# Elucidating the Role of DNAJ Proteins in Muscle Disease

> **NIH NIH K99** · WASHINGTON UNIVERSITY · 2024 · $98,168

## Abstract

PROJECT SUMMARY/ABSTRACT
Muscle diseases caused by mutations in genes that encode for (co-)chaperones, called chaperonopathies, are
characterized by muscle weakness, degeneration, and the accumulation of protein aggregates. These
diseases currently lack a cure, highlighting an urgent need for a better understanding of the underlying
mechanisms. Protein chaperones are needed to recognize misfolded proteins and facilitate their proper folding.
The recognized misfolded proteins are termed “clients.” Classically, DNAJ proteins are thought to diversify the
function of Hsp70 by determining client specificity, but little is known about how DNAJ proteins bind and select
clients for Hsp70 and how dysfunction of DNJ proteins causes chaperonopathies in muscle. Recently,
mutations in DNAJB4 were reported to cause a chaperonopathy with similar myopathology to the known
chaperonopathy caused by DNAJB6 mutations although their phenotypes are distinctive. Our central
hypothesis is that distinct client proteins of DNAJ proteins and chaperone-chaperone availability
contribute to the phenotypic differences and selective muscle vulnerability in chaperonopathies. This
study will experimentally evaluate client proteins of DNAJ proteins in muscle, the combinatory effect of DNAJ
proteins, and skeletal muscle-specific tissue vulnerability in chaperonopathies, using recently developed
innovations (e.g., proximity labeling approach, proteomics, RNAi, RNA-seq, and small animal imaging). In Aim
1, I will Aim 1 test the hypothesis that different DNAJ proteins have common and distinct client proteins in
skeletal muscle. To identify client proteins, I will apply proteomics in TurboID proximity labeling method in
cultured cells and model mice, DNAJ knockout myotubes, and laser microdissections of inclusions from patient
muscle with DNAJB4, DNAJB5, and DNAJB6 mutations. In Aim 2, I will test the hypothesis that DNAJ-DNAJ
interactions play a synergetic role in muscle maintenance. I will employ a knockdown approach to investigate
how this network dysfunction impacts protein homeostasis, using myoblasts and proteostatic stress (e.g., drug,
heat shock). Finally, in Aim 3, I will test the hypothesis that the skeletal muscle-specific tissue vulnerability is
caused by a disruption of proteostasis, where key molecules are compromised. Using chaperonopathy mouse
models, I will thoroughly analyze the myopathology and proteostatic capacity of different skeletal muscle
groups, and perform single nucleus RNA sequencing on the most vulnerable muscle groups in model mice to
identify define vulnerable myofiber subpopulations in chaperonopathies. The proposed study will address an
unmet medical need, providing insight into disease mechanisms and thereby potentially may serve as a basis
for the development of novel treatment for chaperonopathies and a broad range of diseases related to protein
misfolding.

## Key facts

- **NIH application ID:** 10865832
- **Project number:** 1K99AR084062-01
- **Recipient organization:** WASHINGTON UNIVERSITY
- **Principal Investigator:** Michio Inoue
- **Activity code:** K99 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $98,168
- **Award type:** 1
- **Project period:** 2024-05-01 → 2026-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10865832

## Citation

> US National Institutes of Health, RePORTER application 10865832, Elucidating the Role of DNAJ Proteins in Muscle Disease (1K99AR084062-01). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10865832. Licensed CC0.

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