Regulation of astrocyte phagocytosis and other physiological functions by molecules endogenous to the central nervous system

大脑包含神经元和非神经元胶质细胞，这对维持正常的大脑和脊髓功能至关重要。神经胶质细胞主动监测周围环境，对邻近细胞状态的变化做出反应，并通过释放各种分子来调节邻近细胞的功能。关于在正常生理条件下，中枢神经系统(CNS)中不同细胞类型之间用作信号的分子的确切性质，可获得的信息有限。 我的NSERC资助的研究项目的长期目标是通过表征大脑中的新信号分子并研究它们的生理作用来解决这一知识鸿沟。 最近，我们发现了线粒体转录因子A(TFAM)和细胞色素C(CytC)两种新的中枢神经系统信号转导功能。这些蛋白质通常存在于细胞内，但死亡或受刺激的细胞会将它们释放到细胞外空间，在那里它们可以与胶质细胞相互作用并改变其功能。我未来五年研究计划的核心目标是研究TFAM和CytC用来调节星形胶质细胞(最丰富的胶质细胞类型)生理功能的分子机制，并发现CNS细胞用来相互通信的新信号分子。我推测TFAM和CytC是中枢神经系统中的细胞间信号分子，它们通过与星形胶质细胞表面的特定受体相互作用来调节星形胶质细胞的功能。 具体地说，我的团队将描述TFAM对星形胶质细胞的影响的分子结构。我们还将研究细胞外TFAM和CytC对部分星形胶质细胞功能的影响，包括它们的吞噬活性。吞噬作用被用来吞噬细胞碎片和清除不使用的细胞结构；直到最近，它才被认为是星形胶质细胞的关键生理功能。此外，我们将使用蛋白质组学技术来比较星形胶质细胞分泌的蛋白质混合物在TFAM和CytC作用下的变化。 主要预期结果包括：1)研究TFAM参与的星形胶质细胞受体和信号通路；2)确定TFAM分子中负责与细胞受体相互作用的部分；3)表征TFAM和CytC在动物脑中的细胞外效应；4)识别调节星形胶质细胞吞噬作用的内源性中枢神经系统分子；以及5)发现胶质细胞响应TFAM和CytC刺激而释放的其他信号分子。 所获得的数据将为神经生物学家提供对中枢神经系统细胞之间通信机制的新见解。关于细胞间信号分子的大脑网络的知识的预期进展对于我们理解胶质细胞的不同生理功能和激活状态的调节至关重要。这些发现还可以通过识别分子靶标来改变或改善大脑功能，从而导致实际应用。

The brain contains neurons and non-neuronal glia, which are critical for maintaining normal brain and spinal cord functions. Glia actively monitor their environment, respond to changes in the status of neighboring cells, and regulate functions of nearby cells by releasing various molecules. Limited information is available about the exact nature of molecules used as signals between different cell types in the central nervous system (CNS), under normal physiological conditions. The LONG-TERM OBJECTIVE of my NSERC-funded research program is to address this knowledge gap by characterizing new signaling molecules in the brain and studying their physiological roles. Recently, we have identified new CNS signaling functions of two molecules: mitochondrial transcription factor A (TFAM) and cytochrome C (CytC). These proteins are normally found inside cells, but dying or stimulated cells can release them into the extracellular space, where they can interact with glia and change their functions. The CORE GOAL of my research program for the next five years is to examine the molecular mechanisms used by TFAM and CytC to regulate physiological functions of astrocytes, the most abundant type of glia, and to discover new signaling molecules that CNS cells use to communicate with each other. I hypothesize that TFAM and CytC are intercellular signaling molecules in the CNS, which regulate astrocyte functions by interacting with specific receptors located on their surface. Specifically, my group will characterize the molecular structures responsible for the effects of TFAM on astrocytes. We will also study the effects of extracellular TFAM and CytC on select astrocyte functions, including their phagocytic activity. Phagocytosis is used to engulf cell debris and eliminate unused cellular structures; it has only recently been recognized as a key physiological function of astrocytes. In addition, we will employ proteomics techniques to compare changes in the mixture of proteins secreted by astrocytes in response to TFAM and CytC. The key expected outcomes include: 1) investigating astrocyte receptors and signaling pathways engaged by TFAM; 2) determining the part of TFAM molecule responsible for interaction with cellular receptors; 3) characterizing extracellular effects of TFAM and CytC in animal brains; 4) identifying endogenous CNS molecules that regulate astrocyte phagocytosis; and 5) discovering additional signaling molecules that are released by glia in response to TFAM and CytC stimulation. The data obtained will provide neurobiologists with new insights into the mechanisms of communication between CNS cells. The expected advancement of knowledge about the brain network of intercellular signaling molecules is critical for our understanding of regulation of diverse physiological functions and activation states of glia. The discoveries made could also lead to practical applications by identifying molecular targets for altering or improving brain function.