Cooperative Binding of ETS2 and NFAT Link Erk1/2 and Calcineurin Signaling in the Pathogenesis of Cardiac Hypertrophy

Abstract

Background: Cardiac hypertrophy is an independent risk factor for heart failure, a leading cause of morbidity and mortality globally. The calcineurin/NFAT (nuclear factor of activated T cells) pathway and the MAPK/Erk (extracellular signal-regulated kinase) pathway contribute to the pathogenesis of cardiac hypertrophy as an inter-dependent network of signaling cascades. However, how these pathways interact remains unclear, and specifically few direct targets responsible for the pro-hypertrophic role of NFAT have been described. Methods: By engineering a cardiomyocyte-specific ETS2 (a member of E26 transformationspecific sequence (ETS)-domain family) knockout mice, we investigated the role of ETS2 in cardiac hypertrophy. Primary cardiomyocytes were also used to evaluate ETS2 function in cell growth. Results: ETS2 is phosphorylated and activated by Erk1/2 upon hypertrophic stimulation in both mouse (n = 3) and human heart samples (n = 8-19). Conditional deletion of ETS2 in mouse cardiomyocytes protects against pressure overload-induced cardiac hypertrophy (n = 6-11). Furthermore, silencing of ETS2 in the hearts of calcineurin transgenic mice significantly attenuates hypertrophic growth and contractile dysfunction (n = 8). As a transcription factor, ETS2 is capable of binding to the promoters of hypertrophic marker genes, such as ANP, BNP and Rcan1.4 (n = 4). Additionally, we report that ETS2 forms a complex with NFAT to stimulate transcriptional activity through increased NFAT binding to the promoters of at least two hypertrophy-stimulated genes, Rcan1.4 and miR-223 (n = 4-6). Suppression of miR-223 in cardiomyocytes inhibits calcineurin-mediated cardiac hypertrophy (n = 6), revealing miR-223 as a novel pro-hypertrophic target of the calcineurin-NFAT and Erk1/2-ETS2 pathways. Conclusions: In aggregate, our findings point to a critical role for ETS2 in calcineurin-NFAT pathway-driven cardiac hypertrophy and unveil a previously unknown molecular connection between the Erk1/2 activation of ETS2 and expression of NFAT/ETS2 target genes.