Respiratory mucin (MUC)

Respiratory mucins, primarily MUC5AC and MUC5B, are large, heavily glycosylated proteins that constitute the primary structural component of airway mucus. These molecules, historically referred to as mucus mucopolysaccharides due to their high carbohydrate content, form a viscoelastic gel that is essential for the mucociliary escalator to trap and remove inhaled toxins and pathogens. In healthy individuals, these glycoproteins maintain airway hydration and provide a critical physical barrier against infection. However, in chronic respiratory diseases like COPD and cystic fibrosis, mucin hypersecretion and altered biochemical properties lead to the formation of thick, obstructive mucus plugs that impair lung function and promote bacterial colonization. Pharmacological intervention typically involves mucolytic agents that target the disulfide bridges or the carbohydrate-rich structure of these mucins to reduce viscosity and facilitate expectoration. Modern therapeutic research also focuses on modulating the expression and secretion of specific mucin subtypes to restore normal airway clearance mechanisms (Fahy & Dickey, 2010; Boucher, 2019; StatPearls, 2023).

Other names

Mucus mucopolysaccharidesAirway mucinsBronchial mucinsMUC5ACMUC5BGlycosaminoglycans of the respiratory tractMucus glycoproteins

Reduction of disulfide bonds within mucin polymers to decrease mucus viscosity; stimulation of secretomotoric activity to enhance clearance; hydrolysis of extracellular DNA to reduce sputum tenacity.