A conventional protein kinase C inhibitor targeting IRF-3-dependent genes differentially regulates IL-12 family members

Protein kinase C (PKC) isoforms play a critical role in the regulation of innate immune responses. We have previously demonstrated that conventional PKC (cPKC) alpha is involved in interferon regulatory factor 3 (IRF-3) activation and IFN-beta synthesis. Herein, we investigated the role of cPKCs in the regulation of IL-12 family members expression mediated by the Toll-like receptor 3 (TLR3) and TLR4. First, inhibition of cPKCs activity in human DCs by a cPKC-specific inhibitor. Go6976 downregulated the expression of IL-12p70 and IL-27p28 but not IL-12/IL-23p40, IL-23,IL-27EBI3 induced by LPS or poly(1:C). Furthermore, reporter gene assays in RAW 264.7 macrophages showed that cPKCs regulate IL-12p35 and IL-27p28 promoter activities since Go6976 repressed LPS and poly(I:C)-mediated transcriptional activities of IL-12p35 and IL-27p28. In contrast, no effect was observed with IL-12/IL-23p40 and IL-23p19 reporter constructs. These results prompted us to study the role of IRF-3 on IL-23 expression. Bone marrow-derived DC (BMDCs) from IRF-3(-/-) mice produced comparable levels of IL-23 induced by both LPS and poly(1:C) as compared to wild type BMDCs, indicating that IRF-3 is not involved in IL-23 production. Finally, BMDCs from PKC alpha(-/-) mice displayed a reduced synthesis of IL-27 induced by poly(I:C). Collectively, these data identify cPKCs as critical components that control IRF-3-dependent IL-12p35 and IL-27p28 gene expression downstream of TLR3 and TLR4. (C) 2011 Elsevier Ltd. All rights reserved.