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气道疾病的病理生理。气道酸化可由包括气道炎症在内的外源性和内源性来源引起。神经机制已被证明能够介导酸中毒诱导的支气管收缩，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。我们发现ASM表达OGR1， OGR1是G蛋白偶联受体（gpcr）独特亚家族的成员，被认为是“质子感应”的。初步数据表明，OGR1在ASM中表达，并响应细胞外pH值的降低，其信号方式与促收缩gq偶联gpcr一致。此外，观察到气管环在体外收缩，缓冲液pH值适度下降，与OGR1的激活谱相似。由于在综合系统中酸中毒/pH影响的分析中固有的复杂问题，我们建议首先对人类ASM细胞中的OGR1信号传导和功能进行仔细，有限的分析，以确定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酸诱导的ASM信号传导和收缩中的信号事件及其对OGR1的要求。Aim 2将建立OGR1在ASM中的激活涉及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药物的任何作用。如果成功，这些研究将在ASM中发现一种新的信号通路，可能在许多气道疾病的病理生物学中发挥重要作用，并为后续的综合研究提供坚实的基础，研究OGR1在ASM和气道功能中pH调节的能力和相关性。

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.