Unique ADP-ribosylating and vacuolating properties of Mycoplasma pneumoniae CARDS toxin trigger airway inflammation and disease progression

摘要 肺炎支原体是住院儿童细菌性肺炎的主要原因 社区获得性肺炎(CAP)和成人细菌性CAP的第二大常见原因 美国。持续和反复感染肺炎支原体会导致严重的呼吸系统疾病， 包括哮喘和慢性阻塞性肺病，以及一系列肺外病理。直到最近，人们还不知道是如何 呼吸道病原体，如肺炎支原体，会引起细胞病理学和夸大炎症。 导致呼吸道损伤、功能障碍和重塑的反应。我们鉴定出一种新的肺炎支原体ADP- 核糖化和空泡化毒素指定社区获得性呼吸窘迫综合征(CADS) 毒素。卡氏毒素单独引起典型的呼吸道炎症、肺组织病理学、细胞学 中毒的啮齿动物和灵长类动物的空泡化、粘液化生和肺功能障碍 在肺炎支原体感染期间观察。全长(FL)卡片毒素的氨基端结构域 (即N-卡片)保持ADP-核糖基转移酶(ART)活性。N-卡片选择性ADP-核糖化NLRP3 NLRP3炎症体复合体，导致炎症体激活并随后释放IL-2 1β，一种强有力的促炎细胞因子。在初步结果中，我们还显示CARDS毒素具有选择性。 ADP-核糖酸丝氨酸羟甲基转移酶(SHMT2)，参与一种碳代谢，以及 Ef1γ，参与氨酰-tRNA向核糖体的转移。FL独特的羧基区 CARDS毒素(即C-CADS)选择性地与受体表面活性蛋白A(SP-A)、膜联蛋白A2(AnxA2)结合 磷脂、磷脂酰胆碱(PC)和鞘磷脂(SM)。FL卡片毒素的内化 遵循受体介导的结合，随后宿主靶蛋白的ADP核糖化，空泡化， 高度炎症、细胞/组织病理学和损伤。有趣的是，C卡本身就导致了这两种情况 人类细胞中空泡的形成和幼稚小鼠的嗜酸性炎症，导致哮喘样 表型。在这项建议中，我们打算确定ART和CARDS毒素的空泡化特性如何触发 人WT、沉默或敲除细胞以及WT和WT中的促炎和病理反应 基因敲除老鼠。根据我们的初步结果，我们假设ADP-核糖化和空泡化 这些活动有助于CARDS毒素启动和维持疾病发病机制的整体能力。我们 计划通过以下方式验证这一假设：a)研究卡片毒素ART活动如何引发炎症途径 和细胞病理学，b)阐明受体结合在CARDS毒素介导的炎症中的作用，c) 表征空泡化活动如何促进呼吸道炎症和损伤，以及d)分析体内 部分ART和受体靶点参与触发CARS毒素介导的呼吸道炎症和 肺部病理。了解CARDS毒素的ART和空泡化活性的机制 调节宿主的反应应该导致治疗干预和改善社会福祉。

Abstract Mycoplasma pneumoniae is the leading cause of bacterial pneumonia in children hospitalized with community acquired pneumonia (CAP) and the second most common cause of bacterial CAP in adults in the United States. Persistent and recurring M. pneumoniae infection leads to severe respiratory disorders, including asthma and COPD, and a range of extrapulmonary pathologies. Until recently, it was unknown how a respiratory pathogen, like M. pneumoniae, induces cytopathology and exaggerated inflammatory responses that cause airway injury, dysfunction and remodeling. We identified a novel M. pneumoniae ADP- ribosylating and vacuolating toxin designated Community Acquired Respiratory Distress Syndrome (CARDS) toxin. CARDS toxin alone elicits the characteristic airway inflammation, lung histopathology, cellular vacuolation, mucus metaplasia and pulmonary dysfunction in intoxicated rodents and primates that are observed during infection with M. pneumoniae. The amino terminal domain of full length (FL) CARDS toxin (i.e., N-CARDS) retains ADP-ribosyltransferase (ART) activity. N-CARDS selectively ADP-ribosylates NLRP3 of the NLRP3 inflammasome complex, resulting in inflammasome activation and subsequent release of IL- 1β, a potent pro-inflammatory cytokine. In preliminary results, we also show that CARDS toxin selectively ADP-ribosylates serine hydroxymethyltransferase (SHMT2), which is involved in one carbon metabolism, and EF1γ, which is involved in the transfer of aminoacyl-tRNAs to the ribosome. The unique carboxyl region of FL CARDS toxin (i.e., C-CARDS) selectively binds to receptors surfactant protein-A (SP-A), annexin A2 (AnxA2) and phospholipids, phosphatidylcholine (PC) and sphingomyelin (SM). Internalization of FL CARDS toxin follows receptor-mediated binding, with subsequent ADP-ribosylation of host target proteins, vacuolation, hyperinflammation and cell/tissue histopathology and injury. Interestingly, C-CARDS alone causes both vacuole formation in human cells and eosinophilic inflammation in naïve mice, leading to an asthma-like phenotype. In this proposal, we intend to identify how ART and vacuolating properties of CARDS toxin trigger pro-inflammatory and pathologic responses in human WT, silenced or knockout cells and in WT and knockout mice. Based on our preliminary results, we hypothesize that both ADP-ribosylating and vacuolating activities contribute to the overall ability of CARDS toxin to initiate and sustain disease pathogenesis. We plan to test this hypothesis by – a) studying how CARDS toxin ART activities initiate inflammatory pathways and cytopathology, b) elucidating the role of receptor binding in CARDS toxin-mediated inflammation, c) characterizing how vacuolating activity promotes airway inflammation and injury, and d) analyzing the in vivo involvement of select ART and receptor targets in triggering CARDS toxin-mediated airway inflammation and lung pathology. Understanding the mechanisms by which ART and vacuolating activities of CARDS toxin regulate host response should lead to therapeutic interventions and improved societal well-being.