A Cardiac-enriched MicroRNA, miR-378, Blocks Cardiac Hypertrophy by Targeting Ras Signaling

• Published in: The Journal of biological chemistry 2013-04, Vol.288 (16), p.11216-11232
• Main Authors: Nagalingam, Raghu S., Sundaresan, Nagalingam R., Gupta, Mahesh P., Geenen, David L., Solaro, R.John, Gupta, Madhu
• Format: Article
• Language: English
• Subjects: Adrenergic alpha-1 Receptor Agonists - adverse effects; Adrenergic alpha-1 Receptor Agonists - pharmacology; Animals; Cardiac Hypertrophy; Cardiomegaly - chemically induced; Cardiomegaly - genetics; Cardiomegaly - metabolism; Cardiomegaly - pathology; Cell Signaling; Cells, Cultured; Gene Expression Regulation - drug effects; Gene Expression Regulation - genetics; Glycogen Synthase Kinase 3 - genetics; Glycogen Synthase Kinase 3 - metabolism; Glycogen Synthase Kinase 3 beta; Grb2; GRB2 Adaptor Protein - biosynthesis; GRB2 Adaptor Protein - genetics; MAP Kinase Kinase 1 - genetics; MAP Kinase Kinase 1 - metabolism; MAP Kinase Kinase Kinases - genetics; MAP Kinase Kinase Kinases - metabolism; MAP Kinase Signaling System; MAP Kinases (MAPKs); MicroRNA-378; MicroRNAs - genetics; MicroRNAs - metabolism; Mitogen-Activated Protein Kinase 3 - genetics; Mitogen-Activated Protein Kinase 3 - metabolism; Molecular Bases of Disease; Molecular Biology; Muscle Proteins - genetics; Muscle Proteins - metabolism; Phenylephrine - adverse effects; Phenylephrine - pharmacology; Phosphatidylinositol 3-Kinases - genetics; Phosphatidylinositol 3-Kinases - metabolism; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins c-raf; Ras; ras Proteins - genetics; ras Proteins - metabolism; Rats; Rats, Sprague-Dawley; RNA
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M112.442384

Understanding the regulation of cardiomyocyte growth is crucial for the management of adverse ventricular remodeling and heart failure. MicroRNA-378 (miR-378) is a newly described member of the cardiac-enriched miRNAs, which is expressed only in cardiac myocytes and not in cardiac fibroblasts. We have previously shown that miR-378 regulates cardiac growth during the postnatal period by direct targeting of IGF1R (Knezevic, I., Patel, A., Sundaresan, N. R., Gupta, M. P., Solaro, R. J., Nagalingam, R. S., and Gupta, M. (2012) J. Biol. Chem. 287, 12913–12926). Here, we report that miR-378 is an endogenous negative regulator of cardiac hypertrophy, and its levels are down-regulated during hypertrophic growth of the heart and during heart failure. In primary cultures of cardiomyocytes, overexpression of miR-378 blocked phenylephrine (PE)-stimulated Ras activity and also prevented activation of two major growth-promoting signaling pathways, PI3K-AKT and Raf1-MEK1-ERK1/2, acting downstream of Ras signaling. Overexpression of miR-378 suppressed PE-induced phosphorylation of S6 ribosomal kinase, pERK1/2, pAKT, pGSK-3β, and nuclear accumulation of NFAT. There was also suppression of the fetal gene program that was induced by PE. Experiments carried out to delineate the mechanism behind the suppression of Ras, led us to identify Grb2, an upstream component of Ras signaling, as a bona fide direct target of miR-378-mediated regulation. Deficiency of miR-378 alone was sufficient to induce fetal gene expression, which was prevented by knocking down Grb2 expression and blocking Ras activation, thus suggesting that miR-378 interferes with Ras activation by targeting Grb2. Our study demonstrates that miR-378 is an endogenous negative regulator of Ras signaling and cardiac hypertrophy and its deficiency contributes to the development of cardiac hypertrophy. Background: miR-378 is a newly discovered cardiomyocyte-enriched miRNA. Results: By targeting Grb-2, miR-378 blocks activation of the hypertrophic signaling cascade and gene expression. Its deficiency contributes to the development of hypertrophy in a Ras activity-dependent manner. Conclusion: miR-378 is a negative regulator of cardiac hypertrophy. Significance: Cellular restoration of miR-378 will be beneficial in preventing adverse cardiac remodeling.