Cardiovascular Research Advance Access first published online on March 28, 2008
This version [Corrected Proof] published online on April 19, 2008
Cardiovascular Research, doi:10.1093/cvr/cvn083
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Elevated p53 expression is associated with dysregulation of the ubiquitin-proteasome system in dilated cardiomyopathy
1 Heart Science Centre, National Heart and Lung Institute, Imperial College London, Harefield Hospital, Harefield, UK
2 British Heart Foundation Cardiovascular Sciences Unit, National Heart and Lung Institute, Imperial College London, Hammersmith Campus, Du Cane Road, London W12 ONN, UK
3 Department of Cellular Biochemistry, Netherlands Cancer Institute, Amsterdam, The Netherlands
* Corresponding author. Tel: +44 20 838 31619; fax: +44 20 838 31640. E-mail address: paul.evans{at}imperial.ac.uk
Aims: The molecular mechanisms that regulate cardiomyocyte apoptosis and their role in human heart failure (HF) are uncertain. Expression of the apoptosis regulator p53 is governed by minute double minute 2 (MDM2), an E3 enzyme that targets p53 for ubiquitination and proteasomal processing, and by the deubiquitinating enzyme, herpesvirus-associated ubiquitin-specific protease (HAUSP), which rescues p53 by removing ubiquitin chains from it. Here, we examined whether elevated expression of p53 was associated with dysregulation of ubiquitin-proteasome system (UPS) components and activation of downstream effectors of apoptosis in human dilated cardiomyopathy (DCM).
Methods and results: Left ventricular myocardial samples were obtained from patients with DCM (n = 12) or from non-failing (donor) hearts (n = 17). Western blotting and immunohistochemistry revealed that DCM tissues contained elevated levels of p53 and its regulators MDM2 and HAUSP (all P < 0.01) compared with non-failing hearts. DCM tissues also contained elevated levels of polyubiquitinated proteins and possessed enhanced 20S-proteasome chymotrypsin-like activities (P < 0.04) as measured in vitro using a fluorogenic substrate. DCM tissues contained activated caspases-9 and -3 (P < 0.001) and reduced expression of the caspase substrate PARP-1 (P < 0.05). Western blotting and immunohistochemistry revealed that DCM tissues contained elevated expression levels of caspase-3-activated DNAse (CAD; P < 0.001), which is a key effector of DNA fragmentation in apoptosis and also contained elevated expression of a potent inhibitor of CAD (ICAD-S; P < 0.01).
Conclusion: Expression of p53 in human DCM is associated with dysregulation of UPS components, which are known to regulate p53 stability. Elevated p53 expression and caspase activation in DCM was not associated with activation of both CAD and its inhibitor, ICAD-S. Our findings are consistent with the concept that apoptosis may be interrupted and therefore potentially reversible in human HF.
KEYWORDS Dilated cardiomyopathy; Apoptosis; p53; Ubiquitin-proteasome system; Caspases
Time for primary review: 22 days
The first two authors made equal contributions.