Regulation of MD-2 function and expression

MD-2 功能和表达的调节

• 批准号: 7874677
• 负责人: JERROLD P WEISS
• 金额: $ 44.04万
• 依托单位: UNIVERSITY OF IOWA
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-06-01 至 2014-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7874677
• 关键词: Abbreviations; Acids; Acylation; Affect; Agonist; Albumins; Antigens; Bacteria; Binding; Binding Proteins; Binding Sites; Biochemical; Biological; Buffers; CCL4 gene; CD14 gene; Cells; Complex; Development; Diet; Disease; Divalent Cations; E protein; Embryo; Endotoxins; Environment; Epithelial Cells; Epitopes; Fatty Acids; Glycolipids; Gram-Negative Bacteria; Gram-Negative Bacterial Infections; Health; Host Defense; Human; Hydrolase; IL8 gene; Immune; Immune response; Immunomodulators; Infection; Inflammation; Inflammatory Response; Interleukin-8; Invaded; Irrigation; Label; Lead; Ligands; Lipid A; Lipids; Lipopolysaccharides; Membrane; Microbe; Modeling; Monoclonal Antibodies; Mus; Myelogenous; Neisseria meningitidis; Nonesterified Fatty Acids; Nose; Pathology; Phosphate Buffer; Phospholipids; Phosphorylation; Physiological; Physiology; Play; Pneumonic Plague; Proliferating; Property; Receptor Activation; Recombinants; Regulation; Risk; Role; Saline; Serum Albumin; Signal Transduction; Site; Sodium; Sodium Chloride; Solutions; Specific qualifier value; Structure; Surface Properties; System; TLR4 gene; Toll-Like Receptor 2; Toll-like receptors; Translating; Variant; Virulence; bactericidal permeability increasing protein; in vivo; insight; kidney cell; lipooligosaccharide; lipopolysaccharide-binding protein; mutant; neutrophil; novel; novel strategies; pathogen; polyacrylamide gels; polyhistidine; protein E; protein protein interaction; public health relevance; receptor; response; toll-like receptor 4

DESCRIPTION (provided by applicant): Host defense against many invading Gram-negative bacteria (GNB) depends upon innate immune recognition of endotoxin (E), unique, abundant and generally conserved glycolipids of GNB. Optimal TLR4- dependent responses are exquisitely sensitive and robust, but also self-limited. How this is normally achieved and why regulation of TLR4 activation may go awry under various patho-physiological conditions is incompletely known. The most potent inflammatory responses to E require certain canonical structural features of E and ordered protein-E and protein-protein interactions involving the LPS-binding protein (LBP), CD14, MD-2, and Toll-like receptor (TLR) 4. MD-2 plays an essential role in regulation of TLR4 activation by E, by bridging recognition of E, normally initiated by LBP and CD14, to receptor activation or antagonism. Our identification and characterization of monomeric E.MD-2 complexes as potent TLR4 agonists or antagonists, depending on E and/or MD-2 structure, have clearly demonstrated that it is the properties of the E.MD-2 complex, not E alone, that specifies TLR4 activation or receptor occupancy without activation. The unique structural and functional properties of these complexes suggest novel approaches to investigate how endotoxin induces TLR4 activation, how differences in E structure can dictate differences in TLR4 responsiveness, and how these new mechanistic insights may be translated to the development of novel TLR4-directed immunomodulators. Growing evidence of a broader array of molecules that can act as TLR4 agonists or antagonists, including host and/or diet-derived lipids, suggest many other circumstances in which the regulation or dysregulation of MD-2/TLR4 function could be pivotal in host physiology and patho-physiology. We will make use of novel synthetic, biochemical, structural biological, and functional approaches (e.g., metabolically labeled native and synthetic E and lipid A variants, recombinant wild-type and mutant human E-binding proteins and TLR4 ectodomain, monoclonal antibodies, models of airway infection and inflammation) to: 1) Further define the structural properties of ligands that promote binding to MD-2 and the action of ligand.MD-2 complexes as TLR4 agonists or antagonists; 2) Define more specifically the structural properties of E.MD-2 complexes that activate TLR4; and 3) Better define in vivo actions in the murine airway of wt and variant E(lipdA).Md-2. PUBLIC HEALTH RELEVANCE: TLR4-dependent cell activation by endotoxin plays a critical role in host response and defense against many Gram-negative bacteria. The ubiquity of endotoxin in the surrounding environment and the apparent existence of other microbe- and host-derived agonists/antagonists of TLR4 suggest an even broader role of TLR4 in health and disease. Better understanding of how endotoxin induces TLR4 activation and how differences in endotoxin structure dictate differences in TLR4 responsiveness is likely to lead to a better understanding of how mammalian hosts, including humans, normally respond effectively against invading Gram-negative bacteria and how certain Gram-negative bacterial pathogens can evade/resist these normally efficient host responses. The new mechanistic insights may also be translated to the development of novel TLR4-directed immuno-modulators whose application would likely include, but not be limited, to Gram-negative bacterial infections.

