Disease Pathogenesis and Modification for CaV1.1-Associated Hypokalemic Periodic

CaV1.1 相关低钾血症周期性疾病的发病机制和修饰

• 批准号: 8346112
• 负责人: STEPHEN C. CANNON
• 金额: $ 38.77万
• 依托单位: UT SOUTHWESTERN MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-07-01 至 2017-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8346112
• 关键词: Animal Model; Arginine; Biological Models; Biopsy; Calcium Channel; Carbohydrates; Cations; Charge; Coupling; Data; Defect; Dependence; Disease; Environment; Exercise; Extravasation; Failure; Familial Periodic Paralysis; Family; Fiber; Gene Targeting; Genetically Engineered Mouse; Glucose; Goals; Hour; Human; Hypokalemia; Hypokalemic periodic paralysis; In Vitro; Inborn Genetic Diseases; Ingestion; Insulin; Intervention; Ion Channel; Ion Pumps; Link; Missense Mutation; Modeling; Modification; Molecular; Movement; Mus; Muscle; Muscle Fibers; Mutate; Mutation; Oocytes; Paralysed; Pathogenesis; Pathologic; Phenotype; Predisposition; Proteins; Rare Diseases; Recurrence; Reporting; SCN1A protein; Scientific Advances and Accomplishments; Serum; Skeletal Muscle; Sodium Channel; Source; Stress; Testing; Therapeutic; Therapeutic Intervention; Tissues; Treatment Efficacy; Work; base; burden of illness; density; efficacy testing; in vivo; kindred; mouse model; mutant; mutant mouse model; response; sensor; simulation; tool; voltage; voltage clamp

DESCRIPTION (provided by applicant): Hypokalemic periodic paralysis (HypoPP) is a dominantly inherited disorder of skeletal muscle in which recurrent attacks of weakness are caused by intermittent failure of fiber electrical excitability. Episodes occur in association with hypokalemia (K+ < 3 mM) and may be triggered by carbohydrate ingestion, exercise, or stress. The molecular defect in HypoPP is heterogeneous, with 60% of families having missense mutations in CACNA1S encoding the L-type Ca channel CaV1.1, another 20% have missense mutations in SCN4A encoding the voltage-gated Na channel NaV1.4, and the remainder undetermined. Despite this scientific advance, the pathogenic basis for the transient attacks of fiber depolarization with loss of excitability is not fully established. Curiously, all 8 mutationsin NaV1.4 and 6 of 7 in CaV1.1 occur at arginine residues in S4 voltage-sensor domains. Thus far, all 6 NaV1.4-HypoPP mutations studied in the cut-open oocyte have revealed a small anomalous cation current activated at hyperpolarized potentials, via conduction through a "gating pore" between the mutated S4 segment and the channel protein. We recently reported a gating pore current in muscle fibers from NaV1.4-R669H mice. This gating pore conductance is hypothesized to be the source of the inward current that triggers the paradoxical depolarization of HypoPP fibers in low K+. A major unanswered question is whether the homologous R/X mutations in CaV1.1 associated with HypoPP also produce a gating pore current, thereby providing supportive evidence for a common pathomechanism for HypoPP arising from mutations in NaV1.1 or CaV1.1. The overall goal of this project is to gain a greater understanding for the pathologic basis of HypoPP resulting from CaV1.1 mutations. We have used a gene-targeting approach to generate an R528H knockin mutation of CaV1.1 as a model for HypoPP. The Aims of this project are: (1) to extend the phenotypic characterization of the CaV1.1-R528H mouse for features of hypokalemic periodic paralysis, (2) to test the hypothesis that the CaV1.1-R528H channel conducts an anomalous gating pore current (3) to characterize the integrity of Ca2+- release in CaV1.1-R528H muscle fibers, (4) to explore potential disease-modifying agents in the mouse model of CaV1.1-HypoPP. This work will extend our understanding of the pathogenesis for attacks of weakness in HypoPP and will provide a model system to test the efficacy of therapeutic strategies, both as a means to reduce or ameliorate the burden of disease and to provide confirmatory experimental support for the proposed mechanism of disease. PUBLIC HEALTH RELEVANCE: Familial periodic paralysis is a rare disorder of skeletal muscle in which intermittent failure of muscle excitability causes attacks of severe weakness or paralysis lasting for hours to days. The molecular defect has been known for more than a decade to be mutations of either calcium channels or sodium channels, but the mechanisms by which these channel defects cause susceptibility to attacks of weakness are poorly understood and consequently rational therapeutic strategies to modify disease course are lacking. We have developed the only genetically-engineered mouse model of periodic paralysis based on a calcium channel mutation and will use this unique tool to define further the mechanism underlying attacks of paralysis and test potential interventions to modify disease burden.

