Cardiomyocyte-derived USP20 mitigates myocardial ischemia/reperfusion injury through deubiquitinating GRP78

Myocardial ischemia/reperfusion (I/R) injury remains a major clinical challenge characterized by cardiomyocyte loss and adverse remodeling after reperfusion. Ubiquitin-Specific Peptidase 20 (USP20), a deubiquitinase involved in cellular stress responses, has not been fully characterized in the ischemic heart. This study aimed to investigate the function and mechanism of cardiomyocyte-derived USP20 in myocardial I/R injury.

Myocardial I/R models and hypoxia/reoxygenation (H/R)-treated cardiomyocytes were used to evaluate USP20 expression and function. Single-cell transcriptomic analysis, cardiomyocyte-specific USP20 knockout, and USP20 overexpression models were applied. Co-immunoprecipitation, LC-MS/MS, ubiquitination assays, site-directed mutagenesis, and rescue experiments were performed to define the underlying mechanism.

USP20 expression was markedly decreased in I/R-injured mouse hearts and H/R-treated cardiomyocytes, and USP20 was predominantly localized in cardiomyocytes. Cardiomyocyte-specific USP20 deletion aggravated myocardial injury, adverse cardiac remodeling, and cardiac dysfunction after I/R, whereas USP20 overexpression conferred significant cardioprotection. Mechanistically, USP20 directly interacted with glucose-regulated protein 78 (GRP78) and removed K63-linked polyubiquitin chains from GRP78 at K602 through its C154 active site. This deubiquitination activated GRP78, promoted adaptive endoplasmic reticulum stress responses, and reduced myocardial injury.

These findings identify a previously unrecognized USP20-GRP78 regulatory axis that regulates endoplasmic reticulum stress responses and limits myocardial damage during I/R. USP20 may represent a potential therapeutic target for myocardial I/R injury.