Abstract 210: Flavin Containing Monooxygenase 2 Confers Cardiac Protection via Unfolded Protein Response Signaling Modulated by Disulfide Bond Catalysis

Abstract

Introduction: Myocardial infarction (MI) is characterized by cardiac dysfunction and increased cardiomyocyte death, induced mainly by apoptosis. Using an unbiased transcriptome analysis, we identified flavin containing monooxygenase 2 (FMO2) as one of the top-ranked genes involved in the process of MI. In this study, we investigate the roles of FMO2 in ischemic injury and its potential mechanisms. Hypothesis: FMO2 exhibits the cardiac protection from MI injury. Methods: Male SD rats receiving either adeno-associated virus serotype 9 containing FMO2 shRNA particles (AAV-shFMO2) or FMO2 (AAV-FMO2), and FMO2 knockout rats were subjected to myocardial infarction surgery. Cardiac function, fibrosis, and apoptosis were examined in these rats and related cellular and molecular mechanisms were investigated. Results: Cardiac ischemia injury was associated with significant increases of FMO2 levels both in ex vivo and in vivo models. Loss of FMO2 significantly enhanced cardiomyocyte apoptosis and deteriorated cardiac function accompanied by augmented infarct size in infarcted rat hearts, while elevated expression of FMO2 exhibited the opposite results. Mechanically, located on the ER membrane, FMO2 inhibited activation of ER stress-initiated apoptotic proteins including caspase 12 and C/EBP homologous protein (CHOP), via down-regulating upstream unfolded protein response (UPR) pathway. Furthermore, we found that FMO2, as a novel chaperone in ER, directly catalyzed disulfide-bond synthesis to facilitate proteins folding. Finally, structure analysis of FMO2 revealed the active site GVSG for disulfide-bond catalysis, which was confirmed by the molecular docking experiment of GSH with FMO2. However, FMO2 with GVSG mutation failed to catalyze disulfide-bond formation and lost protection from ER stress or apoptosis in cardiomyocytes. Conclusion: FMO2 confers cardiac protection from ischemic damage due to improved cardiomyocyte apoptosis through UPR pathway, which is mediated by disulfide-bond catalysis at GVSG active site. Our findings uncover a novel FMO2-involved regulatory mechanism which could serves as a potential therapeutic target for ischemic cardiovascular diseases.