Lipopolysaccharide activation of the MEK-ERK1/2 pathway in human monocytic cells mediates tissue factor and tumor necrosis factor alpha expression by inducing Elk-1 phosphorylation and Egr-1 expression.
Lipopolysaccharide (LPS) induces human monocytes to express many proinflammatory mediators, including the procoagulant molecule tissue factor (TF) and the cytokine tumor necrosis factor alpha (TNF-alpha). The TF and TNF-alpha genes are regulated by various transcription factors, including nuclear factor (NF)-kappaB/Rel proteins and Egr-1. In this study, the role of the MEK-ERK1/2 mitogen-activated protein kinase (MAPK) pathway in LPS induction of TF and TNF-alpha gene expression in human monocytic cells was investigated. The MAPK kinase (MEK)1 inhibitor PD98059 reduced LPS induction of TF and TNF-alpha expression in a dose-dependent manner. PD98059 did not affect LPS-induced nuclear translocation of NF-kappaB/Rel proteins and minimally affected LPS induction of kappaB-dependent transcription. In contrast, PD98059 and dominant-negative mutants of the Ras-Raf1-MEK-ERK (extacellular signal-regulated kinase) pathway strongly inhibited LPS induction of Egr-1 expression. In kinetic experiments LPS induction of Egr-1 expression preceded induction of TF expression. In addition, mutation of the Egr-1 sites in the TF and TNF-alpha promoters reduced expression of these proinflammatory genes. It was demonstrated that LPS induction of the Egr-1 promoter was mediated by 3 SRE sites, which bound an LPS-inducible complex containing serum response factor and Elk-1. LPS stimulation transiently induced phosphorylation of Elk-1 and increased the functional activity of a GAL4-Elk-1TA chimeric protein via the MEK-ERK1/2 pathway. The data indicate that LPS induction of Egr-1 gene expression is required for maximal induction of the TNF-alpha and TF genes in human monocytic cells.
Guha
M
M
Department of Immunology, The Scripps Research Institute, La Jolla, CA 92037, USA.
O'Connell
M A
MA
Pawlinski
R
R
Hollis
A
A
McGovern
P
P
Yan
S F
SF
Stern
D
D
Mackman
N
N
D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D051766:Early Growth Response Protein 1; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D017874:Immediate-Early Proteins; D008070:Lipopolysaccharides / Q000494:pharmacology*; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009000:Monocytes / Q000187:drug effects* / Q000201:enzymology; D016328:NF-kappa B / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013925:Thromboplastin / Q000096:biosynthesis* / Q000235:genetics; D014157:Transcription Factors / Q000096:biosynthesis* / Q000235:genetics; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis* / Q000235:genetics / Q000494:pharmacology; D050807:ets-Domain Protein Elk-1
D004268:DNA-Binding Proteins; C497325:EGR1 protein, human; C494112:ELK1 protein, human; D051766:Early Growth Response Protein 1; D004791:Enzyme Inhibitors; D005419:Flavonoids; D017874:Immediate-Early Proteins; D008070:Lipopolysaccharides; D016328:NF-kappa B; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D050807:ets-Domain Protein Elk-1; D013925:Thromboplastin; C482128:MAP2K2 protein, human; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; C482125:MAP2K1 protein, human; D020929:Mitogen-Activated Protein Kinase Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one