SWS/NTE function in neurodegeneration and axonopathy

描述（由申请人提供）：本提案的重点是研究由瑞士奶酪（sws）基因突变引起的轴突病和进行性神经退行性变的基本机制。SWS是人类神经病变靶酯酶（NTE）的同源物，是有机磷（OP）诱导的延迟性神经病变（OPIDN）的关键参与者，OPIDN是由许多农药和神经毒剂中发现的有机磷引起的。小鼠NTE的神经元缺失会导致神经系统的进行性退化模式，这与突变的果蝇惊人地相似，而NTE的完全缺失是胚胎致命的。此外，最近描述的人类基因突变导致遗传性痉挛性截瘫，称为NTE相关运动神经元障碍。实验证实了SWS和NTE之间的功能守恒，小鼠NTE可以替代果蝇蛋白，恢复SWS缺失引起的退行性表型。SWS和NTE均能水解相同的人工底物，且均与膜脂稳态有关；然而，它们的内源性功能在很大程度上仍然未知。在之前的资助期内，SWS蛋白中的几个结构域被确定并显示为功能必需。这包括一个结合蛋白激酶a （PKA-C3）的特定催化亚基的结构域，从而抑制其激酶活性。PKA-C3及其在脊椎动物中的同源物人类PrKX和小鼠PKA-C3形成了一类新的催化亚基，它们彼此之间的关系比同一物种中的其他催化亚基更密切。它们都在神经系统中表达，但它们的功能迄今为止尚不清楚。本课题将验证SWS和PKA- c3形成一种非常规的PKA复合物的假设，该复合物具有双重功能：调节PKA- c3的细胞内定位和激酶活性，并控制SWS的酯酶活性。此外，这一独特的PKA亚基在神经存活、sws诱导表型和有机磷诱导毒性中的作用将被研究。由于这些蛋白在果蝇和脊椎动物之间的高度保守性，在这个成熟的模型系统中提出的研究可以为导致相关人类疾病和毒素诱导的神经病变进行性变性的机制提供重要的见解。除了直接提出的范围之外，这些研究还可以扩展我们对轴突病和神经元细胞死亡的共同机制的理解，这也发生在对各种其他神经元损伤的反应中。

DESCRIPTION (provided by applicant): The focus of this proposal is to study the basic mechanisms underlying axonopathy and progressive neurodegeneration that are caused by mutations in the swiss cheese (sws) gene. SWS is the ortholog of human Neuropathy Target Esterase (NTE), a key player in organophosphate (OP)-induced delayed neuropathy (OPIDN) which is caused by organophosphates found in many pesticides and nerve agents. Neuronal loss of NTE in mice results in a pattern of progressive degeneration of the nervous system that is surprisingly similar to mutant flies, while the complete loss of NTE is embryonic lethal. In addition, recently described mutations in the human gene cause a hereditary spastic paraplegia called NTE--related Motor Neuron Disorder. The functional conservation between SWS and NTE was confirmed by experiments showing that mouse NTE can replace the fly protein, reverting the degenerative phenotype caused by the loss of SWS. SWS and NTE can both hydrolyze the same artificial substrate, and both have been connected with membrane lipid homeostasis; however, their endogenous functions are still largely unknown. During the previous funding period, several domains in the SWS protein were identified and shown to be functionally required. This includes a domain that binds a specific catalytic subunit of protein kinase A (PKA-C3), thereby inhibiting its kinase activity. PKA-C3, and its vertebrate orthologs PrKX in human and Pkare in mice, form a novel class of catalytic subunits that are more closely related to each other than to other catalytic subunits within the same species. They are all expressed in the nervous system, but their functions are so far unknown. The current proposal will tests the hypothesis that SWS and PKA-C3 form an unconventional PKA complex that has a dual function: regulating the intracellular localization and kinase activity of PKA-C3, and controlling the esterase activity of SWS. Furthermore, the role of this unique PKA subunit in neural survival, sws-induced phenotypes, and organophosphate induced toxicity will be investigated. Due to the high conservation of these proteins between Drosophila and vertebrates, the proposed studies in this well-established model system can provide important insights into the mechanisms that lead to progressive degeneration in the related human disease and in toxin-induced neuropathy. Beyond the scope of the immediate proposal, these studies may also expand our understanding of common mechanisms of axonopathy and neuronal cell death, which also occurs in response to a variety of other neuronal insults.