Cell autonomous and non autonomous induction of degeneration in Drosophila

项目摘要 在几种人类病理学中观察到神经元或肌肉的退化，包括阿尔茨海默氏症， 帕金森病和遗传性痉挛性截瘫（HSP）的神经元变性，废用性萎缩， 癌症恶病质和肌肉退化的败血症。尽管最近取得了许多进展， 这些退化过程的潜在机制仍不完全清楚。产生这样 基于对热休克蛋白机制的深入了解，PI最近建立了一个果蝇模型。具体重点是 在atlastin（atl，痉挛性截瘫基因3A）中，其编码ER融合蛋白。基于先前的 在神经元中atl敲低导致进行性的、年龄依赖性的运动缺陷的观察中，我们发现， 询问这种基因敲除是否也会导致进行性细胞退化。成人胸部检查 肌肉组织显示，无论是神经元还是肌肉的atl丢失都引起了与 与许多其他病理包括积累的聚集体含有泛素，增加 活性氧（ROS）和JNK/Foxo应激反应途径的活化。施用所述 抑制Tor激酶的药物雷帕霉素或减少Tor基因剂量逆转了其中许多 至少部分病理学，表明atl丧失可能激活肌肉Tor。肌肉Tor和Foxo激活 在去神经诱导的肌肉萎缩中也观察到。在此应用中，提出了实验 以阐明ATL损失引起进行性肌肉病理的机制。目标#1将测试 假设肌肉Tor由atl损失激活，确定Tor活性是否足够以及必要， atl损失表型，并测试Tor活性通过抑制肌肉退化促进肌肉退化的预测。 自噬目标#2将检查激活的Tor和增加的ROS之间的因果关系， ROS和JNK/Foxo应激途径之间的关系。特别是，我们将测试两个非互斥的 解释Foxo激活假设：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激活其靶点S6 K， turn下调胰岛素信号传导，从而降低Foxo抑制剂Akt的活性。目标#3将测试 神经元atl缺失通过减弱交感神经能神经肌肉激活肌肉Tor的假说 传输特别地，将确定是否缺失一种谷氨酸受体，先前显示为 足以激活肌肉Tor，将引起与神经元atl观察到的类似的肌肉病理学。 击倒。此外，将确定神经元atl缺失是否赋予与那些神经元atl缺失类似的神经元表型。 由谷氨酸受体缺失引起。这些实验的成功完成将提供新的和 关键的机制见解，将由ATL丧失赋予的有缺陷的突触输入与肌肉变性联系起来。的 PI预计，这些实验也将提供适用于神经元的机制见解。 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.