A Molecular Target for Atrial Fibrillation

描述(申请人提供)：房颤是美国最常见的持续性心律失常，它仍然是美国发病率和死亡率的主要来源。目前可用于治疗这种心律失常的抗心律失常药物往往无效，它们可能会造成严重的心律失常，因为心室中的离子通道会受到影响。这项建议的目的是研究心房特异性超快K+电流IKur的分子基础，该电流是心房颤动药物治疗的潜在靶点。虽然Kv1.5基因产物是IKUR的一个重要组成部分，但我们的初步数据表明，这个α亚基不能完全概括天然的K+电流。在提出的特定目标中，我们将检验IKUR是由多个通道亚基、信号分子和额外的蛋白质组成的大分子复合体的假设，这些蛋白质可以改变通道功能。Kv 1.5复合体将从人的心房中分离出来，相关的K+通道α和/或β亚基将使用基于抗体的方法进行鉴定。在鉴定的蛋白质异源表达后，将使用电生理技术来确认所产生的K+电流表型是否是IKUR的表型。其他实验将确定通道复合体中是否发生腔室和疾病特异性改变。一个类似的策略将被用来确定A-激酶锚定蛋白(AKAP)在Kv1.5信号复合体中的作用。我们还将测试由我们的初步数据产生的假设，即Kvβ亚基可以作为AKAP发挥作用。最后，将使用蛋白质组学方法来确定Kv 1.5复合体中以前未知的蛋白质伙伴，并使用标准生物化学方法验证蛋白质与蛋白质的相互作用。这项技术还将用于确认相关的Kv亚基和信号分子。从这些研究中获得的知识将加深我们对心房电生理学的分子成分的理解，并有助于开发治疗心房颤动的新策略。

DESCRIPTION (provided by applicant): Atrial fibrillation is the most common sustained cardiac arrhythmia in the United States, and it remains a major source of morbidity and mortality in this country. Antiarrhythmic drugs currently available to treat this arrhythmia are often ineffective, and they can create serious proarrhythmia because ion channels in the ventricle are affected. The goal of this proposal is to investigate the molecular basis of an atrial-specific ultrarapid K+ current, IKur, a potential target for pharmacologic therapy of atrial fibrillation. While the Kv 1.5 gene product is an important component of IKur, our preliminary data indicate that this alpha-subunit cannot fully recapitulate the native K+ current. In the proposed specific aims, we will test the hypothesis that IKur is a macromolecular complex composed of multiple channel subunits, signaling molecules, and additional proteins that can modify channel function. The Kv 1.5 complex will be isolated from human atrium, and associated K+ channel alpha and/or beta-subunits will be identified using antibody-based methods. Following heterologous expression of the proteins identified, electrophysiologic techniques will be used to confirm if the resultant K+ current phenotype is that of IKur. Additional experiments will determine whether chamber and disease-specific alterations in the channel complex occur. An analogous strategy will be used to determine the role of A-kinase anchoring proteins (AKAPs) in the Kv 1.5 signaling complex. We will also test the hypothesis generated by our preliminary data that a Kv beta subunit can function as an AKAP. Finally, a proteomics approach will be employed to identify previously unknown protein partners in the Kv 1.5 complex, with protein-protein interactions validated using standard biochemical approaches. This technology will also be used to confirm associated Kv subunits and signaling molecules. The knowledge gained from these studies will improve our understanding of the molecular components of atrial electrophysiology and facilitate the development of novel strategies in the treatment of atrial fibrillation.