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--体感系统。它包括贯穿我们身体的神经，收集关于周围条件的信息(如我们接触的物体的温度和硬度)，也收集关于我们自己身体完整性的信息。这些神经包含各种分子传感器，通过产生微小的电信号来对特定的外部事件(如触摸热物体)做出反应，然后发送到大脑进行解释。单个神经通常拥有一系列不同的传感器来对不同的刺激做出反应，但不同的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，单个感觉神经细胞如何具体解释不同类型的信号；这一提议的总体目标是试图解决这个问题。基于我们的大量初步数据以及我们和其他人发表的工作，我们提出了一个可能解释这种信号编码的想法：不同的信号机制可能被‘包装’在神经细胞内某些区域的特定空间中的特定位置。这样一种信号机制与另一种机制的物理分离使神经细胞可以使用共同的信号事件和信使分子，而不会混淆消息的含义。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，这一过程通常会导致疼痛(如牙痛或关节炎疼痛)，以及这些反应与神经对其他感官刺激的反应有何不同。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部屏障(“质膜”)和被称为“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。这样的连接形成了与细胞内部其他部分分离得相对较好的微小空间(纳米域)，并包含一系列负责检测组织炎症的传感器。一旦这些传感器被触发，细胞机械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成分及其对炎症性疼痛的总体重要性。然而，几乎没有人知道这些连接是如何形成和维持的，连接内的关键蛋白是如何排列的，以及这些蛋白是如何对炎症做出反应的。我们的项目旨在弥合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。这项建议有三个具体目标：1)确定负责感觉神经连接空间交流的关键部件。2)发现当神经细胞对炎症做出反应时，这些成分是如何相互作用的。3)开发技术来研究神经末梢的这些连接空间。我们开发了一种全面的、多学科的方法，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，这项研究将把我们对神经细胞信号编码的理解带到一个新的洞察水平。具体地说，我们将揭开导致炎症性痛感产生的复杂分子机制。这一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.