CpG-ODN stimulates dendritic cells (DCs) to produce cytokines, which are important for autoimmune disorder development and vaccine strategy for cancer. CpG-ODN activates the TLR9/TRAF6 cascade leading to IKK-NF-κB and IKK-IRF7 activation, which is critical for production of pro-inflammatory cytokines and the type I IFNs, respectively. However, whether other molecules are involved in activation of CpG-ODN signaling is still unclear. Here we report that the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs) is involved in this activation process. DNA-PKcs-deficient DCs exhibited a defect in the IL-6 and IL-12 response to CpG-ODN in a dose- and time- dependent manner. Also, loss of DNA-PKcs impaired the IFNa response to CpG-ODN and blockade of IFNR signaling further reduced the IL-6 and IL-12 response to CpG-ODN in DNA-PKcs deficient DCs. Additionally, loss of DNA-PKcs impaired phosphorylation of IKKa, IκBα, NF-κB, JNK, IRF7 and STAT1 in response to CpG-ODN. Interestingly, TLR9- and DNA-PKcs/TLR9- deficient DCs showed almost no IL-6 and IL-12 response to CpG-ODN, but they exhibited about 2/3 to 3/4 defect in the IFNa production compared to WT controls. Finally, CpG-ODN bound DNA-PKcs in the absence of TLR9, whereas it induced DNA-PKcs’s association with TRAF6 in a TLR9-dependent manner. Our data suggest that DNA-PKcs is a player in CpG-ODN signaling and may explain why DNA-PKcs is implicated in the pathogenic process of autoimmune disease.
- Copyright © 2013 by The American Association of Immunologists, Inc.