Poizat Coralie, Puri Pier Lorenzo, Bai Yan, Kedes Larry
Institute for Genetic Medicine, Keck School of Medicine, University of Southern California, 2250 Alcazar St., CSC 245, Los Angeles, CA 90033, USA.
Mol Cell Biol. 2005 Apr;25(7):2673-87. doi: 10.1128/MCB.25.7.2673-2687.2005.
p300 and CBP are general transcriptional coactivators implicated in different cellular processes, including regulation of the cell cycle, differentiation, tumorigenesis, and apoptosis. Posttranslational modifications such as phosphorylation are predicted to select a specific function of p300/CBP in these processes; however, the identification of the kinases that regulate p300/CBP activity in response to individual stimuli and the physiological significance of p300 phosphorylation have not been elucidated. Here we demonstrate that the cardiotoxic anticancer agent doxorubicin (adriamycin) induces the phosphorylation of p300 in primary neonatal cardiomyocytes. Hyperphosphorylation precedes the degradation of p300 and parallels apoptosis in response to doxorubicin. Doxorubicin-activated p38 kinases alpha and beta associate with p300 and are implicated in the phosphorylation-mediated degradation of p300, as pharmacological blockade of p38 prevents p300 degradation. p38 phosphorylates p300 in vitro at both the N and C termini of the protein, and enforced activation of p38 by the constitutively active form of its upstream kinase (MKK6EE) triggers p300 degradation. These data support the conclusion that p38 mitogen-activated protein kinase regulates p300 protein stability and function in cardiomyocytes undergoing apoptosis in response to doxorubicin.
p300和CBP是参与不同细胞过程的通用转录共激活因子，这些过程包括细胞周期调控、分化、肿瘤发生和细胞凋亡。预计诸如磷酸化等翻译后修饰会在这些过程中选择p300/CBP的特定功能；然而，尚未阐明响应个体刺激调节p300/CBP活性的激酶的鉴定以及p300磷酸化的生理意义。在这里，我们证明心脏毒性抗癌药物阿霉素（多柔比星）可诱导原代新生心肌细胞中p300的磷酸化。磷酸化过度发生在p300降解之前，并与阿霉素诱导的细胞凋亡平行。阿霉素激活的p38激酶α和β与p300相关联，并参与p300的磷酸化介导的降解，因为对p38的药理学阻断可防止p300降解。p38在体外使p300蛋白的N端和C端磷酸化，并且其上游激酶的组成型活性形式（MKK6EE）对p38的强制激活会触发p300降解。这些数据支持以下结论：p38丝裂原活化蛋白激酶在响应阿霉素而发生凋亡的心肌细胞中调节p300蛋白的稳定性和功能。
