Cell autonomous and non autonomous induction of degeneration in Drosophila

项目摘要 在几种人类疾病中都可以观察到神经元或肌肉的退化，包括阿尔茨海默氏症， 帕金森氏症和遗传性痉挛截瘫(HSP)，用于神经元变性和废用性萎缩， 癌症恶病质，肌肉变性败血症。尽管最近取得了许多进展，但分子 这些退化过程背后的机制(S)仍然不完全清楚。为了产生这样的 在机械论的洞察下，PI最近为HSP建立了一个果蝇模型。具体的焦点是 在atlastin(AT1，痉挛截瘫基因3A)中，编码内质网融合蛋白。基于以前的 观察到神经元中的AT1基因敲除会导致进行性的、年龄相关的运动障碍 当被问及这种基因敲除是否也导致了进行性细胞退化。成人胸廓的调查研究 肌肉学研究表明，无论是神经元还是肌肉的ATL丢失都会导致进行性退行性变。 随着包括含有泛素的聚集体堆积在内的许多其他病理现象的增加 活性氧(ROS)和激活JNK/FOXO应激反应通路。管理 药物雷帕霉素可以抑制Tor激酶，或者减少Tor基因的剂量，从而逆转了许多这种情况 至少部分病理改变，表明ATL的丢失可能激活了肌肉Tor。肌肉Tor与FOXO激活 在失神经引起的肌肉萎缩中也观察到了这种情况。在这一应用中，提出了实验 目的：阐明ATL缺失导致进行性肌肉病变的机制。目标1号将测试 假设肌肉Tor是由ATL丢失激活的，确定Tor活动是否充分且必要 ATL丢失表型，并检验Tor活性通过抑制Tor活性促进肌肉退变的预测 自噬。目标#2将研究激活的ToR和增加的ROS之间的因果关系，以及 ROS与JNK/FOXO应激通路之间的关系。特别是，我们将测试两个非互斥 解释FOXO激活的假说；首先，激活的Tor增加ROS，这反过来又负责 JNK激活，最后是FOXO激活，第二，激活的Tor激活其目标S6K，该S6K在 下调胰岛素信号，从而降低FOXO抑制剂Akt的活性。Aim#3将测试 神经元ATL缺失通过减弱谷氨酸能神经肌肉而激活肌肉Tor的假说 变速箱。具体地说，将确定是否缺失一个谷氨酸受体，先前显示为 足以激活肌肉Tor，会引起与神经元ATL相似的肌肉病理 击倒对手。此外，还将确定神经元ATL缺失是否会使神经元表型类似于 谷氨酸受体缺失所致。这些实验的成功完成将提供新的和 将ATL缺失导致的突触输入缺陷与肌肉退变联系起来的关键机制洞察力。这个 PIS预计，这些实验还将提供适用于神经元的机械洞察力 这将使这些实验具有广泛的医学意义。

Project Summary Degeneration of neurons or muscle are observed in several human pathologies, including Alzheimer's, Parkinson's and the hereditary spastic paraplegias (HSP) for neuronal degeneration, and disuse atrophy, cancer cachexia, and sepsis for muscle degeneration. Despite many recent advances, the molecular mechanism(s) underlying these degenerative processes remain incompletely understood. To generate such mechanistic insights, the PIs have recently established a Drosophila model for the HSPs. The specific focus is in atlastin (atl, Spastic Paraplegia Gene 3A), which encodes an ER fusion protein. Based on the previous observation that atl knockdown in neurons causes progressive, age-dependent locomotor deficits, the we asked if this knockdown also caused progressive cellular degeneration. Investigations into the adult thoracic musculature revealed that atl loss from either neuron or muscle caused progressive degeneration associated with a number of other pathologies including accumulation of aggregates containing ubiquitin, increased reactive oxygen species (ROS), and activation of the JNK/Foxo stress response pathway. Administering the drug rapamycin, which inhibits the Tor kinase, or decreasing Tor gene dosage reversed many of these pathologies at least partially, indicating that atl loss might activate muscle Tor. Muscle Tor and Foxo activation have also been observed in denervation-induced muscle atrophy. In this application, experiments are proposed to elucidate the mechanisms by which atl loss causes progressive muscle pathologies. Aim #1 will test the hypothesis that muscle Tor is activated by atl loss, determine if Tor activity is sufficient as well as necessary for atl loss phenotypes, and test the prediction that Tor activity promotes muscle degeneration by inhibiting autophagy. Aim #2 will examine the causal relationship between activated Tor and increased ROS, and between ROS and the JNK/Foxo stress pathway. In particular, we will test two non-mutually exclusive hypotheses explaining Foxo activation; first, that activated Tor increases ROS, which in turn is responsible for JNK activation, and finally Foxo activation, and second, that activated Tor activates its target S6K, which in turn down-regulates insulin signaling, thus decreasing activity of the Foxo inhibitor Akt. Aim #3 will test the hypothesis that neuronal atl loss activates muscle Tor by attenuating glutamatergic neuromuscular transmission. In particular, it will be determined if deletion of one glutamate receptor, previously shown to be sufficient to activate muscle Tor, will cause similar muscle pathologies as is observed by neuronal atl knockdown. In addition, it will be determined if neuronal atl loss confers neuronal phenotypes similar to those conferred by glutamate receptor deletion. Successful completion of these experiments will provide novel and critical mechanistic insights linking defective synaptic input conferred by atl loss to muscle degeneration. The PIs anticipate that these experiments will also provide mechanistic insights applicable to neuronal degeneration as well, which will give these experiments a broad medical relevance.