Subtype-specific expression patterns of inositol 1,4,5-trisphosphate receptors in rat airway epithelial cells.

We investigated the immunohistochemical localization of inositol 1,4,5-trisphosphate receptor (IP3R) Types 1, 2, and 3 in rat airway epithelium using the monoclonal antibodies KM1112, KM1083, and KM1082 specific for each type of IP3R. The epithelium from trachea to distal intrapulmonary airways (bronchioles) showed positive immunoreactivity for all types of IP3R. However, cell type as well as subcellular site immunoreactivity for each type of IP3R varied. IP3R Type 1 was found only in the apical thin cytoplasmic area of ciliated cells throughout all airway levels. IP3R Type 2 was exclusively localized to the entire cytoplasm of ciliated cells from the trachea to bronchioles. IP3R Type 3 was expressed mainly in the supranuclear cytoplasm not only of ciliated cells at all airway levels but also in Clara cells of the bronchiolar epithelium. Double fluorescent staining using combinations of KM1083 and Wisteria floribunda lectin or anti-rat 10-KD Clara cell-specific protein antibody confirmed that the IP3R Typ...