Molecular mechanisms of axon guidance and neural connectivity

轴突引导和神经连接的分子机制

• 批准号: 7741327
• 负责人: JONATHAN R TERMAN
• 金额: $ 35.33万
• 依托单位: UT SOUTHWESTERN MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-20 至 2014-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7741327
• 关键词: Actins; Animals; Axon; Behavior; Binding; Biochemical; Biochemical Genetics; Biological Models; Complex; Cues; Cytoskeleton; Development; Disease; Drosophila genus; Embryo; Emotions; Faculty; Family; GTP-Binding Proteins; GTPase-Activating Proteins; Genes; Genetic; Goals; Guanine Nucleotide Exchange Factors; Guanine Nucleotide-Releasing Factor 2; Guanosine Triphosphate Phosphohydrolases; Human; Integral Membrane Protein; Integrins; Invertebrates; K-Series Research Career Programs; Learning; Ligands; Light; Link; Maintenance; Mammals; Mediating; Mediator of activation protein; Mental disorders; Modeling; Molecular; Monomeric GTP-Binding Proteins; Motor; Nervous system structure; Neuroglia; Neurologic; Neurons; Organism; Oxidation-Reduction; Oxidoreductase; Paper; Play; Positioning Attribute; Protein Family; Proteins; Psyche structure; Recovery; Research; Role; SH3 Domains; Semaphorins; Signal Pathway; Signal Transduction; Site-Directed Mutagenesis; Solutions; Specific qualifier value; Surface; System; Testing; Therapeutic; Thinking; Time; Trauma; United States National Institutes of Health; Vertebrates; Work; axon guidance; extracellular; fly; genetic regulatory protein; human BCAR1 protein; in vivo; insight; plexin; post-doctoral training; programs; public health relevance; ras GTPase-Activating Proteins; ras Guanine Nucleotide Exchange Factors; receptor; relating to nervous system

DESCRIPTION (provided by applicant): A normal functioning human nervous system requires the interconnection of billions of neurons. Improper formation or maintenance of these connections leads to neurological abnormalities that result in a number of mental diseases and disorders. How are these circuits assembled and integrated? The semaphorins are one of the largest protein families involved in the formation and maintenance of axonal connections. Semaphorins are phylogenetically conserved secreted and transmembrane proteins found in invertebrates and in vertebrates. Semaphorins utilize plexins, a family of large transmembrane proteins found on the axonal surface, as receptors to direct their effects. How plexins actually transduce semaphorin signals is poorly understood but is of importance for learning how semaphorins sculpt and maintain the nervous system. So what strategies will further define these important mechanisms by which semaphorins and plexins direct neural connectivity? Work over the past twenty years has revealed that the molecular mechanisms of axon guidance and connectivity are remarkably well-conserved between simple and complex animals. Simple animals like flies use many of the same axon guidance signals as mammals. In light of this conservation, the goal of my research program is to focus on a small group of axons within the simple nervous system of the fly embryo and characterize the molecules and mechanisms that guide them to their targets. Using this strategy, I recently identified a new family of intracellular proteins, the MICALs, that are critical for directing semaphorin/plexindependent neural connectivity. There is one MICAL gene in simple organisms like flies, while three separate MICAL genes are found in mammals including humans that are also important for mediating the effects of semaphorins and plexins. Interestingly, MICAL proteins contain several regions known to interact with the cytoskeletal machinery necessary for allowing axons to grow, navigate, and form their connections. MICALs also contain an oxidoreductase domain, the integrity of which is required for Semaphorin axonal connectivity. The presence of this oxidoreductase domain implicates for the first time oxidation-reduction signaling mechanisms in semaphorin-mediated connectivity. One important question that is the focus of this proposal is to identify the molecules through which MICAL steers an axon. Initial insight into this question has come with our recent identification that MICAL interacts with the SH3-domain containing protein Cas in neurons. Cas is a critical regulator of actin cytoskeletal dynamics in non-neuronal cells and we find that Cas and MICAL link Plexins and integrins to mediate axon guidance. Our preliminary results now reveal that Cas interacts with a specific mediator of G protein signaling suggesting the possibility that MICAL and Cas play a role in regulating GTPases in navigating axons. We will use in vivo genetic and biochemical approaches and the model fly axon system to test the hypothesis that specific GTPases and their regulators are mediators of axon navigation and play an important role in the intracellular signaling mechanisms utilized by semaphorins during axon guidance. PUBLIC HEALTH RELEVANCE: Our nervous systems control such remarkable abilities as putting our thoughts to paper only because our neurons communicate in highly organized networks. The goal of this proposal is to better characterize the molecules and mechanisms that enable neurons to find and connect with one another. Understanding how these networks are assembled, integrated, and maintained will suggest solutions to diminish the burden of mental illness, reveal fundamental mechanisms underlying thought, emotion, and behavior, identify therapeutic strategies for a number of mental disorders, and contribute to healthy recovery following neural trauma.

