Mechanisms of Heat Activation and Multimodal Functions of VR1 Receptor Channels

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。本研究关注伤害感觉的离子通道，特别是克隆香草样蛋白受体TRPV1。最近对该通道的研究表明，其功能和调节具有前所未有的复杂性，并涉及到外源性有害刺激（如热、香草素和酸）和内源性促炎信号的检测和整合。该项目的目标是在分子水平上，利用单通道电生理学和分子生物学相结合的方法，确定受体如何在响应各种刺激时作为多功能有害探测器和积分器发挥作用。第一个目标将集中在通道的多模态激活机制。为了确定热敏性是否需要其他刺激来激活通道，以及不同模态的刺激如何在受体内相互作用，提出了实验。这项工作还将开发统一通道多模态门控的变构模型。第二个目标是研究多模态激活的结构基础。该研究将检查不同刺激的门控机制在多大程度上是分离的，并将描绘每种刺激特有的分子结构域，并确定它们的功能机制。第三个目标涉及通道的脱敏和恢复。我们拟通过实验量化并建立TRPV1激活导致PIP2耗竭的机制，并阐明脱敏状态的性质。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 understanding the biology of pain. This research concerns ion channels underlying nociception, in particular, the cloned vanilloid receptor TRPV1. Recent studies of the channel have shown a previously unsuspected level of complexity in its function and regulation and have implicated it in detection and integration of both exogenous noxious stimuli such as heat, vanilloids and acids and endogenous proinflammatory signals. The goal of the project is to determine, at the molecular level, how the receptor functions as a versatile noxious detector and integrator in response to various stimuli, using methods of single-channel electrophysiology combined with molecular biology. The first aim will focus on the mechanisms of the polymodal activation of the channel. Experiments are proposed to determine whether the heat sensitivity is required by other stimuli to activate the channel and how the stimuli of different modality interact within the receptor. The work will also develop allosteric models that unify the polymodal gating of the channel. The second objective is to investigate the structural basis of the polymodal activation. The study will examine to what extent the gating machinery for different stimuli are separated and will delineate the molecular domains specific to each stimulus and determine their functional mechanisms. The third aim concerns the desensitization and recovery of the channel. Experiments are proposed to quantify and establish the mechanisms of the depletion of phosphatidylinositol-45-bisphosphate (PIP2) caused by activation of TRPV1, and to elucidate the nature of the desensitized states. 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.