Genetics Analysis of Neuronal Hypoxic Stress Resistance

描述（由申请人提供）：创伤性脑损伤（TBI）和缺血性卒中是发病和残疾的主要原因，通过缺氧兴奋性毒性杀死神经元。其潜在机制被认为是谷氨酸受体过度活化、钙稳态失调和线粒体功能障碍的组合。具体而言，由创伤或中风引起的缺氧导致膜去极化，并因此从受影响的神经元释放神经递质谷氨酸。高水平的急性谷氨酸过度激活邻近神经元上的受体，从而导致钙内流和兴奋性毒性。线粒体动力学改变，影响ATP的产生，以及钙和活性氧（ROS）从神经元线粒体的释放。直接干扰谷氨酸受体活化的药物由于其对受体生理功能的显著影响而具有有限的临床应用性。因此，重要的是要确定新的治疗靶点，以减轻TBI或中风后的兴奋性毒性。谷氨酸受体的调节运输可以改变突触功效的发现改变了对神经元创伤后受体促进兴奋性毒性的机制的思考。许多物种，包括哺乳动物，有保护自己免受谷氨酸介导的兴奋性毒性的机制，尽管这些机制知之甚少。事实上，在一些培养的神经元系统中，创伤后缺氧后谷氨酸受体进出突触膜的运动可以调节兴奋性毒性。谷氨酸受体运输的变化是否会导致完整动物的神经元死亡， 是对缺氧的神经保护反应吗什么因素调节谷氨酸受体运输对缺氧的反应？缺氧是如何改变神经元的细胞生物学的？本研究采用遗传学、分子生物学、细胞生物学和电生理学的方法对C. elegans了解缺氧如何影响神经元功能。在目的1中，它检查了缺氧和已知缺氧反应途径的组分如何改变受体的膜运输。在目的2中，它表征了EGL-9（一种感测氧水平并响应缺氧的脯氨酰羟化酶）如何调节LIN-10（一种已知调节谷氨酸受体运输的PTB/PDZ结构域蛋白（与Mint同源））。在目的3中，研究了缺氧和EGL-9如何通过调节线粒体分裂的介质DRP-1来调节线粒体动力学。在目标4中，它检查了这种新途径对几种神经退行性模型中神经元存活的影响。拟议中的实验在几个方面推动了该领域的发展。首先，他们确定了一种新的缺氧反应途径。其次，他们展示了神经元如何使用这种新的途径来保护自己免受缺氧。第三，它们表明受调节的受体运输和受调节的线粒体动力学是潜在的机制。最后，它们提供了潜在的新的治疗靶点，以最大限度地减少TBI和缺血性卒中后的脑损伤。

DESCRIPTION (provided by applicant): Traumatic brain injury (TBI) and ischemic stroke are leading causes of morbidity and disability, excitotoxically killing neurons via hypoxia. The underlying mechanism is thought to be a combination of glutamate receptor overactivation, deregulated calcium homeostasis, and mitochondrial dysfunction. Specifically, the hypoxia resulting from trauma or stroke results in membrane depolarization and hence the release of the neurotransmitter glutamate from affected neurons. High levels of acute glutamate overactivate receptors on neighboring neurons, thereby resulting in calcium influx and excitotoxicity. Mitochondrial dynamics become altered, influencing the production of ATP, as well as the release of calcium and Reactive Oxygen Species (ROS) from neuronal mitochondria. Agents that directly interfere with glutamate receptor activation have had limited clinical applicability because of their dramatic effect on receptor physiological function. Thus, it is important to identify new therapeutic targets in order to mitigate excitotoxicity after TBI or stroke. The discovery that regulated trafficking of glutamate receptors can modify synaptic efficacy has changed the thinking about mechanisms by which receptors contribute to excitotoxicity after neuronal trauma. Many species, including mammals, have mechanisms by which they protect themselves from glutamate-mediated excitotoxicity, although these mechanisms are poorly understood. Indeed, the movement of glutamate receptors into and out of synaptic membranes after post-trauma hypoxia in some cultured neuronal systems can modulate excitotoxicity. Do changes in glutamate receptor trafficking contribute to neuronal death in the intact animal, or are they part of a neuroprotective response to hypoxia? What factors regulate glutamate receptor trafficking in response to hypoxia? How else does hypoxia alter the cell biology of neurons? This proposal takes genetic, molecular, cell biological, and electrophysiological approaches in C. elegans to understand how hypoxia impacts neuron function. In Aim 1, it examines how hypoxia and components of the known hypoxia response pathway alter the membrane trafficking of receptors. In Aim 2, it characterizes how EGL-9, a prolyl hydroxylase that senses oxygen levels and responds to hypoxia, regulates LIN-10, a PTB/PDZ- domain protein (orthologous to the Mints) known to regulate glutamate receptor trafficking. In Aim 3, it examines how hypoxia and EGL-9 regulate mitochondrial dynamics through their regulation of DRP-1, a mediator of mitochondrial fission. In Aim 4, it examines the effects of this novel pathway on neuron survival in several neurodegenerative models. The proposed experiments advance the field in several ways. First, they identify a novel hypoxia response pathway. Second, they demonstrate how neurons use this novel pathway to protect themselves from hypoxia. Third, they show that regulated receptor trafficking and regulated mitochondrial dynamics are the underlying mechanism. Finally, they provide potential new therapeutic targets for minimizing brain damage following TBI and ischemic stroke.