CARDIAC K+ CHANNEL GENE INTERACTIONS AND ARRHYTHMIAS

心律失常导致的心脏性猝死占10%以上 美国自然发生的死亡案例(1)。分子 遗传学最近发现离子通道突变与 遗传性长QT综合征(LQTS)为进一步发展我们的 获得性心律失常机制的洞察(2)。少校 人心肌细胞的复极K+电流为Ikr和Iks。这些 电流分别由HERG和KvLQT1产生。基因突变 这两个基因和一个心脏Na+通道基因SCNA5已经被发现 导致某些形式的遗传性LQT(4，5，6，18)。异源的 这些克隆的通道的表达允许详细研究它们的 然而，克隆的通道的表型经常不同 它们在天然组织中的行为。这些差异一直是 归因于第二信使的调节，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出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 蛋白质及其相互作用。我们已经证明了Herg的身体状况 与另一种蛋白质水貂有关，这种联系 管理IKR活动(7)。使用这个系统，我们也有证据 显性负Herg突变体通过戏剧性地加速 野生型HERG的降解。我们假设相互作用 HERG带有突变的HERG亚基，调节蛋白，如水貂，和 第二信使调节K+电流的表达和倾向 室性心律失常。因此，我们建议研究 从调控角度探讨室性心律失常的机制 HERG K+通道表达及功能的研究。为此，我们将：1. 扩展了MINK和HERG相互作用的泛函分析。2.调查 自然产生的突变体改变IKR表达的机制 赫格的名字。3.研究第二信使对HERG和HERG/minKK+的影响 洋流。4.对以下方面的相互作用进行结构分析 赫尔格和明克。

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.