STRUCTURAL AND FUNCTIONAL ANALYSIS OF AGRIN PROTEINS

处理感官信息和表达复杂行为的能力 依赖于电兴奋细胞之间的快速通讯， 神经系统 电可兴奋细胞之间的信号传递是 主要由化学突触完成。 了解细胞 和化学突触的分子组织， 因此，控制其发展和维护是核心问题 现代神经生物学中。 神经肌肉接头是一个有用的模型 系统来解决这些问题。 与其他化学品一样 突触，神经肌肉接头由精确记录的 突触前和突触后元件，每一个专门的作用， 突触传递 尤其是突触后肌肉运动端- 板具有高浓度的受体（AChR）， 神经递质乙酰胆碱和乙酰胆碱酯酶（AChE）， 负责分解的酶。 富含突触的提取物 电射线的电器官诱导斑块的形成， 肌肉纤维在体外含有乙酰胆碱受体和乙酰胆碱酯酶，模仿 这些突触后成分的积累，发生在正常的 发展 四种结构相关的蛋白质已从 其中两种叫做聚集蛋白的电器提取物能够诱导 AChR/AChE聚集体的形成。剩下的两个agrin样 然而，通过该测定，蛋白质没有活性。 分子相关或 与聚集蛋白相同的存在于神经肌肉接头处，表明 agrin蛋白在其发育和维持中发挥作用。 的 在其他组织中存在类似于聚集蛋白的分子表明， 聚集蛋白可能具有额外的重要功能。 这个目标 建议是在分子水平上表征聚集蛋白， 定义了它们生理特性的结构基础。 这 将增加我们对聚集蛋白作用机制的理解 以及突触发生过程中发生的分子事件。 这些目标 将通过生物化学和免疫学分析来实现， 通过对聚集蛋白基因及其功能的互补分子研究， 产品. 这些研究将提高我们减轻 发育异常的突触和加强神经肌肉 创伤后的再生

The ability to process sensory information and express complex behaviors depends on rapid communication between electrically excitable cells in the nervous system. Signalling between electrically excitable cells is largely accomplished by chemical synapses. Understanding the cellular and molecular organization of chemical synapses and the rules that control their development and maintenance are therefore central questions in modern neurobiology. The neuromuscular junction is a useful model system in which to address these questions. Like other chemical synapses, the neuromuscular junction consists of precisely registered pre-and postsynaptic elements, each specialized for their role in synaptic transmission. In particular, the postsynaptic muscle motor end- plate has high concentrations of receptors (AChR) for the neurotransmitter acetylcholine, and acetylcholinesterase (AChE), an enzyme responsible for its breakdown. Extracts of the synapse-rich electric organ of the electric ray induce the formation of patches on muscle fibres in vitro that contain both AChR and AChE, mimicking the accumulation of these post-synaptic components that occurs during normal development. Four structurally related proteins have been purified from the electric organ extract of which two, called agrin, are able to induce the formation of AChR/AChE aggregates. The remaining two agrin-like proteins however are not active by this assay. Molecules related or identical to agrin are present at the neuromuscular junction, suggesting that agrin proteins play a role in its development and maintenance. The presence of molecules similar to agrin in other tissues suggests that agrin proteins may have additional important functions. The goal of this proposal is to characterize agrin proteins at the molecular level and define the structural basis for their physiological properties. This will add to our understanding of the mechanism of agrin protein action and the molecular events occurring during synaptogenesis. These goals will be realized through biochemical and immunological analyses of native proteins and by complementary molecular studies of agrin genes and their products. These studies will enhance our ability to alleviate developmental anomalies in synaptogenesis and potentiate neuromuscular regeneration following trauma.