TRIF signaling stimulates translation of TNF-alpha mRNA via prolonged activation of MK2.
The adapter protein TRIF mediates signal transduction through TLR3 and TLR4, inducing production of type I IFNs and inflammatory cytokines. The present study investigates the mechanisms by which TRIF signaling controls TNF-alpha biosynthesis. We provide evidence that, in LPS-stimulated murine dendritic cells, TRIF stimulates TNF-alpha biosynthesis selectively at the posttranscriptional level by promoting mRNA translation. In the absence of functional TRIF, the production of TNF-alpha protein was severely impaired, whereas TNF-alpha mRNA levels and stability, as well as transcriptional activity of the Tnfa gene, were not affected. Similarly, TRIF was required for production of LPS-induced TNF-alpha protein, but not of mRNA, in bone marrow-derived macrophages. In peritoneal macrophages, however, TRIF was also required for normal induction of TNF-alpha mRNA, suggesting cell type-related functions of TRIF. The influence of TRIF on dendritic cell TNF-alpha production was independent of type I IFNs. TRIF was required for prolonged activation of MAPKs in LPS-stimulated dendritic cells but was dispensable for the activation of NF-kappaB. Inhibition of late p38 activity attenuated LPS-stimulated elevation of TNF-alpha protein but not mRNA levels. The p38 effector kinase MK2 was directly activated through the TRIF pathway of TLR4. Importantly, stimulation of Mk2(-/-) cells through TLR3 or TLR4 severely impaired TNF-alpha protein production but did not affect TNF-alpha mRNA induction. Together, these results indicate that the TRIF signaling pathway promotes TNF-alpha mRNA translation through activation of the protein kinase MK2.
Gais
Petra
P
Department of Surgery, Technical University of Munich, Munich, Germany.
Tiedje
Christopher
C
Altmayr
Felicitas
F
Gaestel
Matthias
M
Weighardt
Heike
H
Holzmann
Bernhard
B
D033942:Adaptor Proteins, Vesicular Transport / Q000235:genetics / Q000502:physiology*; D000818:Animals; D001854:Bone Marrow Cells / Q000201:enzymology / Q000276:immunology / Q000378:metabolism; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000201:enzymology / Q000276:immunology / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000172:deficiency / Q000378:metabolism* / Q000502:physiology; D020935:MAP Kinase Signaling System / Q000235:genetics / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D014176:Protein Biosynthesis / Q000276:immunology*; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency / Q000378:metabolism* / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism / Q000502:physiology; D000099190:MAP-Kinase-Activated Kinase 2
D033942:Adaptor Proteins, Vesicular Transport; D047908:Intracellular Signaling Peptides and Proteins; D017346:Protein Serine-Threonine Kinases; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D048051:p38 Mitogen-Activated Protein Kinases; D000099190:MAP-Kinase-Activated Kinase 2; C476286:Ticam1 protein, mouse