The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Medical Center, 473 W 12th Ave, Columbus, OH 43210, USA.
Circulation. 2012 Oct 23;126(17):2084-94. doi: 10.1161/CIRCULATIONAHA.112.105320. Epub 2012 Sep 24.
Human gene variants affecting ion channel biophysical activity and/or membrane localization are linked to potentially fatal cardiac arrhythmias. However, the mechanism for many human arrhythmia variants remains undefined despite more than a decade of investigation. Posttranslational modulation of membrane proteins is essential for normal cardiac function. Importantly, aberrant myocyte signaling has been linked to defects in cardiac ion channel posttranslational modifications and disease. We recently identified a novel pathway for posttranslational regulation of the primary cardiac voltage-gated Na(+) channel (Na(v)1.5) by Ca(2+)/calmodulin-dependent protein kinase II (CaMKII). However, a role for this pathway in cardiac disease has not been evaluated.
We evaluated the role of CaMKII-dependent phosphorylation in human genetic and acquired disease. We report an unexpected link between a short motif in the Na(v)1.5 DI-DII loop, recently shown to be critical for CaMKII-dependent phosphorylation, and Na(v)1.5 function in monogenic arrhythmia and common heart disease. Experiments in heterologous cells and primary ventricular cardiomyocytes demonstrate that the human arrhythmia susceptibility variants (A572D and Q573E) alter CaMKII-dependent regulation of Na(v)1.5, resulting in abnormal channel activity and cell excitability. In silico analysis reveals that these variants functionally mimic the phosphorylated channel, resulting in increased susceptibility to arrhythmia-triggering afterdepolarizations. Finally, we report that this same motif is aberrantly regulated in a large-animal model of acquired heart disease and in failing human myocardium.
We identify the mechanism for 2 human arrhythmia variants that affect Na(v)1.5 channel activity through direct effects on channel posttranslational modification. We propose that the CaMKII phosphorylation motif in the Na(v)1.5 DI-DII cytoplasmic loop is a critical nodal point for proarrhythmic changes to Na(v)1.5 in congenital and acquired cardiac disease.
影响离子通道生物物理活性和/或膜定位的人类基因突变与潜在致命性心律失常有关。然而，尽管经过十多年的研究，许多人类心律失常变异的机制仍未得到明确。膜蛋白的翻译后修饰对于正常心脏功能至关重要。重要的是，异常的心肌信号已与心脏离子通道翻译后修饰和疾病缺陷相关。我们最近发现了一种新的途径，可以通过钙/钙调蛋白依赖性蛋白激酶 II（CaMKII）对主要心脏电压门控 Na（+）通道（Na（v）1.5）进行翻译后调节。然而，该途径在心脏疾病中的作用尚未得到评估。
我们评估了 CaMKII 依赖性磷酸化在人类遗传性和获得性疾病中的作用。我们报告了 Na（v）1.5 DI-DII 环中一个短基序与 CaMKII 依赖性磷酸化之间的意外联系，该基序最近被证明对 CaMKII 依赖性磷酸化至关重要，与单基因心律失常和常见心脏病中的 Na（v）1.5 功能有关。在异源细胞和原代心室心肌细胞中的实验表明，人类心律失常易感性变异（A572D 和 Q573E）改变了 CaMKII 对 Na（v）1.5 的依赖性调节，导致异常的通道活性和细胞兴奋性。计算机分析表明，这些变异体在功能上模拟了磷酸化通道，从而增加了心律失常触发后去极化的易感性。最后，我们报告说，在获得性心脏病的大型动物模型和衰竭的人类心肌中，相同的基序也存在异常调节。
我们确定了影响 Na（v）1.5 通道活性的 2 个人类心律失常变异的机制，这些变异通过对通道翻译后修饰的直接影响来实现。我们提出，Na（v）1.5 DI-DII 胞质环中的 CaMKII 磷酸化基序是先天性和获得性心脏疾病中 Na（v）1.5 发生致心律失常变化的关键节点。
