ROLE OF CFTR IN PROCESSING AND FUNCTION OF MUC1 MUCIN

在明确CF基因突变导致呼吸道感染和支气管扩张的机制方面已经取得了重大进展，但异常粘蛋白加工在CF肺部疾病发病机制中的潜在作用仍不清楚。粘蛋白MUC1是人类肺中唯一已知的跨膜粘蛋白，在分化的表面上皮细胞和粘膜下腺的浆液细胞中都有表达，以前有研究表明这些细胞表达高水平的囊性纤维化跨膜传导调节因子(CFTR)。MUC1和CFTR的细胞共定位以及CFTR在糖共轭的翻译后加工中的作用的报道表明，CFTR突变可能会改变MUC1的加工过程。此外，MUC1的结构和空间分布表明，它参与了呼吸道上皮细胞顶膜和腔细菌之间的相互作用。因此，这一建议的中心假设是，Cf突变损害了MUC1的翻译后处理和释放，这削弱了MUC1对正常的呼吸道防御细菌感染的贡献。因此，本研究的具体目标是：1.明确跨膜粘蛋白MUC1在正常和病变的人呼吸道上皮和分泌物中的细胞定位。用免疫细胞化学、流式细胞术和免疫电子显微镜检测MUC1在人呼吸道以及体外培养的原代和非CF型人气道上皮细胞中的表达和细胞分布。2.确定CFTR是否影响MUC1的翻译后加工。MUC1的硫化和唾液酸化将在CALU-3细胞以及原代培养的CF和非CF上皮细胞中确定。在CALU-3细胞中，使用反义方法将下调CFTR的表达。3.确定Cf气道上皮细胞是否异常加工和释放MUC1。在有无cAMP刺激的情况下，MUC1的转运和释放的动力学将在非CF和CF的气道上皮细胞中确定。在有或没有cAMP刺激的情况下，MUC1的转运和释放的动力学将在非CF和CF气道上皮细胞中以及在表达不同水平CFTR的CALU-3细胞中确定。4.确定Cf突变对MUC1与铜绿假单胞菌相互作用的影响。细菌粘附性将在原代呼吸道细胞和CFTR和/或MUC1表达下调的CALU-3细胞中进行比较。这些目标的完成将确定CFTR对人类呼吸道中特定粘蛋白的加工和功能的影响，从而提高对CF呼吸道感染发病机制的理解。

Significant progress has been made towards defining the mechanisms whereby mutations in the CF gene lead to airway infection and bronchiectasis, but the potential role of aberrant mucin processing in the pathogenesis of CF lung disease remains unclear. The mucin MUC1 is the only known transmembrane mucin the human lung, and is expressed in differentiated surface epithelial cells and in the serous cells of submucosal glands, which previously have bene shown to express high levels of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR). The cellular co-localization of MUC1 and CFTR, and the reported role of CFTR in the post-translational processing of glycoconjugates, suggest that CFTR mutations may alter the processing of MUC1. Moreover, the structure and spatial distribution of MUC1 implicate it in the interaction between the apical membrane of airway epithelia and luminal bacteria. The central hypotheses of this proposal re therefore that CF mutations impair the post- translational processing and release of MUC1, and that this impairs the contribution of MUC1 to normal airway defense against bacterial infection. Accordingly, specific aims are: 1. To define the cellular localization of the transmembrane mucin MUC1 in normal and diseased human airway epithelium and secretions. The expression and cellular distribution of MUC1 in human airway and in a clinically relevant in vitro system of primary CF and non-CF human airway epithelium will be determined using immunocytochemistry, flow cytometry, and immunoelectron microscopy. 2. To determine whether CFTR influences the post-translational processing of MUC1. The sulfation and sialylation of MUC1 will be determined in CALU-3 cells and in primary cultures of CF and non-CF epithelia. CFTR expression will be down regulated using an anti-sense approach in CALU-3 cells. 3. To determine whether MUC1 is aberrantly processed and released in CF airway epithelia. The kinetics of MUC1 trafficking and release in the presence and absence of cAMP stimulation will be determined in non-CF and CF airway epithelia. The kinetics of MUC1 trafficking and release in the presence and absence of cAMP stimulation will be determined in non- CF and CF airway epithelia, and in CALU-3 cells expressing various levels of CFTR. 4. To determine the impact of CF mutations in the interaction between MUC1 and Pseudomonas aeruginosa.. Bacterial adhesion will be compare din primary airway cells, and in CALU-3 cells in which CFTR and/or MUC1 expression have been down regulated. Completion of these aims will define the influence of CFTR on the processing and function of a specific mucin in human airway and thereby improve the understanding of the pathogenesis of airway infection in CF.