Polymeric mucin

Polymeric mucins are large, secreted, highly O-glycosylated glycoproteins that polymerize via disulfide bonds to form the structural backbone of mucus gels in the respiratory, gastrointestinal, and other mucosal systems. In the airway, the two primary polymeric mucins are MUC5AC and MUC5B. They are assembled from a protein core dominated by proline-, threonine-, and serine-rich “PTS” domains that are extensively O-glycosylated, resulting in a stiff, extended conformation. The N- and C-terminal regions contain cysteine-rich domains (including von Willebrand factor-like domains) that direct polymerization via disulfide linkages, forming massive, linear or branched polymers. These polymers are stored in granules and secreted upon stimulation to form a viscoelastic gel that traps inhaled pathogens, particles, and toxicants, supporting ciliary clearance and protecting epithelial cells. Disrupted synthesis, secretion, or properties of polymeric mucins are involved in airway diseases such as asthma, COPD, cystic fibrosis, and respiratory infections. Polymeric mucins are not conventional drug targets like receptors or enzymes; rather, therapies focus on modulating their production, secretion, or physical properties to treat mucus-related disease.

Other names

Gel-forming mucinSecreted mucinAirway mucinMUC5ACMUC5B

Not applicable as a primary drug target. Drugs may disrupt or degrade the mucin polymer network (e.g., mucolytics cleaving disulfide bonds or glycosidic linkages).