Respiratory epithelial cell surface mucins

Respiratory epithelial cell surface glycoproteins primarily encompass mucin glycoproteins and pulmonary surfactant-associated proteins that coat the luminal surfaces of airways and alveoli. These molecules, including transmembrane mucins like MUC1 and MUC4 and secreted gel-forming mucins such as MUC5AC and MUC5B, form a protective glycocalyx and mucus barrier that traps pathogens, facilitates mucociliary clearance, and shields underlying epithelium from environmental insults. Surfactant proteins SP-A, SP-B, and SP-D, expressed by type II pneumocytes, reduce alveolar surface tension to prevent collapse, promote phospholipid spreading, and mediate innate host defense via opsonization and immune modulation. In disease, dysregulation leads to mucus hypersecretion in chronic inflammation or infections, impaired surfactant function causing respiratory failure (e.g., SP-B mutations), and altered glycosylation that may enhance pathogen adherence. While not typical drug targets like receptors or enzymes, they serve as biomarkers (e.g., KL-6 for lung injury) and influence therapies addressing mucus clearance in conditions like cystic fibrosis. Their high glycosylation (up to 80-90% by weight) with O-linked chains determines biophysical properties like viscosity and pathogen interactions.

Other names

Mucins (MUC1, MUC4, MUC5AC, MUC5B)pulmonary surfactant glycoproteins (SP-A, SP-B, SP-D)KL-6cell surface (tethered) mucins