描述（由申请人提供）：宿主对许多入侵的革兰氏阴性菌（GNB）的防御取决于内毒素（E）的先天免疫识别，内毒素是GNB独特、丰富且通常保守的糖脂。最佳的TLR 4依赖性反应是非常敏感和稳健的，但也是自限的。这通常是如何实现的，以及为什么TLR 4激活的调节在各种病理生理条件下可能出错，目前还不完全清楚。对E的最有效的炎症反应需要E的某些典型结构特征和有序的蛋白质-E和蛋白质-蛋白质相互作用，涉及LPS结合蛋白（LBP）、CD 14、MD-2和Toll样受体（TLR）4。MD-2通过桥接通常由LBP和CD 14启动的E识别到受体激活或拮抗作用，在E对TLR 4激活的调节中起重要作用。我们根据E和/或MD-2结构鉴定和表征作为有效的TLR 4激动剂或拮抗剂的单体E.MD-2复合物，已经清楚地表明，是E.MD-2复合物的性质，而不是E单独的性质，指定TLR 4活化或受体占有而不活化。这些复合物的独特结构和功能特性表明了研究内毒素如何诱导TLR 4活化、E结构的差异如何决定TLR 4反应性的差异以及这些新的机制见解如何转化为新型TLR 4定向免疫调节剂的开发的新方法。越来越多的证据表明，可以作为TLR 4激动剂或拮抗剂的更广泛的分子，包括宿主和/或饮食来源的脂质，表明许多其他情况下，MD-2/TLR 4功能的调节或失调可能是宿主生理学和病理生理学的关键。我们将利用新的合成，生物化学，结构生物学和功能方法（例如，代谢标记的天然和合成的E和脂质A变体、重组野生型和突变的人E结合蛋白和TLR 4胞外域、单克隆抗体、气道感染和炎症模型），以：1）进一步确定促进与MD-2结合的配体的结构特性和配体MD-2复合物作为TLR 4激动剂或拮抗剂的作用; 2）更具体地定义激活TLR 4的E.MD-2复合物的结构特性;和3）更好地定义wt和变体E（lipdA）.Md-2在鼠气道中的体内作用。公共卫生关系：内毒素对TLR 4依赖性细胞的激活在宿主对许多革兰氏阴性菌的应答和防御中起着关键作用。内毒素在周围环境中的普遍存在以及其他微生物和宿主来源的TLR 4激动剂/拮抗剂的明显存在表明TLR 4在健康和疾病中的作用甚至更广泛。更好地了解内毒素如何诱导TLR 4活化以及内毒素结构的差异如何决定TLR 4反应性的差异，可能会更好地了解哺乳动物宿主（包括人类）通常如何有效地对抗入侵的革兰氏阴性细菌，以及某些革兰氏阴性细菌病原体如何逃避/抵抗这些通常有效的宿主反应。新的机制见解也可以转化为新的TLR 4导向的免疫调节剂的开发，其应用可能包括但不限于革兰氏阴性细菌感染。