"BRONCHIAL SECRETIONS: PHYSICAL AND CHEMICAL STUDIES"

点击翻译按钮获取中文摘要

Our principal objectives are to determine the chemical and physical properties of human lung mucins, to determine how perturbations of particular moities affect these physical properties, and to determine whether there are differences in the chemical and physical properties between mucins obtained from the airways of healthy individuals and from the airways of patients with chronic obstructive pulmonary diseases, such as bronchial asthma (BA), bronchitis, bronchorrhea, and cystic fibrosi (CF). In our studies on 18 samples of lung mucosal gel from a single patient with bronchial asthma, we have defined conditions for the dissolution of the gel and the purification of the mucin glycoprotein and other gel components. During the past several years we have examined the architecture of the mucin molecule--in particular the issue of carbohydraterich and naked peptide domains, and the localization of the thiol groupings implicated in the aggregation and gelation properties of human lung mucins. The analysis involves radiolabeling the thiol residues with 1-14C-iodoacetamide by reductive carboxymethylation, followed by trypsin digestion, chromatography on Sepharose 4B, and peptide mapping. The nature of the trypsin fragmentation pattern has been established and during the forthcoming grant period we will characterize several of the fragments in more detail, particularly the 68K and tr-3 fragments of the naked peptide region. In addition, we will radiolabel the hydrophobic regions of mucins via explant organ culture to aid in determining the localization of the hydrophobic residues in the glycosylated and non-glycosylated regions of the mucins. We will also use the explants to radiolabel the sugars and sulfates in the oligosaccharide chains of lung mucins. We are particularly interested in sulfate localization, since our data on BA mucin is not consistent with localization on the C-6 position of galactose, as has been reported for CF lung mucin (Roussel et al, J. Biol. Chem. 250, 2114). During the past several years we have been examining the issue of whether normal, CF, and bronchial asthmatic mucins have different compositions and structural features. Mucins from only two normals, one asthmatic, and 3 cystics have been analyzed to date. We will continue these studies using more samples and more detailed biochemical and electron microscopy studies to further compare normal and pathological lung mucins.