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

摘要

Calcium and its major downstream effector, calcium/calmodulin-dependent protein kinase II (CaMKH), 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 CaMKH 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-ce in macrophages. Selective inhibition or RNA in-terference of CaMKH significantly suppresses TLR4, 9, 3-triggered production of interleukin-6 (IL-6), tumor necrosis factor-alpha, and interferon-alpha/beta (IFN-o/p) in macrophages. Coincidently, overexpres-sion of constitutively active CaMKII-a significantly enhances production of the above cytokines. In addition to the activation of mitogen-activated protein kinase and nuclear factor kB pathways, CaMKII-a can directly bind and phosphorylate transforming growth factor p-activated kinase 1 (TAK1) and IFN regulatory factor 3 (IRF3;serine on 386) via the N-terminal part of its regulatory domain. Therefore, CaMKH can be activated by TLR ligands, and in turn promotes both myeloid differentiating factor 88 and Toll/IL-1 receptor domain-containing adaptor protein-inducing IFN-p-dependent inflammatory responses by directly activating TAK1 and IRF3. The cross-talk with the calcium/ CaMKH pathway is needed for full activation of TLR signaling in macrophages.