (aSyn). In humans, aSyn is N-terminally acetylated (^NAcaSyn), altering the preferred binding sites for Cu^II and Fe^III. The binding effects of each metal ion alone has been reported but not for dual metal coordination to ^NAcaSyn. Simultaneous coordination resulted in a decrease in parallel and an increase in antiparallel b-sheets. Binding of Cu^II accelerates the formation of parallel b-sheets, coordination of Fe^III inhibits this, while dual metal coordination further modulates the rate of their formation. Fe^III binds preferentially to ^NAcaSyn, though upon aggregation Cu^II outcompetes Fe^III at their shared D121 binding site. Additionally, ^NAcaSyn is known to form dityrosine crosslinks, a recognized biomarker for PD, and it’s possible for the phenolic radicals created during their formation to covalently couple to form other post-translational motifs, such as isodityrosine, which was investigated herein. Thermo Fisher Dynabeads^TM coupled with an antidityrosine antibody were employed as an attempt to isolate dityrosine crosslinks in naturally aggregated ^NAcaSyn samples and those in which crosslinks were photochemically induced. The Dynabeads^TM were unable to completely isolate dityrosine crosslinks due to saturation of the coupled antibody. Although, the results suggest that ^NAcaSyn may cleave after 8.5 days under natural aggregation conditions and is still capable of forming dityrosine crosslinks. All results reported herein help to uncover more information about the role of ^NAcaSyn in the pathogenic mechanism of PD.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

7-16-2024