# Probing the Role of Chaperone-TPR Complexes in Tau Proteostasis

> **NIH NIH RF1** · UNIVERSITY OF CALIFORNIA, SAN FRANCISCO · 2020 · $2,240,412

## Abstract

Abstract. A devastating class of untreatable, neurodegenerative disorders, which includes progressive
supranuclear palsy (PSP), corticobasal degeneration (CBD) and Alzheimer’s disease (AD), are associated with
accumulation of neurofibrillary tangles (NFTs) in the brain. These aggregates are primarily composed of
microtubule-associated protein tau (MAPT/tau), which is heavily modified by post-translational modifications
(PTMs). If we understood how neurons normally regulate tau’s PTMs, we might be able to find ways of restoring
its delicate balance. The objective of this project is to understand how the molecular chaperones, heat shock
protein 70 (Hsp70) and heat shock protein 90 (Hsp90), direct modifications on tau. Hsp70 and Hsp90 are known
to bind key, aggregation-prone locations in tau. While these interactions improve the solubility of tau, they also
recruit a number of critical PTM enzymes including: (i) the E3 ubiquitin ligase CHIP, (ii) the cis-trans prolyl
isomerase FKBP51 and (iii) the protein phosphatase PP5. Specifically, each of these enzymes contains a
tetratricopeptide repeat (TPR) domain, which has affinity for the conserved EEVD-CO2H motif at the C-termini
of Hsp70 and Hsp90. Thus, we hypothesize that complexes between chaperones and TPR domains ultimately
determines tau’s conformation and whether it is ubiquitinated or de-phosphorylated. Thanks to innovations in
cryo-EM and recent breakthroughs in large-scale peptide libraries and antibody design, we are poised to use
structural and chemical approaches to understand how chaperones coordinate with TPR proteins to modify tau.
In preliminary studies, we have measured binding of the chaperone’s EEVD motifs to a panel of TPR domains,
revealing unexpected selectivity of Hsp70 for PP5 and Hsp90 for FKBP51, as well as a key role for
phosphorylation in tuning these affinities. We have also created a library of ~640,000 peptide sequences and
used it to identify a potent (<10 nM) inhibitor of CHIP’s TPR domain that does not bind closely related TPRs.
Finally, we have validated a structural approach to studying the Hsp70-CHIP-tau ternary complex, a project
which has already uncovered a surprising, essential role for ADP. Guided by these exciting findings and fueled
by a team-based approach, we propose to study how tau interacts with: (SA1) Hsp70/Hsp90-CHIP, (SA2)
Hsp90-FKBP51 and (SA3) Hsp70-PP5. Through this effort, we aim to determine how molecular switches at the
key protein interfaces tune the structure and modifications on tau. We anticipate that these studies could also
revealing new drug targets for treating tauopathies.

## Key facts

- **NIH application ID:** 10029781
- **Project number:** 1RF1AG068125-01
- **Recipient organization:** UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
- **Principal Investigator:** Charles Scott Craik
- **Activity code:** RF1 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $2,240,412
- **Award type:** 1
- **Project period:** 2020-09-01 → 2024-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10029781

## Citation

> US National Institutes of Health, RePORTER application 10029781, Probing the Role of Chaperone-TPR Complexes in Tau Proteostasis (1RF1AG068125-01). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10029781. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*