Astroglial Phagocytosis of Degenerating Neurons and Axons: Role of Rac1 and ELMO1

描述（由申请人提供）：我们研究的广泛目标是了解星形胶质细胞感知神经元损伤的机制，触发一组复杂的表型变化和功能改变。吞噬作用是免疫系统中深入研究的基本细胞过程，是摄取和破坏微生物、凋亡细胞和异常颗粒所必需的。最近的进展已经阐明了两个主要的吞噬途径的核心机制和分子组成部分，使识别，吞噬和处置凋亡细胞，而不损害邻近的健康细胞和组织。吞噬细胞清除退化的神经细胞，它们的过程和突触是由星形胶质细胞和小胶质细胞进行的，尽管绝大多数工作都集中在后者。然而，有一个小的，但令人信服的证据表明，星形胶质细胞（广义上定义为GFAP表达神经胶质细胞）在某些生理和病理生理背景下，作为高能力的吞噬细胞。该提案解决了细胞和分子水平上的两个关键问题：-星形胶质细胞在中枢神经系统发育期间对凋亡神经元、轴突和突触的生理清除中是否具有特定作用？- ELMO 1/BAI 1复合物在星形胶质细胞吞噬清除中起重要作用吗？我们建议采用最先进的星形胶质细胞特异性条件性敲除选择性地敲除Rac 1和ELMO 1，这是吞噬机制的两个关键组成部分。该项目将是第一个直接在体内测试星形胶质细胞对神经元、过程和终末进行吞噬清除的能力。细胞培养吞噬测定将补充条件性敲除方法。目标1：使用可诱导的、星形胶质细胞特异性敲除Rac 1作为有效的吞噬失能操作，测试星形胶质细胞吞噬作用在CNS发育和变性中的重要性。目标2.使用可诱导的星形胶质细胞特异性基因敲除小鼠测试ELMO 1和/或BAI 1在体内对星形胶质细胞吞噬作用的必要性公共卫生相关性：在大脑发育期间和脑损伤后，死亡神经细胞的尸体及其长的延伸，轴突，必须被移除以确保适当的功能。这一过程被称为吞噬作用，在免疫系统中得到了深入研究，但在神经系统中却没有。这项建议旨在了解一种脑细胞类型，星形胶质细胞的作用，以及参与吞噬清除变性神经元和轴突的细胞内机制。

DESCRIPTION (provided by applicant): The broad objectives of our research are to understand the mechanisms by which astroglial cells sense neuronal injury, triggering a complex set of phenotypic changes and functional alterations. Phagocytosis is a fundamental cellular process intensely studied in the immune system, required for ingestion and destruction of microorganisms, apoptotic cells and abnormal particles. Recent advances have elucidated core mechanisms and molecular components of two major engulfment pathways enabling recognition, engulfment and disposal of apoptotic cells without damaging neighboring healthy cells and tissues. The phagocytic removal of degenerating neural cells, their processes and synapses is carried out by both astroglia and microglia, although the vast majority of work has focused on the latter. However, there is a small but compelling body of evidence implicating astroglia (broadly defined here as GFAP-expressing neuroglia) as highly capable phagocytes in certain physiological and pathophysiological contexts. This proposal addresses two key questions at both the cellular and molecular levels: -Do astroglial cells have specific roles in the physiological clearance of apoptotic neurons, axons, and synapses during CNS development? -Does the ELMO1/BAI1 complex serve an essential role in astroglial phagocytic clearance? We propose to employ state-of-the art astroglial-specific conditional knockouts to selectively inactivate Rac1 and ELMO1, two key components of the phagocytic machinery. This project will be the first to directly test in vivo the ability of astroglia to perform phagocytic clearance of neurons, processes and terminals. Cell culture phagocytosis assays will complement the conditional knockout approaches. Aim 1: Test the importance of astroglial phagocytosis in CNS development and degeneration using an inducible, astroglial-specific knockout of Rac1 as a potent phagocytosis-disabling manipulation. Aim 2. Test the necessity of ELMO1 and/or BAI1 in vivo for astroglial phagocytosis using an inducible, astroglial specific knockout mouse PUBLIC HEALTH RELEVANCE: During brain development and following brain injury, the corpses of dying nerve cells and their long extensions, axons, must be removed in order to ensure proper function. This process, known as phagocytosis, is intensely studied in the immune system but not in the nervous system. This proposal seeks to understand the roles of one brain cell type, the astrocyte, and intracellular mechanisms involved in the phagocytic clearance of degenerating neurons and axons.