Abstract 14035: Autophagy is Regulated by mir-106b in the Heart
Autophagy is a lysosome-dependent degradation mechanism. In the heart the autophagic flux is induced by starvation and by specific cardiac disorders ranging from pressure overload to myocardial infarction. Recently, microRNAs have been implicated in the control of cardiac autophagy.
We found a significant induction of miR-106b in the heart of mice that had been starved for 48h (1.6±0.2-fold, n=11, p<0.05). Moreover, miR-106b is upregulated in cardiac tissue of patients with dilated cardiomyopathy (14.4±4.4-fold, n=3, p<0.05). Interestingly, miR-106b is induced in failing hearts of MLP knockout mice (11.5±2.6 fold, n=5, p<0.05), an established DCM model, as well.
Using four different target predictions algorithms (DIANA microT v4.0, miRDB, microRNA.org, TargetScan) we reduced the number of potential targets of miR-106b. Among the genes we found Fyco1. Fyco1 is predominantly expressed in striated muscle and interacts with LC3, a key player in autophagy. We have shown before that Fyco1 is sufficient to induce autophagy in cardiomyocytes. Conversely, Fyco1 deficient mice are protected from increased autophagy by starvation or transverse aortic constriction, but suffer from contractile dysfunction after cardiac stress.
Using the mirSVR tool we identified two potential binding sites in the 3’-UTR of murine Fyco1. We inserted each of the predicted binding sites into a luciferase gene based reporter system. Overexpression of miR-106b with either one of the predicted binding sites caused a significant loss of luciferase activity compared to cells that overexpressed a control microRNA or carried a mutated binding site. Interestingly, a fragment that included both target sites reduced the luciferase activity to the same extent (-32%, p<0.001). Overexpression of miR-106b in neonatal rat cardiomyocytes (NRCM) caused a reduction of Fyco1 protein by 72%. Consistently, the overexpression of miR-106b in NRCM prevented the induction of autophagy measured by LC3-II levels after glucose deprivation for 24h.
Taken together our data identify a miR-106b/FYCO1-dependent pathway regulating autophagy in the heart. It will be interesting to see whether experimental manipulation of this axis may alter the progression of cardiomyopathy and heart failure.
Author Disclosures: C. Kuhn: None. L. Boeck: None. S. Hille: None. F. Dierck: None. T. Eschenhagen: None. N. Frey: None.
- © 2014 by American Heart Association, Inc.