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: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=689155
• 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.

吞噬作用是一个进化上保守的过程，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动态平衡所必需的。巨噬细胞A类清道夫受体是一种非调理吞噬受体，能识别许多天然的(如细菌、修饰的脂蛋白)和合成的配体。与其他非光学吞噬细胞受体一样，它们在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知的基序，这些基序有助于吞噬和促炎信号传递，可通过这些目的进行验证：1)利用古代和现代遗传学发现清道夫受体中的功能结构域。2)发现脂成分和瞬时脂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。使用传统生化技术发现新的信号基序的尝试提供了对摄取所需残基的见解，但没有像在光学受体中的类似研究那样富有成果。我们已经证明(PMID：23181696)，一种发现这些受体内进化保守和分歧区的系统发育方法提供了一种丰富和强大的方法来将功能归因于特定序列，并将通过包括古代(前哺乳动物)和现代(灵长类动物)的研究在(OBJ 1)中扩展和完善这一方法。我们最近发现，清道夫受体可能比光学受体(例如Fc受体)更严重地依赖与膜脂的相互作用来启动吞噬作用。我们将使用高分辨率显微镜来跟踪膜上清道夫受体的流动性，以阐明这些脂质相互作用(OBJ 2)。我们还确定清道夫受体与其他先天性免疫受体(即Toll样受体)合作，但它们对信号传递的贡献是根本不同的，这取决于它们是定位于质膜还是定位于内膜。我们已经开发了一些分子生物学和细胞生物学分析来剖析这种相互作用(OBJ3)，并认为这可能是一种迄今未描述的对细菌的生理反应进行“微调”的机制。我的研究计划的长期目标是了解非调理吞噬细胞受体的信号传递过程。由于吞噬细胞受体对低等生物的营养获取、宿主防御和多细胞性以及高等生物的动态平衡和宿主防御是必不可少的，了解这些受体的信号传递能力将有助于许多生物学问题。