Secretory mucins

MUC2, also known as intestinal-type secretory mucin, goblet-type mucin, or gel-forming mucin, is not constitutively expressed in the pancreas or ampullary ductules with the exception of the scattered goblet cells, where it functions as a protective barrier. It is a product... 

Trefoil factor family peptides, (TFF peptides), secretory mucin-associated peptides (trefoil peptides) largely found in ep-ithelia of the gastrointestinal tract. They share the TFF domain, a Cys-rich protein module with a consensus structure of 42 amino acids and six conserved Cys residues forming three intramolecular disulfide bridges between Cys -Cys, Cys -Cys, and Cys -Cys ". The TFF pep-... 

Verdugo, P. (1984). Hydration kinetics of exocyto.sed mucins in cultured secretory cells of the rabbit trachea a new model. Mucus and Mucosa (Ciba Foundation symposium 109), 212-225. 

The coat mucins are thought to be secreted from two major glands in the larval body the oesophageal and secretory glands. The latter, previously termed the excretory cell, is directly connected to the cuticle by a duct opening at the secretory pore (Nichols, 1956). It is not certain whether the panel of secreted mucins are all represented in the coat, or whether there are important differences between the two compartments. 

First, we will describe briefly the biology of secretory cells in general and goblet cells in particular. Next, we will outline our earlier studies on the conformation of mudn networks using dynamic laser scattering. Short discussions on the Donnan swelling properties of the mucin network will bring us to the application of the theory of polymer gel phase transition to explain condensation and decondensation in secretion. 

A direct implication of this hypothesis is that phase transition of the mucus gel should be reversible, and it should exhibit the characteristic features of a critical phenomenon. Studies conducted in isolated giant mucin secretory granules of the terrestrial slug revealed that hydrated mucin gels, released from individual secretory granules, can indeed be recondensed. Recondensation/ decondensation is reversible and exhibits the typical features of a polymer gel phase transition. Namely, it is discontinuous, and is affected by pH, temperature and Ca2 + concentration in a fashion that mimics phase transition in synthetic polymer hydrogels [32, 33] (see Fig. 3). 

Fig. 3. Polymer gel phase transition of the mucin polymer matrix of a giant secretory granule of the terrestrial slug Ariolimax columbianus. Effect of pH...

The columnar epithelial cells of the intestinal mucosa actively absorb and secrete extracellular ions, nutrients, and water. The active secretion of ions by these cells with an accompanying fluid flux acts to dilute and purge microorganisms or toxins in the bowel promotes the transfer of secretory immunoglobulin A, antimicrobial defensin peptides, and mucin into intestinal mucus and the gut lumen and, by affecting intraluminal pH, may alter the growth characteristics of enteric microflora [121]. Mucosal secretion is modulated by several enteric neurotransmitters, as well as inflammatory mediators released by mucosal mast cells that may affect transport indirectly through their ability to stimulate enteric neurons [122],... 

Lidell M.E., Johansson M.E. and Hansson G.C. (2003). An autocatalytic cleavage in the C terminus of the human MUC2 mucin occurs at the low pH of the late secretory pathway. J Biol Chem. 278, 13944-13951... 

Here, we delineate the biosynthetic pathways of the most common types of protein glycosylation occurring in the secretory pathway mucin-type O-linked glycosylation, A-linked glycosylation, and the formation of glycosaminoglycans. In addition, we will briefly visit the biosynthesis of some less-common varieties of protein glycosylation. 

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