Pathophysiology of Myotonia and Periodic Paralysis

肌强直和周期性麻痹的病理生理学

基本信息

批准号：
10641898
负责人：
STEPHEN C. CANNON
金额：
$ 54.61万
依托单位：
UNIVERSITY OF CALIFORNIA LOS ANGELES
依托单位国家：
美国
项目类别：
财政年份：
2021
资助国家：
美国
起止时间：
2021-07-01 至 2026-06-30
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/10641898
关键词：
Acidosis Acute Affect Alleles Biological Assay Biophysics Biopsy Bumetanide Carbohydrates Cells Chlorides Chronic Clinical Trials Computer Models Computer Simulation Coupled Data Defect Development Diet Disease Exercise Extravasation Fasting Fiber Functional disorder Genes Genetically Engineered Mouse Goals Hereditary Disease Hour Human Hyperkalemic periodic paralysis Hypokalemic periodic paralysis Impairment Intervention Investigation Ion Channel Ion Transport Ions K ATPase Knock-in Knock-in Mouse Knowledge Lead Magnetic Resonance Imaging Measurement Microelectrodes Missense Mutation Modeling Mus Muscle Muscle Fibers Mutant Strains Mice Mutation Myopathy Myotonia Oocytes Paralysed Pathogenesis Pathway interactions Patients Phenotype Potassium Channel Preclinical Testing Predisposition Prevention Pump Recovery Recurrence Research Resources Rest Risk Sarcolemma Skeletal Muscle Sodium Sodium Channel Sodium Chloride Specificity Stress System Testing Therapeutic Intervention Validation Variant clinical phenotype cold temperature defined contribution design extracellular gain of function human data improved insight mouse model muscle stiffness mutant mutant mouse model novel strategies novel therapeutic intervention periodic paralysis prevent programs response sensor simulation symporter symptom management therapy design timeline voltage

项目摘要

Project Summary / Abstract Periodic paralysis and myotonia are ion channelopathies of skeletal muscle with debilitating episodes of severe weakness lasting hours to days and activity-dependent muscle stiffness. The long-term goal of this project is to advance our understanding of disease mechanism in these disorders of muscle excitability and to apply this knowledge in the design and pre-clinical testing of therapeutic interventions. Much progress has been made in establishing a causal relationship between the biophysical defect of a mutant channel and the clinical phenotype. For example, over 80 missense mutations have been identified in the NaV1.4 sodium channel, and we have shown by functional expression studies, coupled with simulations of fiber excitability, that mutations with gain of function changes (e.g. impaired inactivation) cause hyperkalemic periodic paralysis (HyperPP) with myotonia. Alternatively, the NaV1.4 mutations in hypokalemic periodic paralysis (HypoPP) are all R/X substitutions in S4 segments of voltage sensor domains that share a common functional defect - the anomalous gating pore leakage current. In all forms of periodic paralysis, the transient attacks of weakness result from sustained depolarization of 𝑉𝑟𝑒௦௧ and loss of excitability, which are often triggered by stress, diet (carbohydrate, salt content, fasting), cold temperature, or exercise. The mechanisms by which these triggers destabilize 𝑉𝑟𝑒௦௧, in the setting of a static defect for a mutant channel, are fundamental open questions in the field and also represent opportunities for therapeutic intervention. A major impediment to progress has been the scarce availability of affected muscle. We created three knock-in mutant mouse models of PP that have robust phenotypes for HyperPP (NaV1.4-M1592V) or HypoPP (NaV1.4-R669H; CaV1.1-R528H). These mouse models have led to new insights on disease mechanism (e.g. recovery from acidosis is a potent trigger of HypoPP) and have led to novel therapeutic interventions that are now in clinical trials (bumetanide inhibition of the NKCC1 cotransporter prevents HypoPP). We will extend our investigations of periodic paralysis by focusing on the impact of ion gradients. Changes in extracellular [K+]o are established triggers for HypoPP (low) or HyperPP (high), but relatively little is known about Na+ and Cl- shifts in PP. Limited human data suggest an acute rise of [Na+]in during an episode of HyperPP or chronically high [Na+]in for HypoPP. In addition, we showed that reducing Cl- influx completely prevents HypoPP attacks. We have developed improved ion-selective microelectrodes, that in combination with the unique resource of our knock-in mutant mice, will enable us to (1) characterize muscle fiber Na+ and Cl- content at rest and during an attack of PP, (2) define the contribution of specific ion transport systems (mutant NaV1.4, NKCC1, Na/K-ATPase, Cl- exchangers) in setting ion concentrations in muscle channelopathies, (3) define the functional consequences of ion gradient perturbations in PP, based on computational modeling and simulation, and (4) use these insights in the design and pre-clinical testing of disease-modifying interventions. .

项目概要/摘要周期性麻痹和肌强直是骨骼肌的离子通道病，伴有严重的衰弱发作持续数小时至数天的无力和活动依赖性肌肉僵硬该项目的长期目标是我们提前了解这些肌肉兴奋性障碍的疾病机制并加以应用治疗干预措施的设计和临床前测试方面的知识。在建立生物物理缺陷之间的因果关系方面已经取得了很大进展。例如，已鉴定出 80 多种错义突变。 NaV1.4 钠通道，我们通过功能表达研究以及模拟表明纤维兴奋性，功能改变（例如失活受损）的突变导致高钾血症周期性麻痹 (HyperPP) 伴有肌强直，或者是低钾性周期性麻痹的 NaV1.4 突变。麻痹 (HypoPP) 是电压传感器域 S4 段中的所有 R/X 替换，它们共享一个共同点功能缺陷——异常的门控孔漏电流在所有形式的周期性麻痹中，瞬态现象。无力发作是由于𝑉𝑟𝑒௦௧持续去极化和兴奋性丧失而引起的，这通常是触发的压力、饮食（碳水化合物、盐含量、禁食）、寒冷温度或运动的机制。这些触发器会破坏稳定，在突变通道静态缺陷的情况下，是根本性的开放问题，也是治疗干预的一个主要障碍。进展是受影响肌肉的稀缺性我们创建了三种基因敲入突变小鼠模型。具有 HyperPP (NaV1.4-M1592V) 或 HypoPP (NaV1.4-R669H; CaV1.1-R528H) 稳健表型的 PP。这些小鼠模型带来了对疾病机制的新见解（例如，从酸中毒中恢复是一种有效的方法） HypoPP 的触发因素）并导致了目前正在进行临床试验的新型治疗干预措施（布美他尼抑制 NKCC1 协同转运蛋白可预防 HypoPP）。我们将通过关注离子梯度的影响来扩展对周期性麻痹的研究。细胞外 [K+]o 的变化是 HypoPP（低）或 HyperPP（高）相对确定的触发因素，但很少有关于 PP 中 Na+ 和 Cl- 变化的已知信息，有限的人类数据表明 [Na+]in 在 PP 发作期间急剧上升。 HyperPP 或 HypoPP 的长期高 [Na+]in 此外，我们还表明可以完全减少 Cl- 流入。我们开发了改进的离子选择性微电极，可防止 HypoPP 攻击。我们的敲入突变小鼠的独特资源将使我们能够 (1) 表征肌纤维 Na+ 和 Cl- 静止时和 PP 攻击期间的含量，(2) 定义特定离子传输系统的贡献（突变体 NaV1.4、NKCC1、Na/K-ATP 酶、Cl- 交换器）在肌肉通道病中设定离子浓度，(3) 基于计算模型和 PP 中离子梯度扰动的功能后果模拟，(4) 在疾病缓解干预措施的设计和临床前测试中使用这些见解。。