Abstract 264: EPRS is a Critical Translational Control Factor in Cardiac Fibrosis

Increased protein synthesis of pro-fibrotic genes is a common feature of cardiac fibrosis, a major manifestation of heart failure (HF). Despite this observation, critical factors and molecular mechanisms for translational control of cardiac fibrosis remain underexplored. Here, we identify a critical house-keeping translational regulator, glutamyl-prolyl-tRNA synthetase (EPRS), which preferentially regulates the translation of proline-rich (PRR) pro-fibrotic genes. In mammals, EPRS catalyzes the attachment of two amino acids, glutamic acid and proline, to their cognate tRNAs for protein synthesis. By overlapping of aminoacyl-tRNA synthetases (ARSs) induced in TGF-β treated human cardiac fibroblasts, human ARSs with genetic mutations in the congenital heart disease, mouse ARSs associated with isoproterenol (ISO)-induced cardiomyopathy by GWAS, and ISO-induced ARSs in mouse failing hearts, we identified EPRS as the only ARS involved in various cardiac pathogenesis. EPRS is induced in failing human heart compared to non-failing donor heart and functions as an integrated node downstream of multiple hypertrophic and fibrotic stimuli in murine hearts, including ISO infusion and transverse aortic constriction (TAC) surgery. Low-dose halofuginone (Halo), a prolyl-tRNA synthetase (PRS)-specific inhibitor, as well as genetic knockout of one allele of EPRS in mouse genome, reduces cardiac hypertrophy and fibrosis in ISO- and TAC-induced HF mouse models. Using RNA-Seq and polysome profiling-Seq in Halo-treated fibroblasts, we identified several novel PRR genes, including Ltbp2, Furin and Sulf1, in addition to collagens, which are translationally regulated by EPRS. Inhibition of Furin by various inhibitors attenuates cardiac fibroblast activation and collagen deposition in vitro . Finally, we found that inactivation of EPRS reduced translational efficiency and enhanced mRNA decay of PRR genes. Taken together, our results indicate that EPRS controls the translational activation of PRR genes in cardiac fibroblasts, and these data provide novel insights into the translational control mechanisms of cardiac fibrosis, which may promote development of novel therapeutics by inhibiting pro-fibrotic translation factors.