c-Jun N-Terminal Kinase 1 Is Required for Toll-Like Receptor 1 Gene Expression in Macrophages

P. 5027-5034The regulation of innate immune responses to pathogens occurs through the interaction of Toll-like receptors (TLRs) with pathogen-associated molecular patterns and the activation of several signaling pathways whose contribution to the overall innate immune response to pathogens is poorly understood. We demonstrate a mechanism of control of murine macrophage responses mediated by TLR1/2 heterodimers through c-Jun N-terminal kinase 1 (JNK1) activity. JNK controls tumor necrosis factor alpha production and TLR-mediated macrophage responses to Borrelia burgdorferi, the causative agent of Lyme disease, and the TLR1/TLR2-specific agonist PAM3CSK4. JNK1, but not JNK2, activity regulates the expression of the tlr1 gene in the macrophage cell line RAW264.7, as well as in primary CD11b cells. We also show that the proximal promoter region of the human tlr1 gene contains an AP-1 binding site that is subjected to regulation by the kinase and binds two complexes that involve the JNK substrates c-Jun, JunD, and ATF-2. These results demonstrate that JNK1 regulates the response to TLR1/2 ligands and suggest a positive feedback loop that may serve to increase the innate immune response to the spirocheteS

Innate immune responses to B. burgdorferi mediated by JNK1 and the cochaperone, methylation controlled DNAJ (MCJ)

The infections agent of Lyme disease, Borrelia Burgdorferi is a complex microorganism with a highly diverse genome. One of the most remarkable aspects of the B. burgdorferi genome is the large number of sequences encoding predicted or known lipoproteins, including outer-surface proteins. The B. burgdorferi genome encodes no recognizable toxins. Instead, this extracellular pathogen causes pathology by migration through tissues, adhesion to host cells, and evasion of immune clearance. Inflammation elicited by infection with B. burgdorferi depends on the ability of the spirochete to survive in the mammalian host, as well as the immune response that arises upon the interaction of the bacterium with phagocytic, T and other cell types. Innate immune responses are critical in recognition and clearance of pathogens, and also play an important role in the outcome of adaptive immune responses. The regulation of innate immune responses to pathogens occurs through the interaction of Toll-like receptors (TLRs) with pathogen-associated molecular patterns (PAMPs) and the activation of several signaling pathways whose contribution to the overall innate immune response to pathogens is poorly understood. In this study we demonstrate a mechanism of control of murine macrophage responses mediated by TLR1/2 heterodimers through c-Jun N-terminal kinase 1 (JNK1) activity. JNK also controls tumor necrosis factor production and TLR-mediated macrophage responses to B. burgdorferi. We also show that the proximal promoter region of the human tlr1 gene contains an AP-1 binding site that is subjected to regulation by the kinase and binds two complexes that involve the JNK substrates c-Jun, JunD, and ATF-2. These results demonstrate that JNK1 regulates the response to TLR1/2 ligands and suggest a positive feedback loop that may serve to increase the innate immune response to the spirochete. MCJ is a newly identified member of the DnaJ protein family of cochaperones that contains unique features different than the normally described DnaJ proteins. However, there is little known about its function and the role it plays in different cells and systems. It has been previously shown that MCJ is required for the repression of the ABCB1 drug transporter expression in breast cancer cells, and that this repression is mediated through the control of c-Jun protein stability. We were therefore interested in determining the role that MCJ plays in macrophages in response to B. burgdorferi antigens. We now provide evidence that MCJ controls inflammatory responses of macrophages through the regulation of c-Jun protein stability, and the expression and release of the inflammatory cytokine TNF through the regulation of the expression of TNF converting enzyme (TACE) inhibitor tissue inhibitor of metalloproteinase 3 (TIMP-3)

p38 Mitogen-Activated Protein Kinase Controls NF-κB Transcriptional Activation and Tumor Necrosis Factor Alpha Production through RelA Phosphorylation Mediated by Mitogen- and Stress-Activated Protein Kinase 1 in Response to Borrelia burgdorferi Antigens

The interaction of Borrelia burgdorferi, the causative agent of Lyme borreliosis, with phagocytic cells induces the activation of NF-κB and the expression of proinflammatory cytokines including tumor necrosis factor alpha (TNF-α). B. burgdorferi-induced TNF-α production is also dependent on the activation of p38 mitogen-activated protein (MAP) kinase. The specific contribution of these signaling pathways to the response of phagocytic cells to the spirochete and the molecular mechanisms underlying this response remain unresolved. We now show that p38 MAP kinase activity regulates the transcriptional activation of NF-κB in response to spirochetal lysate stimulation of phagocytic cells. The regulation occurs at the nuclear level and is independent of the translocation of the transcription factor to the nucleus or its capacity to bind to specific DNA target sequences. In RAW264.7 cells, p38α MAP kinase regulates the phosphorylation of NF-κB RelA. p38 MAP kinase phosphorylates the nuclear kinase mitogen- and stress-activated protein kinase 1 (MSK1). MSK1 in turn phosphorylates the transcriptionally active subunit of NF-κB, RelA. The repression of MSK1 expression with small interfering RNA results in reduced RelA phosphorylation and a significant decrease in the production of TNF-α in response to B. burgdorferi lysates. Overall, these results clarify the contribution of the signaling pathways that are activated in response to the interaction of spirochetes with phagocytic cells to TNF-α production. Our results situate p38 MAP kinase activity as a central regulator of the phagocytic proinflammatory response through MSK1-mediated transcriptional activation of the transcription factor NF-κB

c-Jun N-Terminal Kinase 1 Is Required for Toll-Like Receptor 1 Gene Expression in Macrophages▿

The regulation of innate immune responses to pathogens occurs through the interaction of Toll-like receptors (TLRs) with pathogen-associated molecular patterns and the activation of several signaling pathways whose contribution to the overall innate immune response to pathogens is poorly understood. We demonstrate a mechanism of control of murine macrophage responses mediated by TLR1/2 heterodimers through c-Jun N-terminal kinase 1 (JNK1) activity. JNK controls tumor necrosis factor alpha production and TLR-mediated macrophage responses to Borrelia burgdorferi, the causative agent of Lyme disease, and the TLR1/TLR2-specific agonist PAM3CSK4. JNK1, but not JNK2, activity regulates the expression of the tlr1 gene in the macrophage cell line RAW264.7, as well as in primary CD11b+ cells. We also show that the proximal promoter region of the human tlr1 gene contains an AP-1 binding site that is subjected to regulation by the kinase and binds two complexes that involve the JNK substrates c-Jun, JunD, and ATF-2. These results demonstrate that JNK1 regulates the response to TLR1/2 ligands and suggest a positive feedback loop that may serve to increase the innate immune response to the spirochete