The role of Neurofibromin 2 in heart failure

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Project Summary The heart is a metabolically demanding organ, and derangements in metabolic processes lead to energetic deficits, generation of toxic metabolites, and redox imbalance, which drive pathogenesis to heart failure. However, current therapies for heart failure do not address this fundamental issue, and there remains an unmet clinical need for effective mechanism-based treatments. Altered transcriptional programs are thought to contribute significantly to impaired mitochondrial oxidative phosphorylation and insufficient energy production in heart failure. The estrogen-related receptors (ERRa, b, and g) are key regulators of mitochondrial respiration that are downregulated in the failing heart, yet the molecular mechanisms regulating their expression and activity remain largely unknown. In preliminary studies we have identified a novel molecular pathway that promotes the expression of ERRb, and ERRg in cardiomyocytes, and define a new heart failure pathway linking chronic stress to impairment of mitochondrial oxidative respiration. Our unexpected results demonstrate that the tumor suppressor protein Neurofibromin 2 (NF2) promotes proper metabolic function, and that cardiac deletion of NF2 predisposes the heart to pathological remodeling and failure in response to LV pressure overload stress. Transcriptome profiling of cardiac deficient NF2 cKO hearts indicated downregulation of metabolic pathways and decreased expression/activity of ERRb and ERRg. Using a proteomics-based approach, we identified the transcription factor Zscan21 as an interacting partner of NF2 and a novel positive regulator of metabolic gene expression and mitochondrial oxidative respiration in cardiomyocytes. Therefore, we hypothesize that endogenous NF2 engages the transcription factor Zscan21 to positively regulate expression of ERRb and ERRg and promote energy production during pressure overload stress in the heart. The objectives of the current application are to further define the clinical role of this pathway, and to elucidate the molecular mechanisms by which NF2 regulates expression of myocardial ERRb and ERRg and prevents energy deficit. These objectives will be accomplished in 3 aims. In Aim1, we will establish evidence of NF2 as an important and novel mediator of cardiac metabolic coupling and energy production during the initial and late phases of pressure overload stress. In Aim2, we will investigate in detail the molecular interaction between NF2 and Zscan21 and determine the ability of Zscan21 to regulate expression of ERRb and ERRg, mitochondrial oxidative respiration, and energy production in cardiomyocytes. In Aim3, we will determine the therapeutic potential of normalizing cardiac NF2 for treatment in the pressure overload model of HFrEF. The long-term objective of this project is to define mechanistic events that mediate mitochondrial metabolic dysfunction in heart failure and identify potential candidates for new therapeutic strategies targeting early stages of heart failure.