权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Mechanisms of Innate Immune Evasion by Mycobacterium Tuberculosis

结核分枝杆菌先天免疫逃避的机制

基本信息

批准号：
10078851
负责人：
JENNIFER A PHILIPS
金额：
$ 54.45万
依托单位：
WASHINGTON UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2017
资助国家：
美国
起止时间：
2017-01-01 至 2021-12-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/10078851
关键词：
Attenuated Autophagocytosis Bacillus subtilis Bacteria Bacterial Infections Binding Binding Proteins Biological Assay C Type Lectin Receptors Cause of Death Cell physiology Cells Cessation of life Characteristics Crystallization Data Degradation Pathway Development Disease Drug Targeting Exhibits Generations Goals Gram-Positive Bacteria Human Human T-Cell Leukemia Viruses Immune Immune Evasion Immunity Impairment Infection Inflammatory Innate Immune Response Invaded Ligands Link Lipid Binding Lipids Lysosomes Mediating Membrane Microbe Molecular Mus Mycobacterium tuberculosis NADPH Oxidase Nuclear Organelles Organism Pathway interactions Phagocytosis Phagocytosis Inhibition Phosphoric Monoester Hydrolases Play Population Process Production Proteins Reactive Oxygen Species Relapse Role Streptococcus pneumoniae Structural Models Structure Testing Therapeutic Toll-like receptors Tuberculosis Tuberculosis Vaccines Vaccines Virulence Virulence Factors Work acute infection base catalase chronic infection experience immune clearance in vivo innate immune mechanisms innate immune pathways inorganic phosphate insight macrophage microbial microorganism mutant new therapeutic target novel novel therapeutics novel vaccines paralogous gene pathogen prevent receptor stem success therapy development trafficking translational impact

项目摘要

PROJECT SUMMARY Mycobacterium tuberculosis (Mtb) is the causative agent of the disease tuberculosis (TB) and the leading cause of death worldwide from a bacterial infection. The success of Mtb stems from its ability to evade degradation by macrophages. Recent studies have revealed that macrophages clear microorganisms through two distinct lysosomal trafficking pathways that involve LC3-marked organelles (2, 3). Xenophagy is a process by which LC3-marked, double-membrane organelles capture and degrade invading microbes. LC3-associated phagocytosis (LAP) is similar to xenophagy, but does not involve a double membrane and requires NADPH oxidase and reactive oxygen species (ROS), which are not necessary for xenophagy. These lysosomal degradative pathways are activated by microbial ligands that stimulate pathogen recognition receptors (PRRs). The reason why Mtb, which activates numerous PRRs, fails to provoke substantive LC3-associated phagolysosomal trafficking is not understood. Our extensive preliminary data strongly suggest that CpsA, an uncharacterized protein secreted by Mtb, specifically blocks LAP. We hypothesize that CpsA interferes with the activation of NADPH oxidase, thereby blocking the generation of ROS and the LAP-mediated delivery of Mtb to the lysosome. Consistent with our hypothesis, we found that Mtb strains lacking cpsA exhibit dramatically enhanced colocalization with the LC3 marker of LAP and that they are highly attenuated in macrophages and mice. Moreover, NADPH oxidase and the proteins specifically required for LAP are necessary for macrophages to kill the cpsA mutant. CpsA contains a LytR-CpsA-Psr (LCP) domain, which is commonly found in Gram-positive organisms. In Streptococcus pneumoniae and Bacillus subtilis, the LCP domain binds phosphorylated polyisoprenoid lipids. We modeled the structure of Mtb CpsA using the crystal structures an S. pneumoniae LCP protein and found that all of the lipid phosphate-binding residues are conserved in Mtb CpsA. In addition, we found that CpsA can bind the human T-cell leukemia virus type I binding protein 1 (TAX1BP1), and nuclear dot protein 52 kDa (NDP52). TAX1BP1 and NDP52 are paralogs that are involved in linking bacterial cargo to the autophagy machinery. Thus, we hypothesize that the ability of CpsA to inhibit the NADPH oxidase and LAP depends upon binding lipid phosphate and host proteins TAX1BP1 and NDP52. To test our hypotheses, we will (1) study the pathway by which macrophages kill the cpsA mutant, (2) characterize the mechanism of action of the CpsA protein, and (3) evaluate the importance of this innate immune evasion mechanism in vivo. Combined, our studies will elucidate a novel mechanism of immune evasion by one of the most formidable pathogens. By studying the molecular mechanisms Mtb utilizes to sabotage host cellular functions, we will make fundamental observations that will aid in the development of better therapeutics and vaccines for Mtb.

项目总结