Abstract 11939: Phosphorylation of Serca2 at Serine 663, a Physiological and Clinical Event in Ischemic Heart Diseases, That Regulates Intracellular Ca ²⁺ and Cell Death

Introduction: Despite advances in cardioprotection, new therapeutic strategies capable of preventing acute myocardial ischemia-reperfusion injury and reducing secondary event of patients are still needed. Hypothesis: We hypothesized that limitation of SERCA2 phosphorylation on a serine/threonine residue at reperfusion could provide protection against reperfusion injury, via the activation of the Ca 2+ reuptake into SR/ER which confers detoxification of the cytosolic and mitochondrial Ca 2+ overload during reperfusion . Methods: Combining in silico analysis with in vitro and in vivo genetic approaches, we discovered that the phosphorylation of SERCA2 at serine 663 is a clinical and pathophysiological event of cardiac function. Results: We demonstrated that the phosphorylation level of SERCA2 at serine 663 is increased with heart damage in both patient and mouse ischemic hearts. Mechanistically, we demonstrated that preventing serine 663 phosphorylation significantly increased SERCA2 Ca 2+ pumping activity into the reticulum and protected against hypoxia/reoxygenation-induced cell death, by counteracting the cytosolic and mitochondrial Ca 2+ overload. To link this specific residue event to a physiological role of SERCA2 in heart, we demonstrated that gene therapy for the phosphoresistant form of SERCA2 at serine 663 improved the excitation/contraction coupling of cardiomyocytes and significantly reduced infarct size in an in vivo myocardial infarction model, whereas mice expressing a phosphomimetic form of SERCA2 developed a larger infarct size. Conclusions: Together, these findings establish the pathophysiological role and the therapeutic potential of SERCA2 modulation in acute myocardial infarction, based on the hotspot phosphorylation level of SERCA2 on its serine 663 residue.