MUC4 Mucin and Airway Epithelial Regeneration in COPD

描述(由申请人提供)： 在慢性阻塞性肺疾病，如慢性支气管炎和囊性纤维化中，呼吸道上皮不断暴露于中性粒细胞弹性蛋白酶(NE)，这是一种炎性蛋白酶。细胞对去甲肾上腺素的反应决定了上皮损伤和修复之间的平衡。这种平衡的一个关键因素是表皮生长因子受体(EGFR)的激活，EGFR是ErbB受体酪氨酸激酶家族的成员。EGFR的激活需要受体的同源或异源二聚化。在呼吸道上皮细胞中，一个主要的EGFR异源二聚体是ErbB2。到目前为止，唯一已知的激活ErbB2的配体是MUC4。MUC4是一种主要的膜栓系的呼吸道粘蛋白，具有表皮生长因子(EGF)样结构域。我们有四个关键的观察结果支持MUC4在激活气道上皮细胞对NE的反应中起关键作用：(1)NE作用于气道上皮细胞，增强MUC4基因的稳定性，增加MUC4蛋白水平。(2)NE可诱导EGFR酪氨酸磷酸化。(3)去甲肾上腺素在无血清和无EGF的培养液中均能刺激正常人支气管上皮细胞的增殖。4.MUC4、ErbB2和EGFR在体内共定位于受损的浅层呼吸道上皮细胞。这些观察结果支持这样的假设，即NE通过诱导级联中关键调节分子MUC4的产生，激活ErbB2，从而促进EGFR的异源二聚化/激活，从而在呼吸道上皮细胞中触发了一系列分子级联事件。表皮生长因子受体活化是上皮细胞增殖的重要前提。该方案的具体目的是：(1)确定去甲肾上腺素是否诱导ErbB2/EGFR受体酪氨酸激酶级联反应的MUC4激活，从而导致上皮细胞的增殖。(2)确定调控NE诱导的MUC4表达的RNA稳定结构域和RNA结合蛋白。(3)探讨上述信号转导通路在慢性支气管炎和囊性纤维化中的作用。我们的最终目标是利用这个项目的信息来确定新的生物靶点，用于合理的治疗，以诱导损伤后正常的呼吸道上皮细胞增殖和分化。

DESCRIPTION (provided by applicant): In chronic obstructive pulmonary diseases such as chronic bronchitis, and in cystic fibrosis, the airway epithelium is constantly exposed to neutrophil elastase (NE), an inflammatory protease. The cellular response to NE dictates the balance between epithelial injury and repair. A critical factor in this balance is the activation of the epidermal growth factor receptor (EGFR), a member of the ErbB receptor tyrosine kinase family. Activation of EGFR requires homo- or heterodimerization of the receptor. A major EGFR heterodimerization partner in airway epithelial cells is ErbB2. To date, the only ligand known to activate ErbB2 is MUC4. MUC4 is a major membrane-tethered, respiratory tract mucin with epidermal growth factor (EGF)-like domains. We have made four key observations supporting a critical role for MUC4 in activating the airway epithelial response to NE: (1) NE acts on airway epithelial cells to enhance MUC4 mRNA stability and increase MUC4 protein levels. (2) NE induces tyrosine phosphorylation of EGFR. (3) NE stimulates proliferation of normal human bronchial epithelial cells in serum-free and EGF-free media. 4. MUC4, ErbB2 and EGFR colocalize in injured superficial airway epithelial cells in vivo. These observations support the hypotheses that NE triggers a molecular cascade of events in airway epithelial cells by inducing the production of MUC4, a key regulatory molecule in the cascade, activating ErbB2, and thereby promoting the heterodimerization/activation of EGFR. EGFR activation is a critical prerequisite for epithelial proliferation. The Specific Aims to be tested in this proposal are: (1) To determine whether NE induces MUC4-activation of the ErbB2/EGFR receptor tyrosine kinase cascade, resulting in epithelial cell proliferation. (2) To identify the RNA stability domains and RNA-binding proteins regulating NE-induced expression of MUC4, a key molecule in this signaling cascade. (3) To determine the relevance of these signaling pathways in mediating epithelial proliferation in vivo in chronic bronchitis and cystic fibrosis. Our ultimate goal is to use information from this project to identify new biologic targets for rational therapies to induce normal airway epithelial proliferation and differentiation following injury.