Involvement of TBK1 and IKKepsilon in lipopolysaccharide-induced activation of the interferon response in primary human macrophages

Eur J Immunol. 2007 Feb;37(2):528-39. doi: 10.1002/eji.200636090.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cells, Cultured
  • Electrophoretic Mobility Shift Assay
  • Enzyme Activation / immunology
  • Gene Expression / immunology
  • Humans
  • I-kappa B Kinase / immunology*
  • I-kappa B Kinase / metabolism
  • Immunoblotting
  • Interferon Regulatory Factor-3 / immunology
  • Interferon Regulatory Factor-3 / metabolism
  • Interferon Regulatory Factor-7 / immunology
  • Interferon Regulatory Factor-7 / metabolism
  • Interferon-beta / immunology*
  • Interferon-beta / metabolism
  • Lipopolysaccharides / immunology*
  • Macrophage Activation / immunology*
  • Macrophages / immunology*
  • Macrophages / metabolism
  • Protein Serine-Threonine Kinases / immunology*
  • Protein Serine-Threonine Kinases / metabolism
  • RNA, Small Interfering
  • Reverse Transcriptase Polymerase Chain Reaction
  • Time Factors

Substances

  • Interferon Regulatory Factor-3
  • Interferon Regulatory Factor-7
  • Lipopolysaccharides
  • RNA, Small Interfering
  • Interferon-beta
  • Protein Serine-Threonine Kinases
  • TBK1 protein, human
  • I-kappa B Kinase