Author ORCID Identifier
https://orcid.org/0009-0009-1481-9379
Defense Date
2026
Document Type
Dissertation
Degree Name
Doctor of Philosophy
Department
Physiology and Biophysics
First Advisor
Qinglian Liu, Ph.D.
Abstract
Heat shock proteins (HSPs) are conserved molecular chaperones that preserve cellular proteostasis, particularly during stress. Hsp70s function as ATP-dependent folding machines, while Hsp110s act both as nucleotide exchange factors (NEFs) for Hsp70 and as independent holdase chaperones that stabilize unfolded proteins and prevent aggregation. Despite these essential roles, the mechanisms regulating Hsp110/Hsp70 systems remain incompletely understood.
To investigate this, we examined Msi3, the sole Hsp110 in Candida albicans, focusing on ATP regulation of holdase activity, which led to the identification of a protective role for the intrinsically disordered C-terminal region under destabilizing conditions. While ATP is not required for aggregation suppression, it expands the concentration range over which Msi3 and other holdases support productive downstream refolding. Increasing holdase concentration enhances substrate recovery but slows refolding kinetics, revealing a tradeoff between substrate stabilization and release. Biochemical analyses further suggest that ATP modulates the formation and behavior of substrate-engaged Msi3 assemblies.
We next examined Hsp110-mediated nucleotide exchange in fungal and human systems. Fungal Hsp70–Hsp110 interactions required ATP, whereas the human Hsp70–Hsp110 pair formed a more stable complex in the absence of free ATP. Cross-pairing experiments indicate that these differences may rise from the matched human Hsp70–Hsp110 interface. Cryo-EM analysis of the human complex revealed persistent ATP bound to human Hsp110, consistent with unusually tight nucleotide binding.
Together, these findings define multiple regulatory mechanisms governing Hsp110 function, linking nucleotide binding, chaperone assembly, and species-specific complex behavior.
Rights
© Justin M. Kidd, 2026. All Rights Reserved
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
4-21-2026