Pathophysiology of Myotonia and Periodic Paralysis

肌强直和周期性麻痹的病理生理学

• 批准号: 10277079
• 负责人: STEPHEN C. CANNON
• 金额: $ 55.99万
• 依托单位: UNIVERSITY OF CALIFORNIA LOS ANGELES
• 依托单位国家: 美国
• 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/10277079
• 关键词: Acidosis; Acute; Affect; Alleles; Biological Assay; Biophysics; Bumetanide; Carbohydrates; Cells; Chronic; Clinical Trials; Computer Models; 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; Knock-in; Knock-in Mouse; Knowledge; Lead; Measurement; Microelectrodes; Missense Mutation; Modeling; Mus; Muscle; Muscle Fibers; Mutant Strains Mice; Mutation; Myopathy; Myotonia; Na(+)-K(+)-Exchanging ATPase; Oocytes; Paralysed; Pathogenesis; Pathway interactions; Patients; Phenotype; Potassium Channel; Preclinical Testing; Predisposition; Prevention; Pump; Recovery; Recurrence; Research; Resources; Rest; Risk; Sarcolemma; Skeletal Muscle; Sodium Channel; Sodium Chloride; Specificity; Stress; System; Testing; Therapeutic Intervention; TimeLine; Validation; Variant; base; clinical phenotype; cold temperature; defined contribution; design; extracellular; gain of function; human data; improved; insight; models and simulation; mouse model; muscle stiffness; mutant; mutant mouse model; novel strategies; novel therapeutic intervention; periodic paralysis; prevent; programs; response; sensor; simulation; symptom management; therapy design; voltage

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. .

项目摘要 /摘要 周期性瘫痪和肌瘤是骨骼肌的离子通道路径，严重的发作使人衰弱 弱点持续数小时到几天，依赖活动的肌肉僵硬。该项目的长期目标是 促进我们对肌肉令人兴奋的这些疾病的疾病机制的理解，并应用 在设计和临床前测试治疗干预措施方面的知识。 在建立A的生物物理缺陷之间建立因果关系方 突变通道和临床表型。例如，已经确定了超过80个错义突变 NAV1.4钠通道，我们通过功能表达研究表明 纤维兴奋性，功能变化的突变（例如失活受损）导致高钾血症 肌瘤的周期性麻痹（HyperPP）。或者，降低性周期性的NAV1.4突变 瘫痪（HYPOPP）是电压传感器域的S4段中的所有R/X取代，共有共同 功能缺陷 - 异常的门控孔隙泄漏电流。在各种形式的周期性麻痹中，瞬态 无力的攻击是由于持续沉积𝑉𝑟𝑒௦௧和失去兴奋而导致的，通常会触发这些攻击 压力，饮食（碳水化合物，盐含量，禁食），冷温或运动。所在的机制 这些触发器破坏稳定𝑉𝑟𝑒௦௧，在突变频道的静态缺陷的情况下是基本的开放 该领域的问题，也代表了治疗干预的机会。对 进展一直是受影响肌肉的稀缺性。我们创建了三个敲门突变鼠标模型 具有强大表型的PP（NAV1.4-M1592V）或HYPOPP（NAV1.4-R669H; CAV1.1-R528H）。 这些小鼠模型导致了对疾病机制的新见解（例如，从酸中毒是有效的 HypOPP的触发器），并导致了现在正在临床试验中的新型治疗干预措施（Bumetanide NKCC1共转运蛋白的抑制可防止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）的触发器，但相对较少的IS 关于pp中的Na+和Cl-偏移已知。有限的人类数据表明，在一集中的急性上升 HyperPP或慢性高[Na+]用于HypOPP。此外，我们证明了完全减少CL纳入 防止HypOPP攻击。我们已经开发了改进的离子选择性微电极，结合 我们的敲入突变小鼠的独特资源将使我们能够（1）表征肌肉纤维Na+和Cl- （2）定义特定离子传输系统的贡献（突变体 NAV1.4，NKCC1，Na/k-ATPase，Cl-exchangers）在肌肉通道病中设置离子浓度，（3） 根据计算建模和 模拟，（4）在疾病改良干预措施的设计和临床前测试中使用这些见解。 。