Mechanisms of Airway Smooth Muscle Hypertrophy

描述(由申请人提供)：哮喘患者由于肥大或增生而导致的呼吸道平滑肌质量增加。虽然调控细胞增殖的生化途径已经得到了很好的研究，但对调控气道平滑肌蛋白合成、细胞大小或收缩装置蛋白积累的生化途径知之甚少。最近来自细胞培养模型和哮喘患者的数据表明，气道平滑肌收缩蛋白的表达可能是以转录后方式调节的。在这项修订的应用中，我们提出，气道平滑肌肥大需要激活特定的翻译控制通路。为了验证这一点，我们将研究1)肥大细胞培养模型，在该模型中，原代人支气管平滑肌细胞被转化生长因子(TGF)-β处理；2)两种哮喘小鼠模型；以及3)来自人类哮喘患者的活检样本。我们提出了三个特定的目的：特定的目的：1.确定收缩装置转录和翻译在人气道平滑肌肥大发生发展中的作用。我们假设：1)转化生长因子β通过增加基因转录和翻译效率促进气道平滑肌肥大；2)小鼠的气道重塑部分以平滑肌肥大为特征。具体目的2.研究帽依赖蛋白合成在人气道平滑肌肥大中的作用。我们假设：1)4E-BP的磷酸化，增加了elF4E形成elF4F复合体的可能性，是转化生长因子β诱导的气道平滑肌肥大所必需的；2)MAP激酶信号整合激酶(MNK)-1对elF4E的磷酸化是气道平滑肌肥大所必需的；3)气道重塑的部分特征是4E-BP和elF4E的磷酸化增加。具体目的3.研究帽非依赖性蛋白合成在人气道平滑肌肥大中的作用。我们假设：1)p70核糖体S6激酶(S6激酶)对气道平滑肌肥大既不是必需的，也不是充分的；2)GSK3β的磷酸化和失活是气道平滑肌肥厚所必需的且充分的；3)气道重塑的部分特征是气道平滑肌GSK3β的磷酸化增加。了解哮喘气道重塑的生化机制将有助于改善对该疾病的治疗。

DESCRIPTION (provided by applicant): Increased airway smooth muscle mass, due either to hypertrophy or hyperplasia, is present in patients with asthma. While the biochemical pathways regulating cell proliferation have been well studied, little is known about the biochemical pathways regulating airway smooth muscle protein synthesis, cell size or the accumulation of contractile apparatus proteins. Recent data from cell culture models and patients with asthma suggest that airway smooth muscle contractile protein expression may be regulated in a post- transcriptional manner. In this revised application, we propose that airway smooth muscle hypertrophy requires the activation of specific translational control pathways. To test this, we will study 1) a cell culture model of hypertrophy in which primary human bronchial smooth muscle cells are treated with transforming growth factor (TGF)-beta; 2) two mouse models of asthma; and 3) biopsy samples from human asthmatics. We propose three Specific Aims: Specific Aim 1. Determine the contributions of contractile apparatus transcription and translation in the development of human airway smooth muscle hypertrophy. We hypothesize that: 1) TGFbeta promotes airway smooth muscle hypertrophy by increasing both gene transcription and translational efficiency; and 2) murine airway remodeling is characterized in part by smooth muscle hypertrophy. Specific Aim 2. Examine the contribution of cap-dependent protein synthesis to human airway smooth muscle hypertrophy. We hypothesize that: 1) 4E-BP phosphorylation, which increases the availability of elF4E for elF4F complex formation, is required for TGFbeta-induced airway smooth muscle hypertrophy; 2) elF4E phosphorylation by MAP kinase signal integrating kinase (MNK)-1 is required for airway smooth muscle hypertrophy; and 3) airway remodeling is characterized in part by increased phosphorylation of airway smooth muscle 4E-BP and elF4E. Specific Aim 3. Examine the contribution of cap-independent protein synthesis to human airway smooth muscle hypertrophy. We hypothesize that: 1) p70 ribosomal S6 kinase (S6 kinase) is neither required nor sufficient for airway smooth muscle hypertrophy; 2) GSK3beta phosphorylation and inactivation is required and sufficient for airway smooth muscle hypertrophy; and 3) airway remodeling is characterized in part by increased phosphorylation of airway smooth muscle GSK3beta. Understanding biochemical mechanisms of airway remodeling in asthma will lead to improvements in the treatment of this disease.