TY - JOUR
T1 - Lipopolysaccharide-Binding Protein Critically Regulates Lipopolysaccharide-Induced IFN-β Signaling Pathway in Human Monocytes
AU - Kato, Atsushi
AU - Ogasawara, Takahisa
AU - Homma, Toshiki
AU - Saito, Hirohisa
AU - Matsumoto, Kenji
PY - 2004/5/15
Y1 - 2004/5/15
N2 - LPS binding to Toll-like receptor 4 induces a large number of genes through activation of NF-κB and IFN-regulatory factor-3 (IRF-3). However, no previous reports have tested the role of serum proteins in LPS-induced gene expression profiles. To investigate how serum proteins affect LPS-induced signaling, we investigated LPS-inducible genes in PBMC using an oligonucleotide probe-array system. Approximately 120 genes up-regulated by LPS were hierarchically divided into two clusters. Induction of one cluster, containing only IFN-inducible genes, was serum dependent. Real-time PCR analysis confirmed that IFN-inducible genes were induced only in the presence of serum, whereas inflammatory genes were induced both in the presence and absence of serum. Further analysis demonstrated that addition of LPS-binding protein (LBP), but not of soluble CD14 to the serum-free medium enabled the induction of IFN-inducible genes and IFN-β itself by LPS in human monocytes. The mRNAs for IFN-β and EFN-inducible genes were induced by LPS only in the presence of serum from LBP+/+ mice, and not in the presence of serum from LBP-/- mice. Blocking experiments also confirmed the involvement of LBP in this phenomenon. Immunoblotting analysis showed that phosphorylation of c-Jun N-terminal kinase, p38, IRF-3, tyrosine kinase 2, and STAT1 by LPS, but not of NF-κB and extracellular signal-regulated kinase was abrogated in the absence of LBP. This critical role for LBP implies the presence of possible mechanisms linking LBP to the intracellular signaling between Toll-like receptor 4 and IRF-3, leading to the induction of IFN-β by LPS.
AB - LPS binding to Toll-like receptor 4 induces a large number of genes through activation of NF-κB and IFN-regulatory factor-3 (IRF-3). However, no previous reports have tested the role of serum proteins in LPS-induced gene expression profiles. To investigate how serum proteins affect LPS-induced signaling, we investigated LPS-inducible genes in PBMC using an oligonucleotide probe-array system. Approximately 120 genes up-regulated by LPS were hierarchically divided into two clusters. Induction of one cluster, containing only IFN-inducible genes, was serum dependent. Real-time PCR analysis confirmed that IFN-inducible genes were induced only in the presence of serum, whereas inflammatory genes were induced both in the presence and absence of serum. Further analysis demonstrated that addition of LPS-binding protein (LBP), but not of soluble CD14 to the serum-free medium enabled the induction of IFN-inducible genes and IFN-β itself by LPS in human monocytes. The mRNAs for IFN-β and EFN-inducible genes were induced by LPS only in the presence of serum from LBP+/+ mice, and not in the presence of serum from LBP-/- mice. Blocking experiments also confirmed the involvement of LBP in this phenomenon. Immunoblotting analysis showed that phosphorylation of c-Jun N-terminal kinase, p38, IRF-3, tyrosine kinase 2, and STAT1 by LPS, but not of NF-κB and extracellular signal-regulated kinase was abrogated in the absence of LBP. This critical role for LBP implies the presence of possible mechanisms linking LBP to the intracellular signaling between Toll-like receptor 4 and IRF-3, leading to the induction of IFN-β by LPS.
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U2 - 10.4049/jimmunol.172.10.6185
DO - 10.4049/jimmunol.172.10.6185
M3 - Article
C2 - 15128806
AN - SCOPUS:2442465798
SN - 0022-1767
VL - 172
SP - 6185
EP - 6194
JO - Journal of Immunology
JF - Journal of Immunology
IS - 10
ER -