Reactive oxygen species-induced activation of p90 ribosomal S6 kinase prolongs cardiac repolarization through inhibiting outward K+ channel activity.
Reactive oxygen species-induced activation of p90 ribosomal S6 kinase prolongs cardiac repolarization through inhibiting outward K+ channel activity.
复制标题
活性氧诱导的P90核糖体S6激酶激活通过抑制外向K+通道活性来延长心脏复极化。
DOI：
10.1161/circresaha.107.166678
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发表时间：
2008-08-01
影响因子：
20.1
通讯作者：
Xu H
中科院分区：
文献类型：
--
作者：
Lu Z;Abe J;Taunton J;Lu Y;Shishido T;McClain C;Yan C;Xu SP;Spangenberg TM;Xu H
p90核糖体S6激酶（p90 RSK）在由诸如缺血/再灌注损伤（I/R）和糖尿病（DM）等病症引起的心肌病中被激活，其中心脏复极延长和频繁心律失常是常见的。心脏疾病中电重构的分子机制在很大程度上是未知的。在本研究中，我们确定了p90 RSK激活在调节电压门控性K+通道活性中的作用，该活性决定心脏复极。由于p90 RSK转基因表达（p90 RSK-Tg）导致心脏p90 RSK活性增加的小鼠QT间期和心室肌细胞动作电位持续时间延长。p90 RSK-Tg小鼠心室肌细胞的快瞬时外向钾电流（Ito，f）、慢延迟外向钾电流（IK，slow）和稳态钾电流（ISS）均显著降低。通过定量RT-PCR评估，p90 RSK-Tg和非转基因同窝对照小鼠心室中Kv4.3、Kv4.2、Kv1.5、Kv2.1和KChIP 2的mRNA水平相似，表明p90 RSK通过翻译后修饰调节电压门控K+通道。p90 RSK抑制HEK 293细胞中Kv4.3和Kv1.5编码的通道，而不是Kv4.2和Kv2.1编码的通道。体外磷酸化分析表明，Kv4.3被p90 RSK磷酸化的两个保守位点，Ser 516和Ser 550。p90 RSK表达显著抑制HEK 293细胞中Kv4.3和Kv4.3以及KChIP 2编码的通道活性，而p90 RSK的作用被Kv4.3中磷酸化位点处的氨基酸突变阻断。过氧化氢（H2 O2），诱导心脏p90 RSK激活的I/R和DM的介质，有类似的作用，p90 RSK对Kv4.3或Kv4.3和KChIP 2编码的通道。氟甲基酮，一个特定的p90 RSK抑制剂，消除过氧化氢的影响。这些结果表明，p90 RSK激活是关键的活性氧介导的电压门控K+通道活性的抑制，并导致心脏复极的延长。
p90 ribosomal S6 kinase (p90RSK) is activated in cardiomyopathies caused by conditions such as ischemia/reperfusion injury (I/R) and diabetes mellitus (DM), in which prolongation of cardiac repolarization and frequent arrhythmias are common. Molecular mechanisms underlying the electrical remodeling in cardiac diseases are largely unknown. In the present study, we determined the role of p90RSK activation in the modulation of voltage-gated K+ channel activity determining cardiac repolarization. Mice with increased cardiac p90RSK activity due to transgenic expression of p90RSK (p90RSK-Tg) had prolongation of QT intervals and of ventricular myocyte action potential durations. Fast transient outward K+ current (Ito,f), slow delayed outward K+ current (IK,slow) and steady-state K+ current (ISS) were significantly decreased in p90RSK-Tg mouse ventricular myocytes. mRNA levels of Kv4.3, Kv4.2, Kv1.5, Kv2.1 and KChIP2 from ventricles between p90RSK-Tg and non-transgenic littermate control mice were similar, as assessed by quantitative RT-PCR, indicating that p90RSK regulates voltage-gated K+ channels through post-translational modification. Kv4.3- and Kv1.5- rather than Kv4.2- and Kv2.1-encoded channels in HEK 293 cells were inhibited by p90RSK. In vitro phosphorylation analysis showed that Kv4.3 was phosphorylated by p90RSK at two conserved sites, Ser516 and Ser550. p90RSK expression significantly inhibited Kv4.3-, and Kv4.3 and KChIP2-encoded channel activities in HEK 293 cells while p90RSK’s effects were blocked by amino acid mutation(s) at phosphorylation site(s) in Kv4.3. Hydrogen peroxide (H2O2), a mediator of induced cardiac p90RSK activation in I/R and DM, had effects similar to those of p90RSK on Kv4.3- or Kv4.3 and KChIP2-encoded channels. Fluoromethylketone, a specific p90RSK inhibitor, abolished H2O2 effects. These findings indicate that p90RSK activation is critical for reactive oxygen species-mediated inhibition of voltage-gatedK+ channel activity and leads to prolongation of cardiac repolarization.