Mechanisms of host defense against membrane damage by pore-forming toxins

宿主防御成孔毒素膜损伤的机制

• 批准号: 8699346
• 负责人: Mary O'Riordan
• 金额: $ 38.22万
• 依托单位: UNIVERSITY OF MICHIGAN AT ANN ARBOR
• 依托单位国家: 美国
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-08-01 至 2015-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8699346
• 关键词: Apoptosis; Aspartic Endopeptidases; Bacterial Infections; Bacterial Toxins; Biochemical; Biological; Caspase-1; Cell physiology; Cells; Characteristics; Chemical Agents; Chimera organism; Cholesterol; Cleaved cell; Clostridium perfringens theta-toxin; Cysteine; Cytolysins; Data; Detergents; Disease; Energy Transfer; Enzymes; Event; Future; Gel; Goals; Hemolysin; Host Defense Mechanism; Image; Immune; Immune response; Infection; Inflammation; Kinetics; Knowledge; Lead; Light; Listeria monocytogenes; Listeria monocytogenes hlyA protein; Listeriosis; Mammalian Cell; Mediating; Membrane; Membrane Lipids; Mitochondria; Modeling; Mus; Nature; Necrosis; Outcome; Pathogenesis; Pathology; Pathway interactions; Peptides; Play; Potassium; Process; Proteome; Recombinants; Research; Role; Signal Pathway; Signal Transduction; Sorting - Cell Movement; Streptolysins; Testing; Therapeutic; Tissues; Toxin; Tumor Necrosis Factor-alpha; Work; acid sphingomyelinase; antimicrobial; base; caspase-7; caspase-8; human TNF protein; in vivo; insight; macrophage; microbial; molecular marker; mutant; novel; pathogen; perforin; porin; protective effect; repaired; response

DESCRIPTION (provided by applicant): Membrane damage is a common occurrence during microbial infection, but host signaling pathways responsive to this damage are poorly understood. Moreover, the mechanisms that promote membrane integrity in response to bacterially-induced damage remain incompletely defined. Thus, the goal of this research is to elucidate host pathways that guard against cellular damage, which can contribute to disease pathology during infection and inflammation. The objective of the proposed work is to define specific regulators of cellular defense again membrane damage by microbial pore- forming toxins (PFT). We have identified the cysteine aspartate protease, caspase-7, as a pivotal regulator of the macrophage response to pore formation by bacterial toxins. Caspase-7 activation is triggered during Listeria monocytogenes infection by the cholesterol dependent cytolysin, Listeriolysin O (LLO). Caspase-7 activation is also induced by sublethal concentrations of recombinant purified PFT, but not by sublethal concentrations of detergents. These data suggest that caspase-7 activation is selectively responsive to biological membrane-damaging agents. Finally, our preliminary data reveal a requirement for caspase-7 in maintaining host membrane integrity during Listeria infection. Previous studies had established caspase-7 as an effector of programmed cell death, but the protective effect of caspase-7 during L. monocytogenes infection occurs independently of apoptosis and does not require key adaptors of the TLR, NLR or inflammasome pathways. Thus, we find that caspase-7 plays a novel cytoprotective role during bacterial infection of macrophages. We therefore hypothesize that pore formation by bacterial toxins induces membrane repair mechanisms in a caspase-7 dependent manner. We will test this hypothesis in the following specific aims: (1) Define the nature of the bacterial membrane damage signal that triggers caspase-7 activation; (2) Identify regulators of caspase-7 induction in response to pore formation; (3) Determine the mechanism of caspase-7 dependent membrane repair and its contribution to host responses in vivo. Investigating mechanisms underlying the caspase-7 dependent cytoprotective response will provide fundamental insights into cellular function relevant to many aspects of disease. The expected outcome of this work will be to define a novel cellular function for caspase-7 during infection by bacterial pathogens. In addition to their role in bacterial pathogenesis, mammalian pore-forming proteins also participate in the immune response. Thus, mechanisms by which mammalian cells protect themselves from membrane damage may be relevant to protection from destruction by immune mechanisms as well as microbial toxins. The impact of the proposed research will be to elucidate a previously unappreciated damage control mechanism that could provide insight into future therapeutic approaches to minimizing cell and tissue damage in pathological disease states.

描述（由申请方提供）：膜损伤是微生物感染期间的常见事件，但对这种损伤的宿主信号传导途径知之甚少。此外，促进膜完整性的机制，以应对细菌引起的损害仍然不完全确定。因此，这项研究的目标是阐明宿主途径，防止细胞损伤，这可能有助于感染和炎症期间的疾病病理。本研究的目的是确定微生物致孔毒素（PFT）对细胞膜损伤的特异性防御调节因子。我们已经确定了半胱氨酸天冬氨酸蛋白酶，半胱天冬酶-7，作为一个关键的调节巨噬细胞反应的细菌毒素孔形成。胱天蛋白酶-7激活在单核细胞增生李斯特菌感染期间由胆固醇依赖性溶细胞素李斯特菌溶细胞素O（LLO）触发。半胱天冬酶-7激活也诱导亚致死浓度的重组纯化PFT，但不是由亚致死浓度的洗涤剂。这些数据表明，caspase-7的激活是选择性地响应于生物膜损伤剂。最后，我们的初步数据揭示了在李斯特菌感染过程中，caspase-7在维持宿主膜完整性方面的需求。以前的研究已经证实caspase-7是程序性细胞死亡的效应子，但是caspase-7在L。单核细胞增多症感染独立于细胞凋亡发生，并且不需要TLR、NLR或炎性体途径的关键衔接子。因此，我们发现caspase-7在细菌感染巨噬细胞过程中起着一种新的细胞保护作用。因此，我们假设细菌毒素引起的孔形成以半胱天冬酶-7依赖的方式诱导膜修复机制。我们将在以下具体目标中检验这一假设：（1）定义触发caspase-7激活的细菌膜损伤信号的性质;（2）识别响应于孔形成的caspase-7诱导的调节剂;（3）确定caspase-7依赖性膜修复的机制及其对体内宿主反应的贡献。研究caspase-7依赖性细胞保护反应的机制将为了解与疾病的许多方面相关的细胞功能提供基本的见解。这项工作的预期结果将是确定一种新的细胞功能的caspase-7感染期间的细菌病原体。除了它们在细菌发病机制中的作用之外，哺乳动物孔形成蛋白还参与免疫应答。因此，哺乳动物细胞保护自身免受膜损伤的机制可能与保护免受免疫机制以及微生物毒素的破坏有关。拟议研究的影响将是阐明一种以前未被重视的损伤控制机制，可以为未来的治疗方法提供见解，以最大限度地减少病理疾病状态下的细胞和组织损伤。