Rac1 negatively regulates lipopolysaccharide-induced IL-23 p19 expression in human macrophages and dendritic cells and NF-kappaB p65 trans activation plays a novel role.
IL-23 is a heterodimeric cytokine composed of a unique p19 subunit and of a p40 subunit that is also common to IL-12. We defined the distinct signaling mechanisms that regulate the LPS-mediated induction of IL-23 p19 and p40 in human macrophages and dendritic cells. We found that the overexpression of dominant-negative Rac1 (N17Rac1) enhanced LPS-induced IL-23 p19 expression but did not alter p40 expression or IL-12 p70 production in PMA-treated THP-1 macrophages and in human monocyte-derived dendritic cells. Although the inhibition of either p38 MAPK or JNK enhanced LPS-induced p19 expression, N17Rac1 did not influence either p38 MAPK or JNK activation. By contrast, N17Rac1 augmented both NF-kappaB gene expression and p65 trans activation stimulated by LPS without affecting the degradation of IkappaB-alpha or DNA binding to NF-kappaB. Furthermore, small interference RNA of NF-kappaB p65 attenuated cellular amounts of p65 and suppressed LPS-induced p19 expression but did not affect p40 expression. Our findings indicate that Rac1 negatively controls LPS-induced IL-23 p19 expression through an NF-kappaB p65 trans activation-dependent, IkappaB-independent pathway and that NF-kappaB p65 regulates LPS-induced IL-23 p19, but not p40, expression, which causes differences in the control of IL-23 p19 and p40 expression by Rac1.
Utsugi
Mitsuyoshi
M
Department of Medicine and Molecular Science, Gunma University Graduate School of Medicine, 3-39-15 Showa-machi, Maebashi, Gunma 371-8511, Japan. mutsugi@med.gunma-u.ac.jp
Dobashi
Kunio
K
Ishizuka
Tamotsu
T
Kawata
Tadayoshi
T
Hisada
Takeshi
T
Shimizu
Yasuo
Y
Ono
Akihiro
A
Mori
Masatomo
M
D015152:Blotting, Northern; D015153:Blotting, Western; D003713:Dendritic Cells / Q000276:immunology / Q000378:metabolism*; D015870:Gene Expression; D006801:Humans; D018664:Interleukin-12 / Q000378:metabolism; D053759:Interleukin-23; D053760:Interleukin-23 Subunit p19; D007378:Interleukins / Q000096:biosynthesis*; D008070:Lipopolysaccharides / Q000276:immunology*; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D008264:Macrophages / Q000276:immunology / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D034741:RNA, Small Interfering; D015398:Signal Transduction / Q000276:immunology; D051996:Transcription Factor RelA / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*
C508840:IL23A protein, human; D053759:Interleukin-23; D053760:Interleukin-23 Subunit p19; D007378:Interleukins; D008070:Lipopolysaccharides; C107953:RAC1 protein, human; D012333:RNA, Messenger; D034741:RNA, Small Interfering; C107297:Rab9-binding protein, 40-kDa; D051996:Transcription Factor RelA; D018664:Interleukin-12; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020691:rab GTP-Binding Proteins; D020830:rac1 GTP-Binding Protein