Regulation of Proteolysis in Crustacean Muscles

骨骼肌不仅在动物运动中很重要，而且是蛋白质的主要代谢储存，当饮食摄入不足以满足动物的营养需求时，它可以迅速动员起来。此外，肌肉萎缩可由废用、神经损伤和疾病引起。在一些疾病中，如肌肉萎缩症，消瘦严重到个体死亡。在任何动物中，对蛋白质分解的细胞内调控都知之甚少。甲壳类动物爪肌为阐明蛋白质水解机制提供了一个良好的模型系统。在每个脱模周期中，爪肌都经历了一个连续的萎缩和恢复过程，其中蛋白质含量在脱模前下降40%，在脱模后重新合成。显然，萎缩有助于在蜕壳时抽出一对大爪子。蛋白质降解似乎由五种酶介导：四种钙依赖性蛋白酶（CDPs）和一种多催化蛋白酶（MCP）。这些酶在中性pH值下是活跃的，并降解肌肉的收缩蛋白。这一建议检查了细胞内蛋白水解的肌肉，类似于形态学和生化，脊椎动物骨骼肌的调节。利用生物化学和分子生物学技术分离和表征了两种蛋白酶。这些研究将为所有动物细胞共同的蛋白水解过程的调节提供新的和基本的信息。

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. In addition, muscle atrophy can be induced by disuse, nerve injury, and disease. In some disuse, such as muscular dystrophy, wasting is so severe that individual dies. The intracellular regulation of protein breakdown in any animal 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). The enzymes are active a 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. Biochemical and molecular biological techniques are used to isolate and characterize two proteinases. These studies will yield new and basic information on the regulation of proteolytic processes common to all animal cells.