Recombinant Mtb9.8 of Mycobacterium bovis stimulates TNF-α and IL-1β secretion by RAW264.7 macrophages through activation of NF-κB pathway via TLR2

Sci Rep. 2018 Jan 31;8(1):1928. doi: 10.1038/s41598-018-20433-x.

Abstract

The Mtb9.8 antigenic protein of Mycobacterium bovis/Mycobacterium tuberculosis has been identified as a target of the T-cell response. However, the interaction of Mtb9.8 with Toll-like receptors (TLRs) and the relevant signaling pathways have not been fully clarified. In this study, recombinant Mtb9.8 (rMtb9.8) derived from M. bovis-stimulated RAW264.7 cells initiated the secretion of TNF-α and IL-1β in a dose-dependent manner. Blocking assays show that TLR2-neutralizing antibody decreases the production of TNF-α and IL-1β. Moreover, NF-κB activation is associated with TNF-α and IL-1β production by rMtb9.8 stimulation, and rMtb9.8 stimulation also induces the phosphorylation of NF-κB p65 at Ser536 and its rapid nuclear translocation in RAW264.7 cells. Furthermore, NF-κB luciferase activity is rapidly activated in response to rMtb9.8 in RAW264.7 cells and is also significantly increased in rMtb9.8-induced HEK293-TLR2. However, these activations were abrogated in cells with a dominant-negative mutation of NF-κB p65 and by treatment with anti-TLR2 antibody. We also find that rMtb9.8 induces the activation of IRF-1. These findings indicate that M. bovis-derived rMtb9.8 activates the NF-κB pathway via TLR2 in RAW264.7 cells. In particular, it phosphorylates NF-κB p65 at Ser536 and induces nuclear translocation, thereby leading to the production of TNF-α and IL-1β, which correlates with the induction of IRF-1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bacterial Proteins / pharmacology*
  • Cell Nucleus / drug effects
  • Cell Nucleus / metabolism
  • HEK293 Cells
  • Humans
  • Interleukin-1beta / metabolism*
  • Macrophages / drug effects
  • Macrophages / metabolism*
  • Mice
  • Mycobacterium bovis / metabolism*
  • NF-kappa B / metabolism*
  • Phosphorylation / drug effects
  • Phosphoserine / metabolism
  • RAW 264.7 Cells
  • Recombinant Proteins / pharmacology*
  • Signal Transduction / drug effects
  • Toll-Like Receptor 2 / metabolism*
  • Tumor Necrosis Factor-alpha / metabolism*

Substances

  • Bacterial Proteins
  • Interleukin-1beta
  • NF-kappa B
  • Recombinant Proteins
  • Toll-Like Receptor 2
  • Tumor Necrosis Factor-alpha
  • Phosphoserine