Regulation of brain glial cell functions by extracellularly released mitochondrial transcription factor A and microparticles

大脑包含神经元和被称为神经胶质的非神经元细胞。越来越明显的是，神经胶质对于维持大脑和脊髓的正常功能至关重要。神经胶质细胞根据周围细胞功能状态的变化主动采样周围环境，并通过释放一系列介质调节周围细胞的功能。在正常生理条件下，神经元和神经胶质细胞之间以及神经胶质细胞之间的细胞间信号传递所使用的介质知之甚少。***我的nserc资助的研究项目的长期目标是通过表征大脑中新的细胞间信号介质并研究它们的生理作用来解决这一知识差距。****在先前发现基金的资助下，我已经确定了两种参与细胞间信号传导的新型中枢神经系统（CNS）介质：线粒体转录因子a (Tfam)，一种细胞内蛋白，可以释放到细胞外空间；微颗粒（MPs）是由中枢神经系统细胞释放的小膜泡。我们的初步数据表明，这两种介质影响选择*神经胶质细胞的功能。未来5年的目标是研究Tfam和MPs调控神经胶质功能的分子机制。我的假设是，这两种介质参与了不同中枢神经系统细胞类型之间的信号传递，对维持脑组织稳态至关重要。****具体来说，我的小组将描述Tfam和MPs对两种主要胶质细胞类型，星形胶质细胞和小胶质细胞的影响。我们将利用培养的脑源性神经胶质细胞和模型细胞系来测量不同的神经胶质反应，如细胞因子和活性氧的产生。我们还将研究神经胶质细胞对动物脑内注射Tfam和MP的反应。****我们的初步数据表明，胶质细胞释放MPs的功能状态影响其对靶细胞的作用。这可能是一种新的生理胶质间*信号传导机制，有待进一步研究。此外，我们将采用蛋白质组学技术来比较神经胶质细胞在Tfam和MPs刺激下分泌的蛋白质混合物的整体变化。****关键结果*包括(1)识别受体和*由Tfam和MPs参与的细胞内信号通路；(2)确定Tfam分子中负责与细胞受体相互作用的部分；(3)发现神经胶质细胞在响应Tfam和MPs时释放的额外信号分子。****提出的研究计划将显著推进关于用于维持中枢神经系统稳态的细胞间信号分子的脑网络的知识，这也可能通过确定改变或改善脑功能的分子靶标而导致实际应用

*The brain*contains neurons and non-neuronal cells called glia. It*is increasingly evident that glia are critical for maintaining the normal*functioning of the brain and spinal cord. Glia actively sample their surrounding*environment responding to changes in the functional status of neighbouring cells,*and regulate functions of surrounding cells by releasing a range of mediators. Very*little is known about the mediators that are used for intercellular signaling*between neurons and glia as well as between glial cells themselves under normal*physiological conditions.***The LONG-TERM OBJECTIVE of my NSERC-funded*research program is to address this knowledge gap by characterizing novel*intercellular signaling mediators in the brain and studying their physiological*roles.****With*funding from a previous Discovery Grant, I have identified two novel central*nervous system (CNS) mediators involved in intercellular signaling: mitochondrial transcription factor A (Tfam), an*intracellular protein, which could be released into the extracellular*space; and microparticles (MPs), which are small membrane vesicles that are released*by CNS cells. Our preliminary data show that both these mediators affect select*glial cell functions. The GOAL over*the next five years is to examine the molecular mechanisms involved in*regulation of glial functions by Tfam and MPs. It is my hypothesis that these two mediators participate in the signaling*between different CNS cell types, and are critical for maintaining brain tissue*homeostasis.  ****Specifically, my*group will characterize the effects of Tfam and MPs on*the two main glial cell types, astrocytes and microglia. We will measure different glial responses*such as production of cytokines and reactive oxygen species by using cultured*brain-derived glial cells and model cell lines. We will also study glial cell*responses to Tfam and MP injections into animal brain.****Our preliminary*data show that the functional state of glial cells releasing MPs influences their*effects on target cells. This may be a novel mechanism of physiological interglial*signaling, which will be studied in detail. In addition, we will employ*proteomics techniques to compare global changes in the mixture of proteins*secreted by glial cells in response to stimulation by Tfam and MPs.****The key outcomes*include (1) identifying the receptors and*intracellular signaling pathways engaged by Tfam and MPs; (2) determining the part of the Tfam molecule responsible for interacting with*the cellular receptors; and (3) discovering additional signaling molecules that are released by glia in response*to Tfam and MPs.****The proposed*research program will significantly advance the knowledge about the brain*network of intercellular signaling molecules used to maintain CNS homeostasis,*which could also lead to practical applications through the identification of*molecular targets for altering or improving brain function.**