RAB7 protects against ischemic heart failure via promoting non-canonical TUFM mitophagy pathway.

Rationale: Cardiomyocyte apoptosis critically contributes to ischemic heart failure (IHF) progression. While the endosome-lysosome system governs cellular homeostasis, the functional significance of its master regulator RAB7 in cardiac pathophysiology remains unexplored.

Methods

Using myocardial infarction (MI) models via left anterior descending coronary artery ligation in cardiomyocyte-specific RAB7 knockout mice and adeno-associated virus-mediated RAB7 overexpression models, we assessed cardiac function and adverse remodeling through echocardiography and pathophysiological assessment. Mitophagy flux was quantified using mt-Keima mice and confocal imaging. Molecular mechanisms were dissected through immunoprecipitation coupled with mass spectrometry (IP-MS) analysis and molecular experiment validation.

Results

RAB7 expression decreased in ischemic myocardium. Cardiomyocyte-specific RAB7 ablation exacerbated while RAB7 overexpression attenuated post-MI cardiac dysfunction and maladaptive remodeling. RAB7 enhanced mitophagic clearance of damaged mitochondria, reducing cardiomyocyte apoptosis under ischemic stress both in vitro and in vivo. Mechanistically, TUFM, a mitochondrial translation elongation factor, was identified as a novel effector of RAB7. RAB7 facilitated the recruitment of TUFM and LC3 to damaged mitochondria, thereby enhancing mitophagy. TUFM knockdown significantly diminished the protective effects of RAB7 on mitophagy and cardiomyocyte survival. Finally, administration of ML-098, a chemical RAB7 activator, promoted mitophagy and mitigated IHF progression in mice.

Conclusion

We identify RAB7 as a novel coordinator of cardioprotective mitophagy through TUFM-mediated machinery assembly. The RAB7-TUFM axis represents a therapeutic target for IHF that warrants further clinical evaluation.