The role of protein kinase CK2 in intestinal epithelial cell inflammatory signaling

Background The transcription factor NF-kB is believed to play a key pathophysiological role in chronic intestinal inflammation. Further characterization of its mechanism of regulation, predominantly through cell signaling pathways, may provide clues as to the means of its intervention. One such potential signaling candidate is the protein kinase CK2. Despite its known ability to influence NF-kB activation, it has received no attention in this particular setting. Aim To characterize the aspects of its activation in response to IL-1 beta in the colonic cell lines Caco2 and HCT116. Materials and methods A biochemical analysis of kinase activation was performed using phospho-specific antibodies as well as immune complex kinase assays; transcription factor activity was measured by transient transfection and luciferase-based NF-kB reporter assays; pro-inflammatory molecule expression was determined using RT-PCR. Results In this report, we show an enhanced activation of CK2 bound to IKK-gamma or the p65 subunit of the NF-kB in response to IL-1 beta stimulation of intestinal epithelial cells. Using two established NF-kB reporters, we demonstrate that CK2 is involved in NF-kB regulation through the p65 serine 529 site. Using co-immunoprecipitation studies, we also show that p65 is bound to CK2 predominantly in the nucleus. From a functional perspective, two CK2 specific inhibitors were then shown to attenuate IL-8 reporter activation. Finally, the expression of a series of proinflammatory molecules including IL-8, GRO-alpha, MCP-1, TNF alpha and iNOS were variably affected in response to CK2 inhibition. Conclusion CK2 plays an active role in NF-kB signaling in intestinal epithelial cell lines and may represent a possible target for intervention.