Microbial Pattern Recognition and Signaling by the Adhesion GPCR BAI1

通过粘附 GPCR BAI1 进行微生物模式识别和信号传导

• 批准号: 8082187
• 负责人: James E. Casanova
• 金额: $ 38.5万
• 依托单位: UNIVERSITY OF VIRGINIA
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-07-01 至 2016-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8082187
• 关键词: Adhesions; Adopted; Amino Acids; Antibiotics; Apoptotic; BAI1 gene; Bacteria; Bacterial Infections; Binding; Binding Sites; Biochemical; Biological Assay; C Type Lectin Receptors; C-terminal; Calorimetry; Cells; Charge; Communicable Diseases; Complex; Cytoplasmic Tail; Data; Development; Ectopic Expression; Elements; Exhibits; Extracellular Domain; Family; Fibroblasts; G Protein-Coupled Receptor Genes; Goals; Gram-Negative Bacteria; Gram-Positive Bacteria; Health; Host Defense; Immune response; Immune system; In Vitro; Infection; Infectious Agent; Inflammation; Inflammatory; Inflammatory Response; Interferons; Invaded; Ligand Binding; Ligands; Ligation; Lipopolysaccharides; Liver; MAP Kinase Modules; Mediating; Microbe; Monomeric GTP-Binding Proteins; Mus; Nature; Organism; Orphan; Pathway interactions; Pattern Recognition; Pattern recognition receptor; Phagocytes; Phagocytosis; Physiological; Predisposition; Proteins; Reactive Oxygen Species; Receptor Activation; Receptor Signaling; Research; Role; Salmonella; Salmonella infections; Salmonella typhimurium; Sentinel; Series; Side; Signal Pathway; Signal Transduction; Specificity; Spleen; Structure; Surface; TLR4 gene; Tissues; Toll-like receptors; Work; base; chemokine; cytokine; in vivo; insight; intraperitoneal; macrophage; member; microbial; microorganism; mouse model; next generation; novel; pathogen; pathogenic bacteria; receptor; response; scavenger receptor; uptake

DESCRIPTION (provided by applicant): The innate immune system forms the first line of specific host defense against invading microbial pathogens. Integral to the innate immune response are Pattern Recognition Receptors (PRRs) that recognize conserved determinants expressed by a broad range of pathogenic microorganisms. Among these are the Toll-like receptors, which promote inflammatory signaling and phagocyte recruitment in response to pathogen recognition, and several families of phagocytic PRRs, including scavenger receptors and C-type lectin receptors that mediate phagocytic clearance of microbes from infected tissues. Each receptor family contains multiple members that recognize a unique spectrum of microbial components, and collectively they provide protection against a wide range of infectious organisms. We have identified a novel pattern recognition receptor, BAI1, that is expressed on macrophages and recognizes the surface lipopolysaccharide (LPS) of Gram-negative bacteria using an array of thrombospondin repeats (TSRs) in its extracellular domain. TSRs in several secreted proteins have been shown to bind microbial products, but this is the first evidence of a transmembrane receptor that uses TSRs to mediate the phagocytic clearance of specific pathogens. Binding of bacteria to BAI1 triggers phagocytosis through a mechanism involving activation of the small GTPase Rac by the Elmo/Dock180 GEF complex, which interacts directly with BAI1. An emerging theme is that pattern recognition receptors often cooperate with each other to enhance downstream signaling responses. Our preliminary data suggest that BAI1 acts synergistically with the Toll-like receptor TLR4 to promote the synthesis of inflammatory cytokines/chemokines. BAI1 is an orphan GPCR-like receptor and apart from its ability to activate Rac, almost nothing is known about how it transmits signals to the cell interior or which signaling pathways are activated in response to BAI1 ligation. The overall goal of the proposed research is to define the role of BAI1 in host defense against bacterial infection. In Aim 1, we will define the mode of interaction of LPS with the BAI1 TSRs, using a combination of biochemical, biophysical and structural approaches. In Aim 2, we will identify components of the signaling machinery that interact with BAI1, define the signaling pathways activated in response to LPS or bacterial activation of the receptor, and elucidate the mechanisms of crosstalk between BAI1 and TLR4. In Aim 3, we will characterize the role of BAI1 in host defense in vivo, using a mouse model of Salmonella infection. Together these studies will provide unique structural, biochemical and physiological insights into a new class of pattern recognition receptor that may have important functions in the innate immune response to bacterial pathogens.

描述（由申请人提供）：先天免疫系统构成了针对入侵微生物病原体的特定宿主防御的第一行。先天免疫反应不可或缺的是模式识别受体（PRR），它们识别由广泛的致病微生物表达的保守决定因素。其中包括Toll样受体，这些受体促进响应病原体识别的炎症信号传导和吞噬细胞募集，以及几种吞噬细胞PRR的家族，包括清道夫受体和C型凝集素受体，这些受体介导了受感染组织的微生物的吞噬清除率。每个受体家族都包含多个识别微生物成分范围的成员，并统称它们为广泛的感染生物提供了保护。我们已经确定了一种新型的模式识别受体BAI1，该受体在巨噬细胞上表达，并使用一系列的血小板传播重复序列（TSR）在其细胞外域中识别革兰氏阴性细菌的表面脂多糖（LPS）。已经显示出几种分泌的蛋白质中的TSR结合微生物产物，但这是跨膜受体的第一个证据，该跨膜受体使用TSR介导特定病原体的吞噬性清除率。细菌与BAI1的结合通过涉及ELMO/DOCK180 GEF复合物激活小GTPase RAC的机制触发了吞噬作用，该机制与BAI1直接相互作用。一个新兴的主题是，模式识别受体通常相互配合，以增强下游信号反应。我们的初步数据表明，BAI1与Toll样受体TLR4协同起作用，以促进炎性细胞因子/趋化因子的合成。 BAI1是一种孤儿GPCR样受体，除了它激活RAC的能力外，几乎一无所知，它如何将信号传输到细胞内部或响应于BAI1连接而激活的信号通路。拟议的研究的总体目标是确定BAI1在宿主防御细菌感染中的作用。在AIM 1中，我们将使用生化，生物物理和结构方法的组合来定义LPS与BAI1 TSR的相互作用方式。在AIM 2中，我们将确定与BAI1相互作用的信号机械的组件，定义对响应LPS或受体的细菌激活而激活的信号通路，并阐明BAI1和TLR4之间的串扰机理。在AIM 3中，我们将使用沙门氏菌感染的小鼠模型来表征BAI1在体内宿主防御中的作用。这些研究将共同​​为新的模式识别受体提供独特的结构，生化和生理见解，这些识别受体可能在对细菌病原体的先天免疫反应中可能具有重要功能。