SWS/NTE function in neurodegeneration and axonopathy

描述（由申请人提供）：本提案的重点是研究瑞士奶酪（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是人类神经病靶向酯酶（NTE）的直系同源物，NTE是有机磷酸盐（OP）诱导的迟发性神经病（OPIDN）的关键参与者，OPIDN由许多农药和神经毒剂中发现的有机磷酸盐引起。小鼠NTE的神经元缺失导致神经系统进行性变性的模式，这与突变果蝇惊人地相似，而NTE的完全缺失是胚胎致死的。此外，最近描述的人类基因突变会导致一种称为NTE相关运动神经元障碍的遗传性痉挛性截瘫。SWS和NTE之间的功能保守性通过实验证实，小鼠NTE可以取代苍蝇蛋白，恢复由SWS丢失引起的退化表型。SWS和NTE都可以水解相同的人工底物，并且都与膜脂质稳态有关;然而，它们的内源性功能在很大程度上仍然未知。在上一个资助期间，确定了SWS蛋白中的几个结构域，并显示出功能上的需要。这包括结合蛋白激酶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及其在人类中的脊椎动物直系同源物PrKX和在小鼠中的Pkare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，但它们的功能迄今尚不清楚。目前的建议将测试的假设，SWS和PKA-C3形成一个非常规的PKA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，这种独特的PKA亚基在神经存活，SWS诱导的表型，和有机磷诱导的毒性的作用将进行研究。由于这些蛋白质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的拟议研究可以为相关人类疾病和毒素诱导的神经病变中导致进行性变性的机制提供重要的见解。除了直接提议的范围外，这些研究还可能扩大我们对轴突病和神经元细胞死亡的共同机制的理解，轴突病和神经元细胞死亡也会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.