Mechanism of Polymodal Activation of VR1 Receptors

描述（由申请人提供）：疼痛开始于被称为伤害感受器的特殊感觉神经元的外周神经末梢的传导。了解这些伤害感受器如何对产生疼痛的刺激作出反应是理解疼痛生物学的关键一步。本研究关注伤害感受的离子通道，特别是克隆的vr1受体，它可以检测和整合多种物理和化学刺激，包括热、香兰素和酸。我们的目标是了解，在分子水平上，受体是如何作为一个多功能的有害探测器，对各种刺激作出反应的。我们的方法包括异种表达系统中重组通道的膜片钳记录，结合动力学分析来揭示激活过程中发生的分子事件，以及诱变来识别受体的功能域。我们的第一个目标是了解热量是如何激活通道的。我们将确定热激活的能量景观，并探索受体中可能存在的热传感器及其结构基础。我们的第二个目标是调查辣椒中的辛辣成分辣椒素是如何激活这个通道的。我们将研究辣椒素结合、解结合和通道门控激活过程的生物物理性质，并确定其分子基础。我们将把热和辣椒素激活途径联系起来，并研究是否有不同的机制用于物理和化学刺激检测。第三个目标是了解痛觉介质如酸如何使通道增敏。我们将探讨质子结合促进热和辣椒素活化的可能变构机制。第四个目标是研究通道的电压依赖性。我们将确定活化动力学是如何被电压改变的，以及电压敏感性的来源。提出的研究将提高我们对伤害感觉转导的认识，并将有利于疼痛治疗的临床进展，特别是寻找具有全新作用模式和前所未有的伤害感受器选择性的镇痛药物。

DESCRIPTION (provided by applicant): Pain begins with transduction at peripheral nerve terminals of specialized sensory neurons called nociceptors. Understanding how these nociceptors respond to pain-producing stimuli is a key step towards the understanding of the biology of pain. This research concerns ion channels underlying nociception, in particular, the cloned VR 1 receptor, which detects and integrates multiple physical and chemical stimuli including heat, vanilloids and acids. Our goal is to understand, at the molecular level, how the receptor functions as a versatile noxious detector in response to various stimuli. Our approach involves patch-clamp recordings from recombinant channels in heterologous expression systems, combined with kinetic analysis to unravel the molecular events occurring during activation, along with mutagenesis to identify functional domains of the receptor. Our first objective is to understand how heat activates the channel. We will determine the energetic landscape of heat activation and explore the existence of possible heat sensors in the receptor and their structural basis. Our second objective is to investigate how capsaicin, the pungent ingredient in hot peppers, activates the channel. We will study the biophysical properties of the activation process regarding capsaicin binding, unbinding and channel gating, and determine their molecular basis. We will correlate heat and capsaicin activation pathways and examine whether different mechanisms are used for physical and chemical stimulus detection. The third objective is to understand how hyperalgesic mediators like acids sensitizes the channel. We will probe possible allosteric mechanisms by which proton binding promotes heat and capsaicin activation. The fourth objective is to investigate the voltage dependence of the channel. We will determine how the activation kinetics is altered by voltage and where the voltage sensitivity originates. The proposed research will improve our knowledge of nociceptive sensory transduction and will benefit clinical advances in pain therapy, in particular, the search for analgesic drugs that have an entirely new mode of action and an unprecedented selectivity for nociceptors.