Lazou A, Sugden P H, Clerk A
Laboratory of Animal Physiology, Department of Zoology, School of Biology, Aristotelian University of Thessaloniki, Thessaloniki 54006, Greece.
Biochem J. 1998 Jun 1;332 ( Pt 2)(Pt 2):459-65. doi: 10.1042/bj3320459.
We investigated the ability of phenylephrine (PE), an alpha-adrenergic agonist and promoter of hypertrophic growth in the ventricular myocyte, to activate the three best-characterized mitogen-activated protein kinase (MAPK) subfamilies, namely p38-MAPKs, SAPKs/JNKs (i.e. stress-activated protein kinases/c-Jun N-terminal kinases) and ERKs (extracellularly responsive kinases), in perfused contracting rat hearts. Perfusion of hearts with 100 microM PE caused a rapid (maximal at 10 min) 12-fold activation of two p38-MAPK isoforms, as measured by subsequent phosphorylation of a p38-MAPK substrate, recombinant MAPK-activated protein kinase 2 (MAPKAPK2). This activation coincided with phosphorylation of p38-MAPK. Endogenous MAPKAPK2 was activated 4-5-fold in these perfusions and this was inhibited completely by the p38-MAPK inhibitor, SB203580 (10 microM). Activation of p38-MAPK and MAPKAPK2 was also detected in non-contracting hearts perfused with PE, indicating that the effects were not dependent on the positive inotropic/chronotropic properties of the agonist. Although SAPKs/JNKs were also rapidly activated, the activation (2-3-fold) was less than that of p38-MAPK. The ERKs were activated by perfusion with PE and the activation was at least 50% of that seen with 1 microM PMA, the most powerful activator of the ERKs yet identified in cardiac myocytes. These results indicate that, in addition to the ERKs, two MAPK subfamilies, whose activation is more usually associated with cellular stresses, are activated by the Gq/11-protein-coupled receptor (Gq/11PCR) agonist, PE, in whole hearts. These data indicate that Gq/11PCR agonists activate multiple MAPK signalling pathways in the heart, all of which may contribute to the overall response (e.g. the development of the hypertrophic phenotype).
我们研究了去氧肾上腺素（PE）——一种α-肾上腺素能激动剂，也是心室肌细胞肥大生长的促进剂——在灌注收缩的大鼠心脏中激活三个特征最明确的丝裂原活化蛋白激酶（MAPK）亚家族的能力，这三个亚家族分别是p38-MAPK、SAPKs/JNKs（即应激激活蛋白激酶/c-Jun氨基末端激酶）和ERK（细胞外反应性激酶）。用100微摩尔/升的PE灌注心脏导致两种p38-MAPK亚型迅速（在10分钟时达到最大值）激活12倍，这是通过随后对p38-MAPK底物重组MAPK激活蛋白激酶2（MAPKAPK2）的磷酸化来测量的。这种激活与p38-MAPK的磷酸化同时发生。内源性MAPKAPK2在这些灌注中被激活4至5倍，并且被p38-MAPK抑制剂SB203580（10微摩尔/升）完全抑制。在用PE灌注的非收缩心脏中也检测到了p38-MAPK和MAPKAPK2的激活，这表明这些效应不依赖于激动剂的正性肌力/变时特性。虽然SAPKs/JNKs也被迅速激活，但其激活程度（2至3倍）低于p38-MAPK。ERK通过用PE灌注而被激活，其激活程度至少是1微摩尔/升佛波酯（PMA）——心肌细胞中已鉴定出的最强大的ERK激活剂——所引起激活程度的50%。这些结果表明，除了ERK外，另外两个通常与细胞应激相关的MAPK亚家族在全心中被Gq/11蛋白偶联受体（Gq/11PCR）激动剂PE激活。这些数据表明，Gq/11PCR激动剂在心脏中激活多个MAPK信号通路，所有这些通路都可能对整体反应（如肥大表型的发展）有贡献。
