RNF220 mediates K63-linked polyubiquitination of STAT3 and aggravates pathological cardiac hypertrophy.

Pathological cardiac hypertrophy serves as an independent risk factor for heart failure, which is the final stage of numerous cardiovascular diseases. However, the molecular regulatory mechanisms underlying this pathological process are still poorly characterized. The ubiquitin-proteasome system (UPS) is known to influence the development of pathological cardiac hypertrophy by precisely controlling protein function, localization, and proteostasis. The E3 ubiquitin ligase ring finger protein 220 (RNF220), a component of the UPS, was chosen as the research subject to investigate its role in pathological cardiac hypertrophy. Using Ang II-induced cardiac hypertrophy models combined with RNF220 knockout mice, RNF220 overexpression mice, and primary cardiomyocytes to examine the molecular mechanisms by which RNF220 governs pathological cardiac hypertrophy. We found that RNF220 deficiency promotes resistance to angiotensin II infusion by suppressing myocardial hypertrophy and fibrosis, whereas RNF220 overexpression aggravated cardiac dysfunction and hypertrophic responses. Moreover, using proteomic mass spectrometry and co-immunoprecipitation (Co-IP) experiments, we identified a functional interaction between RNF220 and STAT3. Mechanistically, RNF220 directly binds to the SH2 and TAD structural domains of STAT3 via its N-terminal domain, specifically facilitating K63-linked polyubiquitination at lysine residues 615, 626, 631, and 642 of STAT3, thereby stabilizing its protein to drive pro-hypertrophic responses. Critical rescue experiments demonstrated that STAT3 inhibitors or gene silencing effectively restored the ventricular hypertrophy phenotype caused by RNF220 overexpression. Collectively, these findings reveal a novel mechanism by which RNF220 drives pathological myocardial hypertrophy by regulating STAT3 ubiquitination, indicating a potential therapeutic target for heart failure intervention.