The primary cilium influences interleukin-1β-induced NFκB signalling by regulating IKK activity

The primary cilium is an organelle acting as a master regulator of cellular signalling. We have previously shown that disruption of primary cilia assembly, through targeting intraflagellar transport, is associated with muted nitric oxide and prostaglandin responses to the inflammatory cytokine interleukin-1 beta (IL-1 beta). Here, we show that loss of the primary cilium disrupts specific molecular signalling events in cytosolic NF kappa B signalling. The induction of cyclooxygenase 2 (COX2) and inducible nitrous oxide synthase (iNOS) protein is abolished. Cells unable to assemble cilia exhibit unaffected activation of I kappa B kinase (IKK), but delayed and reduced degradation of I kappa B, due to diminished phosphorylation of inhibitor of kappa B (I kappa B) by IKK. This results in both delayed and reduced NF kappa B p65 nuclear translocation and nuclear transcript binding. We also demonstrate that heat shock protein 27 (hsp27), an established regulator of IKK, is localized to the ciliary axoneme and cellular levels are dramatically disrupted with loss of the primary cilium. These results suggest that the primary cilia compartment exerts influence over NF kappa B signalling. We propose that the cilium is a locality for regulation of the molecular events defining NF kappa B signalling events, tuning signalling as appropriate. (C) 2014 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license