Role of EZH2 in regulating c-Myc stability through the E3 ubiquitin ligase HUWE1 in heart failure and its mechanisms

Objective

Heart failure (HF) is a leading cause of mortality and morbidity. Respecting the role of enhancer of zeste homolog 2 (EZH2) in HF, we examined how EZH2 regulated c-Myc stability through HUWE1 and its mechanism.

Methods

Gain- and loss-of-function assays were performed to investigate the role of EZH2 in HF. Cardiac function and histopathological changes in mice were assessed. EZH2, HUWE1, and c-Myc mRNA levels were determined by RT-qPCR. Cell viability was assessed using CCK-8 assay. HUWE1, EZH2, H3K27me3, c-Myc, atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and β-myosin heavy chain (β-MHC) expression were detected, followed by immunofluorescence to determine cardiomyocyte size. Inflammatory cytokines, TNF-α, IL-6, and IL-1β promoter luciferase activity, and c-Myc enrichment in their promoter regions were evaluated. H3K27me3 enrichment in the HUWE1 promoter region, HUWE1-mediated c-Myc ubiquitination, and c-Myc protein stability were assessed.

Results

EZH2 was up-regulated in myocardial tissues of HF mice. Angiotensin II reduced cell viability, increased cell size, elevated EZH2 and c-Myc expression and ANP, BNP, and β-MHC protein levels, and enhanced TNF-α, IL-6, and IL-1β levels in cells. EZH2 knockdown down-regulated c-Myc, ameliorating cardiomyocyte hypertrophy (CH); this effect was verified by in vivo experiments and partially averted by c-Myc overexpression. EZH2 reduced HUWE1 expression and c-Myc ubiquitination by enhancing H3K27me3 modification, improving c-Myc protein stability. HUWE1 overexpression reduced c-Myc protein stability and partially negated the improvement effect of EZH2 knockdown on CH.

Conclusion

EZH2 curbs HUWE1 transcriptional expression by promoting H3K27me3 modification to enhance c-Myc protein stability, thereby contributing to HF.