The Role Of Cardiac Neurofibromin-2 In Chronic Pressure Overload

Department of Cell Biology and Molecular Medicine, New Jersey Medical School, Rutgers University, Newark, NJ 07103.Neurofibromin 2 (NF2) is a tumor suppressor that can engage the Hippo signaling pathway and modulate cell proliferation and survival. We previously demonstrated that NF2 mediates cardiomyocyte apoptosis and injury caused by acute myocardial infarction. However, the function of NF2 in the heart remains largely uncharacterized. Our current study sought to determine whether NF2 modulates heart failure due to chronic stress. We used a transverse aortic constriction (TAC) model in WT C57BL/6J mice to generate chronic pressure overload (PO) stress, which elicits cardiac remodeling and failure. We found that NF2 is transiently upregulated in mouse myocardium in response to early phase of PO, and is downregulated during late phase PO. We generated cardiomyocyte-specific NF2 knockout (cKO) mice, which had normal cardiac morphology and function at baseline. Following TAC, NF2 cKO hearts unexpectedly showed worsened cardiac function, assessed by echocardiography and hemodynamic analysis, compared to controls. RNAseq analysis indicated downregulation of several metabolic pathways including oxidative phosphorylation and fatty acid oxidation in NF2 cKO hearts at baseline. Additionally, we observed reduced ATP content in baseline NF2 cKO hearts compared to controls. Fractionation experiments indicated that nuclear NF2 is enriched following PO stress. RNAseq revealed the downregulation of ERRβ and ERRγ in NF2 cKO hearts, which was confirmed by qPCR. Experiments employing neonatal rat ventricular myocytes (NRMVs) confirmed that NF2 regulated expression of ERRβ and ERRγ, and DNA pulldown assays demonstrated NF2 association with ERRβ and ERRγ proximal promoters. Luciferase reporter assays demonstrated that NF2 modulates ERR function in NRVMs. Based on these findings, we propose that transient upregulation of myocardial NF2 expression during PO stress is compensatory and regulates metabolic gene expression according to energy demand.