Regulation of Proteolysis in Crustacean Muscles

骨骼肌不仅在动物运动中很重要， 也构成蛋白质的主要代谢储存， 当饮食摄入量不足以满足 动物的营养需求。 在饥饿引起的萎缩过程中， 肌肉蛋白质被降解为氨基酸，然后被 其他组织合成生命所必需的蛋白质。 此外，肌肉萎缩可诱发废用，神经 伤害和疾病。 在某些疾病中，如肌肉 营养不良、消瘦是如此严重，以至于个体死亡。 任何动物体内蛋白质分解的细胞内调节 是很难理解的。 甲壳类动物的爪肌提供了 用于阐明蛋白水解机制的有利模型系统。 在每个蜕皮周期中，爪肌都经历了 随后的萎缩和恢复，其中蛋白质含量 在蜕皮前期减少40%， 在Molt之后。 萎缩明显促进了 在壳脱落时有一对大爪子。 蛋白 降解似乎是由五种酶介导的：四种钙- 依赖性蛋白酶（CDPs）和多催化蛋白酶 （MCP）。 这些酶在中性pH下具有活性，并降解 肌肉的收缩蛋白质。 该建议研究了细胞内 肌肉中的蛋白质水解在形态上和 脊椎动物骨骼肌。 由于萎缩 与类固醇蜕皮激素水平升高相吻合， 实验将研究荷尔蒙对蛋白质的控制 周转（合成和降解）在爪肌文化。 其他实验将确定信号中的主要步骤 控制蛋白水解的途径。 CDPs和内源性 将纯化调节因子用于进一步表征 和抗体的产生。 蜕皮引起的 MCP的表达、含量和细胞内分布 将被量化。 除了定义的功能外， 这些酶在蛋白质分解，这些研究将产生新的 和调节蛋白水解的基本信息 所有动物细胞的共同过程。

Skeletal muscle is not only important in animal locomotion, but also constitutes a major metabolic store of protein that can be quickly mobilized when dietary intake is insufficient to meet an animal's nutritional needs. During starvation-induced atrophy, muscle protein is degraded to amino acids, which are then used by other tissues for the synthesis of proteins essential for life. In addition, muscle atrophy can be induced by disuse, nerve injury, and disease. In some diseases, such as muscular dystrophy, wasting is so severe that the individual dies. The intracellular regulation of protein breakdown in any animal is poorly understood. The crustacean claw muscle provides a favorable model system for elucidating proteolytic mechanisms. During each intermolt cycle, the claw muscle undergoes a sequential atrophy and restoration, in which protein content decreases 40% during the premolt period and is resynthesized following molt. Atrophy apparently facilitates withdrawal of the pair of large claws at the time the shell is shed. Protein degradation appears to be mediated by five enzymes: four calcium- dependent proteinases (CDPs) and a multicatalytic proteinase (MCP). These enzymes are active at neutral pH and degrade the contractile proteins of muscle. This proposal examines the regulation of intracellular proteolysis in a muscle that resembles, both morphologically and biochemically, vertebrate skeletal muscle. Since atrophy coincides with elevated levels of a steroid molting hormone, experiments will investigate the hormonal control of protein turnover (synthesis and degradation) in claw muscles in culture. Other experiments will identify the major steps in the signal pathway controlling proteolysis. The CDPs and endogenous regulatory factors will be purified for further characterization and production of antibodies. Molt-induced changes in the expression, content, and intracellular distribution of the MCP will be quantified. In addition to defining the function of these enzymes in protein breakdown, these studies will yield new and fundamental information on the regulation of proteolytic processes common to all animal cells.