Apoptotic Cell-Induced Macrophage Signaling Pathways that Regulate Phagocytosis

描述（由申请人提供）：吞噬作用对于清除宿主防御中的病原体和因细胞凋亡而死亡的细胞至关重要。不清除病原体就会导致传染病。不能清除凋亡细胞（ACs）可导致发育缺陷、自身免疫或神经退行性变。在我们对吞噬作用的分子机制的认识上有很大的空白。我们不知道吞噬细胞如何感知和整合促进吞噬的交流信号。在我们填补这一知识空白之前，开发新的策略来预防或治疗由吞噬缺陷引起的疾病将是困难的。我们的长期目标是从遗传学角度剖析AC清除的分子机制。我们使用果蝇作为模型系统，这使我们能够通过证明受体在吞噬细胞，蛋白酶体降解和钙稳态中的新作用来推进我们对AC清除的理解。我们的基本原理是果蝇可以作为一个模型来识别进化保守的吞噬调节因子，并揭示其分子机制，并告诉我们交流信号如何激活吞噬细胞。我们的目标是确定新的阳性和阴性调节细胞吞噬。我们的主要假设是：(1)细胞凋亡调节Croquemort （CRQ）的表达，CRQ是一种cd36相关的吞噬清扫剂受体；(2)通过e3 -泛素连接酶活性促进吞噬的F-Box蛋白Pallbearer （PALL）底物是细胞吞噬的负调控因子

DESCRIPTION (provided by applicant): Phagocytosis is critical for the removal of pathogens in host defense, and cells that are dying by apoptosis. Failure to clear pathogens results in infectious diseases. Failure to clear apoptotic cells (ACs) can result in developmental defects, autoimmunity or neurodegeneration. There are substantial gaps in our knowledge of the molecular mechanisms of phagocytosis. We do not know how phagocytes perceive and integrate AC-signals that promote phagocytosis. Until we fill this knowledge gap, developing new strategies to prevent or treat diseases that arise from defective phagocytosis will be difficult. Our long-term goal is to genetically dissect the molecular mechanisms of AC clearance. We use Drosophila as a model system, which has allowed us to advance our understanding of AC clearance by demonstrating novel roles for receptors on phagocytes, proteasomal degradation and calcium homeostasis in this process. Our rationale is that Drosophila can serve as a model to identify evolutionary conserved regulators of phagocytosis and shed new light on its molecular mechanisms, and tell us how AC-signals activate phagocytes. Our objectives are to identify novel positive and negative regulators of phagocytosis of ACs. Our central hypotheses are that: (1) apoptosis regulates the expression of Croquemort (CRQ), a CD36-related phagocytic scavenger receptor; (2) the substrates of Pallbearer, (PALL), an F-Box protein that promotes phagocytosis via its E3-Ubiquitin ligase activity, are negative regulators of phagocytosis; and (3) apoptosis regulates the subcellular localization of PALL, which acts upstream of CRQ. These are based on data showing that CRQ expression and PALL nuclear trafficking are apoptosis-dependent, that proteasomal degradation of PALL substrates promotes phagocytosis, and that CRQ is weakly expressed in pall mutants. Our specific aims are designed to (1) identify and study the role of CRQ regulators, (2) identify the PALL substrate(s) and study its (their) role in phagocytosis, and (3) study the trafficking of PALL in response to apoptosis and its relevance to AC clearance, using genetic and RNAi screens, biochemistry and molecular genetic techniques. This proposal wil advance our understanding of the molecular mechanisms of AC clearance, and identify regulators of this process that may serve as candidate targets for the development of new therapies designed to prevent or treat autoimmune, neurodegenerative and infectious diseases. PUBLIC HEALTH RELEVANCE: Drosophila serves as a powerful genetically tractable model system to dissect the molecular mechanisms of development and innate immunity. Phagocytosis is a cellular immune response that leads to the removal of dying cells and pathogens. We propose to pursue our dissection of the molecular pathways regulating phagocytosis of dying cells in Drosophila and identify novel regulators of this process that will lead to the design of new strategies to fight autoimmune and infectious diseases.