Mycobacterium abscessus activates the macrophage innate immune response via a physical and functional interaction between TLR2 and dectin-1

Cell Microbiol. 2008 Aug;10(8):1608-21. doi: 10.1111/j.1462-5822.2008.01151.x. Epub 2008 Mar 26.

Abstract

Mycobacterium abscessus (Mab) is an emerging and rapidly growing non-tuberculous mycobacterium (NTM). Compared with M. tuberculosis, which is responsible for tuberculosis, much less is known about NTM-induced innate immune mechanisms. Here we investigated the involvement of pattern-recognition receptors and associated signalling in Mab-mediated innate immune responses. Mab activated the extracellular signal-regulated kinase (ERK)1/2 and p38 mitogen-activated protein kinases (MAPKs), and induced the secretion of tumour necrosis factor-alpha, interleukin (IL)-6 and IL-12p40 in murine macrophages via Toll-like receptor (TLR) 2. Notably, the activation of ERK1/2, but not p38, was crucial for Mab-induced pro-inflammatory cytokine production. The ITAM-like motif of dectin-1 critically contributed to Mab internalization and cytokine secretion by macrophages. In addition, dectin-1, in cooperation with TLR2, was required for the efficient phagocytosis of Mab, ERK1/2 activation and pro-inflammatory cytokine secretion. Co-immunoprecipitation and confocal analysis showed the physical interaction and colocalization of dectin-1 with TLR2 following Mab stimulation. Moreover, dectin-1-induced Syk activation was essential for the production of inflammatory cytokines and the release of reactive oxygen species by Mab-infected macrophages. Collectively, these data demonstrate that Mab actively internalizes into and robustly activates innate immune responses in macrophages through a physical and functional interaction between TLR2 and dectin-1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cytokines / immunology
  • Immunity, Innate*
  • Intracellular Signaling Peptides and Proteins / metabolism
  • Lectins, C-Type
  • Macrophage Activation
  • Macrophages / immunology*
  • Membrane Proteins / immunology*
  • Mice
  • Mitogen-Activated Protein Kinases / metabolism
  • Mycobacterium / immunology*
  • Mycobacterium Infections / immunology*
  • Mycobacterium Infections / microbiology
  • Nerve Tissue Proteins / immunology*
  • Phagocytosis
  • Protein-Tyrosine Kinases / metabolism
  • Reactive Oxygen Species / metabolism
  • Syk Kinase
  • Toll-Like Receptor 2 / immunology*

Substances

  • Cytokines
  • Intracellular Signaling Peptides and Proteins
  • Lectins, C-Type
  • Membrane Proteins
  • Nerve Tissue Proteins
  • Reactive Oxygen Species
  • Toll-Like Receptor 2
  • dectin 1
  • Protein-Tyrosine Kinases
  • Syk Kinase
  • Syk protein, mouse
  • Mitogen-Activated Protein Kinases