# Structural and functional studies of Hsp70/Hsp110 molecular chaperones

> **NIH NIH R01** · VIRGINIA COMMONWEALTH UNIVERSITY · 2024 · $81,700

## Abstract

Project Summary
Ubiquitous and conserved molecular chaperones Hsp70s and Hsp110s form one of the most essential
chaperone machineries in maintaining protein homeostasis (proteostasis). However, the molecular mechanisms
and exact role of Hsp110s in this chaperone machinery remain largely unclear. As distant homologs of Hsp70s,
Hsp110s are both independent chaperones and co-chaperones for Hsp70s. As independent chaperones,
Hsp110s demonstrate a unique high chaperone activity in preventing aggregation of denatured proteins, the
“holdase” activity. As co-chaperones, Hsp110s function as the major nucleotide-exchange factors (NEFs) for
Hsp70s. Although the importance and mechanism of the NEF activity is well-characterized, the function and
involvement of the holdase activity is almost completely unknown primarily due to the lack of any available
approach to disrupt this holdase activity without affecting the NEF activity. Msi3 is the sole and essential Hsp110
in Candida albicans, the most prevalent cause of fungal infections in human. Our preliminary studies have
identified a novel inhibitor for Msi3, named 2H. Excitingly, 2H specifically abolishes the holdase activity while
leaving the NEF activity largely intact. Importantly, 2H was seen to reduce protein folding both in vitro and in
vivo, providing the first direct evidence to support the importance of the holdase activity of an Hsp110 in the
Hsp70/Hsp110 chaperone machinery. In addition, as the first inhibitor for fungal Hsp110s, 2H effectively
eliminates the growth of Candida albicans with limited toxicity in human cells, supporting that Hsp110s are an
important target for designing novel and potent therapeutics for fungal infections and 2H may represent a
promising lead compound for a new class of antifungals for future medicinal chemistry efforts.
 Taking advantage of the unique selectivity of 2H, the overall objective of this proposal is two-fold: 1)
to characterize the elusive molecular mechanism and biological function of the holdase activity of Hsp110s, and
2) to increase mechanistic understanding of Hsp110s as a new therapeutic target for fungal infections.
Accordingly, we propose two Specific Aims. Aim 1: Characterize the in vivo function of Hsp110’s holdase activity
in the proteostasis using 2H. Taking advantage of the powerful and facile genetics available to the yeast
Saccharomyces cerevisiae, we aim to directly analyze the conserved functions of the Hsp110s’ holdase activity
in two essential in vivo processes in proteostasis: protein folding and import into endoplasmic reticulum. We
expect to identify and characterize endogenous substrates for Hsp110s for the first time. Aim 2: Elucidate the
inhibitory mechanism via structural characterization of 2H in complex with Msi3. We aim to solve the structures
of Msi3, both alone and complexed with 2H, which will reveal the specific binding interactions between 2H and
Msi3 and the mechanism of 2H’s inhibition of Msi3. We expect that our innovat...

## Key facts

- **NIH application ID:** 11099237
- **Project number:** 3R01GM098592-11S1
- **Recipient organization:** VIRGINIA COMMONWEALTH UNIVERSITY
- **Principal Investigator:** Qinglian Liu
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $81,700
- **Award type:** 3
- **Project period:** 2013-09-01 → 2027-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/11099237

## Citation

> US National Institutes of Health, RePORTER application 11099237, Structural and functional studies of Hsp70/Hsp110 molecular chaperones (3R01GM098592-11S1). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/11099237. Licensed CC0.

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