Modulators of HERG function and pharmacology

描述（由申请人提供）： 人类Ether-a-go-go相关基因（HERG，KCNH 2）编码心脏K+电流IKr的主要成孔亚基。通过遗传突变或药物阻断抑制IKr，可引起室性心律失常（尖端扭转型室性心动过速）导致的猝死。与IKr一样，HERG通道对多种治疗药物敏感，但在实践中，暴露于HERG阻断化合物后心律失常的发生是不可预测的，这表明调节因素对HERG药理学有重要影响。该提案的目标是确定介导药物与IKr复合物相互作用的分子机制。虽然大多数药物的HERG阻滞随着膜去极化和通道开放而发展，但阻滞仍然缓慢发展（超过几分钟），表明药物进入其内孔前庭（S6）中的受体位点是有限的。虽然药物与HERG相互作用的机制还不完全清楚，但我们最近的研究已经确定了HERG C-末端和HERG相互作用蛋白（KCR 1）作为阻滞抑制剂。我们将测试这一假设，即HERG阻断治疗化合物是由涉及HERG亚结构域和其他蛋白组成的IKr复合物的功能相互作用调制。使用电生理学和生物化学方法，C末端缺失突变体，和C-末端肽，我们将确定的机制，HERG C-末端限制药物进入孔。使用相同的方法，我们将阐明人KCR 1抑制药物阻断的分子机制。最后，为了扩大我们对IKr复合物和促发性风险分子底物的理解，我们将利用遗传学上易处理的微生物C。elegans作为一个模式系统，以确定新的HERG相互作用蛋白的候选人，利用之间的关联C。线虫HERG同源物（HERG-103），甲磺酰苯胺药物作用，以及蠕虫咽部泵送的节律模式。从这项研究中对药物通道相互作用的进一步了解应该能够改善药物诱导的心律失常的风险预测，并开发出更好的抗心律失常治疗。

DESCRIPTION (provided by applicant): The Human Ether-a-go-go Related Gene (HERG, KCNH2) encodes the major, pore-forming subunit of the cardiac K+ current IKr. Suppression of IKr, through inherited mutations or pharmacologic blockade, can provoke sudden death from a ventricular arrhythmia (Torsades de Pointes). Like IKr, HERG channels are sensitive to a wide array of therapeutic agents but in practice, the development of cardiac arrhythmias upon exposure to HERG-blocking compounds is unpredictable, suggesting modulating factors critically influence HERG pharmacology. The goal of this proposal is to identify molecular mechanisms that mediate drug interactions with the IKr complex. While HERG block by most pharmacologic agents develops as the membrane is depolarized and channels open, block still develops slowly (over minutes) suggesting that access of drug to its receptor site in the inner pore vestibule (S6) is limited. While the mechanisms that underlie drug interactions with HERG are incompletely understood, our recent studies have identified the HERG C-terminus and a HERGinteracting protein (KCR1) as inhibitors of block. We will test the hypothesis that HERG blockade by therapeutic compounds is modulated by functional interactions involving HERG subdomains and other proteins that compose the IKr complex. Using electrophysiologic and biochemical approaches, Cterminal deletion mutants, and C-terminal peptides, we will determine the mechanism whereby the HERG C-terminus limits drug access to the pore. Using the same approaches, we will elucidate the molecular mechanism whereby human KCR1 inhibits drug block. Finally, to expand our understanding of the IKr complex and the molecular substrates of proarrhythmic risk, we will utilize the enetically tractable organism C. elegans as a model system to identify new HERG-interacting protein candidates, taking advantage of the association among the C. elegans homologue of HERG (UNC-103), methanesulfonanilde drug action, and the rhythmic pattern of pharyngeal pumping in the worm. The improved understanding of drug-channel interactions arising from this research should enable improvements in predicting risk for drug-induced arrhythmias, and the development of improved antiarrhythmic therapies.