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).