PHOSPHOLIPASE-DEPENDENT SIGNALING IN PHAGOCYTOSIS

单核/巨噬细胞是花生四烯酸的主要细胞来源 (Aa)。这种脂肪酸具有相当大的生物重要性。 二十烷基类炎症介质的前体。尽管它的 新陈代谢是众所周知的，刺激再生障碍性贫血的膜事件 释放是不可能的。氨基酸释放磷脂酶(PL)的鉴定 其响应于所定义的膜事件而被激活，将是 对我们理解受体介导的信号转导有非常重要的价值 和潜在的治疗价值。通过控制AA的释放， 这样的PL将为调节 炎症中炎症介质的水平。PI已经描述了 一种独特的单核细胞磷脂酶，在抗体介导的过程中被激活 吞噬作用。这种吞噬细胞磷脂酶选择性地从 磷脂酰乙醇胺，明显不依赖于钙，是必需的 用于摄取免疫球蛋白调理颗粒。一项体外试验已经完成 研究这种酶的细胞生物学并跟踪其 净化。具体地说，1)PL的特征将是 关于其分类为PLA2或PLC，其调制方式 基于机理的抑制剂及其细胞定位，2)酶 将通过液相等电聚焦和标准 生化技术，3)磷脂酶参与非吞噬事件，如 随着附着力和有毒氧代谢物的产生将被评估， 4)细胞因子刺激和单核细胞成熟对PL的影响 将测量Fc受体的表达和5)成分- 调节PL活性的激活信号级联将是 已确认身份。吞噬磷脂酶和α-磷脂酶的性质 对其调控的了解将促进我们对信号的理解 一般的转导，更具体地说，AA作为一种 细胞内的第二信使，并将增加我们对 炎症的分子机制。

Monocyte/macrophages are a major cellular source of arachidonic acid (AA). This fatty acid has considerable biological importance as it is the precursor of the eicosanoid inflammatory mediators. Although its metabolism is well understood, the membrane events which stimulate AA release are not. Identification of an AA-releasing phospholipase (PL), which is activated in response to a defined membrane event, would be invaluable to our understanding of receptor-mediated signal transduction and of potential therapeutic value. By controlling the release of AA, such a PL would provide a powerful regulatory site for modulation of the levels of inflammatory mediators in inflammation. The PI has described a unique monocytic PL which is activated during antibody-mediated phagocytosis. This phagocytic PL selectively releases AA from phosphatidyl-ethanolamine, is apparently Ca-independent and essential for ingestion of IgG-opsonized particles. An in vitro assay has been developed to study the cell biology of this enzyme and to follow its purification. Specifically, 1) the PL will be characterized with respect to its classification as a PLA2 or PLC, its modulation by mechanism-based inhibitors and its cellular localization, 2) the enzyme will be purified by fluid phase isoelectric focusing and standard biochemical techniques, 3) PL involvement in non-phagocytic events, such as adhesion and generation of toxic oxygen metabolites will be assessed, 4) the effect of cytokine stimulation and monocyte maturation on PL expression will be measured and 5) components of the Fc receptor- activated signalling cascade which regulate PL activity will be identified. Characterization of the phagocytic phospholipase and a knowledge of its regulation will advance our understanding of signal transduction in general and, more specifically, the role of AA as an intracellular second messenger and will increase our knowledge of the molecular mechanisms of inflammation.