Role of Merg1, a K+ Channel in the Onset of Skeletal Muscle Atrophy

Merg1（K 通道）在骨骼肌萎缩发生中的作用

• 批准号: 7866650
• 负责人: AMBER L POND
• 金额: $ 7.63万
• 依托单位: PURDUE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-06-10 至 2011-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7866650
• 关键词: 21 year old; Acquired Immunodeficiency Syndrome; Action Potentials; Antibodies; Area; Atrophic; Biological Assay; Biological Models; Cachexia; Calcium; Calpain; Cell Line; Cell model; Characteristics; Contractile Proteins; Data; Development; Diabetes Mellitus; Disease; Dominant-Negative Mutation; Ectopic Expression; Equipment; Exercise; Goals; Growth Factor; Hindlimb; Hindlimb Suspension; In Vitro; Individual; Investigation; Knowledge; Lead; Link; Malignant Neoplasms; Measures; Messenger RNA; Modeling; Molecular; Morbidity - disease rate; Mus; Muscle; Muscle Fibers; Muscular Atrophy; Pathway interactions; Physical therapy; Plasmids; Potassium Channel; Process; Production; Protein Biosynthesis; Proteins; Proteolysis; RNA Splicing; Research; Research Personnel; Role; Ryanodine Receptor Calcium Release Channel; Ryanodine Receptors; Signal Transduction; Skeletal Muscle; Testing; Tissues; Ubiquitin; Variant; Weight-Bearing state; Work; base; density; disability; effective therapy; experience; improved; in vivo; inhibitor/antagonist; innovation; mortality; multicatalytic endopeptidase complex; muscle strength; mutant; novel; response; ubiquitin-protein ligase

DESCRIPTION (provided by applicant): The broad, long range objective is to understand molecular mechanisms that regulate initiation of skeletal muscle (skm) atrophy. The objective of this application is to explore the role of Merg1a in initiation of skm atrophy. The central hypothesis is that Merg1a activates the ubiquitin proteasome pathway (UPP), known to be active in atrophying tissue, and participates in the onset of skm atrophy by modulating sarcolemmal Ca++ channel activity. The hypothesis is based on data which show that Merg1a is present in atrophying muscle and that its function can induce UPP activity and atrophy. Addtionally, data show that E3 ligase (part of the UPP) mRNAs are transcribed in response to Merg1a expression. Two pathways are known to induce E3 ligase synthesis: IKK-2/I:B-1/NF-:B and PI3K/Akt/FOXO. Therefore, our first two specific aims are to determine if: 1) Merg1a expression initiates UPP activity by activating the IKK-2/I:B-1/NF-:B pathway; and 2) Merg1a expression initiates UPP activity by the PI3K/Akt/FOXO pathway. Data also show that a connection exists between Ca++ levels and Merg1a expression. Thus, our third aim is to determine the effect of Merg1a expression on Ca++ current density and intracellular Ca++ concentration and if changes in Ca++ modulation are necessary for increased UPP activity. The first two aims will measure the effect(s) of in vivo ectopic co- expression of Merg1a and either constitutively active or dominant negative forms of proteins known to participate in the pathways leading to E3 ligase production. The third aim will involve use of a C2C12 clonal cell line which conditionally expresses Merg1a to determine the effect(s) of Merg1a expression on Ca++ current density, Ca++ channel subunit expression, intracellular calcium levels, and calpain activity. Finally, various pharmacological modulators of Ca++ handling will be used to determine if Ca++ is involved in Merg1a signaling to the UPP. Relevance. Skeletal muscle atrophy occurs with many pathological conditions (e.g., AIDS, diabetes, cancer cachexia, etc.) and is related to increased disability, morbidity and mortality. This research is significant because it will explore a novel initiator of skm atrophy and produce information that will allow for development of more effective therapies and, thereby, reduce the number of cases of this debilitating condition.

描述（由申请人提供）： 广泛而长期的目标是了解调节骨骼肌（skm）萎缩起始的分子机制。本申请的目的是探讨 Merg1a 在引发 skm 萎缩中的作用。核心假设是 Merg1a 激活泛素蛋白酶体途径 (UPP)，已知该途径在萎缩组织中具有活性，并通过调节肌膜 Ca++ 通道活性参与皮肤萎缩的发生。该假设基于的数据表明 Merg1a 存在于萎缩的肌肉中，并且其功能可以诱导 UPP 活性和萎缩。此外，数据显示 E3 连接酶（UPP 的一部分）mRNA 响应 Merg1a 表达而进行转录。已知有两条途径诱导 E3 连接酶合成：IKK-2/I:B-1/NF-:B 和 PI3K/Akt/FOXO。因此，我们的前两个具体目标是确定：1​​）Merg1a 表达是否通过激活 IKK-2/I:B-1/NF-:B 途径来启动 UPP 活性； 2) Merg1a 表达通过 PI3K/Akt/FOXO 途径启动 UPP 活性。数据还表明 Ca++ 水平和 Merg1a 表达之间存在联系。因此，我们的第三个目标是确定 Merg1a 表达对 Ca++ 电流密度和细胞内 Ca++ 浓度的影响，以及 Ca++ 调节的变化是否是增加 UPP 活性所必需的。前两个目标将测量 Merg1a 和已知参与导致 E3 连接酶产生的途径的组成型活性或显性失活形式的蛋白质的体内异位共表达的影响。第三个目标将涉及使用条件性表达 Merg1a 的 C2C12 克隆细胞系来确定 Merg1a 表达对 Ca++ 电流密度、Ca++ 通道亚基表达、细胞内钙水平和钙蛋白酶活性的影响。最后，Ca++ 处理的各种药理学调节剂将用于确定 Ca++ 是否参与 Merg1a 向 UPP 发出的信号。关联。骨骼肌萎缩与许多病理状况（例如艾滋病、糖尿病、癌症恶病质等）一起发生，并且与残疾、发病率和死亡率的增加有关。这项研究意义重大，因为它将探索一种新型的皮肤萎缩引发剂，并产生有助于开发更有效疗法的信息，从而减少这种使人衰弱的疾病的病例数量。