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）：低钾血症性周期性麻痹（HypoPP）是一种主要遗传的骨骼肌疾病，其中由纤维电兴奋性间歇性失效引起的反复发作的虚弱。发作的发生与