CaMKII promotes TLR-triggered proinflammatory cytokine and type I interferon production by directly binding and activating TAK1 and IRF3 in macrophages

Abstract

Calcium and its major downstream effector, calcium/calmodulin-dependent protein kinase II (CaMKII), are found to be important for the functions of immune cells. Lipopolysaccharide (LPS) has been shown to induce intracellular calcium release in macrophages; however, whether and how CaMKII is required for Toll-like receptor (TLR) signaling remain unknown. Here we demonstrate that TLR 4, 9, and 3 ligands markedly induce intracellular calcium fluxes and activate CaMKII-␣ in macrophages. Selective inhibition or RNA interference of CaMKII significantly suppresses TLR4, 9, 3-triggered production of interleukin-6 (IL-6), tumor necrosis factor-␣, and interferon-␣/␤ (IFN-␣/␤) in macrophages. Coincidently, overexpression of constitutively active CaMKII-␣ significantly enhances production of the above cytokines. In addition to the activation of mitogen-activated protein kinase and nuclear factor B pathways, CaMKII-␣ can directly bind and phosphorylate transforming growth factor ␤-activated kinase 1 (TAK1) and IFN regulatory factor 3 (IRF3; serine IntroductionOn recognition of pathogenic components, Toll-like receptors (TLRs) are activated, leading to a variety of signaling events that initiate innate immunity and activate immune cells to produce proinflammatory cytokines and type I interferon (IFN). 1,2 Most of the members of the TLR family, with the exception of TLR3, trigger immune response via the conserved myeloid differentiation factor 88 (MyD88)-dependent pathway, which involves MyD88, interleukin-1 (IL-1) receptor-associated kinase 1 (IRAK1), tumor necrosis factor (TNF) receptor-associated factor 6 (TRAF6), transforming growth factor-␤ (TGF-␤)-activated kinase 1 (TAK1), downstream mitogen-activated protein kinases (MAPKs), and nuclear factor B (NF-B). 2,3 Toll/IL-1 receptor-domain-containing adaptor protein inducing IFN-␤ (TRIF) has been found to induce the expression of type I IFN in response to TLR4 and TLR3 ligands, which associates with TANK-binding kinase 1 (TBK1) and activates downstream IFN regulatory factor 3 (IRF3). In addition, the TRIF pathway also contributes to TLR3-and TLR4-activated proinflammatory cytokine production. 3,4 TLR activation is essential for provoking the innate immune response and enhancing adaptive immunity against invading pathogens. Less efficient activation of the TLR response may not evoke potent anti-infection or antitumor immunity; however, excessive activation of TLR may also induce immunopathologic processes, such as endotoxin shock and autoimmune diseases. How to manipulate or control the TLR response for prevention and treatment of inflammatory and immunologic diseases largely depends on the understanding of the molecular basis for TLR responses. Up to now, molecular mechanisms for the initiation and regulation of TLR responses remain to be fully understood. In addition to the MyD88-or TRIF-dependent pathway, ligation of TLRs has been found to activate various other intracellular signaling molecules, such as phosphatidylinositol 3-kinase (PI3K)/ AKT 5 and MAPK kinase kinase (ME...

MicroRNAs in the regulation of TLR and RIG-I pathways

“…For example, miR-148 and miR-152 impair TLR signaling by targeting calcium/calmodulin-dependent protein kinase II. 12,93 MicroRNA-132 was shown to target acetylcholinesterase, which attenuates TLR-induced responses in macrophages by blocking NF-kB nuclear translocation. 94 Inhibition of miR-181 can also inhibit TNF-induced cytokine production in epithelial cells by targeting p300/cyclic AMP response element binding protein-associated factor, a coactivator and an acetyltransferase that promotes histone acetylation and gene transcription.…”

“…Many molecules have been identified as positive or negative regulators of TLR signaling, 6,7 including phosphatases (SHP-1, SHP-2, SHIP-1, PTP1B, [8][9][10][11] etc. ), protein kinases (calmodulin-dependent protein kinase II, Btk, MEKK3, [12][13][14] etc. ), ubiquitin-related proteins (A20, Nrdp1, CHIP, [15][16][17] etc.…”

MicroRNA-92a Negatively Regulates Toll-like Receptor (TLR)-triggered Inflammatory Response in Macrophages by Targeting MKK4 Kinase

“…jetSI-ENDO transfection reagents (Polyplus-transfection, Illkirch, France) were used for the cotransfection of plasmids and RNAs as we described previously (44). Thioglycollate-elicited mouse peritoneal macrophages were prepared and cultured as described previously (45). A total of 0.5 ml of 2 ϫ 10 5 cells were seeded onto each well of 24-well plates and incubated overnight, and then transfected with RNAs using INTERFERin (Polyplus-transfection), according to the manufacturer's instructions.…”

DNA-dependent Activator of Interferon-regulatory Factors (DAI) Promotes Lupus Nephritis by Activating the Calcium Pathway

“…Emerging studies reveal that many signal-transducing pathways, such as Toll-like receptor, Fc receptor (FcR), or complement receptor binding, lead to calcium fluxes within monocytes and macrophages through the calcium channel or from mobilization from intracellular stores (44,45). Calcium signaling, therefore, appears to be highly integrated into the modulation of macrophage activity.…”