Dual ligand stimulation of RAW 264.7 cells uncovers feedback mechanisms that regulate TLR-mediated gene expression.
J Immunol, 2006/10/01;177(7):4299-310.
Zhu X[1], Chang MS, Hsueh RC, Taussig R, Smith KD, Simon MI, Choi S
Affiliations
PMID: 16982864
Impact factor: 5.426
Abstract
To characterize how signaling by TLR ligands can be modulated by non-TLR ligands, murine RAW 264.7 cells were treated with LPS, IFN-gamma, 2-methyl-thio-ATP (2MA), PGE(2), and isoproterenol (ISO). Ligands were applied individually and in combination with LPS, for 1, 2, and 4 h, and transcriptional changes were measured using customized oligo arrays. We used nonadditive transcriptional responses to dual ligands (responses that were reproducibly greater or less than the expected additive responses) as a measure of pathway interaction. Our analysis suggests that cross-talk is limited; <24% of the features with significant responses to the single ligands responded nonadditively to a dual ligand pair. PGE(2) and ISO mainly attenuated, while 2MA enhanced, LPS-induced transcriptional changes. IFN-gamma and LPS cross-regulated the transcriptional response induced by each other: while LPS preferentially enhanced IFN-gamma-induced changes in gene expression at 1 h, IFN-gamma signaling primarily attenuated LPS-induced changes at 4 h. Our data suggest specific cross-talk mechanisms: 1) LPS enhances the expression of IFN-gamma-response genes by augmenting STAT1 activity and by activating NF-kappaB, which synergizes with IFN-gamma-induced transcriptional factors; 2) IFN-gamma attenuates the late LPS transcriptional response by increasing the expression of suppressor of cytokine signaling 1 and cytokine-inducible SH2-containing protein expression; 3) 2MA modulates LPS secondary transcriptional response by increasing IFN-beta and inhibiting IL-10 gene expression; 4) PGE(2) and ISO similarly regulate the LPS transcriptional response. They increase IL-10 transcription, resulting in attenuated expression of known IL-10-suppressed genes.
MeSH terms
Adenosine Triphosphate; Animals; Cell Line; Dinoprostone; Gene Expression; Gene Expression Regulation; Interferon-gamma; Isoproterenol; Ligands; Lipopolysaccharides; Mice; Oligonucleotide Array Sequence Analysis; Receptor Cross-Talk; Signal Transduction; Thionucleotides; Toll-Like Receptors; Transcription, Genetic
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