Novel roles for lipopolysaccharide modifications in immune evasion

脂多糖修饰在免疫逃避中的新作用

• 批准号: 10592139
• 负责人: Joern Coers
• 金额: $ 20.66万
• 依托单位: DUKE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-07-17 至 2025-06-30
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10592139
• 关键词: Acceleration; Acylation; Anti-Bacterial Agents; Antibiotics; Apolipoproteins; Bacteria; Bacterial Infections; Bacterial Meningitis; Binding; Binding Proteins; Biological Assay; Biological Process; Cell Death; Cell Wall; Cell secretion; Cells; Cellular Immunity; Cerebrospinal Fluid; Cytosol; Data; Detergents; Disaccharides; Drug Targeting; Encapsulated; Endothelial Cells; Endotoxins; Enzymes; Epithelial Cells; Extracellular Protein; Fatty Acids; Goals; Gram-Negative Bacteria; Host Defense; Human; Immune; Immune Evasion; Immune system; Immunity; In Vitro; Infection; Infection Control; Inflammasome; Innate Immune Response; Interferons; Kinetics; Length; Libraries; Licensing; Lipid A; Lipids; Lipopolysaccharides; Macrophage; Mass Spectrum Analysis; Mediating; Mediator; Membrane; Microcapsules drug delivery system; Modification; Molecular Target; Multi-Drug Resistance; Pathway interactions; Patients; Pattern recognition receptor; Penetration; Permeability; Plasma; Polymyxin B; Protein Secretion; Proteins; Pseudomonas aeruginosa; Pulmonary Cystic Fibrosis; Resistance; Role; Route; Salmonella typhimurium; Shigella flexneri; Side; Structure; Surface; TLR4 gene; Testing; Therapeutic; Virulence Factors; Work; antimicrobial; antimicrobial peptide; bacterial genetics; candidate identification; capsule; cell type; enteric pathogen; extracellular; genetic approach; guanylate; human pathogen; inhibitor; inorganic phosphate; lipopolysaccharide-binding protein; new therapeutic target; novel; novel strategies; novel therapeutic intervention; pathogen; pathogenic bacteria; polypeptide; response; screening; surfactant; synergism; targeted treatment; treatment strategy

The outer membrane of Gram-negative bacteria forms a permeability barrier blocking antimicrobials from efficiently reaching their molecular targets residing within the bacterial cell wall or inside the bacterial cytosol. This barrier function is dependent on one of the outer membrane’s central building blocks, lipopolysaccharide (LPS). The LPS molecule is anchored in the outer bacterial membrane by its lipid A moiety. Lipid A, an acylated disaccharide, is sensed by the pattern recognition receptor TLR4 of the human immune system. To avoid TLR4 sensing, bacteria evolved mechanisms to modify their lipid A structure, for example by changing the number or lengths of its fatty acid side chains, or adding or removing terminal phosphate moieties. However, not all LPS modifications are important for TLR4 avoidance and the biological function of many LPS modifications is only poorly characterized. This proposal will test the novel hypothesis that specific lipid A modifications enable bacteria to escape from host immunity exerted by human guanylate binding protein 1 (GBP1). We recently showed that GBP1 is an additional bona fide LPS-binding protein. Intracellular GBP1 executes at least two functions: i) it accelerates the kinetics of LPS-mediated inflammasome activation and ii) it binds directly to the surface of cytosolic Gram- negative bacteria, where it acts as a surfactant operating synergistically with antimicrobials that need to penetrate the bacterial outer membrane. In Aim1 we will identify specific lipid A modifications that block the binding of GBP1 to the surface of two important human pathogens: the intracellular enteric pathogen Salmonella enterica Typhimurium and the extracellular pathogen Pseudomonas aeruginosa. GBP1 resides in the host cell cytosol but GBP1 is also secreted into the extracellular milieu. Secreted GBP1 can be found at high concentrations in plasma and cerebrospinal fluids of bacterial meningitis patients. However, the biological function of secreted GBP1 is unknown. Because we found that GBP1 binds to the extracellular bacterial pathogen Pseudomonas aeruginosa, we will test whether and how secreted GBP1 can exert host defense to extracellular bacteria in Aim2. Specifically, we will test the hypothesis that secreted GBP1 works synergistically with extracellular antimicrobial peptides. Conceptually related, Aim2 will also identify extant antibiotics that operate synergistically with GBP1. Together, Aims 1 and 2 provide a roadmap towards novel strategies for the treatment of many Gram-negative infections: targeting LPS-modifying enzymes involved in GBP1 evasion combined with the use of antibiotics that operate synergistically with GBP1.

革兰氏阴性菌的外膜形成了一个渗透性屏障， 有效地到达位于细菌细胞壁内或细菌胞质溶胶内的分子靶标。 这种屏障功能依赖于外膜的一个中心组成部分--脂多糖 （LPS）。LPS分子通过其脂质A部分锚定在细菌外膜中。脂质A， 酰化的二糖被人类免疫系统的模式识别受体TLR 4感知。到 为了避免TLR 4传感，细菌进化出了修改其脂质A结构的机制，例如通过改变 其脂肪酸侧链的数目或长度，或者添加或去除末端磷酸基团。 然而，并非所有的LPS修饰对于TLR 4回避和许多LPS的生物学功能都是重要的。 修改只是很差的特点。 这项提议将测试新的假设，即特定的脂质A修饰使细菌能够从 由人鸟苷酸结合蛋白1（GBP 1）产生的宿主免疫。我们最近发现，GBP 1是一个 额外的真正的LPS结合蛋白。细胞内GBP 1执行至少两个功能：i）它加速 LPS介导的炎性小体活化的动力学，以及ii）它直接结合到胞质革兰氏阳性细胞的表面， 阴性细菌，其中它作为表面活性剂与需要 穿透细菌的外膜在Aim 1中，我们将鉴定出特异性的脂质A修饰， GBP 1与两种重要的人类病原体表面的结合：细胞内肠道病原体 肠道沙门氏菌鼠伤寒和细胞外病原体铜绿假单胞菌。 GBP 1存在于宿主细胞胞质溶胶中，但GBP 1也分泌到细胞外环境中。分泌型GBP 1 可以在细菌性脑膜炎患者的血浆和脑脊液中发现高浓度的。 然而，分泌的GBP 1的生物学功能是未知的。因为我们发现GBP 1与 细胞外细菌病原体铜绿假单胞菌，我们将测试是否以及如何分泌GBP 1可以 在Aim 2中对胞外细菌发挥宿主防御作用。具体来说，我们将检验分泌的假设 GBP 1与胞外抗菌肽协同作用。从概念上讲，Aim 2还将 鉴定与GBP 1协同作用的现存抗生素。目标1和目标2共同提供了一个路线图 治疗许多革兰氏阴性菌感染的新策略：靶向LPS修饰 参与GBP 1逃避的酶与抗生素的使用相结合， 1英镑。