描述（由申请人提供）：正常功能的人类神经系统需要数十亿神经元的互连。这些连接的不正确形成或维持会导致神经异常，从而导致许多精神疾病和障碍。这些电路是如何组装和集成的？信号蛋白是参与轴突连接形成和维持的最大的蛋白质家族之一。信号蛋白是在无脊椎动物和脊椎动物中发现的具有系统发育保守性的分泌和跨膜蛋白。信号蛋白利用丛蛋白作为受体来指导其作用，丛蛋白是在轴突表面发现的大型跨膜蛋白家族。神经丛实际上是如何传递信号素信号的，人们知之甚少，但对于学习信号素如何塑造和维持神经系统是很重要的。那么，什么样的策略将进一步定义这些重要的机制，信号素和丛蛋白通过这些机制直接指导神经连接呢？过去二十年的研究表明，在简单动物和复杂动物之间，轴突引导和连接的分子机制是非常保守的。像苍蝇这样的简单动物使用许多与哺乳动物相同的轴突引导信号。鉴于这种保守性，我的研究计划的目标是关注苍蝇胚胎简单神经系统中的一小群轴突，并表征引导它们到达目标的分子和机制。利用这种策略，我最近发现了一个新的细胞内蛋白家族，MICALs，它对指导信号蛋白/丛无关的神经连接至关重要。在像苍蝇这样的简单生物中有一个micical基因，而在包括人类在内的哺乳动物中发现了三个独立的micical基因，它们对调节信号蛋白和丛蛋白的作用也很重要。有趣的是，micical蛋白含有几个已知与细胞骨架机制相互作用的区域，这些机制是允许轴突生长、导航和形成连接所必需的。MICALs还含有氧化还原酶结构域，其完整性是信号蛋白轴突连接所必需的。这种氧化还原酶结构域的存在首次暗示了信号蛋白介导的连接中的氧化还原信号机制。这个提议的一个重点问题是确定micical控制轴突的分子。我们最近发现micical与神经元中含有sh3结构域的Cas蛋白相互作用，从而初步了解了这个问题。在非神经元细胞中，Cas是肌动蛋白细胞骨架动力学的关键调节因子，我们发现Cas和micical连接丛蛋白和整合蛋白介导轴突引导。我们的初步结果现在揭示了Cas与G蛋白信号传导的特定介质相互作用，这表明micical和Cas可能在调节gtpase在轴突导航中的作用。我们将使用体内遗传和生化方法以及模型果蝇轴突系统来验证特定gtpase及其调节因子是轴突导航的介质，并在轴突引导过程中信号蛋白利用的细胞内信号机制中发挥重要作用的假设。与公共健康相关：我们的神经系统控制着把我们的想法写下来这样非凡的能力，仅仅是因为我们的神经元在高度组织的网络中进行交流。这项提议的目标是更好地表征分子和机制，使神经元能够找到并连接彼此。了解这些网络是如何组装、整合和维持的，将为减轻精神疾病的负担提供解决方案，揭示思想、情感和行为的基本机制，确定许多精神障碍的治疗策略，并有助于神经创伤后的健康恢复。