Phosphatidylinositol 3-kinase is involved in Toll-like receptor 4-mediated cytokine expression in mouse macrophages.
Recent evidence suggests a role for phosphatidylinositol (PI) 3-kinase in various inflammatory responses. In this study, the consequences of LPS-induced PI 3-kinase activation on cytokine and chemokine expression and the intracellular mechanisms of inflammatory activation were examined in mouse macrophages. LPS stimulation induced a complex formation between PI 3-kinase and myeloid differentiation factor 88 (MyD88), which was followed by an induction of IL-1beta, tumor necrosis factor-alpha (TNF-alpha) and macrophage inflammatory protein (MIP)-2. The induction of IL-1beta, but not of MIP-2 or TNF-alpha, was blocked by the PI 3-kinase inhibitors LY294002 and wortmannin. The nuclear factor-kappaB (NF-kappaB) inhibitor pyrrolidinedithiocarbamate (PDTC) blocked the induction of IL-1beta and TNF-alpha, but had no effect on MIP-2 expression. Inhibition of PI 3-kinase decreased the LPS-induced transcriptional activity of NF-kappaB, but it had no effect on the nuclear DNA binding activity of NF-kappaB. These findings suggest that, while NF-kappaB nuclear localization and DNA binding are necessary, they are not sufficient for transcriptional activation of the IL-1beta gene in the absence of PI 3-kinase activity. Taken together, our results demonstrate that activation of Toll-like receptor (TLR)-4 results in PI 3-kinase-MyD88 complex formation, and that PI 3-kinase activity selectively leads to cytokine induction downstream of TLR4.
Ojaniemi
Marja
M
Biocenter Oulu and Department of Pediatrics, University of Oulu, PO Box 5000, FIN-90014 Oulu, Finland. Marja.Ojaniemi@Oulu.FI
Glumoff
Virpi
V
Harju
Kirsi
K
Liljeroos
Mari
M
Vuori
Kristiina
K
Hallman
Mikko
M
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D000943:Antigens, Differentiation / Q000502:physiology; D002478:Cells, Cultured; D016207:Cytokines / Q000096:biosynthesis* / Q000235:genetics; D029721:Drosophila Proteins; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000276:immunology*; D008562:Membrane Glycoproteins / Q000502:physiology*; D051379:Mice; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B / Q000502:physiology; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt; D012333:RNA, Messenger / Q000032:analysis; D011956:Receptors, Cell Surface / Q000502:physiology*; D011971:Receptors, Immunologic / Q000502:physiology; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors
D048868:Adaptor Proteins, Signal Transducing; D000943:Antigens, Differentiation; D016207:Cytokines; D029721:Drosophila Proteins; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; C507780:Myd88 protein, mouse