Mucin family of glycoproteins

Mucins are large glycoproteins expressed by epithelial membranes and as components of the mucus secretions that cover epithelia in harsh environments - the air-water interface of the respiratory system, the acidic environment of the stomach, the complex environment of the intestinal tract, and secretory epithelial surfaces of specialized organs such as liver, pancreas, kidneys, gall bladder, salivary glands, lacrimal glands, and eye. Mucins are critical in maintaining homeostasis in environments that fluctuate in molecular composition - including pH, ionic concentration, oxygenation, and hydration. The molecular composition and higher-order structures of mucins offer specialized functions in the external environment, while relaying information about the environment to the cell via signal transduction through membrane-associated mucins.