Functional roles of atrial-specific ion channels in the heart

心房特异性离子通道在心脏中的功能作用

• 批准号: 7795266
• 负责人: Nipavan Chiamvimonvat
• 金额: --
• 依托单位: VA NORTHERN CALIFORNIA HEALTH CARE SYS
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-10-01 至 2013-09-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7795266
• 关键词: Ablation; Action Potentials; Address; Affect; Age; Age-Years; Arrhythmia; Atrial Fibrillation; Biochemical; Biological Assay; Calcium-Activated Potassium Channel; Cardiac; Cardiac Myocytes; Cell surface; Cells; Co-Immunoprecipitations; Cytoskeletal Proteins; Data; Diagnosis; Electrons; Embolism; Functional disorder; Funding; Gene Silencing; Genetic; Grant; Health; Heart; Heart Atrium; Image; Imaging Techniques; In Situ Hybridization; In Vitro; Incidence; Individual; Ion Channel; Laboratories; Lead; Life; Ligands; Location; Mediating; Membrane; Membrane Protein Traffic; Microscopic; Modeling; Molecular; Molecular Structure; Motivation; Muscle Cells; Neuroendocrine Cell; Neurons; Nodal; Patients; Pharmaceutical Preparations; Play; Population; Potassium Channel; Property; Protein Isoforms; Proteins; Published Comment; Reporting; Risk; Role; Source; Staging; Stroke; Surface; Testing; Therapeutic; Tissues; Ventricular; Veterans; abstracting; atrioventricular node; cellular imaging; human disease; in vivo; insight; men; mutant; novel; null mutation; protein complex; protein protein interaction; spatiotemporal; trafficking; treatment strategy

DESCRIPTION (provided by applicant): Project Summary/Abstract: Atrial fibrillation (AF) is the most common atrial arrhythmia affecting veteran population, and is associated with a significant risk of embolism and stroke. The problem is further exacerbated by the fact that treatment strategies have proven largely inadequate. During the last funding period, we uncovered surprising, yet insightful findings that have broad therapeutic ramifications. In contrast to previous reports that suggested that Cav1.3 (a1D) L-type Ca2+ channel (LTCC) is expressed mainly in neurons and neuroendocrine cells, we demonstrated significant expression of Cav1.3 Ca2+ channel in atrial myocytes. Indeed, Cav1.3 Ca2+ channel is preferentially expressed in atrial compared to ventricular myocytes. Additionally, the importance of Cav1.3 Ca2+ channels in atria is underpinned by the revelation that null deletion of the channel results in significant alteration in atrial excitability, atrial arrhythmias as well as profound sinoatrial (SA) and atrioventricular (AV) nodes dysfunction. We further demonstrated that Cav1.2 and Cav1.3 channels form multimeric protein complexes with small conductance Ca2+-activated K+ channels (SK channels) in the heart, which were first uncovered recently in our laboratory. Of major intriguing and functional importance are the findings that SK channels are also preferentially expressed in atrial myocytes as well as pacemaking tissues of the heart. We further demonstrated that SK2 channels associate with Cav1.3 and Cav1.2 through a physical bridge, a- actinin2 in cardiac myocytes. In addition, we have obtained new preliminary data, which demonstrate that cytoskeletal proteins are critical in the proper membrane localization of SK2 channel. Given these relevant data, we will directly examine the molecular determinants of SK channel trafficking. Moreover, the functional roles of the newly described SK channels in pacemaking tissues will be directly delineated. Our findings represent the beginning of a unified molecular and cellular mechanism that demonstrates a functional spatiotemporal cross talk between Cav channels and Ca2+-activated K+ channels (KCa) in atrial cells. Embedded in these findings are relevant paradigm shifts that may be exploited in developing atrial-specific drugs for the treatment of atrial arrhythmia. Hence, the overall thrust of the proposal is to deploy new molecular and functional strategies, many inspired from channel mechanistic studies, for the discovery of fundamental and newly accessible arenas of Ca2+ and K+ channels in the heart. We will directly test the hypothesis using a combination of in vitro interaction assay, confocal microscopic imaging, electron microscopic analyses, gene silencing, biochemical studies and functional analyses. Finally, we hypothesize that all 3 isoforms of SK channels are expressed in SA and AV node cells and contribute critically to the firing and action potential durations of nodal cells. We propose to directly test the hypothesis using null mutant models of SK1, SK2 and SK3 channels. Our proposed studies will substantially expand our understanding of the specific functions of individual Ca2+ and SK channels. Indeed, novel insights into the atrial-specific and pacemaking tissue-specific ion channels may provide new means to target these channels without interfering with the excitability of ventricular tissues. PUBLIC HEALTH RELEVANCE: Project Narrative Atrial fibrillation is the most common arrhythmias affecting VA patients. The incidence of the arrhythmia increases with age of the patients such that the incidence in men over 70 years of age can be as high as 10%. Our present study proposes to use a combination of molecular, biochemical and imaging techniques as well as electrophysiologic recordings to define the roles of atrial-specific ion channels, which will set the stage for a new and more mechanistic approach for our diagnosis and therapy of atrial arrhythmias, a common problem encountered in our VA population. Indeed, specific ligands for atrial-specific ion channels may offer a unique therapeutic opportunity to directly modify atrial and pacemaking cells without interfering with ventricular myocytes. Therefore, understanding of the functional correlates of the molecular structure of cardiac ion channels is not only essential from a basic viewpoint, but also crucial to our treatment of human diseases.

