TRANS-SYNAPTIC SIGNALING DURING NEUROMUSCULAR DEVELOPMENT

描述(申请人提供)：尽管核因子-kB在免疫、炎症和癌症方面已被深入研究，但对核因子-kB在神经系统中的作用了解甚少。在中枢神经系统中，核因子-kB信号系统与神经退行性疾病、癫痫和神经元可塑性有关。在神经肌肉接头，核因子-kB的激活与神经退行性疾病(营养不良和恶病质)和失神经相关的肌肉萎缩机制有关。尽管有这些观察，激活神经系统内的核因子-kB信号的细胞和分子机制仍有待明确。我们最近证明了在果蝇NMJ中，核因子-kB/背侧、IkB/仙人掌和IRAK/Pelle激酶在突触后肌肉中起着控制谷氨酸受体密度的作用，这一过程与脊椎动物NMJ中的核因子-kB的功能有关(Heckscher和Davis，在综述中)。我们现在已经有了初步的数据，确定了一个跨突触的信号系统，可以在NMJ控制NF-kB。在正向遗传筛查中，我们发现了分泌配体(TNFa)及其突触后受体(TNFR2)的突变，这些突变损害了果蝇NMJ的GluR丰度。我们提供的初步数据表明，肿瘤坏死因子-α基因在位于NMJ附近的外周神经胶质细胞中表达，并且这种来源的肿瘤坏死因子-α是控制Glur水平所必需的且足够的。此外，已证实在果蝇肌肉中有TNFR2受体的表达。因此，我们假设，在NMJ，肿瘤坏死因子-α和肿瘤坏死因子受体2基因定义了一个新的、神经胶质细胞到肌肉、跨突触的信号系统。重要的是，已经证明在其他果蝇组织中，TNFR2受体可以激活下游的NFkB信号。因此，我们假设存在一个保守的神经胶质-肌肉信号系统，在胚胎后发育过程中控制Glur水平和神经肌肉功能。我们建议在果蝇NMJ上进行实验来定义和阐述这个信号系统。鉴于这些信号分子在进化上是高度保守的，我们预测我们的数据将与哺乳动物神经疾病和损伤过程中核因子-kB的功能直接相关。公共卫生相关性：在神经系统中，核因子-kB信号系统与神经退行性疾病、癫痫和对神经元损伤的反应机制有关。尽管这个进化上保守的信号系统很重要，但人们对NF-kB如何参与这些不同的过程知之甚少。我们提出的实验不仅将定义神经系统中核因子-kB是如何激活的，而且还将定义可能与核因子-kB在损伤和疾病中的作用直接相关的核因子-kB信号的输出。

DESCRIPTION (provided by applicant): Although NF-kB has been studied intensively in the context of immunity, inflammation and cancer, far less is understood about the function of NF-?B in the nervous system. In the central nervous system, NF-kB signaling system has been implicated in neurodegenerative disease, epilepsy, and neuronal plasticity. At the neuromuscular junction, activation of NF-kB has been implicated in the mechanisms of muscle wasting associated with neurodegenerative disease (dystrophies and cachexia) and denervation. Despite these observations, the cellular and molecular mechanisms that activate NF-kB signaling within the nervous system remains to be clearly defined. We recently demonstrated that NF- kB/Dorsal, IkB/Cactus and IRAK/Pelle kinase function within postsynaptic muscle to control glutamate receptor density at the Drosophila NMJ, a process relevant to the function of NF-kB at the vertebrate NMJ (Heckscher and Davis, in review). We now have preliminary data identifying a trans-synaptic signaling system that could control NF-kB at the NMJ. In a forward genetic screen we identified mutations in a secreted ligand (TNFa) and its postsynaptic receptor (TNFR2) that impair GluR abundance at the Drosophila NMJ. We present preliminary data that the TNF-alpha gene is expressed in peripheral glia that reside near the NMJ, and that this source of TNF-alpha is necessary and sufficient to control GluR levels. In addition, it has been established that the TNFR2 receptor is expressed in Drosophila muscle. Thus, we hypothesize that the TNF-a and TNFR2 genes define a new, glia-to-muscle, trans-synaptic signaling system at the NMJ. Importantly, it has been demonstrated that the TNFR2 receptor can activate downstream NFkB signaling in other Drosophila tissues. Therefore, we hypothesize the existence of a conserved, glial-to-muscle signaling system that controls GluR levels and neuromuscular function during postembryonic development. We propose experiments to define and elaborate upon this signaling system at the Drosophila NMJ. Given that these signaling molecules are highly evolutionarily conserved, we predict that our data will have direct relevance to the function of NF-kB during neural disease and injury in mammals. PUBLIC HEALTH RELEVANCE: In the nervous system, NF-kB signaling system has been implicated in the mechanisms of neurodegenerative disease, epilepsy, and the response to neuronal injury. Despite the importance of this evolutionarily conserved signaling system, very little is known about how NF- kB participates in these diverse processes. We propose experiments that will not only define how NF-kB is activated in the nervous system, but will also define an output for NF-kB signaling that may be directly relevant to the role of NF-kB during injury and disease.