How does the Scar/WAVE complex control actin protrusions and cell migration? A combined cell biology and cryo-EM approach.

我们试图通过爬行来理解细胞迁移，这是一个贯穿生长、生命和死亡的重要过程。在生命早期，胚胎的形状和结构依赖于迁移，随着神经元末端相互爬行，新的神经连接形成。正常的生命是由细胞迁移维持的-组织的生长和正常损伤的修复需要细胞以精确控制的方式移动。免疫反应需要细胞通过组织迁移到像淋巴结这样的结构中，以满足和交换信息。而疾病的过程通常是通过细胞迁移来实现的。也许最著名的例子是癌症转移。癌细胞可能开始从其原始肿瘤中迁移。在此过程中，它们进入血液或淋巴管，并扩散到其他部位，这是癌症造成的大部分损害的基础。这些突起从细胞的前部突出，与局部环境接触并粘附，然后为细胞提供框架，以拉动并驱动自己向前。它们是由一种叫做肌动蛋白的小蛋白质组成的，它们的形成和维持是由一种叫做疤痕/波复合物（WRC）的大蛋白质组装控制的。在这个补助金中，我们试图了解WRC是如何工作的。如果我们能理解这一点，我们就能理解细胞如何选择是否移动，以及当它们移动时它们会向哪个方向移动，我们想了解细胞将非活性WRC转化为活性形式的机制。非活性形式存在于细胞质中，与其他蛋白质相互作用很少。活性形式的行为完全不同-它似乎通过结合，定位和激活许多蛋白质来发挥枢纽作用，这些蛋白质构成了片状和伪足。在本补助金中，我们寻求以下问题的答案：1。主动式WRC最重要的特性是什么？有没有一种蛋白质是特别重要的，如果有的话，是什么？如果没有，它是否只是作为一个通用的枢纽，将细胞需要移动的许多蛋白质聚集在一起？2.如果我们使用冷冻电子显微镜的先进技术揭示WRC的分子结构，我们能否理解这种从非活性到活性形式的变化是如何协调的？我们的初步数据显示，目前关于这一机制的想法可能是错误的。给定WRC的结构，我们能确定细胞中发生了什么来控制WRC的激活吗？和4.我们能找出WRC信号是如何关闭的吗？这四个问题的完整答案将使我们重新关注我们如何理解细胞迁移，并告知每一位研究移动细胞的生物医学科学家。

We seek to understand cell migration by crawling, a process which is important throughout growth, life and death.Early in life, embryos depend on migration for their shape and structure, and new nerve connections form as the ends of neurons crawl towards one another. Normal life is maintained by cell migration - growth of tissues and repair of normal damage require cells to move in precisely-controlled ways. Immune responses require cells that migrate through tissues and into structures like lymph oneds to meet and exchange information. And disease processes often use cell migration. Perhaps the best-known case is cancer metastasis. Cancer cells may start to migrate away from their original tumour. In doing so they enter the bloodstream or lymph vessels, and spread to other sites, underpinning much of the damage caused by cancer.Cells crawl using similar structures called lamellipods and pseudopods. These protrude from the front of the cell, engage with the local environment and adhere, then provide the framework for cells to pull on and drive themselves forwards. They are made of a small protein called actin, and their formation and maintenance are controlled by a large protein assembly called the Scar/WAVE complex, or WRC. In this grant we seek to understand how the WRC works. If we can understand this, we can understand how cells choose whether to move, and which direction they go in when they do so.We want to understand the mechanisms through which cells convert the inactive WRC to the active form. The inactive form resides in the cytoplasm and interacts with few other proteins. The active form behaves completely differently - it seems to act as a hub by binding, localising and activating many the proteins that make lamellipods and pseudopods. In this grant we seek answers to the following questions:1. What is the most important property of active WRC? Is there one protein that is particularly crucial, and if so what is it? And if not, does it just act as a general hub, pulling together many of the proteins a cell needs to move?2. If we reveal the molecular structure of the WRC, using the advanced technique of cryo-electron microscopy, can we understand how this change from inactive to active forms is orchestrated? Our preliminary data show that current ideas for how this works are probably wrong.3. Given a structure for WRC - can we identify what happens in the cell to control the activation of the WRC? And4. Can we find out how the active WRC signal is turned off?A full answer to these four questions would cause a complete refocus in how we understand cell migration, and inform every biomedical scientist who works on cells that move.