MANIPULATING IKS AS A THERAPEUTIC APPROACH TO CARDIAC ARRHYTHMIAS

 描述(由申请人提供)：这个项目提出了一种直接的方法，对离子通道疾病进行合理的药物筛选。离子通道的基本功能是提供膜电流。在一个有多种类型离子通道表达的组织中，一种类型的离子通道的病理变化可能会导致疾病。我们的方法假设，通过补偿细胞产生的任何通道产生的净电流的变化，可以恢复正常的组织功能；所需要的只是恢复正常净电流的合理传真。我们建议将这种方法应用于长Q-T综合征(LQTS)，这种情况可能会导致室性心律失常(尖端扭矩)，从而导致猝死。心室动作电位的持续时间取决于流经平台电位的外向和内向电流的平衡。外向电流包括延迟整流器IKR和IKS，而内向电流包括持续钠电流(INAP)。这些通道蛋白中任何一种导致外向电流减少或内向电流增加的特定突变与先天性长QT综合征(LQTS)有关。还有一个更为普遍的问题，称为获得性LQTS(ALQTS)，它最常与药物的非靶向效应有关，因此给制药业造成了数十亿美元的损失 甚至从市场上移除了一些本可以有效治疗其他疾病的化合物。为此，我们将利用最近有关IKS通道激活的结构信息用于电子药物筛选，以寻找与IKS通道相互作用概率最高的化合物。我们将候选化合物应用于新鲜分离的豚鼠和犬的心肌细胞，以确定它们在对照和LQTS条件下对心室动作电位和潜在离子电流的影响。LQTS时程变化最有利的化合物将被确定为可行的候选化合物。我们的筛选数据库将包括1500多种FDA批准的小分子药物。如果这些FDA批准的药物中有任何一种作为增强IKS的化合物起作用，它应该面临较小的FDA批准的安全障碍。我们的方法将建立在我们最近的工作和用于分子对接的创新计算机算法确定的IKS通道中的新结构位点上。我们的方法的意义既具体又笼统。具体地说，如果成功，将出现先天性和获得性LQTS的候选化合物，允许先天形式的患者避免猝死的危险，同时允许现有药物或候选药物(先前因此副作用而被排除在外) 使临床使用更安全。目前，人们已经识别了组织中的各种离子通道，明确了它们的生理作用，阐明了各种离子通道的结构和功能的结构基础，并发展了强大的计算方法。因此，更广泛地说，如果成功，这种方法可以为定义实验研究和计算机模拟相结合如何导致其他离子通道疾病的合理药物开发指明方向。这一新的范例将有助于离子通道靶向药物的发现变得更快、更便宜、更安全，并将减少动物的使用。

 DESCRIPTION (provided by applicant): This project proposes a straightforward approach to rational drug screening for ion channel-based diseases. The basic function of ion channels is to provide membrane current. In a tissue with the expression of many types of ion channels, a pathologic change in one type of channel may cause diseases. Our approach hypothesizes that the normal tissue function can be restored by compensating for the change in net current from any of the channels produced by the cell; all that is required is that a reasonable facsimile of normal net current flow be restored. We propose to apply this approach to Long Q-T Syndrome (LQTS), a condition that can cause a ventricular arrhythmia (torsades de pointe) that can lead to sudden death. The duration of the ventricular action potential (APD) depends on the balance of outward and inward currents flowing at plateau potentials. The outward currents include the delayed rectifiers IKr and IKs, while the inward currents include persistent sodium current (INaP). Specific mutations in any of these channel proteins that cause a reduction in outward current or increase in inward current are associated with congenital long QT syndrome (LQTS). There is also a much more prevalent problem called acquired LQTS (aLQTS) that is most often associated with off target effects of drugs and therefore cost the pharmaceutical industry billions of dollars and even removes from the market some compounds that could have effectively treated other diseases. To this end, we will use recent structural information concerning IKs channel activation for in silico drug screening to search for compounds with the highest probability of interacting with the IKs channel. We will apply the candidate compounds to freshly isolated guinea pig and canine cardiac ventricular myocytes to determine their effects on the ventricular action potential and the underlying ion currents in both control and LQTS conditions. The compounds that have the most favorable changes in the LQTS APD would be identified as viable candidate compounds. Our screening databases will include more than 1,500 FDA-approved small molecule drugs. If any of these FDA-approved drugs work as an IKs-enhancing compound, it should face smaller safety barriers for FDA approval. Our approach will be built on novel structural sites in the IKs channel identified by our recent work and innovative computer algorithms for molecular docking. The significance of our approach is both specific and general. Specifically if successful, candidate compounds for both congenital and acquired forms of LQTS will emerge, permitting those afflicted with the congenital form to avoid the dangers of sudden death, while allowing existing drugs or drug candidates (previous excluded for this side effect) to be made safer for clinical use. At present the various ion channels in tissues have been identified and their physiological roles defined, the structure and structure basis of function of variety of ion channels have been elucidated, and powerful computational methods have been developed. Therefore, more generally, if successful, this approach can point the way in defining how a combination of experimental studies and computer simulations can lead to rational drug development for other ion channel diseases. This new paradigm will help ion channel-targeting drug discovery be "faster, cheaper, and safer" and will reduce the use of animals.