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Updated: Jan 11, 2026
Isolating Potentiated Hsp104 Variants Using Yeast Proteinopathy Models
Published on: November 11, 2014
Mutations in Hsp40 co-chaperone change the canonical interdomain interactions stimulating LGMDD1 myopathy
Ankan K Bhadra1, Geetika Aggarwal2, Anshuman Jaysingh3
1Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, Missouri, USA.
Insights
Limb-girdle muscular dystrophy D1 (LGMDD1) is caused by mutations in the DNAJB6 gene. Novel mutations lock the DNAJB6 chaperone in an inactive state, hindering its function and offering potential therapeutic targets.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- Limb-girdle muscular dystrophy D1 (LGMDD1) is a rare, inherited neuromuscular disorder.
- It results from mutations in the Hsp40 co-chaperone DNAJB6, leading to protein misfolding.
- Currently, no effective treatments exist for LGMDD1.
Purpose of the Study:
- To investigate the molecular mechanisms underlying LGMDD1 caused by DNAJB6 mutations.
- To understand how specific mutations affect DNAJB6's interdomain interactions and chaperone activity.
- To identify potential therapeutic strategies for LGMDD1.
Main Methods:
- Functional assays were used to assess DNAJB6 mutant activity.
- Advanced molecular simulation studies were employed to analyze interdomain interactions.
- Comparative analysis with yeast DNAJ homolog Sis1 provided insights.
Main Results:
- Disease-causing mutations in DNAJB6's J-domain were found to mimic the substrate-bound state.
- Mutations disrupt J-GF contacts and destabilize the J-CTD inhibitory linkage.
- These disruptions lead to a unified pathway causing premature allosteric switching to an inactive conformation.
Conclusions:
- The study reveals a unified mechanism for DNAJB6 dysfunction in LGMDD1.
- Mutations lock DNAJB6 in an inactive state, preventing substrate and Hsp70 interaction.
- These findings provide crucial mechanistic insights for future LGMDD1 therapeutic development.
Abstract:
Limb-girdle muscular dystrophy D1 (LGMDD1) is a rare, dominantly inherited neuromuscular protein-misfolding chaperonopathy caused by mutations in the Hsp40 co-chaperone DNAJB6, primarily in the glycine-phenylalanine (GF) or J-domains. Currently, no treatments are available, and a challenge in understanding the disease is identifying a specific client protein for DNAJB6 in skeletal muscle. DNAJB6 has homology to the yeast DNAJ family member, Sis1. Our previous research indicated that LGMDD1 GF domain mutants in Sis1 exhibit substrate-specific effects, influenced by Hsp70 activity. Herein, we employed functional assays along with advanced molecular simulation studies to understand the regulatory interdomain interactions in disease-causing mutants of DNAJB6 that cause LGMDD1 myopathy. We found that disease-causing novel mutations in the J-domain mimic the chaperone's substrate-bound state, both directly by disrupting J-GF contacts and indirectly by destabilizing the J-CTD inhibitory linkage. Both routes converge on similar interdomain rearrangements, indicating a unified pathway, wherein this premature allosteric switch locks the chaperone in an inactive conformation, blocking productive interactions with substrates and Hsp70. These mechanistic insights enhance our understanding of LGMDD1 myopathy and facilitate the identification of potential treatment strategies for the future.
