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）：心力衰竭是唯一的心血管疾病，全球发病率增加。美国约有500万人患有心力衰竭，每年首次诊断出55万人。在心脏病中，由于心律不齐引起的失败在2009年造成约37,000例死亡，而2006年心律不齐的估计医疗保健成本总计为31亿。心律不齐的分子基础尚不清楚，但XIN已被确定为与心脏疾病有关3-12。人心肌病的小鼠直系同源物（MXINA和MXINB）分别与cmya1和cmya3的分别进行了蛋白质（分别）编码蛋白质。小鼠心脏缺乏MXINA导致成年后期发作的心肌病，尽管ICD在年轻人中正常出现，但具有传导缺陷和上调MXINB。另一方面，MXINB的完全损失导致形成ICD，舒张功能障碍和早期产后致死性的失败4。 Mxinb-null心脏表现出MXINA的错误定位，因此可能导致传导缺陷和/或心律不齐。我们的长期目标是确定MXIN蛋白影响心律的过程的分子机制。我们发现MXINA-NULL心肌细胞降低了瞬态外钾（ITO）电流密度。类似于KV4.2（ITO的通道形成亚基），MXINA还与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可以促进ITO通道的表面表达。我们的工作假设是，在功能层次结构中，MXINB在控制MXINA的定位中起着至关重要的作用，而MXINA的定位又通过其与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Filamin结合结构域，产生未偶联的突变体，并测试其对通道表面表达的影响。目的2是确定MXINB在产后早期和成人心脏中MXINA和其他ICD成分的ICD定位中的作用。我们预计MXINB，MXINA和ICD组件之间的功能层次结构在其ICD局部作用中。我们将使用诱导的心脏特异性MXINB-NULL小鼠来测试是否需要MXINB来维持成人心脏的ICD组件。在AIM 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节奏的作用和机制。 MXINA和MXINB都代表相对未开发的领土，尽管它们在ICD形成和离子通道表面表达中具有重要作用。通过这些研究，我们将提高对心律不齐和充血性心力衰竭疾病过程中机制的理解，从而希望识别新型，有效的治疗靶标。 公共卫生相关性：我们分别研究了与心肌病相关基因CMYA1和CMYA3的两个小鼠直系同源物（MXINA和MXINB）在心律节奏过程中的作用。在功能层次结构中，MXINB在确定MXINA的正常定位中起着至关重要的作用，然后可以调节瞬时向外钾电流的表面表达和功能。了解这些控制机制将在心律不齐和心力衰竭的疾病过程中提高我们的知识，从而希望识别新颖的有效治疗靶标。