Biochemical and Biophysical Research Communications, Vol.479, No.4, 728-735, 2016
The E3 ubiquitin ligase c-Cbl mediates integrin beta 1 ubiquitination during dilated cardiomyopathy
Dilated cardiomyopathy (DCM) is characterized by dilatation of the ventricular chambers and impaired myocardial contractility. The results of our previous study indicated that a deficiency in matricellular cartilage oligomeric matrix protein (COMP) led to spontaneous and progressive DCM in mice via the ubiquitination/degradation of integrin beta 1. However, the specific ubiquitin enzyme involved in degradation of integrin beta 1 and the pathogenesis of DCM remain elusive. We first compared gene expression profiles in hearts from 3-month-old wild type and COMP-/- mice using microarray analysis. Among the E3 ubiquitin ligases upregulated in COMP-/- hearts, c-Cbl silencing rescued the ubiquitination/degradation of integrin beta 1, myofilament loss, apoptosis and connexin-43 deficiency in cardiomyocytes due to the silencing of COMP. Furthermore, c-Cbl silencing by intramyocardial injections of siRNA into 1-month-old COMP-/- mice ameliorated spontaneous DCM in vivo, as evidenced by the inhibition of the dilation of ventricular chambers, impaired ejection fraction and myofilament loss. A subsequent cellular ubiquitination assay revealed that overexpression of c-Cbl induced ubiquitination of integrin beta 1, whereas the G306E mutation in c-Cbl, which prevented the binding of c-Cbl to its substrates, had no effect on integrin beta 1 ubiquitination, indicating that c-Cbl directly caused the ubiquitination of integrin beta 1 in the hearts. In conclusion, our results demonstrate that c-Cbl mediates the ubiquitination/degradation of integrin beta 1 which leads to COMP deficiency-induced DCM. (C) 2016 Elsevier Inc. All rights reserved.