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(申请人提供)：心力衰竭是唯一在全球范围内发病率上升的心血管疾病1。在美国，大约有500万人患有心力衰竭，每年有超过55万人首次被诊断出心力衰竭。在心脏病中，心律失常导致的衰竭在2009年造成约37000人死亡，2006年心律失常的医疗保健总费用估计为31亿美元。心律失常的分子基础尚不清楚，但Xin已被确定与心脏疾病有关3-12。人类心肌病相关基因(分别为CMYA1和CMYA3)的小鼠同源基因(mXINA和mXINB)编码9种定位于间盘(ICD)的蛋白质。尽管年轻时ICD的外观正常，但mXINA缺乏的小鼠心脏会导致成人迟发性心肌病传导缺陷和mXIb上调。另一方面，mXINB的完全丧失会导致ICD的形成失败、舒张性功能障碍和出生后早期的癫痫4。MXINA基因缺失的心脏表现出mXINA的错误定位，从而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还与Kv通道相互作用蛋白2(Ito的辅助亚基KChIP2)和丝氨酸(一种肌动蛋白交联蛋白)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，mXINA在控制mXINA的定位方面发挥着重要作用，而mXINA又通过与KChIP2和细丝蛋白的相互作用来调节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，产生非偶联突变体，并测试它们对通道表面表达的影响。目的2是确定mXINA和其他ICD组分在出生后早期和成人心脏ICD定位中的作用。我们预计，在其ICD本地化操作中，mXIB、mXINA和ICD组件之间存在功能层次结构。我们将使用可诱导的、心脏特异的mXINB缺失小鼠来测试是否需要mXINB来维持成人心脏的ICD组装。在目标3中，我们将确定mXINB调节表面通道表达、动作电位时程以及进而调节心律的作用和机制。MXINA和mXINB都是相对未知的领域，尽管它们在ICD的形成和离子通道表面的表达中扮演着重要的角色。通过这些研究，我们将进一步了解心律失常和充血性心力衰竭的发病机制，从而希望找到新的、有效的治疗靶点。 公共卫生相关性：我们研究了人类心肌病相关基因的两个小鼠同源基因(mXINA和mXINB)CMYA1和CMYA3在心律失常过程中的作用。在功能层次上，mXINA在决定mXINA的正常定位中起着重要作用，而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促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。