title: Immunostimulation by the synthetic lipopeptide P3CSK4: TLR4-independent activation of the ERK1/2 signal transduction pathway in macrophages.
abstract: Synthetic lipopeptides based on bacterial lipoprotein are efficient activators for monocytes/macrophages inducing the release of interleukin (IL)-1, IL-6, tumour necrosis factor-alpha (TNF-alpha), reactive oxygen/nitrogen intermediates, and the translocation of nuclear factor kappaB (NFkappaB). In this report we investigate the signal transduction pathways involved in leucocyte activation by the synthetic lipopeptide N-palmitoyl-S-[2,3-bis(palmitoyloxy)-(2R,S)-propyl]-(R)-cysteinyl-seryl-(lysyl)3-lysine (P3CSK4). We show that P3CSK4 activates mitogen-activated protein (MAP)-kinases ERK1/2 and MAP kinase (MAPK)-kinases MEK1/2 in bone-marrow-derived macrophages (BMDM) and in the macrophage cell line RAW 264.7. Additionally, we could detect differences between the P3CSK4 and lipopolysaccharide (LPS)-induced phosphorylation of MAP kinases: Different levels in phosphorylation were found both in kinetics and dose-response using RAW 264.7 cells or BMDM from BALB/c and LPS responder mice (C57BL/10ScSn) or LPS non-responder mice (C57BL/10ScCr). The lipopeptide activated the MAPK-signalling cascade in both LPS responder and non-responder macrophages, whereas LPS induced the MAPK signalling pathway only in macrophages derived from LPS responder mice. An approximately 70% decrease of lipopeptide induced NFkappaB translocation and an about 50% reduction of nitric oxide (NO) release was observed in the presence of anti-CD14. These data correspond to the reduction of phosphorylation of ERK1/2 after stimulation with P3CSK4 in the presence of anti-CD14 antibodies. Inhibition of MEK1/2 by PD98059 completely reduced the lipopeptide-induced phosphorylation of ERK1/2 indicating that MEK1/2 are solely responsible for the phosphorylation of the downstream-located MAP kinases ERK1/2.
authors.affiliation: Institut für Molekulare Medizin und Zellforschung der Universität, AK Tumorimmunologie/Vakzine, Freiburg, Germany.
authors.forename: M R
authors.initials: MR
authors.lastname: Müller
authors.forename: S D
authors.initials: SD
authors.lastname: Pfannes
authors.forename: M
authors.initials: M
authors.lastname: Ayoub
authors.forename: P
authors.initials: P
authors.lastname: Hoffmann
authors.forename: W G
authors.initials: WG
authors.lastname: Bessler
authors.forename: K
authors.initials: K
authors.lastname: Mittenbühler
mesh_terms: D000818:Animals; D001853:Bone Marrow / Q000276:immunology; D002460:Cell Line; D029721:Drosophila Proteins; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D018950:Lipopolysaccharide Receptors / Q000276:immunology; D008070:Lipopolysaccharides / Q000276:immunology; D008074:Lipoproteins / Q000276:immunology*; D008262:Macrophage Activation / Q000276:immunology*; D008562:Membrane Glycoproteins / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D019950:Mitogen-Activated Protein Kinase 1 / Q000276:immunology*; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000276:immunology* / Q000378:metabolism; D016328:NF-kappa B / Q000235:genetics; D009569:Nitric Oxide / Q000378:metabolism; D010766:Phosphorylation; D011956:Receptors, Cell Surface / Q000276:immunology; D015398:Signal Transduction / Q000276:immunology*; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D014178:Translocation, Genetic
chemical_list: D029721:Drosophila Proteins; D004791:Enzyme Inhibitors; D005419:Flavonoids; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D008074:Lipoproteins; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D011956:Receptors, Cell Surface; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; C061108:N-palmitoyl-S-(2,3-bis(palmitoyloxy)propyl)cysteinyl-seryl-lysyl-lysyl-lysyl-lysine; D009569:Nitric Oxide; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one