The sensing receptor (CaSR) is an interesting protein initially characterized in the elucidation of parathyroid hormone release by bovine parathyroid glands. A G-protein coupled receptor, described agonists other than calcium include other polycations (Mg2+, Gd3+), polyamines (spermine, neomycin), and aminoglycosides. It has been described to regulate cellular processes in cell types and tissues not associated with calcium homeostasis. Through some initial studies, using immuno-fluorescence, we have shown expression of the CaR in bronchial epithelia grown in culture from human explants. With confocal microscopy and co-localization with a cytoplasmic mucin, we have localized the protein to reside solely on and near the base of bronchial epithelial cilia. We have confirmed the presence of the CaR in human bronchial epithelia with Western blotting. Given CaSR's intriguing location on the apical surface of ciliated bronchial epithelial tissue, and it's rather unique residence on cilia we reason that this protein will prove to be involved in one or several processes unique to the apical environment-ciliary function, ion transport, and host defense. Specifically, we aim to elucidate a function regarding ciliary beat regulation and ion transport as well as investigate second messenger systems generated via CaSR stimulation.