描述（由申请人提供）：低钾性周期性麻痹（HypoPP）是一种显性遗传性骨骼肌疾病，其中反复发作的无力是由纤维电兴奋性间歇性失效引起的。情节发生与 低钾血症 (K+ < 3 mM)，可能由碳水化合物摄入、运动或压力引发。 HypoPP 的分子缺陷是异质性的，60% 的家族在编码 L 型 Ca 通道 CaV1.1 的 CACNA1S 中存在错义突变，另外 20% 在编码电压门控 Na 通道 NaV1.4 的 SCN4A 中存在错义突变，其余家族尚未确定。尽管取得了这一科学进步，但纤维去极化伴有兴奋性丧失的短暂发作的致病基础尚未完全确定。奇怪的是，NaV1.4 中的所有 8 个突变和 CaV1.1 中 7 个突变中的 6 个都发生在 S4 电压传感器域的精氨酸残基处。到目前为止，在切开的卵母细胞中研究的所有 6 个 NaV1.4-HypoPP 突变都揭示了通过突变的 S4 片段和通道蛋白之间的“门控孔”传导，在超极化电位下激活的小异常阳离子电流。我们最近报道了 NaV1.4-R669H 小鼠肌纤维中的门控孔电流。假设这种门控孔电导是内向电流的来源，该内向电流触发低 K+ 下 HypoPP 纤维的矛盾去极化。一个尚未解答的主要问题是与 HypoPP 相关的 CaV1.1 中的同源 R/X 突变是否也产生门控孔电流，从而为 NaV1.1 或 CaV1.1 突变引起的 HypoPP 常见病理机制提供支持证据。该项目的总体目标是更好地了解 CaV1.1 突变引起的 HypoPP 的病理基础。我们使用基因靶向方法生成 CaV1.1 的 R528H 敲入突变作为 HypoPP 模型。该项目的目的是：(1) 扩展 CaV1.1-R528H 小鼠的表型特征，以了解低钾性周期性麻痹的特征，(2) 检验 CaV1.1-R528H 通道传导异常门控孔电流的假设 (3) 表征 CaV1.1-R528H 肌纤维中 Ca2+- 释放的完整性，(4) 探索潜在的 CaV1.1-HypoPP 小鼠模型中的疾病缓解剂。这项工作将扩展我们对 HypoPP 无力发作发病机制的理解，并将提供一个模型系统来测试治疗策略的功效，既可以作为减少或减轻疾病负担的手段，也可以为所提出的疾病机制提供确凿的实验支持。 公众健康相关性：家族性周期性麻痹是一种罕见的骨骼肌疾病，其中肌肉兴奋性间歇性衰竭导致严重虚弱或瘫痪，持续数小时至数天。十多年来，人们已知道这种分子缺陷是钙通道或钠通道的突变，但人们对这些通道缺陷导致虚弱发作易感性的机制知之甚少，因此缺乏改变病程的合理治疗策略。我们开发了唯一基于钙通道突变的基因工程小鼠周期性麻痹模型，并将使用这种独特的工具进一步定义麻痹发作的潜在机制，并测试减轻疾病负担的潜在干预措施。