Hspb7 is a cardioprotective chaperone facilitating sarcomeric proteostasis

Area of Science:

• Cardiovascular Biology
• Molecular Chaperones
• Genetic Disease Mechanisms

Background:

• Small heat shock proteins (sHSPs) are molecular chaperones with diverse functions.
• The specific role of cardiac sHSP, Hspb7, remains largely unknown.
• Genome-Wide Association Studies (GWAS) identified Hspb7 as a potential risk gene for cardiomyopathy.

Purpose of the Study:

• To elucidate the function of Hspb7 in cardiac tissue.
• To investigate the molecular mechanisms underlying Hspb7's role in heart health.
• To explore the link between Hspb7, sarcomeric integrity, and cardiomyopathy.

Main Methods:

• Zebrafish (Danio rerio) models of hspb7 mutation.
• Cardiac fibrosis and sarcomeric structure analysis.
• Identification of Hspb7 binding partners using co-immunoprecipitation.
• Autophagy pathway assessment in zebrafish and human cardiomyocytes.
• Functional assays involving autophagy inhibition.

Main Results:

• Zebrafish hspb7 mutants exhibited cardiac fibrosis and sarcomeric abnormalities.
• Exercise stress led to significant mortality in adult hspb7 mutants, indicating gene-environment interaction.
• Hspb7 directly binds to sarcomeric proteins FilaminC and Titin.
• Loss of Hspb7 induced autophagy and upregulated Hspb5 expression.
• Autophagy inhibition resulted in FilaminC aggregation and cardiomyopathy.

Conclusions:

• Hspb7 plays a critical role in maintaining sarcomeric homeostasis by regulating the autophagic processing of damaged proteins.
• Dysfunction of Hspb7 compromises the heart's ability to handle stress, contributing to cardiomyopathy development.
• Hspb7 is a key component of cardiomyocyte damage-processing networks, with implications for inherited heart conditions.