Gram-negative flagellin-induced self-tolerance is associated with a block in interleukin-1 receptor-associated kinase release from toll-like receptor 5.
Flagellin from a number of Gram-negative bacteria induces cytokine and nitric oxide production by inflammatory cell types. In view of the evidence that flagellin responsiveness is subject to modulation, we explored the possibilities that a prior exposure to flagellin might result in a state of reduced flagellin responsiveness or tolerance and that lipopolysaccharide (LPS) and flagellin may induce a state of cross-tolerance to each other. Our results demonstrate that a prior exposure to flagellin results in a subsequent state of flagellin tolerance in human monocytes, THP1 cells, Jurkat cells, and COS-1 cells. Tolerance occurs within 2 h after addition of flagellin and does not require protein synthesis. Flagellin did not induce tolerance to LPS in monocytes and THP1 cells; however, LPS treatment of monocytes and THP1 cells resulted in a state of flagellin cross-tolerance. Flagellin-induced self-tolerance is not the result of a decrease in the steady-state level of toll-like receptor 5 (TLR5) or interleukin-1 receptor associated kinase (IRAK), but it is associated with a block in the release of IRAK from the TLR5 complex in flagellin-tolerant cells. Release is essential for IRAK activity because the TLR5-associated IRAK lacks kinase activity. LPS-induced cross-tolerance to flagellin is also associated with a block in IRAK release from TLR5. These results provide evidence for a novel mechanism of TLR signaling control.
Mizel
Steven B
SB
Department of Microbiology and Immunology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA. smizel@wfubmc.edu
Snipes
James A
JA
D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism*; D015153:Blotting, Western; D019556:COS Cells; D002460:Cell Line; D002469:Cell Separation; D029721:Drosophila Proteins; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000378:metabolism; D005407:Flagella / Q000378:metabolism*; D005408:Flagellin / Q000737:chemistry* / Q000378:metabolism*; D005434:Flow Cytometry; D017930:Genes, Reporter; D006801:Humans; D053592:Interleukin-1 Receptor-Associated Kinases; D019169:Jurkat Cells; D008070:Lipopolysaccharides / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism*; D009000:Monocytes / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors; D051198:Toll-Like Receptor 5; D051193:Toll-Like Receptors; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D001426:Bacterial Proteins; D029721:Drosophila Proteins; D004791:Enzyme Inhibitors; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D047428:Protein Kinase Inhibitors; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; C495346:TLR5 protein, human; D051198:Toll-Like Receptor 5; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha; D005408:Flagellin; D011494:Protein Kinases; D053592:Interleukin-1 Receptor-Associated Kinases