Modulation of Host Cell Apoptosis By Pathogenic Rickettsiae

致病性立克次体对宿主细胞凋亡的调节

• 批准号: 7211768
• 负责人: Sanjeev K. Sahni
• 金额: $ 19.25万
• 依托单位: UNIVERSITY OF ROCHESTER
• 依托单位国家: 美国
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-07-15 至 2009-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7211768
• 关键词: Actins; Address; Affect; Anaplasma; Apoptosis; Apoptosis Promoter; Apoptotic; Applications Grants; Arts; Bacteria; Bacterial Infections; Bartonella; Behavior; Biochemical; Blood Vessels; Caspase; Categories; Cell Death; Cell Line; Cells; Centers for Disease Control and Prevention (U.S.); Cessation of life; Characteristics; Child; Chlamydia; Class; Clinical; Coagulants; Complex; Cytolysis; Cytoplasm; Data; Development; Disease Outcome; Elderly; Endothelial Cells; Ensure; Environment; Epidemic; Equilibrium; Event; Family; Fever; Gene Proteins; Genes; Genetic; Genomics; Geographic Locations; Growth; Host Defense; Host Defense Mechanism; Human; In Vitro; Infection; Inflammatory; Invaded; Kinetics; Knowledge; Laboratories; Life; Maintenance; Mediating; Microscopic; Mitochondria; Molecular; Molecular Genetics; NF-kappa B; Necrosis; Numbers; Organism; Pathogenesis; Pathology; Pathway interactions; Patients; Pattern; Phenotype; Prevention; Property; Proteins; Proteomics; Regulation; Research Personnel; Resistance; Rickettsia; Rickettsia Infections; Rocky Mountain Spotted Fever; Scourge; Signal Pathway; Signal Transduction; Signal Transduction Pathway; Spottings; Staging; Stimulus; TP53 gene; Tail; Testing; Time; Typhus; Vascular Endothelium; base; cell motility; comparative; cytotoxicity; design; disability; human MAPK14 protein; improved; insight; interest; microbial; microorganism; novel; pathogen; pathogenic bacteria; programs; research study; response; vascular inflammation

DESCRIPTION (provided by applicant): The obligate intracellular bacteria belonging to Rickettsia species are etiological agents of the spotted fever and typhus groups (SFG and TG) of rickettsial diseases in almost all geographic locations worldwide. Rocky Mountain spotted fever and epidemic typhus, caused respectively by R. rickettsii and R. prowazekii, are serious infections that can be fatal in children, elderly, and immunodeficient or misdiagnosed/untreated patients. A major clinical hallmark is the infection of endothelial cell lining of vessels, ultimately leading to vascular inflammation and damage. While apoptosis serves as an important host defense mechanism to restrict proliferation and ensuing pathogenesis during bacterial infections, intracellular rickettsiae require intimate association with the target host cells for their growth/spread. It is thus possible that like other intracellular pathogens, rickettsiae may also utilize strategies to inhibit host apoptosis early during the infection for sake of their own survival. Identified and described by our laboratory, one such strategy during endothelial cell infection of R. rickettsii is the activation of NF-?B, but nothing is known about cell signaling events during infection with and potential anti-apoptotic activities of typhus group organisms. To address this critical gap in the existing knowledge of rickettsial pathogenetic mechanisms is highly significant because of distinctive differences in the intracellular behavior of SFG and TG organisms and the potential for intentional use of R. prowazekii (Class B on CDC list) and R. rickettsii (Category C) as bioterror agents. The objectives of this exploratory grant application are to investigate the hypothesis that early during the infection, rickettsiae trigger anti-apoptotic mechanism(s) in host cells to facilitate the establishment and progression of infection and to define potential similarities or differences in host signaling mechanisms exploited by SFG and TG rickettsiae by conducting simultaneous and thorough comparative analyses. Aim 1 is designed to identify apoptotic and anti-apoptotic signaling pathways induced by representative Rickettsia species and will focus on 'shift(s)' in the equilibrium between pro- and anti-apoptotic genes and proteins of Bcl-2, IAP, and p53 families. Aim 2 will further decipher the complex mechanistic aspects of apoptosis regulation during Rickettsia infection by discerning the involvement of extrinsic or intrinsic cascades and identifying the upstream initiator and downstream effector caspases. Employing a combination of conventional biochemical and state of the art microscopic/molecular genetic approaches, we will reveal novel insights into the molecular basis of Rickettsiae-mediated modulation of apoptosis and improve our understanding of the unique perspective of manipulation of host functions by parasitic intracellular pathogens. Acquisition of this new knowledge regarding adaptations in host cell signaling and recent progress in the genomic and proteomic characterization of Rickettsia organisms will enable us to identity and isolate potential rickettsial anti-apoptotic activity(ies), which can be targeted to develop new and improved strategies aimed at enhancing clearance of infected cells early to avoid disseminated endothelial infection and associated vascular pathologies.

描述（由申请人提供）：属于立克次体种的专性细胞内细菌是全世界几乎所有地理位置的立克次体疾病的斑疹热和斑疹伤寒组（SFG和TG）的病原体。落基山斑疹热和流行性斑疹伤寒分别由立克次体和普瓦兹基立克体引起，是严重的感染，对于儿童、老年人和免疫缺陷或误诊/未经治疗的患者可能致命。一个主要的临床标志是血管内皮细胞内壁的感染，最终导致血管炎症和损伤。虽然细胞凋亡是限制细菌感染期间增殖和随后发病机制的重要宿主防御机制，但细胞内立克次体需要与靶宿主细胞密切相关才能生长/扩散。因此，像其他细胞内病原体一样，立克次体也可能在感染早期利用策略抑制宿主细胞凋亡，以求自身生存。我们的实验室鉴定并描述了立氏立克次体感染内皮细胞期间的一种策略是激活NF-κB，但对于斑疹伤寒菌感染期间的细胞信号转导事件和潜在的抗凋亡活性一无所知。由于 SFG 和 TG 生物体的细胞内行为存在明显差异，并且有可能有意使用立克次氏体（CDC 名单上的 B 类）和立克次体（C 类）作为生物恐怖剂，因此解决立克次体致病机制现有知识中的这一关键空白非常重要。这项探索性拨款申请的目的是研究以下假设：在感染早期，立克次体触发宿主细胞中的抗凋亡机制，以促进感染的建立和进展，并通过同时进行全面的比较分析，确定 SFG 和 TG 立克次体利用的宿主信号传导机制的潜在相似性或差异。目标 1 旨在鉴定代表性立克次体物种诱导的凋亡和抗凋亡信号通路，并将重点关注 Bcl-2、IAP 和 p53 家族的促凋亡和抗凋亡基因和蛋白质之间平衡的“转变”。目标 2 将通过辨别外在或内在级联的参与并识别上游启动子和下游效应子半胱天冬酶，进一步破译立克次体感染期间细胞凋亡调节的复杂机制。采用传统的生化和最先进的微观/分子遗传学方法相结合，我们将揭示立克次体介导的细胞凋亡调节的分子基础的新见解，并提高我们对寄生细胞内病原体操纵宿主功能的独特视角的理解。获得有关宿主细胞信号传导适应的新知识以及立克次体生物体基因组和蛋白质组学表征的最新进展将使我们能够识别和分离潜在的立克次体抗凋亡活性，从而可以有针对性地开发新的和改进的策略，旨在尽早增强感染细胞的清除，以避免播散性内皮感染和相关的血管病变。