Tumor progression locus 2-dependent oxidative burst drives phosphorylation of extracellular signal-regulated kinase during TLR3 and 9 signaling

J Biol Chem. 2014 Dec 26;289(52):36089-100. doi: 10.1074/jbc.M114.587121. Epub 2014 Nov 5.


Signal transduction via NFκB and MAP kinase cascades is a universal response initiated upon pathogen recognition by Toll-like receptors (TLRs). How activation of these divergent signaling pathways is integrated to dictate distinct immune responses to diverse pathogens is still incompletely understood. Herein, contrary to current perception, we demonstrate that a signaling pathway defined by the inhibitor of κB kinase β (IKKβ), MAP3 kinase tumor progression locus 2 (Tpl2/MAP3K8), and MAP kinase ERK is differentially activated by TLRs. TLRs 2, 4, and 7 directly activate this inflammatory axis, inducing immediate ERK phosphorylation and early TNFα secretion. In addition to TLR adaptor proteins, IKKβ-Tpl2-ERK activation by TLR4 is regulated by the TLR4 co-receptor CD14 and the tyrosine kinase Syk. Signals from TLRs 3 and 9 do not initiate early activation of IKKβ-Tpl2-ERK pathway but instead induce delayed, NADPH-oxidase-dependent ERK phosphorylation and TNFα secretion via autocrine reactive oxygen species signaling. Unexpectedly, Tpl2 is an essential regulator of ROS production during TLR signaling. Overall, our study reveals distinct mechanisms activating a common inflammatory signaling cascade and delineates differences in MyD88-dependent signaling between endosomal TLRs 7 and 9. These findings further confirm the importance of Tpl2 in innate host defense mechanisms and also enhance our understanding of how the immune system tailors pathogen-specific gene expression patterns.

Keywords: Extracellular-signal-regulated Kinase (ERK); Mitogen-activated Protein Kinase (MAPK); Reactive Oxygen Species (ROS); Signal Transduction; Toll-like Receptor (TLR).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Vesicular Transport / metabolism
  • Animals
  • Autocrine Communication
  • Cells, Cultured
  • Extracellular Signal-Regulated MAP Kinases / metabolism*
  • I-kappa B Kinase / metabolism
  • Interleukin-10 / genetics
  • Interleukin-10 / metabolism
  • Intracellular Signaling Peptides and Proteins / metabolism
  • Lipopolysaccharide Receptors / metabolism
  • Lipopolysaccharides / pharmacology
  • MAP Kinase Kinase Kinases / physiology*
  • MAP Kinase Signaling System
  • Macrophages / immunology
  • Macrophages / metabolism
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Myeloid Differentiation Factor 88 / metabolism
  • Phosphorylation
  • Protein Processing, Post-Translational*
  • Protein-Tyrosine Kinases / metabolism
  • Proto-Oncogene Proteins / physiology*
  • Reactive Oxygen Species / metabolism
  • Respiratory Burst
  • Syk Kinase
  • Toll-Like Receptor 3 / metabolism*
  • Toll-Like Receptor 4 / metabolism
  • Toll-Like Receptor 9 / metabolism*
  • Transcriptional Activation
  • Tumor Necrosis Factor-alpha / genetics
  • Tumor Necrosis Factor-alpha / metabolism


  • Adaptor Proteins, Vesicular Transport
  • IL10 protein, mouse
  • Intracellular Signaling Peptides and Proteins
  • Lipopolysaccharide Receptors
  • Lipopolysaccharides
  • Myd88 protein, mouse
  • Myeloid Differentiation Factor 88
  • Proto-Oncogene Proteins
  • Reactive Oxygen Species
  • TICAM-1 protein, mouse
  • TLR3 protein, mouse
  • Tlr4 protein, mouse
  • Tlr9 protein, mouse
  • Toll-Like Receptor 3
  • Toll-Like Receptor 4
  • Toll-Like Receptor 9
  • Tumor Necrosis Factor-alpha
  • Interleukin-10
  • Protein-Tyrosine Kinases
  • Syk Kinase
  • Syk protein, mouse
  • I-kappa B Kinase
  • Extracellular Signal-Regulated MAP Kinases
  • MAP Kinase Kinase Kinases
  • Map3k8 protein, mouse