Mucin 5B

Mucin-5B (MUC-5B) is a protein that in humans is encoded by the MUC5B gene and by the Muc5b gene in the mouse. It is one of the five gel-forming mucins. MUC-5B can be found in whole saliva, normal lung mucus, and cervical mucus. In some diseases, such as COPD, chronic rhinosinusitis (CRS), and H. pylori-associated gastric disease, the gene has been found to be upregulated, and this may be related to the pathogenesis of these conditions.

Synthesis
All mucins are synthesized in secretory cells known as goblet cells or mucous cells, depending on the tissue location. Their creation, while still not completely understood, begins in the endoplasmic reticulum. From there, the Golgi apparatus builds the O-linked glycans found in mucins. Finally, they are packaged into secretory granules.