Molecular Mechanisms Regulating Axon Guidance Receptor Activity

调节轴突引导受体活性的分子机制

• 批准号: 7679878
• 负责人: WILLIAM G WADSWORTH
• 金额: $ 34.13万
• 依托单位: UNIV OF MED/DENT NJ-R W JOHNSON MED SCH
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-03-01 至 2014-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7679878
• 关键词: Acetylcholine; Affect; Alleles; Axon; C-Type Lectins; Caenorhabditis elegans; Cell surface; Cells; Cues; Defect; Development; Disease; Dorsal; Environment; Failure; Genes; Genetic; Genetic Screening; Immigration; Injury; Ligands; Link; Mediating; Missense Mutation; Molecular; Molecular Conformation; Mutate; Mutation; Nature; Nerve; Nervous System Physiology; Nervous system structure; Neurons; Pathway interactions; Pattern; Process; Proteins; Regulatory Pathway; Research; Role; Signal Transduction; Site; Source; Surface; System; Testing; Therapeutic Agents; axon guidance; base; extracellular; in vivo; insight; loss of function; member; migration; mutant; neuron loss; neuronal cell body; presynaptic; public health relevance; receptor; response; synaptogenesis; transmission process

DESCRIPTION (provided by applicant): As the nervous system develops, axons are guided along specific pathways to find their targets and make functional connections. The precise pattern of connections is essential for proper nervous system function. Axon migrations are directed by guidance cues in the extracellular environment. On the surface of migrating axons, receptors detect the cues and produce signals that control cytoskeletal dynamics to direct where an axon extends. Several classes of guidance cues and receptors have been identified, including the UNC-6/netrin cue and the UNC-40/DCC receptor. The molecular mechanisms that determine the directional response when a receptor is ligated by a guidance cue are not well understood. To explore the molecular basis of axon responses, we preformed a genetic screen in C. elegans for mutations that suppress axon guidance defects caused by a specific unc-6 missense allele, rh46. Our results indicate that we uncovered mutations that enhance UNC-40 signaling when UNC-40 is ligated by UNC-6. One mutation is a loss-of-function allele of clec-38, which encodes a protein with a transmembrane and extracellular C-type lectin-like domains. Our preliminary results indicate that clec-38 negatively regulates UNC-40 signaling in several different neurons. In one case, loss of clec- 38 function causes the failure of a neuron cell body to migrate and the precocious UNC-6-dependent formation of its axon. We also uncovered a missense mutation within the unc-40 ectodomain sequence that in combination with unc-6(rh46) causes new axons migration patterns. This response is suppressed when unc- 6(rh46) is replaced with unc-6(rh46ur282) or unc-6(rh46ur301), alleles that have second site mutations that suppress the original rh46 mutation. These intragenic mutations were also recovered from the screen. These observations indicate an interaction between UNC-6 and the UNC-40 ectodomain in vivo and they suggest that the ligated confirmation of the receptor influences the nature of the axon response. We propose to further study the molecular mechanisms through which the UNC-40 signals are regulated. We plan to further characterize CLEC-38, determine other components that regulate UNC- 40 signaling, genetically dissect the signaling which controls the UNC-40 axon response, and extend our genetic screening. PUBLIC HEALTH RELEVANCE: Neurons must make the proper connections in order for a nervous system to function. Understanding the molecular mechanisms that enable molecules to direct neurons to their targets could provide new insights into disorders that affect the wiring of the nervous system and could also prove useful for developing therapeutic agents to treat nerves damaged by injuries or disease.

描述（由申请人提供）：随着神经系统的发展，轴突沿特定途径引导以找到目标并建立功能连接。确切的连接模式对于适当的神经系统功能至关重要。轴突迁移由细胞外环境中的指导提示指导。在迁移轴突的表面上，受体检测线索并产生信号，以控制细胞骨架动力学直接轴突延伸的位置。已经确定了几类引导提示和受体，包括UNC-6/Netrin CUE和UNC-40/DCC受体。确定受体通过引导提示绑扎时确定方向反应的分子机制尚不清楚。为了探索轴突反应的分子基础，我们在秀丽隐杆线虫中预先形成了一个遗传筛选，以抑制由特定的UNC-6错过等位基因RH46引起的轴突引导缺陷。我们的结果表明，当UNC-40与UNC-6连接时，我们发现了增强UNC-40信号传导的突变。一种突变是Clec-38的功能丧失等位基因，该等位基因用跨膜和细胞外C型凝集素样结构域编码蛋白质。我们的初步结果表明，CLEC-38在几种不同的神经元中负调控UNC-40信号传导。在一种情况下，Clec-38功能的丧失会导致神经元细胞体的失败迁移，并且早熟的UNC-6依赖性形成轴突。我们还发现了UNC-40胞外域序列中的错义突变，该序列与UNC-6（RH46）结合起来会导致新的轴突迁移模式。当UNC-6（RH46）被UNC-6（RH46UR282）或UNC-6（RH46UR301）取代时，该反应被抑制，这是具有抑制原始RH46突变的第二个位点突变的等位基因。这些基因内突变也从屏幕上回收了。这些观察结果表明在体内UNC-6与UNC-40胞外域之间存在相互作用，它们表明对受体的连接确认会影响轴突反应的性质。我们建议进一步研究UNC-40信号的分子机制。我们计划进一步表征CLEC-38，确定调节UNC 40信号传导的其他组件，遗传剖析控制UNC-40轴突响应的信号传导，并扩展我们的基因筛选。公共卫生相关性：神经元必须建立适当的连接才能使神经系统发挥作用。了解使分子能够将神经元引导到目标的分子机制可以为影响神经系统接线的疾病提供新的见解，也可能证明对开发治疗剂治疗受伤或疾病受损的神经有用。