MDH2 S246 phosphorylation protects mitochondria against hypoxia/reoxygenation injury due to acetate/lactate metabolism

Ischemic cardiomyopathy (ICM) is characterized by impaired myocardial function resulting from reduced coronary blood flow, resulting in heart failure. Emerging evidence from proteomic studies indicates that ischemic preconditioning confers cardioprotection against ICM through the regulation of mitochondrial proteins. Proteomic analyses have identified phosphorylation in mitochondrial proteins, including malate dehydrogenase 2 (MDH2), as mediators of cardioprotective mechanisms. However, the mechanism by which MDH2 phosphorylation contributes to cardioprotection in cardiovascular diseases remains poorly understood. This study investigates the role of MDH2 phosphorylation, particularly at S246, in regulating cardiac function. Analysis of patients with dilated cardiomyopathy indicated no significant change in <i>MDH2</i> expression, similar to a trend observed in ischemic patient data. Considering that a previous proteomic analysis of ischemic preconditioned rat hearts indicated phosphorylation at S246, we analyzed the functional role of this phosphorylation by introducing S246A phosphomutation. S246A phosphomutation significantly decreased MDH2 activity, accompanied by an increased accumulation of acetate and lactate as demonstrated by metabolomics. S246A phosphomutation also lowers mitochondrial membrane potential and ATP production. Under hypoxia/reoxygenation (H/R) conditions, S246A phosphomutation downregulates mitochondrial biogenesis and fusion proteins such as PGC1α and OPA1. Overall, these findings suggest that MDH2 phosphorylation at S246 is important in protecting against H/R injury through mitochondrial function regulation and activation of metabolic pathways. This discovery establishes a potential therapeutic strategy and a clear direction for drug development to specifically address conditions such as ICM.