Divide and rule: localised Ca2+ signalling in sensory neurons

为了感知和评估环境，动物和人类都配备了神经系统的一个特殊部分，即体感系统。它包括贯穿我们身体的神经，收集有关周围条件的信息（例如我们触摸的物体的温度和硬度）以及我们自己身体的完整性。这些神经包含各种分子传感器，它们通过产生微型电信号来响应特定的外部事件（如触摸热物体），然后将这些信号发送到大脑进行解释。单个神经通常具有一系列不同的传感器来响应不同的刺激，但不同刺激产生的电信号非常相似。感觉生理学领域的一个主要难题是不同类型的信号是如何被单个感觉神经细胞特异性地解释的;这个提议的首要目标是试图解决这个难题。基于我们的初步数据和我们小组和其他人发表的大量工作，我们提出了可能解释这种信号编码的想法：不同的信号传导机制可能被“包装”在神经细胞内的某些区域的空间中分离的特定点中。这样一个信号机制与另一个信号机制的物理分离允许神经细胞使用共同的信号事件和信使分子，而不会“混淆”信息的含义。我们专注于一个特定的方面：神经如何对局部炎症做出反应，这是一个经常导致疼痛（如牙痛或关节炎疼痛）的过程，以及这些反应如何与神经对其他感官刺激的反应不同。我们小组的工作指出了一种特殊的结构，它形成于神经细胞的外屏障（“质膜”）和一种被称为“内质网”的池状细胞器之间的连接处，这种细胞器存在于神经细胞本身中。这种连接形成微小的空间（“纳米结构域”），与细胞内部的其余部分相对较好地分离，并包含负责检测组织炎症的传感器。一旦这些传感器被触发，细胞机制就会激活感觉神经细胞，最终导致炎症性疼痛的感觉。我们已经确定了这种连接结构的一些组成部分及其对炎症性疼痛的整体重要性。然而，关于这些连接是如何形成和维持的，连接中的关键蛋白质是如何排列的，以及这些蛋白质是如何响应炎症而变化的，几乎一无所知。我们的项目旨在缩小我们知识中的这一差距，最终目标是学习如何干扰这一途径并将炎症与疼痛分开。该建议有三个具体目标：1）识别负责感觉神经交界区通信的关键组件。2)发现当神经细胞对炎症做出反应时这些成分如何相互作用。3）开发技术来研究神经末梢尖端的这些连接空间。我们开发了一种全面的多学科方法，结合了超分辨率显微镜、蛋白质组学、分子和细胞生物学方法以及动物行为研究等尖端方法。我们相信，这项研究将使我们对神经细胞信号编码的理解达到一个新的水平。具体来说，我们将解开复杂的分子机制负责生产炎症疼痛的感觉。这些新知识可能会塑造未来的疼痛治疗方法。

In order to perceive and evaluate the environment, animals and humans are equipped with a special part of the nervous system, the somatosensory system. It includes nerves that run through our body and collect information about surrounding conditions (such as temperature and stiffness of objects we touch) and also about our own body's integrity. These nerves contain various molecular sensors that respond to specific external events (like touching a hot object) by producing miniature electrical signals that are then sent to the brain for interpretation. A single nerve usually possesses a range of different sensors to respond to different stimuli, yet the electrical signals produced by different stimuli are very similar. A major puzzle in the field of sensory physiology is how different types of signals are specifically interpreted by a single sensory nerve cell; the overarching aim of this proposal is to attempt to solve this puzzle.Based on the wealth of our preliminary data and published work from our group and others, we propose the idea that may explain such signal coding: different signalling mechanisms might be 'packed' in specific spots separated in space at certain areas within the nerve cell. Such physical separation of one signalling machinery from another allows nerve cells to use common signalling events and messenger molecules without 'mixing up' the meaning of the message. We are focusing on one specific aspect: how a nerve responds to local inflammation, a process that often results in pain (such as toothache or arthritic pain) and how these responses are different form nerve's responses to other sensory stimuli. Our group's work points to one specific structure formed at junctions between the outer barrier ('plasma membrane') of a nerve cell and a cistern-like organelle called the 'endoplasmic reticulum', which is found in the nerve cell itself. Such junctions form tiny spaces ('nanodomains') which are relatively well separated from the rest of the cell interior and contain a slew of sensors responsible for detection of tissue inflammation. Once these sensors are triggered, the cellular machinery activates the sensory nerve cell and ultimately results in the feeling of inflammatory pain. We have already identified some components of this junctional structure and its overall importance for inflammatory pain. However, hardly anything is known about how these junctions are formed and maintained, how the key proteins within the junction are arranged and how these change in response to inflammation. Our project aims to close this gap in our knowledge with an ultimate goal of learning how to disturb this pathway and separate inflammation from pain. This proposal has three specific aims: 1) Identify key components responsible for communication in the sensory nerve's junctional space. 2) Discover how these components interact when a nerve cell responds to inflammation.3) Develop techniques to study these junctional spaces at the tips of nerve endings. We have developed a well-rounded and multidisciplinary approach combining cutting-edge methods such as super-resolution microscopy, proteomics, molecular and cell biology approaches and animal behavioural studies. We are confident that this research will bring our understanding of nerve cell signal coding to a new level of insight. Specifically, we will unravel complex molecular machinery responsible for production of inflammatory pain sensation. This new knowledge may shape future methods for pain treatment.