Lim H W, New L, Han J, Molkentin J D
Department of Pediatrics, University of Cincinnati, Children's Hospital Medical Center, Cincinnati, Ohio 45229-3039, USA.
J Biol Chem. 2001 May 11;276(19):15913-9. doi: 10.1074/jbc.M100452200. Epub 2001 Feb 22.
Multiple intracellular signaling pathways have been shown to regulate the hypertrophic growth of cardiac myocytes including mitogen-activated protein kinase (MAPK) and calcineurin-nuclear factor of activated T-cells. However, it is uncertain if individual regulatory pathways operate in isolation or if interconnectivity between unrelated pathways is required for the orchestration of the entire hypertrophic response. To this end, we investigated the interconnectivity between calcineurin-mediated cardiac myocyte hypertrophy and p38 MAPK signaling in vitro and in vivo. We show that calcineurin promotes down-regulation of p38 MAPK activity and enhances expression of the dual specificity phosphatase MAPK phosphatase-1 (MKP-1). Transgenic mice expressing activated calcineurin in the heart were characterized by inactivation of p38 and increased MKP-1 expression during early postnatal development, before the onset of cardiac hypertrophy. In vitro, cultured neonatal cardiomyocytes infected with a calcineurin-expressing adenovirus and stimulated with phenylephrine demonstrated reduced p38 phosphorylation and increased MKP-1 protein levels. Activation of endogenous calcineurin with the calcium ionophore decreased p38 phosphorylation and increased MKP-1 protein levels. Inhibition of endogenous calcineurin with cyclosporin A decreased MKP-1 protein levels and increased p38 activation in response to agonist stimulation. To further investigate potential cross-talk between calcineurin and p38 through alteration in MKP-1 expression, the MKP-1 promoter was characterized and determined to be calcineurin-responsive. These data suggest that calcineurin enhances MKP-1 expression in cardiac myocytes, which is associated with p38 inactivation.
多种细胞内信号通路已被证明可调节心肌细胞的肥大生长，包括丝裂原活化蛋白激酶（MAPK）和钙调神经磷酸酶-活化T细胞核因子。然而，尚不确定各个调节通路是独立运作，还是整个肥大反应的协调需要不相关通路之间的相互连接。为此，我们在体外和体内研究了钙调神经磷酸酶介导的心肌细胞肥大与p38 MAPK信号之间的相互连接。我们发现钙调神经磷酸酶促进p38 MAPK活性的下调，并增强双特异性磷酸酶MAPK磷酸酶-1（MKP-1）的表达。在心脏中表达活化钙调神经磷酸酶的转基因小鼠，其特征在于在出生后早期发育阶段，即在心肌肥大开始之前，p38失活且MKP-1表达增加。在体外，用表达钙调神经磷酸酶的腺病毒感染并经去氧肾上腺素刺激的培养新生心肌细胞，显示p38磷酸化降低且MKP-1蛋白水平增加。用钙离子载体激活内源性钙调神经磷酸酶可降低p38磷酸化并增加MKP-1蛋白水平。用环孢素A抑制内源性钙调神经磷酸酶可降低MKP-1蛋白水平，并增加对激动剂刺激的p38激活。为了通过改变MKP-1表达进一步研究钙调神经磷酸酶与p38之间潜在的相互作用，对MKP-1启动子进行了表征，并确定其对钙调神经磷酸酶有反应。这些数据表明，钙调神经磷酸酶增强心肌细胞中MKP-1的表达，这与p38失活有关。
