Bmi‐1‐RING1B prevents GATA4‐dependent senescence‐associated pathological cardiac hypertrophy by promoting autophagic degradation of GATA4

AIMS: Senescence‐associated pathological cardiac hypertrophy (SA‐PCH) is associated with upregulation of foetal genes, fibrosis, senescence‐associated secretory phenotype (SASP), cardiac dysfunction and increased morbidity and mortality. Therefore, we conducted experiments to investigate whether GATA4 accumulation induces SA‐PCH, and whether Bmi‐1‐RING1B promotes GATA4 ubiquitination and its selective autophagic degradation to prevent SA‐PCH. METHODS AND RESULTS: Bmi‐1‐deficient (Bmi‐1(−/−) ), transgenic Bmi‐1 overexpressing (Bmi‐1(Tg) ) and wild‐type (WT) mice were infused with angiotensin II (Ang II) to stimulate the development of SA‐PCH. Through bioinformatics analysis with RNA sequencing data from cardiac tissues, we found that Bmi‐1‐RING1B and autophagy are negatively related to SA‐PCH. Bmi‐1 deficiency promoted GATA4‐dependent SA‐PCH by increasing GATA4 protein and hypertrophy‐related molecules transcribed by GATA4 such as ANP and BNP. Bmi‐1 deficiency stimulated NF‐κB‐p65‐dependent SASP, leading to cardiac dysfunction, cardiomyocyte hypertrophy and senescence. Bmi‐1 overexpression repressed GATA4‐dependent SA‐PCH. GATA4 degraded by Bmi‐1 was mainly dependent on autophagy rather than proteasome. In human myocardium, p16 positively correlated with ANP and GATA4 and negatively correlated with LC3B, Bmi‐1 and RING1B; GATA4 positively correlated with p62 and negatively correlated with Bmi‐1 and LC3B. With increased p16 protein levels, ANP‐, BNP‐ and GATA4‐positive cells or areas increased; however, LC3B‐positive cells or areas decreased in human myocardium. GATA4 is ubiquitinated after combining with Bmi‐1‐RING1B, which is then recognised by p62, is translocated to autophagosomes to form autophagolysosomes and degraded. Downregulated GATA4 ameliorated SA‐PCH and cardiac dysfunction by reducing GATA4‐dependent hypertrophy and SASP‐related molecules. Bmi‐1 combined with RING1B (residues 1–179) and C‐terminus of GATA4 (residues 206–443 including zinc finger domains) through residues 1–95, including a RING‐HC‐finger. RING1B combined with C‐terminus of GATA4 through the C‐terminus (residues 180–336). Adeno‐associated viral vector serotype 9 (AAV9)‐cytomegalovirus (CMV)‐Bmi‐1‐RING1B treatment significantly attenuated GATA4‐dependent SA‐PCH through promoting GATA4 autophagic degradation. CONCLUSIONS: Bmi‐1‐RING1B maintained cardiac function and prevented SA‐PCH by promoting selective autophagy for degrading GATA4. TRANSLATIONAL PERSPECTIVE: AAV9‐CMV‐Bmi‐1‐RING1B could be used for translational gene therapy to ubiquitinate GATA4 and prevent GATA4‐dependent SA‐PCH. Also, the combined domains between Bmi‐1‐RING1B and GATA4 in aging cardiomyocytes could be therapeutic targets for identifying stapled peptides in clinical applications to promote the combination of Bmi‐1‐RING1B with GATA4 and the ubiquitination of GATA4 to prevent SA‐PCH and heart failure. We found that degradation of cardiac GATA4 by Bmi‐1 was mainly dependent on autophagy rather than proteasome, and autophagy agonists metformin and rapamycin could ameliorate the SA‐PCH, suggesting that activation of autophagy with metformin or rapamycin could also be a promising method to prevent SA‐PCH.