OGR1 is a proton-sensing GPCR in airway smooth muscle

描述(由申请人提供)：大量研究表明，气道pH值的改变有助于阻塞性呼吸道疾病的病理生理学。呼吸道酸化可由外源性和内源性因素引起，包括呼吸道炎症。神经机制已被证明能够介导酸中毒引起的支气管收缩，但气道微环境中pH降低是否对气道平滑肌(ASM)有直接影响尚不清楚。我们已经发现，ASM表达OGR1，这是一个独特的G蛋白偶联受体(GPCRs)亚家族的成员，被认为是“质子传感”。初步数据表明，OGR1在ASM中表达，并在响应细胞外pH降低时，以与促收缩GQ偶联GPCRs一致的方式发出信号。此外，观察到气管环在体外收缩，缓冲液pH略有下降，与OGR1的激活曲线平行。由于酸中毒/pH在整合系统中的影响分析中固有的复杂问题，我们建议首先对人ASM细胞中的OGR1信号和功能进行仔细的、限制性的分析，以建立ASM OGR1的相关性。目的1将使用药理学和分子生物学技术来描述在ASM中酸诱导的信号和收缩过程中OGR1的信号事件及其要求。AIM 2将确定在ASM中OGR1的激活涉及到质子对受体的直接激活，同时试图排除酸激活的自分泌或旁分泌试剂的任何作用。如果成功，这些研究将发现ASM中一条新的信号通路，该信号通路可能在多种呼吸道疾病的病理生物学中发挥重要作用，并为后续研究OGR1在ASM中的pH调节能力及其与呼吸道功能的相关性提供坚实的基础。 与公共健康相关：许多研究表明，由环境来源(空气污染)或肺部内部(吸入胃酸，或通过呼吸道炎症)引起的呼吸道酸化(pH值降低)可导致呼吸道平滑肌收缩，从而引起或促成哮喘或慢性阻塞性肺病等疾病。我们发现，气道平滑肌细胞表达OGR1受体，该受体最近被认为可被酸化/降低pH激活。因此，OGR1代表了一种新的途径，当暴露于环境或内源性酸源时，气道平滑肌可能通过这种途径收缩。我们提出了一项全面的分析，以阐明OGR1在人类呼吸道平滑肌细胞中的信号和功能能力。这些研究的成功完成将确定一种新的呼吸道平滑肌收缩机制，并为阻塞性肺疾病的治疗提供新的靶点。

DESCRIPTION (provided by applicant): Numerous studies suggest alterations in airway pH contribute to the pathophysiology of obstructive airway diseases. Airway acidification can be caused by exogenous as well as endogenous sources including airway inflammation. Neural mechanisms have been shown capable of mediating acidosis-induced bronchoconstriction, but whether reduced pH in the airway microenvironment has direct effects on airway smooth muscle (ASM) is unknown. We have discovered that ASM expresses OGR1, a member of a unique subfamily of G protein-coupled receptors (GPCRs) proposed to be "proton-sensing." Preliminary data suggest OGR1 is expressed in ASM and, in response to reductions in extracellular pH, signals in a manner consistent with pro-contractile Gq-coupled GPCRs. Moreover, tracheal rings are observed to contract ex vivo with modest step decreases in buffer pH that parallel the activation profile of OGR1. Because of the complex issues inherent in analysis of the effect of acidosis/pH in integrative systems, we propose to first undertake a careful, restricted analysis of OGR1 signaling and function in human ASM cells, to establish the relevance of ASM OGR1. Aim 1 will use pharmacological and molecular biology techniques to delineate the signaling events and their requirement for OGR1 in acid-induced signaling and contraction in ASM. Aim 2 will establish activation of OGR1 in ASM involves direct activation of the receptor by protons, while attempting to exclude any role for acid-activated autocrine or paracrine agents. If successful, these studies will identify a novel signaling pathway in ASM that could play a prominent role in the pathobiology of numerous airways diseases, and provide a solid basis for subsequent integrative studies examining the capacity and relevance of pH regulation of OGR1 in ASM and airway function. PUBLIC HEALTH RELEVANCE: Numerous studies suggest that acidification (reduced pH) of the airway, caused by either environmental sources (air pollution) or from within the lung (aspiration of stomach acid, or via airway inflammation) can cause airway smooth muscle to contract and thereby cause or contribute to diseases such as asthma or chronic obstructive pulmonary disease. We have discovered that airway smooth muscle cells express the receptor OGR1 which has recently been proposed to be activated by acidification/reduced pH. Thus OGR1 represents a novel means by which airway smooth muscle might contract when exposed to environmental or endogenous sources of acid. We propose a comprehensive analysis to clarify the ability of OGR1 to signal and function in human airway smooth muscle cells. Successful completion of these studies will identify a novel mechanism of airway smooth muscle contraction and a new target for therapies for obstructive lung diseases.