Carbachol Activates IκB Kinase in Isolated Canine Gastric Parietal Cells

IκB kinase (IKK) is a recently discovered kinase complex composed of the kinases IKKα and β, which plays a crucial role in the activation of NF-κB. In this study we examined the regulation of IKK by carbachol in isolated gastric parietal cells. IKKα and β activities were measured by immune complex kinase assay. Carbachol induced both IKK α and β in a time-dependent fashion, with a maximal stimulatory effect detected after 5 min of incubation. The action of carbachol was inhibited by the intracellular Ca++ chelator BAPTA-AM, the PKC inhibitor GF109203X, and the NF-κB inhibitor PDTC. Carbachol also induced degradation of IκBα, which was reversed by addition of both GF109203X and PDTC and stimulated the activity of a NF-κB-luciferase reporter gene plasmid in COS-7 cells stably expressing the human M3 muscarinic receptor. In conclusion, carbachol induces IKK in the parietal cells via intracellular Ca++- and PKC-dependent signaling pathways. This observation represents a novel mechanism for the regulation of NF-κB through the activation of seven transmembrane G-protein-coupled receptors.