Xin proteins and cardiac rhythms

Xin蛋白和心律

• 批准号: 8082245
• 负责人: Jim Jung-Ching Lin
• 金额: $ 37.5万
• 依托单位: UNIVERSITY OF IOWA
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-05-18 至 2015-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8082245
• 关键词: Actins; Action Potentials; Adolescent; Adult; Appearance; Arrhythmia; Binding; Binding Sites; Cardiac; Cardiac Myocytes; Cardiomyopathies; Cardiovascular Diseases; Cessation of life; Congestive Heart Failure; Connexin 43; Data; Defect; Diagnosis; Disease; Exhibits; Failure; Functional disorder; Genes; Goals; Health Care Costs; Heart; Heart Diseases; Heart failure; Human; Intercalated disc; Ion Channel; Knock-out; Knockout Mice; Knowledge; Kv channel-interacting protein 2; Lead; Microfilaments; Molecular; Mus; N-Cadherin; Null Lymphocytes; Orthologous Gene; Play; Population; Potassium; Process; Property; Proteins; Regulation; Role; Single Nucleotide Polymorphism; Surface; Testing; Therapeutic; Time; Tissues; United States; Work; base; density; direct application; filamin; heart rhythm; mutant; novel; postnatal; protein crosslink; spatiotemporal; therapeutic target; trafficking

DESCRIPTION (provided by applicant): Heart failure is the only cardiovascular disease with an increasing worldwide incidence1. Approximately 5 million people in the United States have heart failure, with over 550,000 diagnosed for the first time each year. Among heart diseases, failure due to arrhythmias is causing about 37,000 deaths in 2009 and the total estimated health care costs for arrhythmias in 2006 totaled 3.1 billion2. The molecular basis of arrhythmias is unclear, but Xin has been identified as being related to heart diseases3- 12. The mouse orthologs (mXina and mXinb) of human cardiomyopathy-associated genes (CMYA1 and CMYA3, respectively)9 encode proteins localized to the intercalated discs (ICDs). Mouse hearts deficient in mXina lead to adult late-onset cardiomyopathy with conduction defects and up-regulate mXinb, despite a normal appearance of ICD at young ages7. On the other hand, complete loss of mXinb results in failure of forming ICD, diastolic dysfunction, and early postnatal lethality4. The mXinb-null hearts exhibit mis-localization of mXina, and thus could lead to conduction defects and/or arrhythmias. Our long-term goal is to determine the molecular mechanisms by which mXin proteins influence the process of cardiac rhythms. We found that the mXina-null cardiomyocytes had reduced transient outward potassium (Ito) current density. Similar to Kv4.2 (a channel-forming subunit of Ito), mXina also interacted with Kv channel interacting protein 2 (KChIP2, an auxiliary subunit of Ito) and filamin (an actin crosslinking protein). Through these interactions, mXina may promote the surface expression of the Ito channel. Our working hypothesis is that in a functional hierarchy, mXinb plays essential role in controlling the localization of mXina, which, in turn, regulates the surface expression of Ito channel via its interactions with KChIP2 and filamin. In the Aim 1, we will establish the roles and the mechanisms by which mXina regulates the surface expression and functioning of Ito channels. We will define KChIP2 and filamin binding domains on mXina, generate uncoupled mutants, and test their effects on channel surface expression. The Aim 2 is to establish the roles of mXinb in the ICD localizations of mXina and other ICD components in early postnatal and adult heart. We anticipate a functional hierarchy among mXinb, mXina, and ICD components, in their ICD localized actions. We will use inducible, cardiac-specific mXinb-null mice to test if mXinb is required for maintaining ICD assembly in adult heart. In the Aim 3, we will determine the role and the mechanisms by which mXinb regulates surface channel expression, action potential duration and then cardiac rhythm. Both mXina and mXinb represent relatively unexplored territories, despite their essential roles in the ICD formation and ion channel surface expression. Through these studies, we will advance our understanding of the mechanisms in the disease processes of arrhythmias and congestive heart failure and thus hope to identify novel, effective therapeutic targets. PUBLIC HEALTH RELEVANCE: We investigate the roles of two mouse orthologs (mXina and mXinb) of human cardiomyopathy-associated genes, CMYA1 and CMYA3, respectively, in the process of cardiac rhythms. In a functional hierarchy, mXinb plays an essential role in determining the normal localization of mXina, which could then regulate surface expression and functioning of the transient outward potassium currents. Understanding these controlling mechanisms will advance our knowledge in the disease processes of arrhythmias and heart failure and thus hope to identify novel, effective therapeutic targets.

