Isolation and characterization of tracheobronchial mucin from a laryngectomee

Human tracheobronchial mucin: purification and binding to Pseudomonas aeruginosa

Colonization of the respiratory tract with Pseudomonas aeruginosa is a serious problem in cystic fibrosis and seriously ill hospitalized patients. Human tracheobronchial mucin (HTBM), the major glycoprotein of human tracheobronchial secretions, is known to interact with this pathogen, which may then be cleared by mucociliary action. However, the mechanism of interaction is not known. To understand this process, pure HTBM was isolated from tracheobronchial secretions of a laryngectomee. Following initial fractionation on Sepharose CL-2B, the HTBM-containing fraction was subjected to reductive methylation and then gel filtration. Pure HTBM was employed in an overlay binding assay to identify the bacterial adhesin(s) and mucin receptors that participate in mucin-P. aeruginosa interactions. An approximately 16-kDa nonpilus protein component(s) of P. aeruginosa was found to be the adhesin(s) for HTBM. The mucin receptor for the 16-kDa component(s) was found in the peptide moiety. This study confirms that P. aeruginosa utilizes the nonpilus adhesin(s) to bind to HTBM. Identification of the specificity of the HTBM-P. aeruginosa interactions can lead to a better understanding of the predominance of P. aeruginosa colonization in individuals with cystic fibrosis.

Immunochemistry and immunogenicity of low molecular weight human salivary mucin

The purposes of this study were to examine the immunogenicity of the low molecular weight human salivary mucin (MG2) and determine its distribution within major and minor human salivary glands. Anti-MG2 sera were produced in Balb/c mice by a variety of immunization schedules. Chromatographically or electrophoretically purified MG2 and partially purified mucin chromatographic fractions exposed to mild denaturing conditions were not immunogenic. Only MG2 without prior exposure to urea or guanidine was able to elicit an immune response. A murine anti-MG2 monoclonal antibody (clone 1/F9) was produced and its monospecificity confirmed by immuno-dot blotting and SDS-PAGE Western transfer. Clone 1/F9 (IgG1; kappa) was of moderate affinity and was directed to a Pronase- and TPCK trypsin-sensitive but periodate-resistant epitope which was not blood group- or sialic acid-specific. Immunocytochemical studies of frozen tissue sections with clone 1/F9 using both indirect and direct methods revealed that MG2 was more heterogeneously distributed within submandibular than labial glands and was not found in parotid or palatine glands. The use of a polyclonal rabbit anti-MG2 reagent in either frozen or paraffin-embedded tissues gave the same immunocytochemical results as those obtained with the monoclonal antibody.

Structural analysis of purified human tracheobronchial mucins

Light scattering has been used to investigate the structure of human tracheobronchial mucin glycoproteins (HTBM) from the sputum of cystic fibrosis patients. The specimen was extracted using 6M guanidinium hydrochloride solution and fractionated by gel exclusion chromatography on Sephacryl S-1000. The fractionated HTBM was purified by density gradient ultracentrifugation. Purity of the resulting material was confirmed by SDS polyacrylamide gel electrophoresis and uv spectroscopy. Light scattering measurements on the fractionated mucins yield weight-average molecular weights Mw, and z-average radii of gyration Rg,z. The native cystic fibrosis HTBM consisted of a high molecular weight fraction with Mw = 9.3 X 10(6) daltons and a lower molecular weight fraction containing partly degraded mucins. After reduction and carboxymethylation of the high molecular weight native fraction, the resulting material was separated into three pools with Mw values of 5.1 X 10(6), 1.6 X 10(6), and 400,000. The derived molecular weights for the protein cores Mp,w, and the experimental radii of gyration are found to be consistent with the Mp,w -Rg relation established previously for submaxillary, cervical, and gastric mucins. These results imply that HTBM has the same extended-coil conformation reported for other mucins and has a molecular structure consisting of subunits, linked into linear chains via covalent (disulfide) bonds.

Immunochemistry of high molecular-weight human salivary mucin

The purpose of this study was to determine the distribution of mucin glycoprotein 1 (MG1) within submandibular, parotid, labial and palatine salivary tissues. Formalin-fixed and frozen tissue sections were examined histochemically with PAS, Alcian blue and Meyer's mucicarmine, and immunocytochemically with an anti-mucin glycoprotein 1 monoclonal antibody (clone 3/E8). Clone 3/E8 was produced in Balb/c mice using mucin-enriched chromatographic fractions from submandibular-sublingual saliva. The monospecificity of 3/E8 was confirmed by immuno-dot blotting and SDS-PAGE/electrophoretic transfer. Clone 3/E8 (IgG1; kappa) was of moderate affinity, and was directed to a carbohydrate-containing, TPCK-trypsin-insensitive and pronase-insensitive epitope on this mucin, which was not blood-group specific. The location of mucin glycoprotein 1 was determined by both indirect (peroxidase-antiperoxidase) and direct methods. Mucin glycoprotein 1 was localized within all labial acini examined, but was not found within parotid tissues. Histochemical methods stained all submandibular, palatine and labial acini, but immunocytochemistry with monoclonal antibody revealed heterogeneous staining with clone 3/E8 in submandibular and palatine tissues. These findings suggest the presence of mucin glycoprotein 1-specific acinar cell subpopulations within human submandibular and palatine salivary tissues.

