Abstract Body: Background: Neurofibromin 2 (NF2) is a tumor suppressor that can engage signaling pathways to modulate cell proliferation and survival. We previously demonstrated that NF2 mediates cardiomyocyte apoptosis and cardiac injury caused by acute myocardial infarction.
Research Aim: The role of NF2 in heart failure remains uncharacterized. This study sought to determine whether NF2 modulates heart failure due to chronic stress.
Approach: We generated cardiomyocyte-specific NF2 knockout (cKO) mice and used transverse aortic constriction (TAC) to generate chronic pressure overload (PO) stress, which elicits cardiac remodeling and failure. Complementary cell-based experiments were performed in neonatal rat ventricular myocytes (NRVMs). We analyzed cardiac function by echocardiographic and hemodynamic analysis. We used RNAseq and validated the novel findings using promoter pulldown, Seahorse metabolic profiling, and biochemical analyses to investigate underlying mechanisms.
Results: We found that NF2 is transiently upregulated in wild-type mouse myocardium in response to early phase of PO, but is downregulated during heart failure. Following TAC, NF2 cKO hearts unexpectedly showed significantly worsened cardiac function, compared to controls. RNAseq analysis followed by qPCR indicated downregulation of several metabolic pathways and impaired Estrogen Related Receptor (ERR) signaling in NF2 cKO hearts. Luciferase experiments employing NRVMs confirmed that NF2 promoted expression of ERR isoforms (a, g), and DNA pulldown assays demonstrated NF2 association with ERR proximal promoters. Analysis of NRVM bioenergetics demonstrated that NF2 depletion impaired mitochondrial respiration, which was reversed by concomitant expression of ERRg. Moreover, AAV9-mediated restoration of ERRg in NF2 cKO mice normalized cardiac function in response to PO. As NF2 does not directly bind DNA, leveraging a proteomics-based approach we identified the transcription factor linking NF2 to ERR isoform expression and further validated its regulation using NRVMs based experiments.
Conclusion: Based on these findings, we conclude that NF2 is essential and therefore transiently upregulated during PO stress to compensate and regulate metabolic demand.