Abstract 164: MicroRNA-29c Reduces Serca2 Expression During Myocardial Hypoxia
The cardiac response to a hypoxic challenge is coordinated by the transcription factor Hypoxia Inducible Factor-1 (HIF-1), which drives the transcription of a large number of genes pertinent to angiogenesis, metabolism, and calcium cycling. Expression of HIF-1alpha that has been mutated to remove oxygen regulation recapitulates many of the changes in gene expression seen in hypoxia. It also results in reversible cardiac dysfunction associated with marked decrease of Sarco-Endoplasmic Reticulum Calcium-Dependent ATP-ase (SERCA2). This decrease in SERCA was more rapid and more substantial than a moderate decrease seen in the mRNA for this protein.
In this study, we tested the hypothesis that the decrease in SERCA2 is mediated by the up-regulation of microRNA (miRNA) in the heart. We identified 30 miRNAs that are dysregulated upon induction of oxygen stable HIF1 expression. Three of these have evident binding sites in the 3’ untranslated region of the SERCA2 gene. Transient co-transfection of a mimic molecule for these three miRs with a luciferase reporter construct that includes the 3’ UTR of SERCA2 showed that mi-29c produced a substantial decrease in reporter expression. This effect is abolished by the mutagenesis of the predicted target site within the 3’UTR. Similarly, transfection of this mimic molecule into a cell line that expresses SERCA2 results in a reduction in SERCA2 protein levels. An antagomir to this miR rescues the reduction in SERCA seen with HIF expression. We conclude that miR-29c, is responsible for an important portion of the down-regulation of SERCA2, and thus the contractile dysfunction, seen in hypoxia.
- © 2012 by American Heart Association, Inc.