NF-κB and STAT5 Play Important Roles in the Regulation of Mouse Toll-Like Receptor 2 Gene Expression

Abstract

Toll-like receptor 2 (TLR2) is involved in the innate immunity by recognizing various bacterial components. We have previously reported that TLR2 gene expression is rapidly induced by LPS or inflammatory cytokines in macrophages, and by TCR engagement or IL-2/IL-15 stimulation in T cells. Here, to investigate the mechanisms governing TLR2 transcription, we cloned the 5′ upstream region of the mouse TLR2 (mTLR2) gene and mapped its transcriptional start site. The 5′ upstream region of the mTLR2 gene contains two NF-κB, two CCAAT/enhancer binding protein, one cAMP response element-binding protein, and one STAT consensus sequences. In mouse macrophage cell lines, deletion of both NF-κB sites caused the complete loss of mTLR2 promoter responsiveness to TNF-α. NF-κB sites were also important but not absolutely necessary for LPS-mediated mTLR2 promoter activation. In T cell lines, mTLR2 responsiveness to IL-15 was abrogated by the 3′ NF-κB mutation, whereas 5′ NF-κB showed no functional significance. The STAT binding site also seemed to contribute, as the deletion of this sequence significantly reduced the IL-15-mediated mTLR2 promoter activation. EMSAs confirmed nuclear protein binding to both NF-κB sites in macrophages following LPS and TNF-α stimulation and to the 3′ NF-κB site in T cells after IL-15 treatment. Thus, NF-κB activation is important but differently involved in the regulation of mTLR2 gene expression in macrophages and T cells following LPS or cytokine stimulation.

Direct recognition of LPS by human but not murine CD8+ T cells via TLR4 complex

“…(b) The surface expression of TLRs on naïve CD8 1 T cells is inducible upon TCR activation. While the mechanism is currently unknown, since TLR promoter contains NF-kB binding sites and TCR signals trigger NF-kB activity, it is likely that TCR signals drive TLR expression via activating NF-kB translocation [24]. (c) Once surface located, TLR allow CD8 1 T cells to directly recognise microbial products and further enhance TCR-initiated T-cell activation, suggesting that TLR signals may be essential for optimal antigen-specific CD8 1 T-cell response.…”

Ligand-induced differential cross-regulation of Toll-like receptors 2, 4 and 5 in intestinal epithelial cells

“…3A and 5B), suggesting a common signalling pathway. Such a pathway may include the central TLR regulator NF-B, which has been shown to play an essential role in the activation of the mouse TLR2 promoter (Musikacharoen et al, 2001;Wang et al, 2001). The mouse TLR4 promoter does not contain NF-B sites but carries several other elements involved in positive (AP-1, Ets, PU.1) and negative (GATA-1 and Oct-1) regulation of TLR4 transcription (Pedchenko et al, 2005;Roger et al, 2005).…”

Lipopolysaccharide and Double-stranded RNA Up-regulate Toll-like Receptor 2 Independently of Myeloid Differentiation Factor 88

“…7). The promoter region of mouse TLR2 contains binding sites for several transcription factors (36), and NF-B is not the only factor contributing to maximal promoter activity. It is suggested that a signal transducer and activator of transcription-binding element also has an impact on the promoter activation (36), and TLR2 could be a gene regulated possibly by TBK1 (70) and interferon regulatory factors.…”

“…The promoter region of mouse TLR2 contains binding sites for several transcription factors (36), and NF-B is not the only factor contributing to maximal promoter activity. It is suggested that a signal transducer and activator of transcription-binding element also has an impact on the promoter activation (36), and TLR2 could be a gene regulated possibly by TBK1 (70) and interferon regulatory factors. We suggest that different requirements for NF-B, signal transducer and activator of transcriptions, and interferon regulatory factors in activating the promoters for TLR2, TNF, and RANTES underlie differences in regulation of these three genes induced by different TLR ligands (Fig.…”