The role of talin and vinculin in neuronal mechanosensing.

在发育过程中，数十亿个神经元形成称为轴突的长细胞延伸，这些轴突找到通往特定目标部位（如其他神经元）的途径。通过这些连接，神经元形成了一个高度组织化的网络，并以电信号和化学信号的形式传输信息，这些信号控制着我们的器官功能。神经元不仅在神经系统发育期间需要找到特定的目标，而且在受伤后，当它们必须通过受损组织再生时也需要找到特定的目标。无法重新连接通常会导致严重的健康问题-例如，迄今为止，脊髓损伤后没有恢复功能的治疗方法。几十年来，神经科学一直专注于调节神经元生长和再生的化学信号，但我们仍然远远没有理解为什么人类大脑和脊髓中的神经元不能再生。大脑中的环境在发育、正常衰老、受伤和某些疾病期间会发生巨大变化。脑组织非常柔软。然而，它在衰老过程中变得更硬（男性比女性更硬），在病理条件下，它的结构和硬度会发生显着变化。突出的例子是受伤或中风后的疤痕，以及阿尔茨海默氏症等疾病中刚性斑块或缠结的形成。神经元感觉到它们环境中的这种机械变化，并以它们行为的剧烈变化作出反应，正如脊髓损伤后由于疤痕的存在而导致轴突再生失败所最好地说明的那样。因此，了解神经元如何对力学环境做出反应是很重要的，如果我们想更进一步治疗脊髓损伤，神经元可以通过对环境施加力并探测其变形来感受环境的刚度。为了传递力，它们使用特殊的蛋白质“抓住”邻近的结构，这种蛋白质被称为整合素。这些整合素不仅与细胞的环境结合，而且还连接到细胞内的骨架。这种联系不是直接的，而是由将两者耦合或解耦的组件调节的。我们做了一些初步实验，表明其中两种耦合蛋白（称为talin和vinculin）允许神经元测量其环境的硬度，但它们如何做到这一点仍然不清楚。为了研究这些蛋白质如何调节神经元对机械环境的反应，以及它们在多大程度上参与告诉神经元在哪里生长，曼彻斯特和剑桥的两个实验室合作，联合收割机将他们长期以来的专业知识与整合素，神经元和力结合起来。拟议的研究旨在（i）确定talin和vinculin如何在外部世界和内部骨骼之间传递机械信息，（ii）研究它们在感知神经元环境中的刚度差异方面的作用以及这如何影响神经元的生长和指导，以及（iii）了解talin和vinculin如何相互作用以及与另一种名为RIAM的蛋白质相互作用，这可能解释了机械信号如何控制轴突生长和寻路。为了实现我们的目标，我们不仅将使用尖端的显微镜，生物物理学和分子生物学技术，而且还将开发新的工具来模拟神经元遇到的机械改变的环境条件。我们的研究结果将被结合到一个模型中，该模型概述和预测环境信号和细胞内过程如何在发育，衰老和疾病过程中促进神经元的生长和指导。最终，所获得的知识可能会导致我们目前治疗不同神经元疾病患者的方式发生重要变化，例如，它可能有助于脊髓损伤的成功治疗方法。

During development, billions of neurons form long cellular extensions called axons, which find their way to specific target sites such as other neurons. Through these connections neurons form a highly organised network and transmit information in form of electrical and chemical signals that govern our organ functions. Neurons need to find specific targets not only during the development of the nervous system but also after injury, when they have to regrow through damaged tissue. Failure to reconnect often leads to severe health problems - for example, to date there is no treatment for recovering function after spinal cord injuries. Neuroscience has focused on chemical signals regulating growth and regrowth of neurons for decades, but we are still far from understanding why neurons in human brains and spinal cords do not regenerate.The environment in the brain alters enormously during development, normal ageing, injury and certain diseases. Brain tissue is extremely soft. However, it becomes stiffer during ageing (in men more than in women), and under pathological conditions it can change dramatically in structure and stiffness. Prominent examples are scarring after injury or stroke, and the formation of rigid plaques or tangles in diseases such as Alzheimer's. Neurons sense such mechanical changes in their environment and respond with drastic changes in their behaviour, as best illustrated by the failure of axons to regrow after spinal cord injury due to the presence of scars. Therefore, understanding how neurons respond to their mechanical environment is important if we want to get a step closer to treating, for example, spinal cord injuries.Neurons can feel the stiffness of their environment by exerting forces on it and probing its deformation. In order to transmit forces, they 'grab' neighbouring structures using special proteins, which are called integrins. These integrins not only bind to the environment of the cells but also connect to a skeleton inside the cells. This link is not direct but is regulated by components that couple or uncouple the two. We did some first experiments that suggest that two of these coupling proteins (which are called talin and vinculin) allow neurons to measure the stiffness of their environment, but how they do this is still unclear. In order to investigate how these proteins regulate the neuronal response to their mechanical environment, and to what extent they are involved in telling neurons where to grow, two laboratories in Manchester and Cambridge team up and combine their long-standing expertise with integrins, neurons and forces. The proposed research aims to (i) determine how talin and vinculin transmit mechanical information between the outside world and the inside skeleton, (ii) investigate their role in sensing stiffness differences in the environment of neurons and how this affects neuronal outgrowth and guidance, and (iii) understand how talin and vinculin interact with each other and with another protein named RIAM, which likely explains how mechanical signals control axon outgrowth and pathfinding. To reach our goals, we will not only use cutting edge microscopy, biophysics and molecular biology techniques but also develop new tools to mimic the mechanically altered environmental conditions that neurons encounter. Our results will be combined into a model that outlines and predicts how environmental signals and intracellular processes contribute to neuronal outgrowth and guidance during development, ageing and disease. Ultimately, the knowledge gained may lead to important changes in how we currently treat patients with different neuronal disorders, and it might thus, for example, contribute to successful treatment approaches to spinal cord injuries.