Subverted host cell signaling by AnkA in Anaplasma phagocytophilum infection

描述(申请人提供)：吞噬细胞无形体，是一种感染中性粒细胞并引起人类粒细胞埃立克体病的人类病原体。在美国，它是仅次于莱姆病的第二种最常见的扁虱相关感染。虽然中性粒细胞在杀菌方面非常有效，但吞噬细胞性假单胞菌是个例外，因为它不仅能逃脱中性粒细胞的杀戮，还能在中性粒细胞内生活和复制。吞噬巨噬细胞干扰超氧化物介导的杀伤并延迟中性粒细胞的凋亡。吞噬细胞性假单胞菌是如何完成这些重大壮举的，目前还知之甚少。这项提议试图确定吞噬细胞菌如何操纵这些细胞过程的基本机制。我们最近在吞噬阿糖胞菌中发现了第一个细菌毒力因子ANKA，它可能在中性粒细胞功能的调控中发挥关键作用。因此，嗜中性粒细胞的吞噬弧菌感染为研究中性粒细胞生物学和细菌杀伤途径提供了一个理想的模型。全球假说是，移位的Anka干扰了中性粒细胞中的宿主信号通路，导致抑制超氧化物生成和延缓细胞凋亡。当细菌与宿主细胞结合后，ANKA被转移到宿主细胞细胞质中，然后迅速被酪氨酸磷酸化(在几秒钟到几分钟内)。酪氨酸磷酸化使Anka与宿主细胞中关键信号蛋白的SH2结构域结合。此外，Anka还可能通过SH3结构域和Ankyrin重复序列与蛋白质结合。通过这些假定的蛋白质相互作用，ANKA可能改变宿主细胞的信号，并导致中性粒细胞的细胞变化。目的1试图确定与Anka结合的宿主细胞蛋白的特异性相互作用。Aim 2建议研究Anka在抑制中性粒细胞杀伤中的作用。目的3研究Anka在延缓中性粒细胞凋亡中的作用。长期的目标是：1)鉴定导致嗜中性粒细胞吞噬弧菌存活的机制，2)开发操纵中性粒细胞的新途径，导致潜在的炎症或感染的新治疗方法，以及3)加强我们对中性粒细胞生物学与免疫系统相关的理解。公共卫生相关性：人类粒细胞性埃立克体病，由吞噬细胞性弧菌引起，是美国第二种最常见的扁虱相关疾病。这项建议旨在研究吞噬细胞性假丝酵母菌如何在中性粒细胞中存活。这可能有助于更好地了解中性粒细胞在免疫系统中的功能，并可能导致潜在的炎症和感染的新疗法。

DESCRIPTION (provided by applicant): Anaplasma phagocytophilum, is a human pathogen that infects neutrophils and causes Human Granulocytic Ehrlichiosis. In the Unites States it is the second most common tick-associated infection, only surpassed by Lyme disease. Although neutrophils are very efficient in killing bacteria, A. phagocytophilum is the exception as it not only escapes killing by neutrophils, it lives and replicates inside neutrophils. A. phagocytophilum interferes with superoxide-mediated killing and delays neutrophil apoptosis. It is poorly understood how A. phagocytophilum accomplishes these major feats. This proposal seeks to identify the basic mechanism how A. phagocytophilum manipulates these cellular processes. Our recent identification of the first bacterial virulence factor in A. phagocytophilum, AnkA, may play a pivotal role in manipulating neutrophil functions. Consequently, A. phagocytophilum infection of neutrophils provides an ideal model to study the pathways involved in neutrophil biology and bacterial killing. The global hypothesis is that translocated AnkA interferes with host signaling pathways in the neutrophil, resulting in the inhibition of superoxide generation and the delay of apoptosis. Upon bacterial binding to the host cell, AnkA is translocated into the host cell cytoplasm and is then rapidly tyrosine phosphorylated (within seconds to minutes). Tyrosine phosphorylation allows AnkA to bind to SH2 domains of key signaling proteins in the host cell. Further, AnkA may also bind proteins via SH3 domains and ankyrin repeats. Through these putative protein interactions AnkA may alter host cell signaling and cause the cellular changes in neutrophils. Aim 1 seeks to identify the specific interactions of host cell proteins that bind to AnkA Aim 2 proposes to study the role of AnkA in inhibition of killing by the neutrophil. Aim 3 will examine the role of AnkA in the delay of neutrophil apoptosis. The long-term goals are: 1) the identification of the mechanism leading to survival of A. phagocytophilum in neutrophils, 2) the development new avenues to manipulate neutrophils, leading to potential new treatments of inflammation or infections, and 3) enhancement of our understanding of neutrophil biology as it relates to the immune system. PUBLIC HEALTH RELEVANCE: Human Granulocytic Ehrlichiosis, caused by A. phagocytophilum, is the second most common tick- associated disease in the United States. This proposal seeks to investigate how A. phagocytophilum can survive in neutrophils. This may lead to a better understanding of the function of neutrophils within the immune system and may lead to potential new treatments of inflammation and infections.