Deubiquitinase USP43 exacerbates myocardial ischemia-reperfusion injury by stabilizing ASK1 and activating the JNK/P38 MAPK pathway.

Myocardial ischemia-reperfusion injury (MIRI) remains a major challenge in reperfusion therapy for acute myocardial infarction. The role of deubiquitinating enzyme ubiquitin-specific protease 43 (USP43) in this process, however, remains largely unexplored. In this study, we found that USP43 expression was significantly upregulated in murine hearts subjected to ischemia/reperfusion and in primary cardiomyocytes following hypoxia/reoxygenation. Genetic knockout of Usp43 conferred substantial protection against ischemia/reperfusion-induced myocardial injury, inflammation, and cardiomyocyte death, whereas cardiac-specific overexpression of USP43 exacerbated these detrimental effects. Consistent with these findings, USP43 knockdown attenuated hypoxia/reoxygenation-induced damage in primary cardiomyocytes, while its overexpression promoted cell death. Mechanistically, integrated transcriptomic and biochemical assays revealed apoptosis signal-regulating kinase 1 (ASK1) as a key USP43 substrate. USP43 directly binds to ASK1 and removes its K48-linked ubiquitin chains, thereby shielding ASK1 from proteasomal degradation. This post-translational modification leads to ASK1 protein stabilization and hyperactivation of the downstream ASK1-JNK/P38 mitogen-activated protein kinase (MAPK) signaling. Importantly, pharmacologically inhibiting ASK1 rescued the detrimental phenotype caused by USP43 overexpression. In summary, we identify USP43 as a novel regulator that exacerbates MIRI by promoting ASK1-mediated cell death. Targeting the USP43-ASK1 signaling axis may therefore warrant further investigation as a research target to elucidate the mechanisms of MIRI.