Biochemical and biophysical comparison of two mucins from human submandibular-sublingual saliva

A high-molecular-weight mucin-glycoprotein (MG1) was isolated from human submandibular-sublingual saliva and was comprised of 14.9% protein, 29.0% N-acetylglucosamine, 9.4% N-acetylgalactosamine, 10.5% fucose, 24.2% galactose, 0.9% mannose, 4.0% N-acetylneuraminic acid, and 7.0% sulfate. Carbohydrate units were O-glycosidically linked and ranged in size from 4 to 16 residues. The biophysical properties of MG1 were compared to those of a smaller mucin (MG2) also isolated from submandibular-sublingual saliva. Fluorescence spectroscopy demonstrated that MG1 bound both 1-anilino-8-naphthalenesulfonate (ANS) and N-phenyl-1-naphthylamine (NPNA) in stable hydrophobic binding sites (melting temperature, 47 +/- 2 degrees C), whereas MG2 did not bind these hydrophobic probes. These hydrophobic domains occurred on nonglycosylated or naked portions of MG1 since Pronase treatment eliminated ANS binding. Reduction of disulfide bridges in MG1 increased the number of available hydrophobic binding sites. High ionic strength (0 to 2 M NaCl) had no effect on ligand binding, whereas lowering pH (9 to 2) increased ANS binding without affecting NPNA complexation. Circular dichroism (CD) data suggested that MG1's carbohydrate chains dominated its spectrum. In contrast, the peptide backbone dominated the CD spectrum of MG2. Collectively, the results of this study indicate that human submandibular-sublingual saliva contains two structurally distinct mucins.

Modulation of bone metabolism by two chemically distinct lipopolysaccharide fractions from Bacteroides gingivalis

Two separate species of lipopolysaccharide (LPS) from Bacteroides gingivalis 381 have been isolated. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis demonstrated not only the heterogeneity of each species, but also that they represented high- and low-molecular-weight LPS entities. Although both contained the same carbohydrate and fatty acid components, the proportions of these differed between the LPS species. The direct effects of these two species in modulation of bone resorption and bone collagen and noncollagen protein synthesis have been examined. In a bone resorption assay, these two species stimulated 45Ca release from prelabeled fetal rat bones in a concentration range of 0.5 to 3.0 micrograms/ml. The two LPS species also elicited a 30 to 40% reduction in collagen protein formation at 10 micrograms/ml. Responses of the same order of magnitude were observed with LPS from Salmonella minnesota at 10 micrograms/ml. The higher-molecular-weight LPS species also significantly inhibited noncollagen protein formation. This is the first report that LPS from B. gingivalis 381, a suspected periodontal pathogen, inhibits bone collagen formation and, in conjunction with the bone resorption potency, further implicates LPS in alveolar bone loss associated with periodontal disease.

Isolation and characterization of a mucin-glycoprotein from rat submandibular glands

A blood group A+ mucin-glycoprotein was purified from aqueous extracts of rat submandibular glands by sequential chromatography on columns of Sepharose CL-6B and Sephacryl S-300 in urea-containing buffers. Final purification was facilitated by reductive methylation which appeared to release contaminating (hydrophobic) peptides. Homogeneity of the purified mucin was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis at varying concentrations of acrylamide, lectin affinity chromatography, and Western blot analysis. In contrast to previously described preparations, the purified mucin contained only trace amounts of N-acetylglucosamine and aromatic amino acids. In addition, only low levels of basic amino acids were present.

Masticatory lubrication. The role of carbohydrate in the lubricating property of a salivary glycoprotein-albumin complex

We report for the first time a masticatory-lubrication assay system to assess the lubricating properties of salivary constituents. The lubricating ability of the proline-rich glycoprotein (PRG) of parotid saliva was enhanced by human serum albumin. The interactive effect of albumin was abolished by chemically deglycosylating the glycoprotein. Fluorescence spectroscopy with a hydrophobic probe verified the existence of a PRG-albumin complex and demonstrated that deglycosylation of the PRG altered the nature of its interaction with albumin.