Abstract 18089: Alterations in the Cardiac Mitochondrial and Myofilament Subproteome upon Targeted Dicer Deletion
Background: Dicer is critical for the processing of double stranded RNAs, including microRNAs (miRNAs). In patients with dilated cardiomyopathy and heart failure, a reduction in the expression levels of Dicer is observed. Subsequent loss-of-function studies in mice resulted in a heart failure phenotype.
Methods and Results: To assess the effect of conditional Dicer gene deletion on the cardiac proteome, hearts from double-transgenic tamoxifen-treated MHC-MCM/DicerF/F mice and control tamoxifen-treated DicerF/F mice were subfractionated and analyzed by mass spectrometry. KEGG pathway and protein interaction network analyses of the top 150 differentially expressed proteins revealed that most changes were confined to mitochondria, in particular protein complexes of the oxidative phosphorylation chain. This is consistent with previous observations that miRNAs regulate mitochondrial gene expression and that mitochondria isolated from Dicer depleted cardiomyocytes were primarily uncoupled and showed a reduction in energy-dependent pore openings. The mitochondrial changes coincided with an upregulation of sorcin, a ryanodine receptor modulator that regulates the contractile state of the myocardium by affecting intracellular calcium. In addition, our proteomic study indicated degradation of myofibril proteins, such as titin, as well as changes in other Z-disc or titin-interacting proteins (four and a half LIM domains protein 2, LIM domain-binding protein 3, myozenin 2, etc.) known to be central to myofilament regulation. Z-disks in Dicer-depleted hearts showed abnormal morphology associated with frequent disruption in sarcomere structures. Proteolysis of titin was observed at the N-terminus, consistent with cleavage by calpain-1.
Conclusions: This is the first global proteomics analysis of the effect of Dicer depletion in the heart. Dicer gene deletion results in mitochondrial alterations as well as fragmentation of a specific subset of myofilament proteins providing insights into the regulation of myofilament disassembly and its interplay with cardiac metabolism.
- © 2012 by American Heart Association, Inc.