离子通道在带髓鞘轴突中的转运机制

项目名称： 离子通道在带髓鞘轴突中的转运机制

项目编号： No.31471021

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 神经、认识与心理学

项目作者： 顾琛

作者单位： 浙江大学

项目金额： 93万元

中文摘要： 钠(Nav)和钾(Kv)离子通道的顺序激活和不同定位是神经冲动的启动和跳跃传导的产生机制。 Nav通道和锚蛋白-G(AnkG)聚集在有髓鞘轴突起始段和郎飞氏结， 而Kv1通道聚集在节两侧(JXP)。 这些通道的突变可导制人的神经疾病。 AnkG为躁郁症风险基因， 而JXP粘附蛋白CASPR2的突变与自闭症相关。 此项目将验证一个新的假说：Nav和其他节点蛋白由分子马达KIF5通过AnkG转运，而Kv1和JXP蛋白则由KIF3转运。　其中，节点和JXP蛋白在不同的囊泡中预组装。 将采用蛋白生化分析，神经髓鞘共培养，影像，电生理和小鼠模型，(1)检验AnkG, KIF5和其他节点蛋白的结合; (2)观察Nav和Kv1通道及相关蛋白在有髓轴突中的动态转运; (3)确定两种分子马达转运这些蛋白的体内特异性。　结果将有助于发展对一些神经和精神疾病的早期诊断和治疗。

中文关键词： 离子通道；神经元；神经疾病；轴突转运；动作电位

英文摘要： Action potentials (APs) propagating along axons play a central role in cell-to-cell communication in the nervous system. AP firing minimally requires sequential activation of two types of voltage-gate ion channels, Na+ (Nav) and K+ (Kv) channels. Although these channels have been extensively studied, how they are properly transported into axons-a prerequisite for AP firing-remains poorly understood. Crucial for efficient initiation and saltatory conduction of APs along myelinated axons, Nav channels are clustered at the axon initial segment and nodes of Ranvier through ankyrin-G (AnkG). Genome-wide association studies identified AnkG as a risk gene for bipolar disorder. In contrast, Kv1 channels are clustered in juxtaparanodal (JXP) regions flanking the nodes to prevent repetitive firing. A JXP cell adhesion protein, Caspr2, is involved in clustering Kv1 channels and implicated in autism spectrum disorder. Due to the lack of a suitable myelin coculture system, dynamic transport of channels and their associated proteins has never been visualized along myelinated axons. Although we previously showed that Kv1.2 axonal transport requires KIF3A/kinesin-2, how AnkG and Nav channels are transported into axons remains a mystery. In our recent studies, we found that AnkG directly binds to KIF5, raising the intriguing possibility that AnkG links Nav channels to KIF5 motors. Importantly, we established a novel myelin coculture of hippocampal neurons, allowing us to directly visualize channel transport along myelinated central axons. Based on our preliminary data, we hypothesize that crucial for proper AP firing, Nav channels are transported by KIF5 via AnkG to the AIS and nodes of Ranvier, whereas Kv1 channels are transported by KIF3 to JXP regions. Nodal and JXP complexes partially pre-assemble during transport. Using a multidisciplinary approach, including protein biochemical assays, hippocampal myelin coculture, imaging, patch-clamp recording, and conditional knockout mice, we will (1) determine interactions of AnkG, KIF5, and Nav channels, (2) elucidate dynamics of transport of Nav and Kv channels along myelinated axons, and (3) determine in vivo specificity of KIF-mediated transport of these axonal ion channels. This project will not only contribute to a better understanding of axonal transport of ion channels, but also provide novel mechanistic insights into pre-assembly of nodal and JXP complexes at the level of intracellular transport.

英文关键词： ion channel;neuron;neurological disease;axonal transport;action potential