Signal integration in lipopolysaccharide (LPS)-stimulated murine macrophages.
Using a panel of LPS-inducible genes, selected for the capacity of their products to contribute to endotoxicity, normal macrophages were compared to macrophages deficient in CD14, CD11b/CD18, or TLR4 to elicit gene expression in response to Escherichia coli LPS or the LPS mimetic, Taxol. All genes were TLR4-dependent. At low doses of LPS or Taxol, all genes were also CD14-dependent; however, IP-10 and ICSBP remained poorly inducible even at much higher concentrations. A distinct subset of genes (COX-2, IL-12 p40, and IL-12 p35) was CD11b/CD18-dependent. NF-B translocation and MAPK phosphorylation were dysregulated in receptor-deficient macrophages. In contrast to E. coli LPS, a Porphyromonas gingivalis LPS preparation was found to be TLR2-, rather than TLR4-dependent, and resulted in differential expression of genes within the panel. These data suggest that: (i) TLR4 is necessary, but not sufficient, to induce the full repertoire of genes examined; (ii) CD14 and CD11b/CD18 facilitate signaling for induction of select subsets of genes that are also TLR4-dependent; and (iii) signaling through TLR2 versus TLR4 differs quantitatively/qualitatively. These data support an LPS signaling complex on murine macrophages that minimally includes CD14, CD11b/CD18, and TLR4 to respond to E. coli LPS to elicit the full spectrum of gene expression.
Vogel
S
S
Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, USA. vogel@bob.usuhs.mil
Hirschfeld
M J
MJ
Perera
P Y
PY
D000818:Animals; D018821:CD18 Antigens / Q000235:genetics*; D029721:Drosophila Proteins; D004926:Escherichia coli / Q000378:metabolism; D015870:Gene Expression; D018950:Lipopolysaccharide Receptors / Q000235:genetics*; D008070:Lipopolysaccharides / Q000276:immunology*; D016177:Macrophage-1 Antigen / Q000235:genetics*; D008264:Macrophages / Q000276:immunology*; D008562:Membrane Glycoproteins / Q000235:genetics*; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D011956:Receptors, Cell Surface / Q000235:genetics*; D015398:Signal Transduction; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors
D018821:CD18 Antigens; D029721:Drosophila Proteins; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D016177:Macrophage-1 Antigen; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors