Molecular Regulation of Pulmonary Vascular KCa Channel

描述(由申请人提供)：本提案旨在解决钙敏感钾(BKCa)通道的分子调控问题，BKCa是一种离子通道，在平滑肌细胞(SMC)中普遍表达，并在有意义的程度上决定血管SMC张力。我们实验室以前的工作已经证明，在肺动脉(PA)SMC中，BKCa通道具有发育调节和生物学必要性，因为生理刺激，如氧合、换气和一氧化氮的急剧增加，至少部分地通过激活BKCa通道引起围产期肺血管扩张。通道的门控特性被几个亚基改变，其中表达最广泛的是？1亚基，它增强了通道的钙敏感性，从而抑制了对收缩刺激的反应。？1亚单位的表达具有生理学意义，因为KCNMB1基因中的功能获得多态可以预防舒张期高血压，而小鼠中缺乏？1亚单位会导致高血压。该亚单位可能与呼吸道反应性有关，因为非裔美国人的特定多态增加了严重哮喘的风险。1亚基的表达是如何调节的，以及它是否在决定肺血管张力中起作用，目前尚不清楚。基于令人信服的初步证据表明，低氧诱导PASMC中缺氧诱导因子-1的表达增加，我们提出了总体假设：在PASMC中，(I)低氧能力增加KCNMB1的表达；(Ii)正常的KCNMB1表达，是发育调节的。在三个密切相关的具体目标中，我们试图通过在目标1中证明1亚单位的丢失会在小鼠模型中加剧缺氧性肺动脉高压来严格检验工作假说。在目标2中，我们计划阐明KCNMB1低氧诱导的转录调控。最后，在目标3中，我们计划解决表观遗传因素或特定的微RNA分子随年龄增长限制KCNMB1表达的可能性。即将进行的研究将清楚地确定？1亚单位在调节肺血管张力中的重要性，并有望提供一个新的靶点，可能被用来治疗肺血管，甚至可能是呼吸道的SMC张力病理性增加的疾病。

DESCRIPTION (provided by applicant): The present proposal seeks to address the molecular regulation of the calcium-sensitive potassium (BKCa) channel, an ion channel that is ubiquitously expressed in smooth muscle cells (SMC) and determines, to a meaningful degree, vascular SMC tone. Prior work from our lab has demonstrated a developmentally regulated and biologically imperative role for the BKCa channel in pulmonary artery (PA) SMC, as physiologic stimuli such as an acute increase in oxygenation, ventilation, and nitric oxide cause perinatal pulmonary vasodilation, at least in part, through activation of the BKCa channel. The gating characteristics of the channel are modified by several subunits, with the most widely expressed, the ¿1 subunit, enhancing calcium sensitivity of the channel and thereby dampening the response to constrictor stimuli. ¿1 subunit expression has physiologic implications as gain-of-function polymorphisms in the KCNMB1 gene protect against diastolic hypertension, and absence of the ¿1 subunit in mice causes hypertension. The subunit likely has implications for airways reactivity as a specific polymorphism in African Americans increases the risk for severe asthma. How ¿1 subunit expression is regulated and whether it plays a role in determining pulmonary vascular tone remains unexplored. Based on compelling preliminary evidence demonstrating that hypoxia induces an increase in ¿1 expression that is mediated by hypoxia-inducible factor-1¿ in PASMC, we formulated the overall hypothesis that in PASMC: (i) the capacity for hypoxia to increase KCNMB1 expression; and (ii) normoxic KCNMB1 expression, are developmentally regulated. In three closely related specific aims, we seek to rigorously test the working hypothesis by demonstrating in Aim 1 that loss of the ¿1 subunit accentuates hypoxic pulmonary hypertension in a murine model. In Aim 2, we plan to elucidate the transcriptional regulation that accounts for the hypoxic induction of KCNMB1. Finally, in Aim 3, we plan to address the potential that either epigenetic factors or specific micro-RNA molecules constrain KCNMB1 expression with aging. The studies to be performed will clearly establish the importance of ¿1 subunit in the regulation of pulmonary vascular tone and hold the promise of providing a novel target that might be exploited to address diseases wherein pulmonary vascular, or potentially even airway, SMC tone is pathologically increased.