Muciiniproteiinit

Muciiniproteiinit, or mucin proteins, are a family of high molecular weight glycoproteins that form the major component of mucus on mucosal surfaces. They are produced by goblet cells and various glandular epithelia in the respiratory, gastrointestinal, and reproductive tracts. Mucins exist in two main forms: secreted gel-forming mucins that create a protective mucus layer, and membrane-associated mucins that are anchored to epithelial cells and contribute to boundary properties.

Structurally, mucins are extensively O-glycosylated, with serine- and threonine-rich tandem repeat regions that create a highly hydrated, viscoelastic gel. Secreted mucins such as MUC2, MUC5AC, MUC5B, and MUC6 assemble into polymer networks that trap water and particulates, while membrane-associated mucins like MUC1, MUC4, MUC16, and MUC17 extend from the cell surface to modulate signaling and surface lubrication. The glycosylation pattern and polymerization state determine protective function and barrier characteristics.

Functions of mucin proteins include lubrication of mucosal surfaces, hydration maintenance, and protection against mechanical stress, chemical irritants, and pathogen invasion. They also influence the composition and behavior of the resident microbiota and participate in immune responses. Secretion and expression of mucins are dynamically regulated by cytokines, infections, and environmental stimuli, with turnover balancing production and shedding.

Clinical relevance includes associations between altered mucin expression or glycosylation and diseases such as cystic fibrosis, inflammatory bowel disease, chronic obstructive pulmonary disease, and several cancers. Mucins serve as biomarkers (for example, MUC1 and MUC16) and are investigated as therapeutic targets and as components in mucoadhesive drug-delivery systems.