USP49 stabilizes MDMX and suppresses PPARα activity to mitigate isoproterenol-induced heart failure in preclinical models

Background Ubiquitin-specific peptidase 49 (USP49) has been implicated in cardioprotection, yet its role in heart failure (HF) and the associated mechanism are poorly understood. This study deciphered the function of USP49 in HF and its interaction with MDM4 regulator of p53 (MDMX) and peroxisome proliferator-activated receptor α (PPARα), with a focus on defining the regulatory hierarchy of the USP49-MDMX-PPARα axis in ISO-induced HF. Methods CCC-HEH-2 cells were subjected to isoproterenol (ISO) treatment and gene transfection. Cell viability, apoptosis, and lipid accumulation were assessed. USP49-MDMX interaction was validated via co-immunoprecipitation (Co-IP). In ISO-induced HF mice, cardiac function, myocardial hypertrophy, apoptosis, and lipid deposition were evaluated. Protein and mRNA levels of USP49, MDMX, PPARα, phosphorylated PPARα (p-PPARα), and hypertrophy/lipid metabolism-related genes were determined by western blotting and quantitative real-time polymerase chain reaction (qRT-PCR). Results USP49 directly stabilized MDMX through deubiquitination. In CCC-HEH-2 cells, USP49 overexpression or PPARα knockdown reduced ISO-induced apoptosis/lipid deposition, and downregulated lipid metabolism-related genes, whereas USP49 or MDMX knockdown, or PPARα overexpression aggravated injury by enhancing PPARα activation and lipid metabolism-related gene expressions. Consistent with in-vitro findings, USP49 overexpression in ISO-induced mice improved cardiac dysfunction, reduced myocardial hypertrophy, apoptosis and lipid accumulation, restored gene expressions, and inhibited PPARα signaling. These effects were counteracted by the PPARα agonist WY-14643 and intensified by the PPARα antagonist GW6471, confirming that PPARα activity critically regulated USP49-mediated cardioprotection. Collectively, these data indicated that USP49 exerted protective effects through MDMX stabilization and subsequent PPARα suppression. Conclusion USP49 alleviates ISO-induced HF by stabilizing MDMX and consequently suppressing PPARα activity, highlighting the USP49-MDMX-PPARα axis as a promising target and biomarker for HF management.