PKCε signaling in ciliated and basal airway epithelial cells

Abstract

The mucociliary layer of the upper airway provides a crucial internal defense against environmental challenges. Viral infection in the upper airway has a profound effect on ciliated epithelial cells within the airway, including reduction of ciliary motility and detachment of ciliated cells from the basal epithelium, though this mechanism is poorly understood. We hypothesize that signaling mediated by the protein kinase C epsilon (PKCε) novel isoform is required for ciliated bovine bronchial epithelial cell (BBEC) attachment to the basal epithelium. We localized PKCε to the cytosol in resting, methanol-fixed, non-ciliated BBECs using immunohistochemistry and confocal scanning microscopy. Prior to characterization of PKCε binding complexes, we also localized the PKC-targeting protein receptor of activated c-kinase 1 (RACK1) to the membrane of non-ciliated primary BBECs. PKCε translocates to the membrane following activation by the known PKC-activator phorbol 12-myristate 13-acetate and co-localizes with RACK1 within approximately 20 minutes in these cells. However, in ciliated airway epithelial cells, PKCε is expressed primarily in the apical region. This differential expression pattern in the airway epithelial cell types suggests that PKCε signaling has distinct roles. In ciliated airway epithelial cells, PKCε is uniquely positioned at the base of the axoneme to regulate mucociliary clearance, while in the non-ciliated airway epithelial cells, the PKCε/RACK1 complex may modulate ciliated cell detachment following environmental insult. This work was supported by ALA grant and VA Merit.