NF-kappa B and STAT5 play important roles in the regulation of mouse toll-like receptor 2 gene expression

Toll-like receptor 2 (TLR2) is involved in the innate immunity by recognizi ng various bacterial components. We have previously reported that TLR2 gene expression is rapidly induced by LPS or inflammatory cytokines in macropha ges, and by TCR engagement or IL-2/IL-15 stimulation in T cells. Here, to i nvestigate the mechanisms governing TLR2 transcription, we cloned the 5' up stream region of the mouse TLR2 (mTLR2) gene and mapped its transcriptional start site. The 5' upstream region of the mTLR2 gene contains two NF-kappa B, two CCAAT/enhancer binding protein, one cAMP response element-binding pr otein, and one STAT consensus sequences. In mouse macrophage cell lines, de letion of both NF-kappaB sites caused the complete loss of mTLR2 promoter r esponsiveness to TNF-alpha. NF-kappaB sites were also important but not abs olutely necessary for LPS-mediated mTLR2 promoter activation. In T cell lin es, mTLR2 responsiveness to IL-15 was abrogated by the 3' NF-kappaB mutatio n, whereas 5' NF-kappaB showed no functional significance. The STAT binding site also seemed to contribute, as the deletion of this sequence significa ntly reduced the IL-15-mediated mTLR2 promoter activation. EMSAs confirmed nuclear protein binding to both NF-kappaB sites in macrophages following LP S and TNF-alpha stimulation and to the 3' NF-kappaB site in T cells after I L-15 treatment. Thus, NF-kappaB activation is important but differently inv olved in the regulation of mTLR2 gene expression in macrophages and T cells following LPS or cytokine stimulation.