NFAT-induced Regional Variations in Kv4 Channel Expression in Heart

描述（由申请人提供）：电压门控K+（Kv）电流在左心室壁中差异分布。Kv 4电流在左心室心外膜（EPI）细胞中比在内皮细胞（ENDO）细胞中大。Kv 4通道功能的这种非均匀分布对于正常心肌复极是必不可少的。我们最近报道，在[Ca 2 +]i的变化被转导到Kv 4表达的变化，通过激活的Ca 2+敏感的磷酸酶钙调神经磷酸酶和转录因子NFATc 3。这导致我们发现，跨左心室游离壁的差异[Ca 2 +]i/钙调神经磷酸酶/NFATc 3信号传导是Kv 4表达的跨壁变化的基础。然而，[Ca 2 +]j，钙调神经磷酸酶和NFATc 3信号传导的区域差异的机制知之甚少。本申请中提出的工作采用了我们小组开发的一系列新技术和方法来解决这些重要问题。我们的初步数据表明，所提出的实验不仅是可行的，但将提供新的基本信息，在心脏的KV通道调节。拟议的工作解决了三个具体假设。首先，我们将测试的假设，在[Ca 2 +]j的区域变化的基础异质性钙调磷酸酶在心室的活动。其次，我们将测试的假设，局部和全局[Ca 2 +]i信号调节NFAT易位和基因表达在心室肌细胞。然后，我们将使用这些数据来确定ENDO和EPI细胞之间的[Ca 2 +]j信号的变化如何导致NFAT活性的区域差异。最后，我们将测试的假设，钙调磷酸酶/NFATc 3信号是必不可少的维持心室Kv电流的异质性。总之，这项工作将提供心脏中钙信号传导，兴奋性和收缩性的第一个综合观点，并显着提高我们对健康和疾病中调节Kv通道功能的基本机制的理解。

DESCRIPTION (provided by applicant): Voltage-gated K+ (Kv) currents are differentially distributed across the left ventricular wall. Kv4 currents are larger in left ventricular epicardial (EPI) cells than in endocardial (ENDO) cells. This non-uniform distribution of Kv4 channel function is essential for normal myocardial repolarization. We recently reported that variations in [Ca2+]i are transduced into changes in Kv4 expression through the activation of the Ca2+-sensitive phosphatase calcineurin and the transcription factor NFATc3. This led to our discovery that differential [Ca2+]i/calcineurin/NFATc3 signaling across the left ventricular free wall underlies transmural variations in Kv4 expression. However, the mechanisms underlying regional differences in [Ca2+]j, calcineurin, and NFATc3 signaling are poorly understood. The work proposed in this application employs a series of novel techniques and approaches developed by our group to address these important issues. Our preliminary data suggest that the proposed experiments are not only feasible but will provide new fundamental information regarding Kv channel regulation in the heart. The proposed work addresses three specific hypotheses. First, we will test the hypothesis that regional variations in [Ca2+]j underlie heterogeneous calcineurin activity in the ventricle. Second, we will test the hypothesis that local and global [Ca2+]i signals modulate NFAT translocation and gene expression in ventricular myocytes. We will then use these data to determine how variations in [Ca2+]j signals between ENDO and EPI cells lead to regional differences in NFAT activity. Finally, we will test the hypothesis that calcineurin/NFATc3 signaling is essential for maintaining Kv current heterogeneity in the ventricle. Taken together, this work will provide the first integrated view of calcium signaling, excitability, and contractility in the heart and significantly enhance our understanding of the basic mechanisms, which regulate Kv channel function in health and disease.