Molecular Mechanisms Regulating Axon Guidance Receptor Activity

描述（由申请人提供）：随着神经系统的发育，轴突被沿着特定的途径引导以找到它们的目标并建立功能性连接。连接的精确模式对于神经系统的正常功能至关重要。轴突迁移是由细胞外环境中的引导线索引导的。在迁移轴突的表面，受体检测到线索并产生控制细胞骨架动力学的信号，以指导轴突延伸。已经鉴定了几类引导线索和受体，包括β-6/netrin线索和β-40/DCC受体。当受体被引导信号连接时，决定定向反应的分子机制还没有很好的理解。为了探索轴突反应的分子基础，我们在C. elegans的突变，抑制由特定UNC-6错义等位基因rh 46引起的轴突导向缺陷。我们的研究结果表明，我们发现了突变，增强了β-40信号时，β-40连接的β-6。一个突变是clec-38的功能丧失等位基因，其编码具有跨膜和细胞外C型凝集素样结构域的蛋白质。我们的初步研究结果表明，CLEC-38负调控在几个不同的神经元中的α-40信号。在一种情况下，clec- 38功能的丧失导致神经元细胞体迁移的失败和其轴突的早熟的依赖于clec-6的形成。我们还发现了unc-40胞外域序列中的错义突变，它与unc-6（rh 46）结合会导致新的轴突迁移模式。当unc- 6（rh 46）被unc-6（rh 46 ur 282）或unc-6（rh 46 ur 301）取代时，这种反应受到抑制，这些等位基因具有抑制原始rh 46突变的第二位点突变。这些基因内突变也从筛选中回收。这些观察结果表明，在体内的α-6和α-40胞外域之间的相互作用，它们表明，连接确认的受体影响轴突反应的性质。我们建议进一步研究通过其调节的信号的分子机制。我们计划进一步表征CLEC-38，确定调节α- 40信号传导的其他组分，从遗传学上剖析控制α-40轴突反应的信号传导，并扩展我们的遗传筛选。公共卫生相关性：神经元必须建立适当的连接，以使神经系统发挥作用。了解使分子能够将神经元引导到其目标的分子机制可以为影响神经系统布线的疾病提供新的见解，并且还可以证明对于开发治疗药物以治疗因损伤或疾病而受损的神经是有用的。

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.