NEURONAL GROWTH CONE SIGNAL TRANSDUCTION MECHANISMS

延伸轴突远端的生长锥体是一种特化的 将细胞外信号转化为生长的感觉器官 沿着适当的路径纠正突触靶标。这是恰当的 功能是神经系统发育的关键，因此也是功能的关键。 这一提议寻求对信号的分子理解。 神经元生长锥体的转导机制。特例 重点放在崩溃蛋白-1的作用上，它是 新近发现的抑制轴突的信号素家族蛋白 延伸和末端分枝。 Rho家族单体G蛋白的重要作用 背根神经节(DRG)生长锥中的异三聚体G蛋白 信号转导将通过引入突变激活的 和显性负性蛋白。假设GAP-43 增加生长锥对细胞外信号的敏感性将是 在培养的小鼠背根神经节神经元中检测到靶向缺失 GAP-43基因突变。最近发现的一个神经元家族 CRMP蛋白似乎是抑制崩解蛋白-1所必需的 生长锥体函数。该项目将通过以下方式进一步定义CRMP行动 鉴定与CRMP相互作用的蛋白质，探索酶促反应 CRMP的活性及不同CRMP性质的比较 家庭成员。细胞突起生长与塌陷蛋白-1敏感性 过度表达不同形式的CRMP将被研究。一个 崩解蛋白-碱性-磷酸酶融合蛋白将用于鉴定 崩塌蛋白结合蛋白可能在血管内皮细胞中作为崩塌蛋白受体 神经元生长锥体。一旦这种受体被识别出来，它们的 可以描述与CRMP、GAP-43和G蛋白的相互作用。 这些实验一起详细描述了 作为生长锥反应基础的分子事件 细胞外抑制信号，如崩溃蛋白-1。了解这些知识 路径为理解 人类大脑发育异常的病理生理学。 同样的机制很可能在成人紧张时起作用。 退行性神经病学中的系统损伤和功能改善 疾病。

The growth cone at the distal tip of the extending axon is a specialized sensory apparatus which transduces extracellular signals into growth along appropriate pathways to correct synaptic targets. Its proper function is crucial to nervous system development and hence function. This proposal seeks a molecular understanding of the signal transduction mechanisms at the neuronal growth cone. Particular emphasis is focused on the action of collapsin-1, a member of the semaphorin family of proteins recently recognized to inhibit axonal extension and terminal arborization. The essential role of monomeric G proteins of the rho family and of heterotrimeric G proteins in dorsal root ganglion (DRG) growth cone signal transduction will be examined by introducing mutant activated and dominant negative proteins. The hypothesis that GAP-43 augments sensitivity of the growth cone to extracellular signals will be examined in cultured DRG neurons from mice with a targeted deletion mutation in the GAP-43 gene. A recently identified family of neuronal CRMP proteins appear to be required for collapsin-1 inhibition of growth cone function. This project will further define CRMP action by identifying proteins interacting with CRMP, exploring enzymatic activities of CRMP and comparing the properties of different CRMP family members. Neurite outgrowth and collapsin-1 sensitivity of cells overexpressing different forms of CRMP will be examined. A collapsin-alkaline-phosphatase fusion protein will be used to identify collapsin binding proteins which may serve as collapsin receptors in the neuronal growth cone. Once such receptors are identified their interaction with CRMP, GAP-43, and G proteins can be delineated. Together these experiments provide a detailed description of the molecular events which underlie the growth cone responsiveness to extracellular inhibitory signals such as collapsin-1. Knowledge of these pathways provides necessary groundwork for understanding the pathophysiology of human developmental abnormalities of the brain. The same mechanisms are likely to function during adult nervous system injury and improve function in degenerative neurologic diseases.