The Role of Flagellar Motility to Innate Immune Recognition of Bacteria

摘要 革兰氏阴性菌，包括铜绿假单胞菌，引起大量的 发病率和死亡率：细菌性肺炎、败血症和慢性病约占总数的15% 死亡在美国。因此，我们必须开发一种更好的细胞和分子 了解宿主与细菌病原体的相互作用，细菌如何避免或操纵 我们的目标是提高宿主的反应，并制定新的战略，以预防疾病和改善病人护理。 细菌的游动运动，由其鞭毛赋予，已经被认识超过25年， 影响细菌感染宿主并在宿主中定居的能力。重要的是，最初感染需要运动性， 宿主，但细菌必须成为非运动的持续在临床慢性感染。一个描述得很好的 例如，铜绿假单胞菌运动性的丧失与细菌负荷的增加直接相关， 增加囊性纤维化患者的疾病严重程度。然而，为什么和如何的根本原因 细菌运动性的变化改变感染和疾病的过程是未知的。我们最近 第一次正式证明，这是细菌运动性的丧失，而不是鞭毛的丧失。 表达，其赋予逃避免疫应答的优势。具体来说，我们已经证明， 在许多细菌属中，细菌运动性的丧失导致细菌对吞噬作用的抗性， 在体外和体内。因此，能动性代表了一种新颖而广泛的机制， 免疫系统识别细菌并作出反应，是细菌成功地 在慢性感染期间逃避免疫反应。因此，本提案的中心目标是 确定免疫细胞对细菌运动性作出反应的机制。我们最近的发现 吞噬细胞PI 3 K和Akt活性对细菌鞭毛运动性有反应，这鉴定了新的调节 的细胞内途径，决定吞噬命运的Pa。我们利用这一发现， 确定了两个新的关键分子环节，在这个运动诱导的信号转导途径。基于我们 初步数据，在具体目标1中，我们的工作假设是Pa运动刺激的吞噬细胞 信号通过CIN 85/src-家族激酶途径转导至PI 3 K/Akt。我们的假设是 具体目标2是c-Abl通路也响应于运动诱导的运动诱导的运动，并且是运动诱导的运动诱导的运动所需的。 吞噬作用因此，我们建议鉴定有助于运动诱导的细胞凋亡的c-Abl分子。 吞噬作用，以及该途径如何在功能上与PI 3 K/Akt轴相交。实现这些 目的将提供一个机制的理解如何损失的细菌能动性，使免疫逃避 和感染的持续性，并将确定分子靶点， 治疗清除慢性感染中存在的非运动性耐药细菌。

Abstract The Gram-negative bacteria, which include Pseudomonas aeruginosa, cause substantial morbidity and mortality: bacterial pneumonia, septicemia and chronic disease account for ~15% of the total deaths in the USA. Therefore, it is imperative that we develop a better cellular and molecular understanding of the host interactions with bacterial pathogens, how bacteria avoid or manipulate the host's response, and to develop new strategies to prevent disease and improve patient care. Bacterial swimming motility, conferred by their flagella, has been recognized for over 25 years to influence the ability of bacteria to infect and colonize a host. Importantly, motility is required to initially infect the host, but bacteria must become non-motile to persist during clinical chronic infection. A well-described example is that the loss of P. aeruginosa motility directly correlates with increased bacterial burdens and increased disease severity in Cystic Fibrosis patients. However the underlying reasons for why and how changes in bacterial motility alter the course of infection and disease are unknown. We have recently provided the first formal demonstration that it is loss of bacterial motility, rather than loss of flagellar expression, that confers an advantage towards evasion of immune responses. Specifically, we have shown that loss of bacterial motility, in a variety of bacterial genera, results in bacterial resistance to phagocytosis in vitro and in vivo. Thus motility represents a novel and widespread mechanism by which the innate immune system recognizes and responds to bacteria – and is a mechanism by which bacteria successfully elude immune responses during chronic infection. Therefore this proposal has the central goal of identifying the mechanisms by which immune cells respond to bacterial motility. Our recent finding that phagocyte PI3K and Akt activity are responsive to bacterial flagellar motility identifies novel regulation of an intracellular pathway that determines the phagocytic fate of Pa. We have leveraged this finding to identify two new critical molecular links in this motility-induced signal transduction pathway. Based on our preliminary data, in Specific Aim 1 our working hypothesis is that the Pa motility-stimulated phagocytic signal is transduced through a CIN85/src-family kinase pathway to PI3K/Akt. Our working hypothesis for Specific Aim 2 is that the c-Abl pathway is also responsive to, and required for, motility-induced phagocytosis. Therefore we propose to identify the c-Abl molecule(s) that contribute to motility-induced phagocytosis, and how this pathway functionally intersects with the PI3K/Akt axis. Achievement of these Aims will provide a mechanistic understanding of how loss of bacterial motility enables immune evasion and persistence of infection, and will identify molecular targets which can potentially be targeted to effect the therapeutic clearance of the non-motile, antibiotic-resistant bacteria present in chronic infections.