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

基本信息

批准号：
9528467
负责人：
STEPHEN C. CANNON
金额：
$ 45.13万
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：
2012
资助国家：
美国
起止时间：
2012-07-01 至 2022-06-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/9528467
关键词：
Acidosis Address Affect Animal Model Arginine Calcium Channel Carbohydrates Charge Chlorides Clinical Clinical Trials Computer Simulation Coupling Defect Dependence Disease Environment Exercise Extravasation Failure Family Fiber Genetically Engineered Mouse Hereditary Disease Hour Human Hypokalemia Hypokalemic periodic paralysis Impairment Ingestion Intervention Investigation Ions Knock-in Knock-in Mouse Membrane Missense Mutation Modeling Modification Molecular Molecular Chaperones Morphology Movement Mus Muscle Muscle Fibers Mutation Myopathy Oocytes Paralysed Pathogenesis Pathogenicity Patients Periodicity Phenotype Predisposition Recovery Recurrence Resources Role Scientific Advances and Accomplishments Serum Severities Skeletal Muscle Sodium Channel Soleus Muscle Strenuous Exercise Stress Structural defect System Testing Therapeutic Triad Acrylic Resin Work Xenopus oocyte base biophysical properties burden of illness cell motility clinical phenotype design disability efficacy testing insight kindred models and simulation mutant mutant mouse model novel novel strategies periodic paralysis post intervention pre-clinical preservation sensor tool trafficking treatment strategy voltage voltage clamp

项目摘要

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 excitability. Episodes occur in association with hypokalemia (K+ <3 mM) and are often 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, and 20% have missense mutations in SCN4A encoding the voltage-gated Na channel NaV1.4. Despite this scientific advance, the pathogenic basis for the transient attacks of fiber depolarization and loss of excitability is not fully established, and effective clinical interventions are lacking. The proposed studies are designed to advance our understanding of the functional defects caused by CaV1.1 HypoPP mutations and to apply this information in model simulations to gain insights on disease mechanism and thereby identify experimentally testable strategies for disease modification. All 10 HypoPP mutations in NaV1.4 and 9 of 11 in CaV1.1 occur at arginine residues in S4 segments of voltage-sensor domains (VSD). For NaV1.4 HypoPP, these R/X mutations make channels leaky because of a small anomalous “gating pore current”. By homology, a similar defect has been proposed for CaV1.1 HypoPP, but experimental confirmation has been limited. In the prior cycle of this project, we detected a CaV1.1 gating pore current in our R528H knockin mutant mouse model of HypoPP. This finding supports the notion that the anomalous gating pore current is a feature in common between NaV1.4 and CaV1.1 HypoPP mutant channels, and thereby explains how mutations of either channel can produce the same clinical phenotype. The CaV1.1-R528H mice have a robust HypoPP phenotype and are a unique resource for investigating mechanisms by which environmental triggers elicit loss of excitability and weakness. For example, we recently discovered that recovery from acidosis is a potent trigger for a transient loss of force in soleus muscle of R528H mice, which may provide the first insight on why attacks of weakness frequently occur after strenuous exercise in HypoPP patients. The availability of fully-differentiated HypoPP muscle fibers provides an excellent system to study excitation-contraction coupling, and Ca2+ release is markedly suppressed in homozygous R528H fibers. In other preliminary studies, we have achieved a 50-fold increase of CaV1.1 expression in Xenopus oocytes by co-expressing Stac3, a chaperone that promotes CaV trafficking to the membrane. This new high-expression system now makes it possible to determine whether the other CaV1.1 HypoPP mutations, especially the two atypical mutations not at R residues in S4, also support a gating pore current. The CaV1.1-R528H HypoPP mouse and the enhanced membrane expression of CaV1.1 in Xenopus oocytes will be used to address the following Specific Aims: (1) Test the hypothesis that an anomalous gating pore current is a pathomechanism in common with CaV1.1 mutations associated with HypoPP, (2) In the pH-shift model for post-exercise weakness in HypoPP, test the hypothesis that a shift in the Cl- gradient causes susceptibility to depolarization-induced loss of excitability and that maneuvers to limit Cl- accumulation reduce the severity of weakness. (3) Test whether impaired Ca2+ release is a pervasive defect in CaV1.1 R528H muscle and explore whether the defect is intrinsic to the channel mutation.

低体血症周期性瘫痪（HypOPP）是骨骼肌的主要遗传疾病，其中通过刺激性的抗衰变引起的反复发作是弱点。 SCN4A中编码电压门控的NA通道NAV 1中的错义突变。尽管有科学的进步，纤维去极化的转移攻击的致病基础和恢复的ESTAB损失的损失却旨在提高我们对我们对我们对我们对我们对的理解CAV1的功能缺陷。 S4的电压传感器域（VSD）。但是在我们的R528H敲门蛋白突变体模型中，实验确认是有限的。 .1 HypOPP突变通道，提出两种通道的解释可以产生相同的临床现象表型。发现从酸中毒中恢复是R528H小鼠比目鱼肌肉的转移力损失的一种触发，这可能提供第一个见解，为什么在Hypoppp患者中经常发生弱点的攻击完全差异化的肌肉纤维的可用性为研究激发反应提供了一个极好的系统耦合和Ca2+释放在纯合R528H纤维中明显抑制。 .1 S4中的HypOPP突变T R残基也支持门控孔电流。电流是一种与cav1.1突变相关的病理机制。