Phospholipase C-activating plasma membrane receptors and calcium signaling in immortalized human airway epithelial cells.

Mechanical clearance of inhaled dust particles and microorganisms is an important part of the innate defense mechanisms of mammalian airways. Airway epithelia are composed of various cell types with different degrees of cell polarity. Serous cells regulate composition and volume of luminal periciliary fluid and mucus. Autocrine, paracrine, or neuronal messengers determine the secretory and reabsorptive rates of electrolytes and water via cAMP-or inositol triphosphate/calcium-mediated intracellular signals. Comparison of the expression of calcium-mobilizing receptor types (G protein-coupled-, growth factor-, and cytokine receptors) in two types of human immortalized airway epithelial cells (S9, 16HBE14o-) revealed that receptor populations were qualitatively and quantitatively different in the two cell types. Sustained calcium signals were elicited by activation of purinergic receptors in 16HBE14o-cells or muscarinic acetylcholine or histamine receptors in S9 cells. These G protein-coupled receptors mobilized calcium from intracellular stores and activated capacitative calcium influx. The experimental cells may represent different types of original airway epithelial cells and seem to be suited as model cells to study cell signaling and protein expression during interaction with pathogens or their secretory products (e.g., virulence factors).