Signal Integration in Neutrophil Chemotaxis

描述（由申请人提供）：中性粒细胞是先天免疫细胞，利用定向迁移来寻找和杀死细菌。这种定向迁移依赖于几个基本的信号功能。中性粒细胞可以迁移到几个数量级的趋化梯度上，需要信号适应，以便细胞对相对变化而不是配体的稳态浓度作出反应。中性粒细胞产生一致的内部极性，不依赖于外部梯度的陡峭程度，需要正反馈来放大微妙的信号不对称和远程抑制，以便突起可以相互竞争以产生优势前沿。通过基因和药理学功能丧失实验，我们知道了趋化性所需的许多核心成分。然而，我们对这些信号成分如何相互作用以产生细胞极性和运动的理解仍然存在根本差距。由于极性的整体过程非常复杂，我们开发了工具来分离和剖析信号级联中的各个步骤，以更好地理解整个信号电路。在过去的一段时间里，我们开发了一种用于定量光遗传学控制哺乳动物细胞内信号传导的一般方法。该系统为我们提供了前所未有的对大范围细胞内信号的空间和时间控制，并使我们能够以传统工具无法实现的方式剖析信号处理的逻辑。细胞内信号的定量控制在揭示动作电位的逻辑中起着重要的作用

DESCRIPTION (provided by applicant): Neutrophils are innate immune cells that use directed migration to hunt and kill bacteria. This directed migration depends on several fundamental signaling capabilities. Neutrophils can migrate up chemotactic gradients spanning several orders of magnitude, requiring signaling adaptation so that cells respond to relative changes rather than steady-state concentrations of ligand. Neutrophils generate a consistent internal polarity that does not depend on the steepness of the external gradient, requiring positive feedback to amplify subtle signaling asymmetries and long-range inhibition so that protrusions can compete with one another to generate a dominant leading edge. Through genetic and pharmacological loss-of-function experiments, we know many of the core components required for chemotaxis. However, there are still fundamental gaps in our understanding of the how these signaling components interact to generate cell polarity and movement. Because the overall process of polarity is highly complex, we have developed tools to isolate and dissect individual steps in the signaling cascade to better understand the overall signaling circuit. In the last gran period, we developed a general approach for quantitative optogenetic control of intracellular signaling in mammalian cells. This system gives us unprecedented spatial and temporal control of a wide range of intracellular signals and will enable us to dissect the logic of signal processing in a manner that has not been possible with conventional tools. Quantitative control of intracellular signals has played a fundamental role in uncovering the logic of action potentials and bacterial chemotaxis, and we envision that our optogenetic tools will be similarly transformative for understanding cell polarity in neutrophils. Our specific aims are to understand the sensory adaptation that accounts for the remarkable dynamic range of chemotaxis (Aim 1) and to dissect the positive feedback loops (Aim 2) and long-range inhibition (Aim 3) that make neutrophil polarity possible.