描述（由申请人提供）： 项目摘要/摘要：心房颤动（AF）是影响退伍军人人群的最常见心律失常，并且与栓塞和中风的显着风险有关。事实证明，这一事实在很大程度上不足，这一事实进一步加剧了问题。在最后一个资金时期，我们发现了具有广泛治疗后果的令人惊讶但有见地的发现。与以前的报道相反，表明CAV1.3（A1D）L型Ca2+通道（LTCC）主要在神经元和神经内分泌细胞中表达，我们在心肌细胞中表现出CAV1.3 Ca2+通道的显着表达。实际上，与心室肌细胞相比，在心房中优先表达CAV1.3 Ca2+通道。此外，心房中Cav1.3 Ca2+通道的重要性是由启示的基础，即该通道的无效删除导致心房兴奋性，心律不齐以及深刻的露丝（SA）以及心律不足（SA）和心房（AV）Nodes Nodes Nodes功能障碍。我们进一步证明，CAV1.2和CAV1.3通道形成多聚体蛋白质复合物，具有小电导Ca2+活化的K+通道（SK通道），该通道最近在我们的实验室中首次发现。引人入胜且功能重要性的是，SK通道在心肌细胞和心脏的起搏组织中也优先表达SK通道。我们进一步证明了SK2通道通过物理桥（心肌细胞中的Actinin2）与CAV1.3和CAV1.2相关。此外，我们还获得了新的初步数据，这些数据表明，细胞骨架蛋白在SK2通道的适当膜定位中至关重要。鉴于这些相关数据，我们将直接检查SK通道运输的分子决定因素。此外，新描述的起搏组织中新描述的SK通道的功能作用将直接划定。我们的发现代表了统一的分子和细胞机制的开始，该机制证明了心房细胞中CAV通道与Ca2+激活的K+通道（KCA）之间的功能时空交叉讲座。这些发现中嵌入的是相关的范式偏移，可以在开发心房特异性药物治疗心律失常时被利用。因此，该提案的总体目的是部署新的分子和功能策略，这是从通道机械研究中启发的，以发现心脏中的Ca2+和K+通道的基本和新近访问的领域。 我们将使用体外相互作用测定，共聚焦微观成像，电子显微镜分析，基因沉默，生化研究和功能分析的组合直接检验假设。最后，我们假设SK通道的所有3种同工型均在SA和AV节点细胞中表达，并为淋巴结细胞的发射和动作潜在持续时间做出了重要贡献。我们建议使用SK1，SK2和SK3通道的无空突变模型直接检验假设。我们提出的研究将大大扩展我们对单个CA2+和SK渠道的特定功能的理解。确实，对心房特异性和起搏组织特异性离子通道的新见解可能会提供新的手段来靶向这些通道，而不会干扰心室组织的兴奋性。 公共卫生相关性： 项目叙述性心房颤动是影响VA患者的最常见心律不齐。心律不齐的发生率随患者年龄的增长而增加，因此70岁以上男性的发病率可能高达10％。我们的本研究建议将分子，生化和成像技术以及电生理记录的结合使用来定义心房特异性离子通道的作用，这将为我们的心律失常诊断和治疗的新机械方法奠定了阶段，这将为我们的心律失常，这是一个常见的问题，它在我们的VA群体中遇到了一个常见问题。实际上，心房特异性离子通道的特定配体可能会提供独特的治疗机会，以直接修改房屋和起搏细胞而不会干扰心室心肌细胞。因此，了解心脏离子通道分子结构的功能相关性不仅是必不可少的，而且对于我们对人类疾病的治疗至关重要。