Annkatrin Herrmann

MUC5AC, but not MUC2, is a prominent mucin in respiratory secretions

Airway mucus was collected from healthy and chronic bronchitic subjects. The chronic bronchitic sputum was separated into gel and sol phase by centrifugation and mucins were isolated using isopycnic density-gradient centrfugation in CsCl. The presence of the MUC5AC and MUC2 mucins was investigated with antisera raised against synthetic peptides with sequences from the respective apoproteins. The gel and sol phase of chronic bronchitic sputum as well as healthy respiratory secretions were shown to contain MUC5AC whereas the MUC2 mucin could not be detected. Rate-zonal centrifugation showed that the MUC5AC mucin was large, polydisperse in size and that reduction yielded subunits. Ion-exchange HPLC revealed the presence of two subunit populations in all secretions, the MUC5AC subunits always being the more acidic. MUC5AC is thus the first large, subunit-based, gel-forming respiratory mucin identified and this glycoprotein is biochemically distinct from at least one other population of large, gel-forming mucins also composed of subunits but lacking a genetic identity.

Expression of a Core 3 Disialyl-Le(x) Hexasaccharide in Human Colorectal Cancers: A Potential Marker of Malignant Transformation in Colon.

Cancer-associated alterations in cell surface and secreted glycoproteins have been catalogued for many years but many of the studies of alterations in mucin carbohydrate have relied on histochemical or immunohistochemical methods, with little direct chemical analysis. In this study, we analyzed the O-glycosylation pattern of MUC2 glycoprotein isolated from colorectal carcinomas, transitional mucosa and resection margins from three patients with blood group A, B and O, respectively. After alkaline borohydride treatment, the released oligosaccharides were structurally characterized by nanoESI Q-TOF tandem mass spectrometry without prior fractionation or derivatization. As expected, we found an increased expression of sialyl-Tn antigen in the colonic cancer mucins. A more interesting feature was the increased expression of a core 3 sialyl-Le(x) hexasaccharide, NeuAcalpha2-3Galbeta1-4(Fucalpha1-3)GlcNAcbeta1-3(NeuAcalpha2-6)GalNAc in tumor, which appeared to compete with its sulfo-Le(x) counterpart in normal tissue, SO3-3Galbeta1-4(Fucalpha1-3)GlcNAcbeta1-3(NeuAcalpha2-6)GalNAc. This antigen, whose structure was confirmed by NMR experiments, is based on a core 3 glycan and may be a potential marker for the malignant transformation of colonic cells. Unexpectedly, most of the glycans recovered in normal and carcinomas extracts were based on a sialylated core 3, GlcNAcbeta1-3(NeuAcalpha2-6)GalNAcol. Moreover, the pattern of glycosylation was very similar between mucins isolated from each sample, the main differences related to the level of expression of the major oligosaccharides. The data obtained in this investigation may have value for future screening studies on colorectal cancer.

TRPV1 and TRPA1 stimulation induces MUC5B secretion in the human nasal airway in vivo.

Aim:  Nasal transient receptor potential vanilloid 1 (TRPV1) stimulation with capsaicin produces serous and mucinous secretion in the human nasal airway. The primary aim of this study was to examine topical effects of various TRP ion channel agonists on symptoms and secretion of specific mucins: mucin 5 subtype AC (MUC5AC) and B (MUC5B).

Glycosylation of the two O-glycosylated domains of human MUC2 mucin in patients transposed with artificial urinary bladders constructed from proximal colonic tissue.

Transposition of intestinal segments is frequently used for bladder reconstruction. Following transposition, bowel segments continue to produce mucus and a correlation between excessive mucus production and complications such as urinary tract infection or catheter blockage has been observed for a long time. However, no information is currently available on the change of mucin expression and glycosylation under these abnormal conditions. In this study, the variable number tandem repeat region and the irregular repeat domain of human MUC2 were isolated as two glycopeptide populations after reduction and trypsin digestion followed by gel chromatography from urine of patients transposed with urinary bladders. After alkaline borohydride treatment, the oligosaccharides released from the whole MUC2 mucin and the two glycosylated domains were investigated by nanoESI Q-TOF MS/MS (electrospray ionization quadrupole time-of-flight tandem mass spectrometry). More than 60 different glycans were identified, mainly based on sialylated core 3 structures. Some core 1, 2 and 4 oligosaccharides were also found. Most of the structures were acidic with NeuAc residues mainly α2–6 linked to the N-acetylgalactosaminitol and sulphate residues exclusively 3-linked to galactose. No expression of blood group A and B or Sda/Cad determinants was observed. Similar patterns of glycosylation were found in the tandem repeat region and the irregular repeat domain and the level of expression of the major oligosaccharides were in the same order of magnitude. The most interesting feature of this study was that sialyl-Tn antigen, which is considered as a tumour antigen, was the oligosaccharide most highly expressed. This result suggests that mucins from intestinal transposed segments are abnormally glycosylated.