Redox Sensing By Yeast Hsp70 Facilitates Modulation of Protein Quality Control and The Cytoprotective Response

<p>Neurodegenerative disease affects millions of Americans every year, through diagnoses such as Alzheimer’s, Parkinson’s, and Huntington’s diseases. One factor linked to formation of these aggregates is damage sustained to proteins by oxidative stress. Cellular protein homeostasis (proteostasis) relies on the ubiquitous Hsp70 chaperone family. Hsp70 activity has been previously shown to be modulated by modification of two key cysteines in the ATPase domain by oxidizing or thiol-modifying compounds. To investigate the biological consequences of cysteine modification on the Hsp70 Ssa1 in budding yeast, I generated cysteine null (cysteine to serine) and oxidomimetic (cysteine to aspartic acid) mutant variants of both C264 and C303 and demonstrate reduced ATP binding, hydrolysis and protein folding properties in both the oxidomimetic as well as hydrogen peroxide-treated Ssa1. In contrast, cysteine nullification rendered Ssa1 insensitive to oxidative inhibition. The oxidomimetic <em>ssa1-2CD</em> (C264D, C303D) allele was unable to function as the sole Ssa1 isoform in yeast cells and also exhibited negative effects on cell growth and viability. Ssa1 binds to and represses Hsf1, the major transcription factor controlling the heat shock response, and the oxidomimetic Ssa1 failed to stably interact with Hsf1, resulting in constitutive activation of the heat shock response. Consistent with the in vitro findings, <em>ssa1-2CD </em>cells were compromised for <em>de novo </em>folding, post-stress protein refolding and in regulated degradation of a model terminally misfolded protein. Together these findings pinpoint Hsp70 as a key link between oxidative stress and proteostasis, information critical to understanding cytoprotective systems that prevent and manage cellular insults underlying complex disease states.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Thesis (MS)

Year dc:date.available

2022

Authors dc:creator

• Santiago, Alec
• <p>https://orcid.org/0000-0001-7794-477X</p>

Contributors dc:contributor

• Kevin A. Morano, PhD
• Ambro van Hoof, PhD
• Anna Konovalova, PhD

• neurodegenerative
• Hsp70
• Ssa1
• oxidative stress
• stress response
• cysteine
• yeast
• heat shock
• Molecular Genetics

Repository record dc:identifier

https://digitalcommons.library.tmc.edu/utgsbs_dissertations/1224

OAI identifier oai:identifier

oai:digitalcommons.library.tmc.edu:utgsbs_dissertations-2281