Abstract 3609: MicroRNA-19a (miR-19a) Regulates gp130 Signaling by Inhibiting Suppressor of Cytokine Signaling-3 (SOCS3) Protein Translation
The dysregulation of gene expression via microRNAs has been etiologically linked to heart diseases. It has been reported that miR-19a is increased in the heart with acute-pressure overload and hypertrophy. Based on a computational analysis, we found that miR-19a could inhibit the expression of SOCS3, a crucial negative-feedback regulator for gp130 signaling. We recently found that cardiac-specific SOCS3 knockout mice (SOCS3 cKO) develop dilated cardiomyopathy (DCM) in a gp130 dependent manner. We hypothesized that miR-19a-mediated SOCS3 inhibition can induce DCM by affecting gp130 signaling. We found that transfection of miR-19a inhibited SOCS3 protein expression after stimulation with cardiotrophin-1 (CT-1), a gp130 ligand, in HEK293 cells. In contrast, transfection of miR-19a inhibitor significantly increased SOCS3 protein expression post CT-1 stimulation. In both experiments, there were no significant differences in SOCS3 mRNA expression between miR-19a or miR-19a inhibitor transfected cells and negative control miR transfected cells. This indicated that miR-19a decreased SOCS3 by inhibiting the protein translation but not the mRNA transcription. To confirm the specificity of the inhibitory effect, we generated a luciferase (luc) reporter plasmid harboring luc cDNA followed by SOCS3 3′ untranslated region that has a putative miR-19a binding site. We also made a similar construct by inserting two point mutations in the binding site. Co-transfection of miR-19a with the luc reporter decreased the expression of luc protein in a miR-19a dose-dependent manner while miR-19a had no effect on the luc expression when transfected with the reporter containing the mutations. This demonstrated that miR-19a inhibited SOCS3 protein translation by binding to the site specifically. Finally, we expressed miR-19a in neonatal mouse myocytes by generating adenovirus vector. SOCS3 expression post CT-1 stimulation was completely inhibited with enhanced STAT3 phosphorylation in the miR-19a expressed myocytes. In conclusion, these results demonstrate that miR-19a regulates gp130 signaling by inhibiting SOCS3 protein translation in the cardiac myocyte. Considering the SOCS3 cKO cardiac phenotype, miR-19a might be involved in the pathogenesis of DCM.
This research has received full or partial funding support from the American Heart Association, National Center.