Na+ channel mRNA splicing in heart failure

心力衰竭中的 Na 通道 mRNA 剪接

• 批准号: 8154997
• 负责人: SAMUEL C DUDLEY
• 金额: $ 39.75万
• 依托单位: UNIVERSITY OF ILLINOIS AT CHICAGO
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-08-15 至 2015-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8154997
• 关键词: A Mouse; Adjuvant Therapy; Affect; Alleles; Alternative Splicing; American; Amiodarone; Angiotensin II; Arrhythmia; Binding; Blood Tests; Cardiac; Clinical; Clinical Trials; Complex; Data; Defibrillators; Dominant-Negative Mutation; Down-Regulation; Embryo; Endoplasmic Reticulum; Exons; Figs - dietary; Genes; Half-Life; Heart Diseases; Heart failure; Human; Hypoxia; Implant; Lead; Length; Leukocytes; Measures; Messenger RNA; Morbidity - disease rate; Myocardial Infarction; Outcome; Pathologic; Pathway interactions; Pharmaceutical Preparations; Phase; Physiological; Prevention strategy; Process; Proteins; RNA Splicing; Regulation; Reporting; Research; Risk; Sampling; Severities; Shock; Signal Transduction; Sodium Channel; Splicing Regulation Pathway; Sudden Death; Systolic heart failure; Time; Tissues; Titrations; Transcript; Translations; Variant; Ventricular; Ventricular Premature Complexes; Ventricular Tachycardia; Work; base; drug efficacy; mRNA Expression; mortality; mouse model; novel; open label; response

DESCRIPTION (provided by applicant): Despite the extensive research and novel treatments, human systolic heart failure (HF) remains a substantial clinical problem affecting millions of Americans and HF associated arrhythmia still remains a cause of the high morbidity and mortality. Recently, three SCN5a cardiac Na+ channel mRNA alternative splicing variants were found to be upregulated in human HF tissue. These splicing variants resulted from splicing at cryptic splice sequences in the terminal exon of SCN5a (i.e., exon 28) and encoded cardiac Na+ channels truncated before the pore forming segment of domain IV. Variant levels reached greater that >50% of the total SCN5a mRNA. As expected, these variants did not form functional channels. Moreover, the presence of the variants caused reduced abundance of the full-length SCN5a mRNA without alteration of total SCN5a mRNA. This application proposes to establish the mechanism whereby the abnormal splicing occurs in HF and how the presence of truncated Na+ channel variants causes a dominant negative downregulation of the full-length channel mRNA. Preliminary data suggest hypoxia and angiotensin II (AngII) can signal pathological SCN5a splicing regulation by inducing expression of the mRNA splicing factor, CROP/hLuc7A, and its co-factor RBM25, which alter SCN5a splicing regulation by interacting with one or more RBM25 binding sequences CGGGC(A) in SCN5a exon 28, the exon where abnormal splicing of SCN5a occurs. Furthermore, data show that truncated Na+ channels accumulate in endoplasmic reticulum (ER) and initiate the unfolded protein response (UPR) pathway, causing reduced Na+ channel translation and a shortened half-life of the full-length SCN5a transcript. Hypothesis. Based on the above, we hypothesized that the hLuc7A/RBM25 complex contributes to abnormal Na+ channel mRNA splicing and that the UPR contributes to the dominant negative effect the abnormally spliced transcripts have on the Na+ channel. Specific Objectives. Specific aim 1: To establish whether the hLuc7A/RBM25 splicing regulation pathway is involved in the mechanism to increase SCN5a mRNA variant expression. Specific aim 2: To determine to what extent the three major pathways in the unfolded protein response (UPR) are responsible for the reduction in functional Na+ channels. Specific aim 3: To demonstrate the relationship of hLuc7A/RBM25 regulation, the unfolded protein response (UPR) activation, Na+ channel mRNA variants, and Na+ channel measures in human heart failure samples. PUBLIC HEALTH RELEVANCE: The cause of sudden death in heart failure is unknown. This application will explore one potential cause, abnormal sodium channel processing, establishing the mechanism and possible elucidating prevention strategies. Moreover, if white cells show similar abnormalities, this work may lead to a blood test to predict sudden death risk in heart failure.

描述（由申请人提供）：尽管进行了广泛的研究和新颖的治疗，人类收缩性心力衰竭（HF）仍然是影响数百万美国人的重大临床问题，并且与 HF 相关的心律失常仍然是高发病率和死亡率的原因。最近，发现三种 SCN5a 心脏 Na+ 通道 mRNA 选择性剪接变体在人心力衰竭组织中上调。这些剪接变体是由 SCN5a 末端外显子（即外显子 28）中隐秘剪接序列的剪接产生的，编码的心脏 Na+ 通道在结构域 IV 的孔形成片段之前被截断。变异水平达到超过总 SCN5a mRNA 的 50%。正如预期的那样，这些变体没有形成功能通道。此外，变体的存在导致全长SCN5a mRNA的丰度降低，但总SCN5a mRNA没有改变。本申请提出建立 HF 中异常剪接发生的机制，以及截短的 Na+ 通道变体的存在如何导致全长通道 mRNA 的显性负向下调。初步数据表明，缺氧和血管紧张素 II (AngII) 可以通过诱导 mRNA 剪接因子 CROP/hLuc7A 及其辅助因子 RBM25 的表达来发出病理性 SCN5a 剪接调节信号，这些因子通过与一个或多个 RBM25 结合序列相互作用来改变 SCN5a 剪接调节SCN5a 外显子 28 中的 CGGGC(A)，该外显子存在异常剪接SCN5a发生。此外，数据显示，截短的Na+通道在内质网（ER）中积累并启动未折叠蛋白反应（UPR）途径，导致Na+通道翻译减少和全长SCN5a转录物的半衰期缩短。假设。基于上述，我们假设 hLuc7A/RBM25 复合物导致 Na+ 通道 mRNA 剪接异常，并且 UPR 导致异常剪接转录本对 Na+ 通道产生显性负面影响。具体目标。具体目标1：确定hLuc7A/RBM25剪接调控通路是否参与SCN5a mRNA变异表达增加的机制。具体目标 2：确定未折叠蛋白反应 (UPR) 中的三个主要途径在多大程度上导致功能性 Na+ 通道的减少。具体目标 3：证明人类心力衰竭样本中 hLuc7A/RBM25 调节、未折叠蛋白反应 (UPR) 激活、Na+ 通道 mRNA 变异和 Na+ 通道测量之间的关系。 公共卫生相关性：心力衰竭猝死的原因尚不清楚。该应用将探索一个潜在原因，即钠通道处理异常，建立机制并阐明可能的预防策略。此外，如果白细胞表现出类似的异常，这项工作可能会导致血液测试来预测心力衰竭的猝死风险。