Molecular analysis of neural circuit excitation and inhibition

 描述(申请人提供)：由离子型(烟碱型)乙酰胆碱受体(IAChRs)介导的胆碱能信号在哺乳动物神经系统中发挥关键作用。IAChRs调节不同类型突触的神经递质释放，几乎遍及大脑和脊髓的每一个区域，此外，还调节关键脑区抑制性中间神经元的活动。IACHR信号的改变与一些衰弱的神经疾病有关，包括阿尔茨海默病、精神分裂症和某些形式的癫痫。此外，尼古丁与神经系统中的尼古丁受体结合，启动了导致尼古丁成瘾的细胞和分子级联反应。尽管IACHR信号在正常的大脑生理和健康中具有明显的重要性，但我们对调节大脑中胆碱能信号的细胞机制的理解存在重大差距。我们已经做了令人兴奋的观察，iAChRs也调节遗传易驯化的模式生物秀丽线虫的抑制性神经元活性。我们已经开发了一个强大的系统来研究这些受体在抑制性神经元树突中的运输、定位和功能，该树突位于一个简单的三层回路中，控制线虫的运动。这项提议旨在使用我们为操纵这一回路中的活动水平而产生的遗传工具，以及线虫中可用的一系列强大的分子遗传学方法，来探索IACHR生物学中的基本问题。在本项目中，我们将(目标1)研究IACHR亚细胞定位、亚单位组成、体内动力学和负责将iAChRs运送到抑制性神经元上特定亚细胞区域的分子途径；(目标2)研究GABA神经元胆碱能神经支配的改变如何导致GABA突触的发育或维持缺陷；(目标3)确定新的neuresin信号通路在塑造GABA突触发育中的作用。我们期待着我们对蠕虫中这一实验上易处理的回路的研究将为大脑中iAChRs的生物调节机制及其在调节抑制信号中的重要作用提供令人兴奋的新见解。此外，在我们的实验中，对调节突触形成和功能的保守遗传路径的识别和功能表征最终将为治疗策略产生新的药物靶点，该治疗策略旨在治疗涉及胆碱能信号的神经疾病。

 DESCRIPTION (provided by applicant): Cholinergic signaling mediated by ionotropic (nicotinic) acetylcholine receptors (iAChRs) plays key roles in the mammalian nervous system. iAChRs modulate neurotransmitter release at diverse synapse types across virtually every area of the brain and spinal cord, and in addition, regulate the activity of inhibitory interneurons in critical brain areas. Alterations in iAChR signaling are associated with a number of debilitating neurological disorders including Alzheimer's disease, schizophrenia and certain forms of epilepsy. Moreover, nicotine binding to nicotinic receptors in the nervous system initiates the cellular and molecular cascade that results in nicotine addiction. Despite the clear importance of iAChR signaling in normal brain physiology and health, there are major gaps in our understanding of the cellular mechanisms that regulate cholinergic signaling in the brain. We have made the exciting observation that iAChRs also regulate inhibitory neuron activity in the genetically tractable model organism Caenorhabditis elegans. We have developed a powerful system to study the trafficking, localization and function of these receptors in the dendrites of inhibitory neurons located in a simple 3-layer circuit that controls C. elegans movement. This proposal aims to use the genetic tools we have generated for manipulation of activity levels in this circuit, along with the powerful array of molecular genetic approaches available in C. elegans, to explore fundamental questions in iAChR biology. In this project we will (Aim 1) characterize iAChR subcellular localization, subunit composition, in vivo dynamics, and molecular pathways responsible for delivery of iAChRs to specific subcellular domains on inhibitory neurons; (Aim 2) investigate how altered cholinergic innervation of GABA neurons leads to defects in the development or maintenance of GABA synapses; (Aim 3) determine the role of a novel neurexin signaling pathway in shaping GABA synapse development. We expect that our studies of this experimentally tractable circuit in the worm will provide exciting new insights into mechanisms for biological regulation of iAChRs in the brain, and their important roles in regulating inhibitory signaling. Additionally, the identification and functional characterization of conserved genetic pathways that regulate synapse formation and function in our experiments will ultimately yield novel drug targets for therapeutic strategies designed to treat neurological disorders involving cholinergic signaling.