Structural Basis for Antiarrhythmic Drug Action

描述(申请人提供)：抗心律失常药物作用的结构基础摘要电压门控钠(Na)通道在心肌细胞中启动动作电位，它们是用于控制生命的I类抗心律失常药物(AADs)的分子靶点。 严重的心律失常。抗心律失常药物作用的结构基础尚不清楚。NA通道是一种具有24个跨膜片段的大型完整膜蛋白。我们最近测定了祖先细菌钠通道(NAAB)的晶体结构，分辨率为2.7A，处于预打开状态，电压传感器被激活，但孔关闭。这种非凡的结构定义了电压传感、孔的打开和关闭以及离子选择性的结构基础。此外，这种结构揭示了一个完全意想不到的特征--窗口 这将从脂质双层横向进入孔道，并潜在地为疏水孔道阻断AADs进入其封闭的钠通道中的受体位置提供一条通道。抗心律失常药物的受体位置位于小孔的管腔内。AADS更有效地阻断快速激发细胞中的钠通道，因为当毛孔打开时，它们更快地到达受体位置。这些药物还可以更有效地阻断受损、去极化的心肌细胞中的钠通道，因为它们与去极化的膜电位首选的通道失活状态具有最高的亲和力。三组不同的I类AAD(Ia、Ib和Ic)以不同的方式改变钠通道功能，并 用于治疗不同类型的心律失常。第一个高分辨率N通道结构的问世现在使我们能够确定AADS复杂的阻断机制、使用依赖性和亚类特异性的结构基础，这些对于它们的临床应用是必不可少的。我们将确定与AADS亲和力最高的灭活状态下的Navab的结构。我们将通过X射线结晶学确定与抗心律失常药物结合的Navab通道的结构，并确定状态依赖药物结合的结构基础。此外，我们将在NAVAB中构建一个人AAD受体位点，确定药物结合的人源化Na通道的结构，并确定Ia、Ib和Ic类AADs亚类选择性作用的结构基础。这些结果将通过揭示钠离子通道状态依赖的药物结合和阻断的结构基础，开启钠通道药理学的新纪元。我们的结果对于阐明高亲和力结合的结构决定因素、药物与AAD受体位点复杂的、状态依赖的访问途径的潜在机制以及Ia、Ib和Ic类AADS的选择性结合和作用的结构基础将是至关重要的。这些信息将为发现和开发更安全、更有效的反兴奋剂系统提供结构基础。

DESCRIPTION (provided by applicant): Structural Basis for Antiarrhythmic Drug Action Abstract Voltage-gated sodium (Na) channels initiate action potentials in cardiac myocytes, and they are the molecular targets for Class I antiarrhythmic drugs (AADs) used in the control of life- threatening cardiac arrhythmias. The structural basis for antiarrhythmic drug action is unknown. Na channels are large integral membrane proteins with 24 transmembrane segments. We have recently determined the crystal structure of an ancestral bacterial Na channel (NavAb) at 2.7 A resolution in a pre-open state with voltage sensors activated but the pore closed. This remarkable structure defines the structural basis for voltage sensing, pore opening and closing, and ion selectivity. Moreover, this structure reveals an entirely unexpected feature- fenestrations that lead laterally from the lipid bilayer into the pore and potentially provide an access pathway for entry of hydrophobic pore-blocking AADs to their receptor site in closed Na channels. The receptor site for antiarrhythmic drugs is located within the lumen of the pore. AADs block Na channels in rapidly firing cells more effectively because they reach their receptor site more rapidly when the pore is open. These drugs also block Na channels more effectively in damaged, depolarized cardiac myocytes because they bind with highest affinity to the inactivated state of the channel that is preferred at depolarized membrane potentials. Three different groups of Class I AADs (Ia, Ib, and Ic) modify Na channel function differentially and are useful in treatment of distinct classes of arrhythmias. Availability of the first high-resolution N channel structure now allows us to determine the structural basis for the complex blocking mechanism, use-dependence, and subclass specificity of AADs, which are essential for their clinical use. We will determine the structure of NavAb in the inactivated state, which has highest affinity for AADs. We will determine the structure of the NavAb channel with an antiarrhythmic drug bound by x-ray crystallography and define the structural basis for state-dependent drug binding. In addition, we will construct a human AAD receptor site in NavAb, determine the structure of the drug-bound, humanized Na channel, and define the structural basis for subclass-selective actions of Class Ia, Ib, and Ic AADs. These results will open a new era of Na channel pharmacology by revealing the structural basis for the state-dependent drug binding and block of this ion channel. Our results will be crucial in illuminating the structural determinants of high-affinity binding, the underlying mechanism for the complex, state- dependent access pathway of drugs to the AAD receptor site, and the structural basis for the selective binding and action of the Class Ia, Ib, and Ic AADs. This information will provide the structural basis for discovery and development of safer and more effective AADs.