Uncovering mechanisms of phagocytosis by class A scavenger receptors

揭示 A 类清道夫受体的吞噬机制

• 批准号: RGPIN-2015-05757
• 负责人: Bowdish, Dawn
• 金额: $ 3.28万
• 依托单位: McMaster University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=613731
• 关键词: Uncovering; mechanisms; phagocytosis; class; scavenger

Phagocytosis is an evolutionarily conserved process that likely originated to facilitate nutrient uptake in single-celled organisms and subsequently became essential to host-defence and homeostasis in multi-cellular organisms. The macrophage class A scavenger receptors are non-opsonic phagocytic receptors that recognize a number of natural (e.g. bacteria, modified lipoproteins) and synthetic ligands. Like other non-opsonic phagocytic receptors, they have no conventional signalling motifs in their cytoplasmic domains and yet transmit a phenomenal amount of information upon ligand recognition and uptake. We hypothesize that that the scavenger receptors contain previously uncharacterized motifs that contribute to phagocytosis and pro-inflammatory signalling, testable by these objectives;1) Discover functional domains in the scavenger receptors using ancient and modern genetics.2) Discover the role of lipid composition and transient lipid phases in scavenger receptor uptake. 3) Understand how cellular localization affects scavenger receptor signalling. Attempts to use traditional biochemical techniques to discover novel signalling motifs have provided insights into residues required for uptake, but have not been as fruitful as similar studies in opsonic receptors. We have shown (PMID:23181696) that a phylogenetic approach to discover evolutionarily conserved and divergent areas within these receptors provides a rich and robust method of attributing function to specific sequences and will expand and refine this approach in (Obj 1) by including studies of ancient (pre-mammalian) and modern (primates "> We have recently discovered that the scavenger receptors may depend more heavily on interactions with membrane lipids to initiate phagocytosis than the opsonic receptors (e.g. Fc receptors). We will elucidate these lipid interactions using high resolution microscopy to track scavenger receptor mobility in membranes (Obj 2). We have also determined that scavenger receptors collaborate with other innate immune receptors (i.e. the toll like receptors) but that their contribution to signalling is fundamentally different based on whether they are localized to the plasma membrane or the endosomal membrane. We have developed a number of molecular biology and cellular biology assays to dissect this interaction (Obj 3) and believe that this may be a heretofore undescribed mechanism of "fine-tuning" physiological responses to bacteria. The long-term goal of my research program is to understand the signalling processes of the non-opsonic phagocytic receptors. Since phagocytic receptors are essential for nutrient acquisition, host defence and multi-cellularity in lower organisms, and homeostasis and host defence in higher organisms, understanding the signalling capacity of these receptors will contribute to many biological questions.

吞噬作用是一种进化上保守的过程，可能起源于促进单细胞生物体的营养吸收，随后成为多细胞生物体的宿主防御和体内平衡所必需的。巨噬细胞 A 类清道夫受体是非调理性吞噬细胞受体，可识别多种天然配体（例如细菌、修饰脂蛋白）和合成配体。与其他非调理性吞噬受体一样，它们的细胞质结构域中没有传统的信号基序，但在配体识别和摄取时传递大量信息。我们假设清道夫受体包含以前未表征的基序，这些基序有助于吞噬作用和促炎信号传导，可通过这些目标进行测试；1）利用古代和现代遗传学发现清道夫受体中的功能域。2）发现脂质成分和瞬时脂质相在清道夫受体摄取中的作用。 3) 了解细胞定位如何影响清道夫受体信号传导。尝试使用传统的生化技术来发现新的信号基序，为摄取所需的残基提供了见解，但尚未像调理性受体的类似研究那样富有成效。我们已经表明（PMID：23181696），发现这些受体内进化保守和发散区域的系统发育方法提供了一种将功能归因于特定序列的丰富而稳健的方法，并将通过包括古代（前哺乳动物）和现代（灵长类动物）的研究来扩展和完善这种方法（Obj 1）“我们最近发现清道夫受体可能更严重地依赖于与膜脂的相互作用 比调理受体（例如 Fc 受体）更能启动吞噬作用。我们将使用高分辨率显微镜来追踪膜中清道夫受体的流动性来阐明这些脂质相互作用（目标 2）。我们还确定清道夫受体与其他先天免疫受体（即 toll 样受体）协作，但根据它们是否定位于 质膜或内体膜。我们开发了许多分子生物学和细胞生物学检测方法来剖析这种相互作用（目标3），并相信这可能是迄今为止未描述的对细菌的“微调”生理反应的机制。 我的研究计划的长期目标是了解非调理性吞噬受体的信号传导过程。由于吞噬细胞受体是 对于低等生物体的营养获取、宿主防御和多细胞性以及高等生物体的稳态和宿主防御至关重要，了解这些受体的信号传导能力将有助于解决许多生物学问题。