描述（由申请人提供）：心力衰竭是唯一一种全球发病率不断上升的心血管疾病1。美国大约有 500 万人患有心力衰竭，每年有超过 55 万人首次诊断出心力衰竭。在心脏病中，心律失常引起的衰竭在 2009 年导致约 37,000 人死亡，2006 年因心律失常导致的医疗费用估计总额达 31 亿美元2。心律失常的分子基础尚不清楚，但 Xin 已被确定与心脏病相关3- 12。人类心肌病相关基因（分别为 CMYA1 和 CMYA3）9 的小鼠直系同源物（mXina 和 mXinb）9 编码定位于嵌入的蛋白质光盘 (ICD)。尽管小鼠心脏在年轻时 ICD 表现正常，但缺乏 mXina 的小鼠心脏会导致伴有传导缺陷的成人迟发性心肌病，并上调 mXinb 7。另一方面，mXinb 完全缺失会导致 ICD 形成失败、舒张功能障碍和产后早期死亡4。 mXinb 缺失的心脏表现出 mXina 的错误定位，因此可能导致传导缺陷和/或心律失常。我们的长期目标是确定 mXin 蛋白影响心律过程的分子机制。我们发现 mXina 缺失的心肌细胞瞬时外向钾 (Ito) 电流密度降低。与 Kv4.2（Ito 的通道形成亚基）类似，mXina 也与 Kv 通道相互作用蛋白 2（KChIP2，Ito 的辅助亚基）和 filamin（肌动蛋白交联蛋白）相互作用。通过这些相互作用，mXina 可能促进 Ito 通道的表面表达。我们的工作假设是，在功能层次中，mXinb 在控制 mXina 的定位中发挥着重要作用，mXina 反过来又通过与 KChIP2 和 filamin 的相互作用来调节 Ito 通道的表面表达。在目标 1 中，我们将建立 mXina 调节 Ito 通道表面表达和功能的作用和机制。我们将在 mXina 上定义 KChIP2 和细丝蛋白结合域，生成解偶联突变体，并测试它们对通道表面表达的影响。目标 2 是确定 mXinb 在 mXina 和其他 ICD 成分在产后早期和成人心脏的 ICD 定位中的作用。我们预计 mXinb、mXina 和 ICD 组件在其 ICD 本地化操作中存在功能层次结构。我们将使用可诱导的心脏特异性 mXinb 缺失小鼠来测试是否需要 mXinb 来维持成人心脏中的 ICD 组装。在目标 3 中，我们将确定 mXinb 调节表面通道表达、动作电位持续时间以及心律的作用和机制。 mXina 和 mXinb 都代表了相对未开发的领域，尽管它们在 ICD 形成和离子通道表面表达中发挥着重要作用。通过这些研究，我们将加深对心律失常和充血性心力衰竭疾病过程机制的理解，从而希望找到新的、有效的治疗靶点。 公共健康相关性：我们研究了人类心肌病相关基因 CMYA1 和 CMYA3 的两种小鼠直系同源物（mXina 和 mXinb）在心律过程中的作用。在功能层次中，mXinb 在确定 mXina 的正常定位方面发挥着重要作用，然后 mXina 可以调节瞬时外向钾电流的表面表达和功能。了解这些控制机制将增进我们对心律失常和心力衰竭疾病过程的了解，从而有望找到新的、有效的治疗靶点。