CYTOSKELETON AND SIGNAL TRANSDUCTION IN HOST DEFENSE

细胞骨架组装和拆卸的过程对于许多细胞来说是必不可少的。 关键的吞噬细胞功能，包括运动，粘附，从 血管系统、吞噬作用和细胞因子或整合素刺激的 呼吸爆发了解细胞骨架 组装是受调节的，并反过来指导宿主的功能 防御细胞是增强宿主免疫力的主要机制的核心 在炎症部位的防御，并可能导致新的机制， 进行药物干预以增强宿主防御。但 这种调节及其对白细胞影响的分子细节 激活很难研究。我的实验室最近 一系列的实验，大大提高了对 细胞骨架在白细胞活化的生物化学中的作用。我们 已经发现肌动蛋白相关的细胞骨架是一种新的 细胞内Ca+2释放的IP 3非依赖性途径 在吞噬细胞中。该途径由IgG Fc受体的连接启动 也可能连接整联蛋白补体受体CR 3。 此外，我们还发现了一种名为l- [Ca+2]i的增加需要纤维蛋白酶。L-plastin具有 这些特征表明它可能在白细胞中起重要作用 activation.它仅在白细胞中表达，其肌动蛋白结合是 受Ca+2影响，当白细胞 都被激活了本申请的总体实验计划是 验证l-plastin是吞噬细胞必需蛋白质的假设 activation.为此，该提案有三个相互依存的目标： 了解吞噬细胞中l-plastin的细胞生物学和生物化学; 以确定在纤维蛋白原表达和纤维蛋白原表达的改变的影响， 在吞噬细胞中的细胞骨架和信号转导上的功能;以及 测定质膜受体突变对l-纤溶酶原激活剂的影响 功能这些研究将明确测试l-plastin在 白细胞活化，并将增强对IP 3非依赖性 吞噬细胞胞内钙释放。L-的相互作用 具有肌动蛋白的纤维蛋白酶可能代表治疗的重点靶点， 增强宿主防御和用于治疗自身免疫性和过敏性疾病 也

The process of cytoskeleton assembly and disassembly is essential for many critical phagocyte functions including locomotion, adhesion, egress from the vasculature, phagocytosis, and cytokine or integrin-stimulated respiratory burst. Understanding the mechanisms by which cytoskeleton assembly is regulated and acts in turn to direct the function of host defense cells is at the core of a major mechanism for augmentation of host defense at sites of inflammation, and likely will lead to novel mechanisms for pharmacological intervention to enhance host defense. However, the molecular details of this regulation and of its influence on leukocyte activation have been difficult to study. My laboratory has recently done a series of experiments which significantly advance understanding of the role of the cytoskeleton in the biochemistry of leukocyte activation. We have found that the actin-associated cytoskeleton is required for a novel IP3-independent pathway for the release of Ca+2 from intracellular stores in phagocytes. This pathway is initiated by ligation of IgG Fc receptors and perhaps ligation of the integrin complement receptor CR3 as well. Furthermore, we have found that a specific actin binding protein called l- plastin is required for this increase in [Ca+2]i. L-plastin has characteristics which suggest it may play an important role in leukocyte activation. It is expressed only in leukocytes, its actin binding is affected by Ca+2, and it undergoes serine phosphorylation when leukocytes are activated. The overall experimental plan of this application is to test the hypothesis that l-plastin is an essential protein in phagocyte activation. For this, the proposal has three interdependent goals: to understand the cell biology and biochemistry of l-plastin in phagocytes; to determine the effects of alterations in plastin expression and plastin function on cytoskeleton and signal transduction in phagocytes; and to determine the effect of plasma membrane receptor mutations on l-plastin function. These studies will definitively test the role of l-plastin in leukocyte activation and will enhance understanding of IP3-independent Ca+2 release from intracellular stores in phagocytes. Interaction of l- plastin with actin likely represents a focused target for therapies to augment host defense and for treatment of autoimmune and allergic diseases as well.