REGULATION OF NEURAL CELL ADHESION MOLECULE IN MUSCLE

本研究的长期目标是了解 调节神经细胞粘附分子（NCAM）是肌肉 发育过程中的变化以及细胞机制影响 NCAM修改。 希望这一知识将进一步 我们对NCAM分子机制的理解 介导细胞粘附，因为目前没有精确的分子 模型存在。 这些问题将通过两种类型的 问题研究 首先，将通过生物合成方法研究NCAM生物合成。 放射性标记培养的鸡肌管。 周转时间，周转率 将检查多聚唾液酸化、硫酸化和磷酸化。 一 与神经NCAM生物合成的早期研究相比， 建立它的多肽是相同的修饰，在这两个 可能具有重要功能的组织 第二，将研究三类监管因素 因为它们在肌管培养物中调节NCAM的能力。 第一章 将测试影响肌肉功能活动的条件 因为它们改变总NCAM水平的能力（如由 ELISA）、多肽大小和聚唾液酸化（如在SDS-PAGE上测定的）。 PAGE）。 体内神经元调节下调NCAM 多肽合成和聚唾液酸化。 因此肌管培养 提供了一个系统，在该系统中，可以孤立地测试因素， 它们模拟神经元调节的能力2）NCAM的调节 类固醇激素将同样检查治疗 用地塞米松和各种类固醇培养几个 天 3)第二信使参与细胞内的 将探索介导NCAM调节的控制机制 通过研究影响几种激酶的因素，如环 核苷酸和甘油二酯。 NCAM将被量化， 长时间治疗后研究聚唾液酸化，而 在较短的处理后研究磷酸化。 NCAM调节似乎在以下发育中很重要： 神经肌肉接头，并在成人疾病中改变， 多发性肌炎、杜氏和贝克肌营养不良症，以及 肩胛带和肢带营养不良。 了解其 调控将有助于开发一个精确的分子模型， NCAM功能，这可能解释了它参与 退行性肌肉疾病，以及它的假定作用， 组织发生

The long term goals of this study are to understand how the regulation of the neural cell adhesion molecule (NCAM) is muscle changes during development and what cellular mechanisms affect NCAM modification. It is hoped that this knowledge will further our understanding of the molecular mechanism by which NCAM mediates cell adhesion, since at present no precise molecular model exists. These questions will be addressed by two types of studies. First, NCAM biosynthesis will be studied by biosynthetic radiolabelling cultured chick myotubes. Turnover time, rate of polysialation, sulfation and phosphorylation will be examined. A comparison with earlier studies on neural NCAM biosynthesis will establish it the polypeptides are identically modified in the two tissues which could be of functional importance. Second, regulatory factors of three categories will be examined for their ability to regulate NCAM in myotube culture. 1) Conditions that affect muscle functional activity will be tested for their ability to alter total NCAM levels (as determined by ELISA), polypeptide size and polysialation (as determined on SDS- PAGE). Neuronal regulation in vivo down-regulated NCAM polypeptide synthesis and polysialation. Hence myotube culture provides a system where factors can be tested in isolation for their ability to mimic neuronal regulation 2) Regulation of NCAM by steroid hormones will be similarly examined by treating cultures with dexamethasone and a variety of steroids for several days. 3) The involvement of second messengers in the cellular control mechanism mediating NCAM regulation will be explored by studying factors affecting several kinases, such as cyclic nucleotides and diacylglycerol. NCAM will be quantified and polysialation studied after prolonged treatment, while phosphorylation will be studied after shorter treatments. NCAM regulation appears to be important in the development of neuromuscular junction and is altered in adult diseases such as polymyositis, Duchenne and Becker muscular dystrophies, and tascio-scapular and limb girdle dystrophies. Understanding its regulation will assist in developing a precise molecular model of NCAM function which may explain its involvement in degenerative muscle diseases, as well its presumed role in histogenesis.