Document Type
Poster
Original Publication Date
2025
Date of Submission
March 2026
Keywords
molecular chaperones, Hsp110, Hsp70, ATP, holdase, protein folding, protein aggregation
Abstract
Hsp110s are a unique class of heat shock proteins (HSPs) and distant homologs of Hsp70s. They act not only as nucleotide exchange factor co-chaperones for Hsp70s (i.e., NEF activity) but also as independent chaperones capable of preventing the aggregation of proteins exposed to cellular stresses (i.e., ”holdase” activity). While Hsp110 NEF activity is well characterized, the mechanisms of holdase activity are less clear. In particular, the role of ATP-binding in regulating holdase activity is poorly understood and has been disputed. In this study, we discovered an undocumented divalent cation inhibitory effect that is reversed by ATP. This finding led us to reveal a novel function of the enigmatic C-terminal segment that differentiates in importance between a pair of human/fungal Hsp110 homologs. Furthermore, we have shed light on the role of ATP binding in regulating Hsp110’s holdase activity as it pertains to preserving downstream protein refolding competency. Specifically, Hsp110s display a concentration-dependent reduction in the rate of downstream luciferase refolding in exchange for enhanced recovery. However, when using concentrations of holdase beyond a threshold, the reduction of refolding kinetics translates to suboptimal recovery. ATP alleviates this negative effect, which was further validated by testing an ATP-binding knockout mutant of Hsp110. Overall, our biochemical analyses have revealed unique properties of ATP binding as it relates to holdase function. Our current investigations are aimed to characterize the overall effect of Hsp110s on substrates to dissect the mechanisms of holdase activity.
Rights
@ The Author(s) 2025
Is Part Of
VCU Physiology and Biophysics Publications
Comments
This work was supported by NIH/NIGMS (R01GM098592), the Virginia Commonwealth University (Bridge awards), Virginia Commonwealth University CTSA (UL1TR002649 from the National Center for Advancing Translational Sciences) and the CCTR Endowment Fund of Virginia Commonwealth University (CCTR Award).
The poster was presented at multiple conferences, namely the 2025 Annual Midwest Stress Response and Molecular Chaperone Meeting and Conference (MWSM) in Chicago, IL, and the 2025 Biophysical Society Meeting (BPS) in Los Angeles, CA.
Project faculty sponsor: Qinglian Liu