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

描述（由申请人提供）：我们研究的主要目标是了解星形胶质细胞感知神经元损伤的机制，从而引发一系列复杂的表型变化和功能改变。吞噬作用是免疫系统中一个被广泛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种主要吞噬途径的核心机制和分子成分，这些途径能够在不损害邻近健康细胞和组织的情况下识别、吞噬和处置凋亡细胞。吞噬清除退化的神经细胞及其过程和突触是由星形胶质细胞和小胶质细胞共同完成的，尽管绝大多数工作都集中在后者。然而，有少量但令人信服的证据表明星形胶质细胞（这里广泛定义为表达gmap的神经胶质细胞）在某些生理和病理生理背景下是高能力的吞噬细胞。这一建议在细胞和分子水平上解决了两个关键问题：星形胶质细胞在中枢神经系统发育过程中凋亡神经元、轴突和突触的生理清除中是否具有特定的作用？ELMO1/BAI1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特异性条件敲除来选择性地灭活Rac1和ELMO1，这是吞噬机制的两个关键组成部分。这个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。细胞培养吞噬试验将补充条件敲除方法。目的1：测试星形胶质细胞吞噬在中枢神经系统发育和退化中的重要性，使用可诱导的星形胶质细胞特异性敲除Rac1作为一种有效的吞噬功能禁用操作。目标2。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延伸，轴突，必须被移除，以确保正常功能。这个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。本研究旨在了解星形胶质细胞这一脑细胞类型在吞噬清除退化神经元和轴突过程中的作用以及细胞内机制。

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.