Role of Rac and Rac Effectors in Controlling Chemotaxis

描述（由申请人提供）：趋化性在多种细胞中起着核心作用。 生物过程，包括癌细胞的转移、炎性 反应涉及中性粒细胞和巨噬细胞的运动，神经细胞的迁移， 嵴细胞、胚胎形态发生和聚集。的 在真核细胞中控制趋化性的基本过程是高度 在网骨藻和人类之间保守，并利用共同的因子， 集成电路，以控制细胞朝向 化学引诱物这个过程的关键是细胞的能力， 在化学引诱物方向的前缘产生伪足 细胞后部的来源和收缩。我们的目标是了解 细胞感知化学引诱物方向的机制 梯度并利用下游信号通路来控制这一点 细胞骨架的重组。在这个应用程序中，我们专注于角色 的Dictyosteoprotein PAK/Ste 2 O家族成员PAKa，我们已经证明， 在趋化性过程中对肌球蛋白组装的调节至关重要， 小GTP酶的Rac家族。我们建议阐明的机制， PAKa响应于化学引诱物信号传导而被激活，并理解PAKa的作用。 调节其亚细胞定位和功能的分子相互作用 在趋化细胞的后部。此外，我们还提出了一些实验， 研究Rac 1的激活机制，我们已经证明这是一个 在趋化过程中控制肌动蛋白细胞骨架的关键角色。这些 研究包括研究Rac 1激活的动力学和调节 并确定Rac 1在细胞内亚细胞定位的可能变化， 细胞对化学引诱物梯度的反应。了解上游 调节Rac激活，我们建议检查推定的Rac的作用， 交换因子（GEF），其控制Rac蛋白的活化以响应 各种细胞刺激。利用细胞生物学和分子遗传学 在Dictyosteoblasts的方法，我们将定义Rac GEFs的作用，以及它们如何 是受调控的，特别关注检查其亚细胞 定位和这种变化在调节定向反应中的作用。 我们提出的研究也应该有助于阐明PAKa和Rac如何整合到 其他信号通路，是必不可少的控制能力， 网骨藻细胞定向感受和响应化学引诱物 梯度。了解调节PAKa、Rac 1和RacGEFs的机制 将有助于确定控制细胞的一般机制 极化和运动，应该适用于确定如何 趋化性在广泛的细胞中受到调节。

DESCRIPTION (provided by applicant): Chemotaxis plays a central role in diverse biological processes, including metastasis of cancer cells, inflammatory responses involving movement of neutrophils and macrophage, migration of neural crest cells, embryonic morphogenesis, and aggregation in Dictyostelium. The underlying processes that control chemotaxis in eukaryotic cells are highly conserved between Dictyostelium and man and utilize common factors in integrated circuits to control directional cell movement toward a chemoattractant. The key component of this process is the ability of cells to produce a pseudopod at the leading edge in the direction of the chemoattractant source and contraction of the posterior of the cell. Our goal is to understand the mechanisms by which cells sense the direction of the chemoattractant gradient and utilize downstream signaling pathways to control this reorganization of the cytoskeleton. In this application, we focus on the role of the Dictyostelium PAK/Ste2O family member PAKa, which we have demonstrated is essential for the regulation of myosin assembly during chemotaxis, and the Rac family of small GTPases. We propose to elucidate the mechanisms by which PAKa is activated in response to chemoattractant signaling and understand the molecular interactions that regulate its subcellular localization and function in the posterior of chemotaxing cells. In addition, we propose experiments to examine the mechanism of activation of Rac1, which we have demonstrated is a key player in the control of the actin cytoskeleton during chemotaxis. These studies include investigating the kinetics and regulation of Rac1 activation and determining the possible changes in the subcellular localization of Rac1 in cells responding to a chemoattractant gradient. To understand the upstream regulation of Rac activation, we propose to examine the role of putative Rac exchange factors (GEFs) that control the activation of Rac proteins in response to various cellular stimuli. Using cell biological and molecular genetic approaches in Dictyostelium, we will define the role of Rac GEFs and how they are regulated, with a specific focus on examining changes in their subcellular localization and the role of such changes in regulating directional responses. Our proposed studies should also help elucidate how PAKa and Rac integrate into other signaling pathways that are essential for controlling the ability of Dictyostelium cells to directionally sense and respond to chemoattractant gradients. Understanding the mechanisms that regulate PAKa, Rac1, and RacGEFs in Dictyostelium will help define general mechanisms controlling cell polarization and movement that should be applicable to determining how chemotaxis is regulated in a broad range of cells.