Cardiomyocyte-Enriched USP20 Ameliorates Pathological Cardiac Hypertrophy by Targeting STAT3 Deubiquitination

Although pathological cardiac hypertrophy is a key driver of heart failure, the underlying mechanisms remain incompletely elucidated. This study investigates the role and mechanism of deubiquitinating enzyme (DUB) ubiquitin-specific protease 20 (USP20) in cardiac hypertrophy. Transcriptomic profiling of hypertrophic hearts shows significant alterations in the expression of DUBs, including a remarkable downregulation of USP20. USP20 is predominantly expressed in cardiomyocytes. Co-immunoprecipitation (Co-IP) followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) is used to identify USP20 substrates. Cleavage Under Targets and Tagmentation assay (CUT&Tag) sequencing is employed to identify downstream targets of signal transducer and activator of transcription 3 (STAT3). Functionally, USP20 deficiency exacerbates cardiac hypertrophy induced by either angiotensin II (Ang II) or transverse aortic constriction (TAC), whereas USP20 overexpression alleviates hypertrophic responses. Mechanistically, USP20 deubiquitinates STAT3 by removing K63-linked ubiquitin chains at K177 via its H645 active site, reducing STAT3 phosphorylation and nuclear translocation. This inhibites STAT3's transcriptional activity at coactivator-associated arginine methyltransfer (Carm1) promoter, leading to upregulated CARM1 expression and mitigated hypertrophy. Importantly, the STAT3 inhibitor Stattic confirms STAT3 serves as a key substrate mediating the cardiac protective effects of USP20. These findings unveil a novel USP20/STAT3/CARM1 axis in cardiomyocytes and reveal its therapeutic potential for cardiac hypertrophy.