Rab32 exacerbates myocardial ischemia/reperfusion injury via PKA/P300/H3K18la-dependent glucose metabolic reprogramming

Glucose metabolic reprogramming, defined by uncoupling between glycolysis and glucose oxidation, is a critical determinant of cardiac dysfunction after ischemia/reperfusion (I/R), yet its upstream drivers remain elusive. RAB32, a mitochondrial Rab GTPase with A-kinase anchoring protein (AKAP) activity, participates in mitochondrial homeostasis, but its role in myocardial I/R injury and glucose metabolic reprogramming is unknown. We used cardiomyocyte-specific RAB32 knockout mice subjected to left anterior descending coronary artery ligation and H9c2 cells exposed to hypoxia/reoxygenation (H/R), combined with integrated transcriptomic profiling of I/R myocardium and metabolomic profiling of RAB32-knockdown cardiomyocytes. Using these complementary approaches, we identify RAB32 as a key driver of glucose metabolic reprogramming after I/R. RAB32 was upregulated in I/R myocardium and H/R cardiomyocytes. Cardiomyocyte-specific RAB32 deletion reduced infarct size, decreased CK, cTnI, and LDH levels, preserved cardiac function, and maintained mitochondrial homeostasis. Conversely, RAB32 knockdown attenuated, whereas RAB32 overexpression aggravated, H/R-induced cardiomyocyte injury and mitochondrial dysfunction. Mechanistically, RAB32 bound protein kinase A (PKA) through its AKAP domain, promoting PKA-dependent P300 phosphorylation and H3K18la elevation. H3K18la was enriched at promoter regions of HK2 and PDK4 and drove their transcription; HK2 enhanced glycolysis, whereas PDK4 phosphorylated and inhibited PDHA1, blocking pyruvate oxidation and uncoupling glycolysis from glucose oxidation. RAB32 ablation reversed these metabolic alterations, restoring ATP levels and coupling between glycolysis and glucose oxidation. These findings identify the RAB32/PKA/P300/H3K18la axis as a previously unappreciated epigenetic checkpoint governing glucose metabolic reprogramming in mouse hearts following I/R, nominating RAB32 and its downstream pathway as potential therapeutic targets for myocardial I/R injury.