Details

Autor(en) / Beteiligte

• Ambort, Daniel
• Johansson, Malin E. V
• Gustafsson, Jenny K
• Nilsson, Harriet E
• Ermund, Anna
• Johansson, Bengt R
• Koeck, Philip J. B
• Hebert, Hans
• Hansson, Gunnar C

Titel

Calcium and pH-dependent packing and release of the gel-forming MUC2 mucin

Ist Teil von

• Proceedings of the National Academy of Sciences - PNAS, 2012-04, Vol.109 (15), p.5645-5650

Ort / Verlag

United States: National Academy of Sciences

Erscheinungsjahr

2012

Quelle

Elektronische Zeitschriftenbibliothek (Open access)

Beschreibungen/Notizen

• MUC2, the major colonic mucin, forms large polymers by N-terminal trimerization and C-terminal dimerization. Although the assembly process for MUC2 is established, it is not known how MUC2 is packed in the regulated secretory granulae of the goblet cell. When the N-terminal VWD1-D2-D'D3 domains (MUC2-N) were expressed in a goblet-like cell line, the protein was stored together with full-length MUC2. By mimicking the pH and calcium conditions of the secretory pathway we analyzed purified MUC2-N by gel filtration, density gradient centrifugation, and transmission electron microscopy. At pH 7.4 the MUC2-N trimer eluted as a single peak by gel filtration. At pH 6.2 with Ca2+ it formed large aggregates that did not enter the gel filtration column but were made visible after density gradient centrifugation. Electron microscopy studies revealed that the aggregates were composed of rings also observed in secretory granulae of colon tissue sections. The MUC2-N aggregates were dissolved by removing Ca2+ and raising pH. After release from goblet cells, the unfolded full-length MUC2 formed stratified layers. These findings suggest a model for mucin packing in the granulae and the mechanism for mucin release, unfolding, and expansion.