Background and Purpose Myocardial ischemia–reperfusion (I/R) injury is a major cause of ischemic cardiomyopathy and chronic heart failure, underscoring the need for new cardioprotective strategies. ATP synthase inhibitory factor 1 (IF1) maintains mitochondrial function and limits oxidative damage during I/R injury. Our previous work showed that IF1 protects the heart through AMPK activation; however, IF1 protein levels decline sharply during I/R despite stable mRNA expression, suggesting post-translational regulation. This study aimed to elucidate the molecular mechanism underlying IF1 instability and to characterize a newly identified phosphorylation site at serine 27 (S27). Experimental Approach Mass spectrometric analysis of HEK293 cells revealed a significant upregulation of IF1 phosphorylation at serine 27 (S27) during the I/R process. The functional role of IF1 was further investigated in a IF1-KO mouse model of myocardial I/R, comparing the effects of wild-type IF1 (WT) and a non-phosphorylatable IF1 mutant (S27A). Key Results Mass spectrometric analysis revealed S27 as a novel phosphorylation site of IF1 that is markedly induced during I/R injury. This phosphorylation promoted the interaction between IF1 and the E3 ubiquitin ligase NEDD4, enhancing IF1 ubiquitination and proteasomal degradation. In vivo, restoration of IF1—either WT or S27A—attenuated acute and chronic myocardial injury, preserved mitochondrial integrity, and improved cardiac function. Notably, the S27A mutant, resistant to phosphorylation-dependent degradation, provided superior cardioprotection compared with WT IF1. Conclusion and Implications GSK3β-mediated phosphorylation of IF1 at the newly identified S27 site destabilizes IF1 via the ubiquitin–proteasome pathway, contributing to myocardial I/R injury. Blocking this modification stabilizes IF1 and enhances cardioprotection. These findings reveal a previously unrecognized mechanism of IF1 regulation and identify S27 phosphorylation as a promising therapeutic target against reperfusion-induced cardiac damage.

Objectives: To date, there is no consensus on optimal speed for rotational atherectomy (RA) in patients with coronary heart disease (CHD). Here, we aimed to investigate interventional outcomes of RA at different rotational speeds and analyze its clinical effect in the patients with CHD. Methods: A total of 372 CHD patients were retrospectively analyzed between February 2017 and December 2021. The patients received RA at different rotational speeds. The patients were divided into four groups based on the maximum RA speed: group 1 (˂150,000rpm, 76 cases), group 2 (150,000rpm, 156 cases), group 3 (160,000rpm, 90 cases) and group 4 (≥170,000rpm, 50 cases). The perioperative endpoints included hypotension, vasospasm, dissection, slow flow, perforation, bradyarrhythmia, burr entrapment, rotawire fracture during RA as well as the incidence of heart failure, stent thrombosis, and cardiac death during hospitalization. Six-months incidence of major cardiovascular and cerebrovascular events (MACCE) such as a composite of myocardial infarction (MI), stent thrombosis, target vessel revascularization (TVR), cardiogenic death, all-cause death or stroke were the long-term primary endpoints. On the other hand, long-term secondary endpoint was chronic heart failure. Results: Our analysis showed that patients in group 4 had a higher incidence of slow flow during the RA operation (P=0.025). There was no significant difference in other complications among the four groups. Besides, there was no significant difference in six-month MACCE among the four groups (P=0.452). After adjusting for confounding factors, increase in rotational speed led to a higher probability of slow flow (P for non-linearity = 0.131; adjusted model) and MACCE (P for non-linearity = 0.183; adjusted model). Logistic regression analysis showed that rotational speed was a predictor of slow flow during RA operation (OR=1.24, 95%CI:1.05~1.47, P=0.013), as well as six-month incidence of MI (OR=2.22, 95%CI:1.04~4.71,p=0.038). Moreover, the analysis demonstrated that a rotational speed of ˂150,000rpm was a predictor of vasospasm during RA operation (OR=3.62, 95% CI:1.21~10.8, P=0.021). Conclusion: Our findings showed that CHD patients treated with RA at a rotational speed of ≥170,000rpm had a higher risk of slow flow. In contrast, a rotational speed of ˂150,000rpm was shown to be an independent risk factor for spasm during RA in CHD patients. Moreover, rotational speed is an independent risk factor for slow flow and six-month MI in CHD patients. There was no significant difference in six-month outcomes in comparison to elective CHD patients with different rotational speeds, and the probability of MACCE was intensified with increase in rotational speed.