Toll-like receptor (TLR) signaling in response to Aspergillus fumigatus

J Biol Chem. 2002 Oct 18;277(42):39320-6. doi: 10.1074/jbc.M201683200. Epub 2002 Aug 8.

Abstract

Aspergillus fumigatus causes life-threatening infections in patients with qualitative and quantitative defects in phagocytic function. Here, we examined the contribution of Toll-like receptor (TLR)-2, TLR4, the adapter protein MyD88, and CD14 to signaling in response to the three forms of A. fumigatus encountered during human disease: resting conidia (RC), swollen conidia (SC), and hyphae (H). Compared with elicited peritoneal macrophages obtained from wild-type and heterozygous mice, TLR2(-/-) and MyD88(-/-) macrophages produced significantly less tumor necrosis factor-alpha (TNFalpha) following A. fumigatus stimulation. In contrast, following stimulation with RC, SC, and H, TLR4(-/-) and CD14(-/-) macrophages exhibited no defects in tumor necrosis factor-alpha release. TLR2(-/-), TLR4(-/-), MyD88(-/-), and CD14(-/-) macrophages bound similar numbers of RC and SC compared with wild-type macrophages. RC, SC, and H stimulated greater activation of a nuclear factor kappa B (NFkappaB)-dependent reporter gene and greater release of tumor necrosis factor-alpha from the human monocytic THP-1 cell line stably transfected with CD14 compared with control cells stably transfected with empty vector. A. fumigatus stimulated NFkappaB-dependent reporter gene activity in the human embryonic kidney cell line, HEK293, only if the cells were transfected with TLR2. Moreover, activity increased when TLR2 and CD14 were co-transfected. Taken together, these data suggest that optimal signaling responses to A. fumigatus require TLR2 in both mouse and human cells. In contrast, a role for CD14 was found only in the human cells. MyD88 acts as a central adapter protein mediating signaling responses following stimulation with RC, SC, and H.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Aspergillus fumigatus / metabolism*
  • Cell Line
  • Cell Nucleus / metabolism
  • Drosophila Proteins*
  • Escherichia coli / metabolism
  • Heterozygote
  • Humans
  • Lipopolysaccharide Receptors / biosynthesis
  • Lipopolysaccharides / metabolism
  • Macrophages / metabolism
  • Membrane Glycoproteins / metabolism*
  • Mice
  • Mice, Inbred C3H
  • Mice, Inbred C57BL
  • NF-kappa B / metabolism
  • Protein Binding
  • Receptors, Cell Surface / metabolism*
  • Signal Transduction*
  • Toll-Like Receptor 2
  • Toll-Like Receptor 4
  • Toll-Like Receptors
  • Transfection
  • Tumor Necrosis Factor-alpha / metabolism

Substances

  • Drosophila Proteins
  • Lipopolysaccharide Receptors
  • Lipopolysaccharides
  • Membrane Glycoproteins
  • NF-kappa B
  • Receptors, Cell Surface
  • TLR2 protein, human
  • TLR4 protein, human
  • Toll-Like Receptor 2
  • Toll-Like Receptor 4
  • Toll-Like Receptors
  • Tumor Necrosis Factor-alpha