Developmental change in signal transduction regulating neurite outgrowth

本研究旨在阐明神经突起生长的信号转导机制，这些信号转导机制随发育过程呈现动态变化。钙在多种细胞功能的细胞内信号通路中扮演着重要的第二信使角色。细胞内的钙离子受到严格的调控，其最佳浓度是正常突起生长所必需的。我们首先研究了培养的鸡胚胎早期或晚期背根神经节(DRG)神经元中突起生长和钙依赖信号的钙来源。在早期发育阶段，通过三磷酸肌醇(IP3)受体从内库释放的钙被发现有助于鸡背根神经节神经元突起的生长，而通过质膜内流和通过兰尼定受体从内库释放的钙被发现对突起的生长起重要作用。接下来，我们研究了钙信号级联调节神经细胞…。在发育早期发育出更多的TE。神经元钙传感器-1(NCS-1)是一种高亲和力、低容量的钙结合蛋白，在神经系统中特异表达。我们发现NCS-1在鸡背根神经节神经元突起远端的生长锥内有聚集现象。免疫细胞化学显示NCS-1与1型IP3受体共定位于生长锥内。药物抑制IP3受体可减少NCS-1在生长锥内的聚集分布，抑制轴突生长，但不影响生长锥形态。生色团辅助激光灭活(CALI)导致生长锥内NCS-1功能的急性局部性丧失，导致神经突起生长停滞和板脂回缩，但不引起丝状回缩。这些结果表明，NCS-1介导的生长锥内钙信号可能调节细胞内钙信号，调控生长锥形态和轴突生长，并可能与生长锥中的Insp3R1功能连锁，促进早期发育阶段的轴突生长。较少

The aid of this study is to clarify signal transduction mechanisms regulating neurite outgrowth which show dynamic change in accordance with developmental process. Calcium acts important second messenger in the intracellular signal pathways in a variety of cell function. Intracellular calcium ion is strictly regulated and its optimal concentration is required for a proper neurite outgrowth. We first examined source of calcium for neurite outgrowth and calcium-dependent signaling in cultured dorsal root ganglion (DRG) neurons from early or late stages of chick embryos. In early developmental stages, calcium release from internal stores through inositol 1.4.5-trisphosphate (IP3) receptors was found to contribute on neurite outgrowth of chick DRG neuron, while calcium increases by influxes through plasma membrane and by release form internal stores through ryanodine receptors were found to be important for the neurite outgrowth. We next examined the calcium signal cascade regulating neuri … More te outgrowth in the early developmental stage. Neuronal calcium sensor-1 (NCS-1) is a high-affinity and low-capacity calcium binding protein that is specifically expressed in the nervous system. We found the clustering of NCS-1 in the growth cone that is located at a distal tip of neurite in chick DRG neurons. Immunocytochemistry revealed that NCS-1 was co-localized with type 1 IP3 receptor in the growth cone. Pharmacological inhibition of IP3 receptors decreased clustering distribution of NCS-1 in the growth cones and inhibited neurite outgrowth, but not affect growth cone morphology. Acute localized loss of NCS-1 function in the growth cone induced by chromophore-assisted laser inactivation (CALI) resulted in growth arrest of neurites and lamellipodial retraction, but not filopodial retraction. These findings suggest that calcium signaling mediated by NCS-1 in growth cone may regulate the intracellular calcium signaling regulating both of growth cone morphology and neurite outgrowth, and may functionally linked to InsP_3R1 in growth cone may promote neurite outgrowth in the earty developmental stages. Less