CARDIAC K+ CHANNEL GENE INTERACTIONS AND ARRHYTHMIAS

心律失常导致的心脏性猝死占到了 在美国自然发生的死亡（1）。分子 遗传学最近确定了离子通道突变， 遗传性长QT综合征（LQTS）提供了进一步研究的工具， 获得性心律失常的机制的见解（2）。主要 人心肌细胞的复极化K+电流是IKr和IKs。 这些 电流分别由HERG和KvLQT 1产生。 突变 这两个基因和心脏Na+通道基因SCNA 5已经被证明， 导致某些形式的遗传性LQTS（4，5，6，18）。 异源 这些克隆通道的表达允许对其进行详细研究 然而，克隆通道的表型经常不同， 在自然组织中的行为。 这些差异已经 归因于第二信使，辅助蛋白， 多个剪接变体或不同亚基的异源组装。 我们的实验室已经开发了一种哺乳动物表达系统来研究 克隆的K+通道的功能和生化特性，辅助 蛋白质及其相互作用我们已经证明，HERG在物理上 与另一种蛋白质minK相关联， 调节IKr活性（7）。 利用这个系统，我们也有证据 一个显性负性HERG突变体的作用是 野生型HERG的降解。 我们假设， 具有突变的HERG亚基的HERG、调节蛋白如minK，和 第二信使调节K+电流的表达和 室性心律失常 因此，我们建议研究 室性心律失常的机制，通过研究调节 HERG K+通道的表达和功能。 为此，我们将：1. 扩展minK和HERG相互作用的功能分析。 2.探讨 天然突变体改变IKr表达的机制 关于HERG 3.研究第二信使对HERG和HERG/minKK+的影响 水流 4.执行结构分析的相互作用， HERG和MinK。

Sudden cardiac death from arrhythmias accounts for more than 10 percent of naturally occurring deaths in the United States (1). Molecular genetics has recently identified ion channel mutations involved in hereditary Long-QT syndrome (LQTS) providing tools to further our insights into mechanisms of acquired arrhythmias (2). The major repolarizing K+ currents in human myocardiocytes are IKr and IKs. These currents are produced by HERG and KvLQT1, respectively. Mutations in these two genes and a cardiac Na+ channel gene, SCNA5, have been shown to cause some forms of hereditary LQTS (4,5,6,18). Heterologous expression of these cloned channels allows detailed study of their function, however, the phenotype of cloned channels frequently differs from their behavior in native tissue. These differences have been attributed to regulation by second messengers, accessory proteins, multiple splice variants or heterologous assembly of different subunits. Our lab has developed a mammalian expression system to study the functional and biochemical properties of cloned K+ channels, accessory proteins and their interactions. We have shown that HERG physically associates with another protein, minK, and that this association regulates IKr activity (7). Using this system, we also have evidence that a dominant negative HERG mutant acts by dramatically accelerating the degradation of wild-type HERG. We hypothesize that interaction of HERG with mutant HERG subunits, regulatory proteins such as minK, and second messengers modulates K+ current expression and propensity for ventricular arrhythmias. Accordingly, we propose to study the mechanisms of ventricular arrhythmias by investigating the regulation of HERG K+ channel expression and function. To this end we will: 1. Extend functional analysis of minK and HERG interaction. 2. Investigate the mechanism of alterated IKr expression by naturally occurring mutants of HERG. 3. Investigate second-messenger effects on HERG and HERG/minKK+ currents. 4. Perform a structural analysis of the interaction between HERG and minK.