Involvement of TBK1 and IKKepsilon in lipopolysaccharide-induced activation of the interferon response in primary human macrophages.
Interferon (IFN) is an important effector of the innate immune response, induced by different viral or bacterial components through Toll-like receptor-dependent and -independent mechanisms. In human macrophages and macrophage-activated killer cells, we demonstrate that (i) the type I IFN response to lipopolysaccharide (LPS) is weak compared to the host response to virus infection; (ii) there is a temporal difference in the induction of tank-binding kinase-1 (TBK1) and IkappaB kinase (IKK)-related kinase epsilon (IKKepsilon) kinase activities in response to LPS, with TBK1 activated early and IKKepsilon induced in the late phase of IFN induction; and (iii) interferon regulatory factor (IRF)-7 is induced following LPS treatment, but there is no evidence that IRF-7 becomes activated by phosphorylation in vivo. Specifically, TBK1 kinase activity is rapidly increased after LPS stimulation (15 min) whereas IKKepsilon activation occurs at 8 h. RNA interference-mediated inhibition of TBK1 and IKKepsilon expression in macrophages interfere with IFNB and IRF7 gene expression following LPS activation. Macrophage priming with rIFN-alpha increased IRF-7 expression, led to a sharp up-regulation of the IFNB gene and to a rapid induction of IFNA2 upon LPS stimulation. These data support a differential role of TBK1 and IKKepsilon in the downstream response mediated by IRF-3 and IRF-7 to LPS in primary human macrophages.
Solis
Mayra
M
Terry Fox Molecular Oncology Group, Lady Davis Institute for Medical Research, Montreal, QE, Canada.
Romieu-Mourez
Raphaëlle
R
Goubau
Delphine
D
Grandvaux
Nathalie
N
Mesplede
Thibault
T
Julkunen
Ilkka
I
Nardin
Alessandra
A
Salcedo
Margarita
M
Hiscott
John
J
D002478:Cells, Cultured; D024202:Electrophoretic Mobility Shift Assay; D004789:Enzyme Activation / Q000276:immunology; D015870:Gene Expression / Q000276:immunology; D006801:Humans; D051550:I-kappa B Kinase / Q000276:immunology* / Q000378:metabolism; D015151:Immunoblotting; D050838:Interferon Regulatory Factor-3 / Q000276:immunology / Q000378:metabolism; D050839:Interferon Regulatory Factor-7 / Q000276:immunology / Q000378:metabolism; D016899:Interferon-beta / Q000276:immunology* / Q000378:metabolism; D008070:Lipopolysaccharides / Q000276:immunology*; D008262:Macrophage Activation / Q000276:immunology*; D008264:Macrophages / Q000276:immunology* / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000276:immunology* / Q000378:metabolism; D034741:RNA, Small Interfering; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors
D050838:Interferon Regulatory Factor-3; D050839:Interferon Regulatory Factor-7; D008070:Lipopolysaccharides; D034741:RNA, Small Interfering; D016899:Interferon-beta; D017346:Protein Serine-Threonine Kinases; C403191:TBK1 protein, human; D051550:I-kappa B Kinase