The Wingless Transduction Pathway in Synapse Development

描述（由申请人提供）：该项目的长期目标是阐明突触发育和可塑性的信号机制。我们在上一个资助周期的研究表明，wnt是关键的和系统发育上保守的突触组织者，通过外泌体（含有蛋白质和rna的细胞外囊泡）在果蝇幼虫神经肌肉连接处（NMJ）的突触按钮释放。我们的研究也提供了由Synaptotagmin 4介导的逆行信号传递Wnt信号，并且也受突触前按钮释放的外泌体控制。这些研究将跨突触外泌体通信作为突触前和突触后修饰的关键协调者。通过外泌体的细胞-细胞信号传导在免疫、癌症扩散和中枢神经系统的细胞间朊病毒传播过程中刚刚开始被记录。此外，外泌体正在成为递送靶向治疗的有希望的载体。然而，大多数关于外泌体的研究都是在细胞培养中进行的，外泌体在神经系统中的功能几乎是未知的。我们证明了外泌体在体内介导跨突触信号传导，建立了果蝇作为一个强大的模型系统来有效地揭示外泌体释放和跨突触转移的机制。Wnt失调与许多认知障碍有关，如精神分裂症和阿尔茨海默病。因此，了解神经系统中Wnt信号传导的机制对设计治疗这些疾病的临床策略具有重要意义。在这个项目中，我们的实验策略将广泛使用遗传学和体内最先进的细胞方法，来阐明外泌体在突触位点释放的机制以及外泌体调节突触发育和可塑性的原理。我们将(1)确定通过突触按钮介导外泌体释放的分子机制，(2)确定通过外泌体逆行信号的突触特异性或全局性，以及(3)表征Wnt蛋白在Synaptotagmin 4介导的逆行信号传导中的作用。该项目的结果将构成我们对突触中Wnt信号传导的理解的重大进展，并有望加速外泌体靶向治疗的发展。

DESCRIPTION (provided by applicant): The long-term goal of this project is to elucidate signaling mechanisms underlying synapse development and plasticity. Our studies in the previous funding cycle demonstrate that Wnts, pivotal and phylogenetically conserved synaptic organizers, are released via exosomes, extracellular vesicles containing proteins and RNAs, at synaptic boutons of the Drosophila larval neuromuscular junction (NMJ). Our studies also provide evidence that a retrograde signal mediated by Synaptotagmin 4 conveys Wnt signals, and is also controlled by exosome release from presynaptic boutons. These studies place trans-synaptic exosome communication as a key coordinator of pre- and postsynaptic modifications. Cell-cell signaling through exosomes is just beginning to be documented during immunity, the spread of cancer, and intercellular prion transmission in the CNS. In addition, exosomes are emerging as promising vectors for the delivery of targeted therapies. However, most studies of exosomes have been carried out in cell culture, and exosome function in the nervous system is virtually unknown. Our demonstration that exosomes mediate trans-synaptic signaling in vivo, establish Drosophila as a powerful model system to efficiently unravel mechanisms of exosome release and trans-synaptic transfer. Wnt misregulation is associated with a number of cognitive disorders, such as Schizophrenia and Alzheimer's disease. Thus, understanding the mechanisms of Wnt signaling in the nervous system has important implications for the design of clinical strategies to treat these conditions. In this project our experimental strategies will mak extensive use of genetics and state-of the art cellular approaches in vivo, to elucidate the mechanisms of exosome release at synaptic sites and the principles underlying the exosome regulation of synapse development and plasticity. We will (1) identify the molecular machinery mediating exosome release by synaptic boutons, (2) determine the synapse specificity or global nature of retrograde signaling through exosomes, and (3) characterize the role of a Wnt protein in Synaptotagmin 4-mediated retrograde signaling. The outcomes of this project will constitute a significant advancement in our understanding of Wnt signaling at synapses, and promises to accelerate the development of exosomes for targeted therapies.