Regulation of Human Phagocyte Function by Rac Proteins

Rac 蛋白对人类吞噬细胞功能的调节

• 批准号: 6703079
• 负责人: ULLA G. KNAUS
• 金额: $ 46.3万
• 依托单位: SCRIPPS RESEARCH INSTITUTE, THE
• 依托单位国家: 美国
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-05-01 至 2007-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6703079
• 关键词: NAD(P)H dehydrogenase; biological signal transduction; clinical research; enzyme activity; free radical oxygen; genetically modified animals; guanine nucleotide binding protein; human subject; infection; laboratory mouse; leukocyte activation /transformation; microglia; microorganism immunology; mitogen activated protein kinase; neutrophil; phagocytosis; phosphorylation; point mutation; protein kinase; tissue /cell culture; toll like receptor

DESCRIPTION (provided by applicant): Reactive oxygen species (ROS) formed by the NADPH oxidase of phagocytic cells play a primary role in host defense and inflammation. A central feature of leukocyte activation upon encountering microbial products is a two-phased response, leading at first to a pre-activated, primed state, which generates a vastly enhanced response upon a secondary, activating stimulus. The molecular patterns associated with microbial pathogens are recognized by Toll-like receptors (TLRs). This recognition leads to TLR activation and signaling events that prime neutrophils for subsequent stimulation by chemoattractants. To understand the molecular basis for this coordinated neutrophil response in respect to ROS generation, we will investigate the signaling pathways from the receptors involved to the final sequence of NADPH oxidase activation. We have shown that oxidase activity is regulated by the GTPase Rac2 and the effector p21-activated kinase (Pak). Our studies so far point to a role of Pak in several aspects of the fMLP-induced respiratory burst including multiple phosphorylation events and association with cytochrome b558. The involvement of Pak in NADPH oxidase assembly at the membrane will be investigated in detail. Studies with Pak-null or transgenic mice harboring a Pak kinase inhibitory fragment will define Pak function in vivo. The signaling sequences emanating from activated TLRs seem to diverge between monocytes and neutrophils, leading to ROS generation versus priming. We hypothesize that Rac-regulated pathways are key elements for understanding how different innate immune cells regulate bacterial killing and we will investigate the molecular mechanisms involved. A common trait connecting TLR2 activation, priming and chemoattractant-induced ROS generation is the dependence on tyrosine phosphorylations. We will elucidate potential associations of TLRs or formyl peptide receptors with tyrosine kinase receptors and evaluate how these complexes relay their signals in neutrophils and microglia. These studies will yield novel insights into the overall control of oxidant formation by innate immune cells.

描述（申请人提供）：吞噬细胞的NADPH氧化酶形成的活性氧（ROS）在宿主防御和炎症中起主要作用。白细胞在遇到微生物产物时激活的一个中心特征是两阶段反应，首先导致预激活的启动状态，该状态在二次激活刺激下产生大大增强的反应。 Toll 样受体 (TLR) 可以识别与微生物病原体相关的分子模式。这种识别导致 TLR 激活和信号事件，为中性粒细胞做好后续化学引诱剂的刺激。为了了解中性粒细胞对 ROS 产生的协调反应的分子基础，我们将研究从涉及的受体到 NADPH 氧化酶激活的最终序列的信号传导途径。 我们已经证明氧化酶活性受 GTPase Rac2 和效应器 p21 激活激酶 (Pak) 调节。迄今为止，我们的研究表明 Pak 在 fMLP 诱导的呼吸爆发的几个方面发挥作用，包括多个磷酸化事件以及与细胞色素 b558 的关联。将详细研究 Pak 在膜上 NADPH 氧化酶组装中的参与。对 Pak 缺失或携带 Pak 激酶抑制片段的转基因小鼠的研究将确定 Pak 的体内功能。 激活的 TLR 发出的信号序列似乎在单核细胞和中性粒细胞之间存在差异，导致 ROS 生成与启动。我们假设 Rac 调节途径是了解不同先天免疫细胞如何调节细菌杀伤的关键要素，我们将研究其中涉及的分子机制。连接 TLR2 激活、引发和化学引诱剂诱导的 ROS 生成的一个共同特征是对酪氨酸磷酸化的依赖性。我们将阐明 TLR 或甲酰肽受体与酪氨酸激酶受体的潜在关联，并评估这些复合物如何在中性粒细胞和小胶质细胞中传递信号。这些研究将为先天免疫细胞对氧化剂形成的总体控制提供新的见解。