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以及因细胞凋亡而死亡的细胞至关重要。不能清除病原体会导致传染病。未能清除凋亡细胞（AC）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中存在着大量的空白。我们不知道吞噬细胞如何感知和整合促进吞噬作用的AC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。我们使用果蝇作为一个模型系统，这使我们能够推进我们的理解AC清除证明新的作用，受体上的吞噬细胞，蛋白酶体降解和钙稳态在这个过程中。我们的理由是，果蝇可以作为一个模型，以确定进化保守的调节吞噬作用，并揭示其分子机制的新的光，并告诉我们如何AC信号激活吞噬细胞。我们的目标是确定新的积极和消极的调节吞噬AC。我们的中心假设是：（1）细胞凋亡调节Croquemort（CRQ）的表达，CRQ是一种CD 36相关的吞噬清道夫受体;（2）Pallbearer（PALL）的底物，PALL是一种通过E3-泛素连接酶活性促进吞噬作用的F-Box蛋白，是细胞凋亡的负调节因子。 细胞凋亡调节PALL的亚细胞定位，其作用于CRQ的上游。这些都是基于数据显示，CRQ的表达和PALL核运输是依赖性的，PALL底物的蛋白酶体降解促进吞噬作用，CRQ是弱表达的PALL突变体。我们的具体目标是（1）鉴定和研究CRQ调节剂的作用，（2）鉴定PALL底物并研究其在吞噬作用中的作用，（3）使用遗传和RNAi筛选、生物化学和分子遗传学技术研究PALL响应细胞凋亡的运输及其与AC清除的相关性。这一提议将促进我们对AC清除的分子机制的理解，并确定该过程的调节剂，其可作为开发旨在预防或治疗自身免疫性疾病、神经退行性疾病和感染性疾病的新疗法的候选靶标。

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.