Mechanisms of Heterocellular Signaling at the Myoendothelial Junction

描述（由申请人提供）：我们最近发现血红蛋白α在肌内皮连接处富集，肌内皮连接处是内皮细胞和平滑肌细胞在阻力动脉中接触的解剖位置。这是一个重要的发现，因为它表明血红蛋白α在红细胞外具有重要和积极的作用。这种蛋白质是仅有的几种真正极化的蛋白质之一，被定位到内皮衍生的肌内皮连接，和siRNA诱导的蛋白质的量的减少显着改变动脉的反应性，包括收缩苯肾上腺素和扩张乙酰胆碱。我们推导的机制是基于证据表明单体血红蛋白α是一种有效的一氧化氮清除剂，并且发现内皮型一氧化氮合酶（eNOS）和血红蛋白α是一种大分子复合物。基于这项工作，以及大量强有力的初步数据，我们假设肌内皮连接处的血红蛋白α是一种新型的一氧化氮信号转导调节剂，可以影响血压调节。我们将使用两个特定的目标来测试这个假设：1。研究内皮血红蛋白A基因消融/过表达对动脉功能的影响，以及2.）阐明血红蛋白稳定蛋白和内皮型一氧化氮合酶如何调节MEJ的血红蛋白α表达和双加氧酶活性。这些目的将通过首先关注floxed血红蛋白α小鼠以及血红蛋白过表达小鼠的研究来阐明，以确定内皮中该蛋白的缺失/过表达对动脉反应性、全组织血流量、外周阻力和血压的影响。此外，将使用血红蛋白a的2个等位基因缺失的疾病α地中海贫血的人类模型来研究这种全基因组杂合缺失对血管系统的影响。接下来，我们将研究血红蛋白α伴侣血红蛋白α稳定蛋白（AHSP）如何将血红蛋白α运输到肌内皮连接处或直接作为血红蛋白α氧化还原状态的调节剂，改变一氧化氮结合的能力。这一建议的总和统一和建立在我们以前的R 01获得的数据之上，使我们第一次能够直接询问完整动物中肌内皮连接的功能。事实上，我们相信部分答案可以为外周血管系统控制血压的全新理解提供基础，以及推导出用于控制高血压的未探索的药理学靶点。

DESCRIPTION (provided by applicant): We have recently discovered that hemoglobin α is enriched in myoendothelial junctions, the anatomical location where endothelial cells and smooth muscle cells make contact in the resistance arteries. This was a significant finding because it demonstrated that hemoglobin α had an important and active role outside of erythrocytes. This protein is one of only a few truly polarized proteins to be localized to endothelial-derived myoendothelial junctions, and the siRNA-induced decrease in the amount of the protein significantly altered arterial reactivity, including constriction to phenylephrine and dilation to acetylcholine. The mechanism we derived was based on evidence indicating that monomeric hemoglobin α is a potent scavenger of nitric oxide, and that endothelial nitric oxide synthase (eNOS) and hemoglobin α were found to be in a macromolecular complex. Based on this work, as well as a plethora of strong preliminary data, we hypothesize that hemoglobin α at the myoendothelial junction is a novel regulator of nitric oxide signaling which can impact blood pressure regulation. We will test this hypothesis using two specific aims: 1.) investigate the effects of endothelial hemoglobin a gene ablation/over-expression on arterial function and 2.) elucidate how AHSP and eNOS regulate hemoglobin α expression and dioxygenase activity at the MEJ. These aims will be elucidated using studies focused first on a floxed hemoglobin α mouse as well as a hemoglobin a over-expressing mouse to determine the effects of deletion/over-expression of this protein in endothelium on arterial reactivity, whole tissue blood flow, peripheral resistance and blood pressure. In addition, a human model of the disease alpha thalassemia where 2 alleles of hemoglobin a are deleted will be used to study the effects of this genome-wide heterozygous deletion on the vasculature. Next we will investigate how the hemoglobin α chaperone hemoglobin α stabilizing protein (AHSP) may traffic hemoglobin α to the myoendothelial junction or act directly as a regulator of the hemoglobin α redox state, altering the ability of nitric oxide to bind. The sum of this proposal unites and builds on the dat obtained from our previous R01 by allowing us for the first time to ask the direct question as to the function of the myoendothelial junction in intact animals. Indeed, we believe part of the answers could provide the basis for a completely new understanding of blood pressure control by the peripheral vasculature, as well as the derivation of unexplored pharmacological targets for control of hypertension.