Inhibition of DNAJ-HSP70 interaction improves strength in muscular dystrophy
Rocio Bengoechea, … , Heather L. True, Conrad C. Weihl
Rocio Bengoechea, … , Heather L. True, Conrad C. Weihl
Published May 19, 2020
Citation Information: J Clin Invest. 2020;130(8):4470-4485. https://doi.org/10.1172/JCI136167.
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Research Article Cell biology Muscle biology

Inhibition of DNAJ-HSP70 interaction improves strength in muscular dystrophy

Abstract

Dominant mutations in the HSP70 cochaperone DNAJB6 cause a late-onset muscle disease termed limb-girdle muscular dystrophy type D1 (LGMDD1), which is characterized by protein aggregation and vacuolar myopathology. Disease mutations reside within the G/F domain of DNAJB6, but the molecular mechanisms underlying dysfunction are not well understood. Using yeast, cell culture, and mouse models of LGMDD1, we found that the toxicity associated with disease-associated DNAJB6 required its interaction with HSP70 and that abrogating this interaction genetically or with small molecules was protective. In skeletal muscle, DNAJB6 localizes to the Z-disc with HSP70. Whereas HSP70 normally diffused rapidly between the Z-disc and sarcoplasm, the rate of diffusion of HSP70 in LGMDD1 mouse muscle was diminished, probably because it had an unusual affinity for the Z-disc and mutant DNAJB6. Treating LGMDD1 mice with a small-molecule inhibitor of the DNAJ-HSP70 complex remobilized HSP70, improved strength, and corrected myopathology. These data support a model in which LGMDD1 mutations in DNAJB6 are a gain-of-function disease that is, counterintuitively, mediated via HSP70 binding. Thus, therapeutic approaches targeting HSP70-DNAJB6 may be effective in treating this inherited muscular dystrophy.

Authors

Rocio Bengoechea, Andrew R. Findlay, Ankan K. Bhadra, Hao Shao, Kevin C. Stein, Sara K. Pittman, Jil A.W. Daw, Jason E. Gestwicki, Heather L. True, Conrad C. Weihl

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Figure 1

LGMDD1 mutations are toxic in yeast Sis1 and rescued by impairing HSP70 association.

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LGMDD1 mutations are toxic in yeast Sis1 and rescued by impairing HSP70 ...
(A) Domain alignment of DNAJB6 and Sis1. Amino acid alignment of the G/F domains denotes sequence homology. Amino acids in bold red represent the mutations used in the study. Amino acids in red represent other disease mutations. Underlined amino acids represent DNAJB6 and Sis1 homologous residues mutated in LGMDD1. The amino acids with asterisks represent residues mutated in our 2 animal models. (B) Yeast cells propagating single-dot medium [RNQ+] were transformed with constructs overexpressing Sis1-WT, Sis1-F106L (DNAJB6-F93L homologous), Sis1-F115I (DNAJB6-F100I homologous), or empty vector control (EV). Yeast were also transformed with Sis1-mutant constructs containing a second mutation that impairs HSP70 association (L268P) or blocks Sis1 dimerization (ΔDD). Cultures were normalized and serially diluted 5-fold and were spotted on medium (SD-trp) to select for the plasmid or medium (yeast extract peptone dextrose [YPD]) that provided no selection. (C) Western blot analysis from lysates of yeast expressing the Sis1 constructs in B. Pgk1 was used as a loading control. Images in A and B are representative of 3 independent experiments.