Myocardial regulation of p300 and p53 by doxorubicin involves ubiquitin pathways.
BACKGROUND
Doxorubicin (Dox) depletes p300 from cardiac myocytes and induces apoptosis of these cells. p300 protein possesses ubiquitin ligase activity for the p53 tumor suppressor gene product, catalyzes p53 polyubiqutination, and facilitates p53 degradation in an ubiquitin-dependent manner. The present study investigated the ubiquitin-dependent regulation of p53 by Dox and p300 in cardiac myocytes.


RESULTS
Primary cardiac myocytes from neonatal rats were exposed to a proteasome inhibitor, MG132, in culture. MG132 increased both p300 and p53 protein levels in these cells, suggesting that ubiquitin-dependent degradation is involved in the homeostasis of these proteins. Notably, treatment of cardiac myocytes with Dox decreased the protein levels of p300 but markedly increased those of p53. By immunoprecipitation-Western blotting, it was shown that treatment with Dox decreased poly-ubiquitinated p53 but increased that of p300 in cardiac myocytes. Finally, the overexpression of p300 in cardiomyocytes suppressed the Dox-mediated increase in the p53 level in addition to inhibiting Dox-induced apoptosis.


CONCLUSIONS
Dox reciprocally regulates p300 and p53 through ubiquitin-dependent pathways and that p300, by its ubiquitin ligase activity, is partially involved in the ubiquitin-dependent degradation of p53 in cardiac myocytes.
Morimoto
Tatsuya
T
Division of Translational Research, Kyoto Medical Center, National Hospital Organization, Department of Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan. mori@kuhp.kyoto-u.ac.jp
Fujita
Masatoshi
M
Kawamura
Teruhisa
T
Sunagawa
Yoichi
Y
Takaya
Tomohide
T
Wada
Hiromichi
H
Shimatsu
Akira
A
Kita
Toru
T
Hasegawa
Koji
K
D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D002478:Cells, Cultured; D004317:Doxorubicin / Q000494:pharmacology*; D050881:E1A-Associated p300 Protein / Q000096:biosynthesis*; D005786:Gene Expression Regulation / Q000187:drug effects* / Q000502:physiology; D009124:Muscle Proteins / Q000096:biosynthesis*; D009206:Myocardium / Q000166:cytology / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis*; D025801:Ubiquitin / Q000378:metabolism*
D000903:Antibiotics, Antineoplastic; D009124:Muscle Proteins; D016159:Tumor Suppressor Protein p53; D025801:Ubiquitin; D004317:Doxorubicin; D050881:E1A-Associated p300 Protein