Oxidation-dependent Regulation of MEF2D in Neuronal Stress

描述(申请人提供)：神经元，当面对内源性和外源性毒性应激时，动员它们的生存机制。许多人类神经系统疾病，如阿尔茨海默氏症和帕金森氏病，都涉及神经元存活改变和神经元病理性丢失。本实验室这项研究的长期目标是从分子水平上了解神经元对应激的反应以及存活反应障碍在神经退变过程中的作用。在目前的应用中，我们建议研究神经元存活蛋白肌细胞增强因子2D(MEF2D)是如何在神经元和神经退行性疾病模型中受到毒性氧化信号的调节的，MEF2D在不同的细胞间隔中发挥关键作用。不同的毒性信号导致神经退变过程的关键共同途径之一涉及氧化应激和线粒体功能障碍。事实上，与AD和PD相关的几种环境毒物和基因改变破坏了线粒体的活动，并诱导了氧化应激。最近，自噬过程的功能障碍也被证明在神经元应激中起着重要作用。然而，最初的氧化损伤在多个亚细胞间传播以传递应激和损害生存的关键环节仍然很大程度上不清楚。我们以前的工作表明，核转录因子MEF2D强烈促进几种类型神经元的存活。我们最近在上一个资金周期的研究表明，MEF2D存在于线粒体中，直接调节线粒体的功能，而非功能的MEF2D通过伴侣介导的自噬(CMA)被移除。这两个过程中的任何一个过程的中断都会使神经元对压力敏感，导致死亡。这些新发现将MEF2D置于多个亚细胞细胞器中的关键位置，在那里它感知和调节神经元对应激的反应。我们的初步研究表明，氧化应激直接修饰MEF2D分子，损害其在这些细胞器中的功能和调节。综上所述，这些发现支持了一个有趣的假设，即MEF2D是神经元氧化的关键靶点，其功能受损是氧化应激下的多个亚细胞器的基础，并有助于神经退化过程。我们将结合分子和细胞学方法以及动物模型来确定：在Aim I中，应激是否导致神经元中MEF2D的氧化修饰；在Aim II中，MEF2D的氧化修饰是否损害其在神经元多个亚细胞器中的功能和调节；以及在Aim III中，MEF2D的氧化修饰是否在神经毒素诱导的变性模型和人死后脑中发生。这项研究将确定MEF2D是几个关键细胞器中氧化应激的关键靶点，并揭示氧化修饰对MEF2D的失调可能会损害神经元的存活。这种新的机制可能与神经退行性疾病的发病机制有关，并为开发治疗这些疾病的新的治疗策略提供依据。

DESCRIPTION (provided by applicant): Neurons, when faced with endogenous and exogenous toxic stress, mobilize their survival machinery. Many human neurological diseases such as Alzheimer's and Parkinson's diseases involve altered neuronal survival and pathological loss of neurons. The long-term objective of this research in our laboratory is to understand at molecular level how neurons respond to stress and the role of dysfunction of survival response in neurodegenerative process. We propose in the current application to study how a neuronal survival protein myocyte enhancer factor 2D (MEF2D), which plays key roles in distinct cellular compartments, is regulated by toxic oxidative signals in neurons and models of neurodegenerative diseases. One of the key common pathways by which diverse toxic signals lead to neurodegenerative process involves oxidative stress and dysfunction of mitochondria. Indeed, several environmental toxicants and genetic alterations associated with AD and PD disrupt mitochondrial activity and induce oxidative stress. Recently, dysfunction of autophagic process has also been shown to play an important role in neuronal stress. However, the key links which propagate the initial oxidative insult in multi subcellular compartments to signal stress and impair survival remain largely unclear. Our previous work showed that nuclear transcription factor MEF2D strongly promotes the survival of several types of neurons. Our recent studies during the last funding cycle revealed that MEF2D is present in mitochondria to directly modulate mitochondrial function and non functional MEF2D is removed by chaperone mediated autophagy (CMA). Disruption of either process sensitizes neurons to stress, leading to death. These novel findings place MEF2D at a key position in multiple subcellular organelles, where it senses and modulates neuronal response to stress. Our preliminary studies suggest that oxidative stress directly modifies MEF2D molecule, impairing its function and regulation in these organelles. Together, these findings support the intriguing hypothesis that MEF2D is a key target of neuronal oxidation and impairment of its function at multi subcellular organelles underlies oxidation-induced stress and contribute to neurodegenerative process. We will combine molecular and cellular methods and animal models to determine in Aim I whether stress causes oxidative modifications of MEF2D in neurons; in Aim II whether oxidative modifications of MEF2D impair its function and regulation in multiple subcellular organelles in neurons; and in Aim III whether oxidative modifications of MEF2D occur in in vivo models of neurotoxin- induced degeneration and human postmortem brains. This study will identify MEF2D as a key target of oxidative stress in several key organelles and reveal that dysregulation of MEF2D by oxidative modifications may undermine neuronal survival. This novel mechanism may be relevant to the pathogenesis of neurodegenerative diseases and provide basis for developing novel therapeutic strategies for their treatment.