Purification and characterization of a human pancreatic adenocarcinoma mucin.

Pancreatic mucins consist of core proteins that are decorated with carbohydrate structures. Previous studies have identified at least two physically distinct populations of mucins produced by a pancreatic adenocarcinoma cell line (HPAF); one is the MUC1 core protein, which includes an oligosaccharide structure identified by a monoclonal antibody (MAb) recognizing the DU-PAN-2 epitope. In this study, we purified and characterized a second mucin fraction, which also shows reactivity with the DU-PAN-2 antibody, but which has an amino acid composition that is not consistent with the MUC1 core protein. This new mucin was purified by ammonium sulfate precipitation, molecular sieve chromatography, and density gradient centrifugation. It eluted in the void volume of a Sepharose 4B column together with an associated low molecular weight protein, which could be further resolved. The mucin is highly polyanionic due to numerous sulfated and sialylated saccharide chains. Carbohydrate analyses of the purified mucin showed the presence of galactose, glucosamine, galactosamine, and sialic acid, but no mannose, glucose, or uronic acid. The purified and deglycosylated mucin shows no reactivity with anti-MUC1 apomucin antibody, but reacts with antiserum against deglycosylated tracheal mucins and antiserum against the MUC4 tandem repeat peptide. Analysis of mucin expression in HPAF cells revealed high levels of MUC1 and MUC4 mRNA, and moderate levels of MUC5AC and MUC5B mRNA. The amino acid composition of the purified mucin shows a high degree of similarity to the MUC4 core protein.

In vivo effect of wood smoke on the expression of two mucin genes in rat airways.

A short-term, time-dependent smoke exposure of rats in a nose-only chamber to burning wood and 24-h recovery time revealed inflammation of the airways with varying degrees of injury from loss of cilia, degeneration of epithelium, and squamous metaplasia to submucosal edema. These histological changes were reflected in variable expression of the secretory Muc5AC and low expression of membrane-associated Muc4 mucin genes. 20-min smoke exposure in extended recovery experiments showed marked disorder of tracheal epithelium for up to 72 h of recovery with a return to normal by 7 days. Gene expressions were elevated at 24 and 48 h of recovery. 30-min smoke exposure showed a more severe degeneration of the epithelium and a longer recovery time. Muc5AC expression decreased after 72 h of recovery, while there was upregulation of Muc4 gene from 48 through 96 h. Because Muc4 upregulation and histological results correlate and it has reportedly been associated with epithelium renewal, Muc4 gene may be a useful marker for the regeneration of tracheal epithelium.