CircPUM1 regulates March5-mediated Pyruvate Kinase M2 (PKM2) ubiquitination to modulate ferroptosis in myocardial ischemia-reperfusion injury

Background/Introduction Myocardial ischemia-reperfusion (I/R) injury is a critical determinant of poor outcomes in acute myocardial infarction. Ferroptosis, a regulated form of cell death driven by iron-dependent lipid peroxidation, plays a pivotal role in myocardial I/R injury. Our previous studies identified E3 ubiquitin ligase March5 as a key regulator of myocardial I/R injury, but its molecular mechanism in ferroptosis remains unclear. Purpose This study aims to elucidate the role of March5 in ferroptosis during myocardial I/R injury and explore the regulatory effects of circPUM1 on March5 and its downstream target, pyruvate kinase M2 (PKM2). Methods Using in vitro and in vivo models of myocardial I/R injury, we employed chromatin immunoprecipitation (ChIP), RNA immunoprecipitation (RIP), and co-immunoprecipitation (Co-IP) to investigate the interactions between circPUM1, March5, and PKM2. PKM2 ubiquitination, dimerization, and nuclear translocation were assessed, along with its transcriptional regulation of acyl-CoA synthetase long-chain family member 4 (ACSL4), a key mediator of ferroptosis. Results We found that March5 expression was significantly reduced following myocardial I/R injury. Mechanistically, March5 deficiency led to decreased ubiquitination and degradation of PKM2, promoting PKM2 dimerization and nuclear translocation. Nuclear PKM2 upregulated ACSL4 expression, driving ferroptosis. Furthermore, circPUM1 was identified as a regulator of March5 expression, suggesting a novel circPUM1-March5-PKM2 axis in ferroptosis regulation. Conclusions Our findings reveal that circPUM1 regulates March5-mediated PKM2 ubiquitination to modulate ferroptosis in myocardial I/R injury. Targeting this pathway may provide a novel therapeutic strategy for acute myocardial infarction.