title: Temporal resolution of two-tracked NF-kappaB activation by Legionella pneumophila.
abstract: The intracellular pathogen Legionella pneumophila activates the transcription factor NF-kappaB in macrophages and human epithelial cells, contributing to cytokine production and anti-apoptosis. The former is important for the innate immune response to infection, the latter for intracellular replication by securing host cell survival. Here, we demonstrate biphasic activation of NF-kappaB by L. pneumophila in human epithelial cells, using a p65-GFP expressing variant of A549 cells. Early in infection, a strong but transient nuclear translocation of p65 was observed. Only flagellin-deficient (DeltafliA and DeltaflaA) mutants could not induce this first, TLR5 and MyD88-dependent activation. The second p65 translocation event, however, is a long-term activation, independent of flagellin, TLR5 and MyD88, and marked by permanent nuclear localization of p65-GFP without oscillation for 30 h. Persistent p65 translocation also involved degradation of IkappaBalpha and upregulation of anti-apoptotic genes. L. pneumophila mutants lacking a functional Dot/Icm secretion system (DeltadotA; DeltaicmB/dotO), Dot/Icm effectors (DeltasdbA; DeltalubX) and two bacterial effector mutants (DeltaenhC; DeltaptsP) could not induce persistent p65 translocation. Strikingly, all these mutants were deficient in intracellular replication in A549 cells. Our data underline the strong connection between NF-kappaB activation and intracellular replication and hints at an active interference of NF-kappaB signalling by L. pneumophila.
authors: Max Planck Institute for Infection Biology, Department of Molecular Biology, Berlin, Germany.
authors: Sina
authors: S
authors: Bartfeld
authors: Cecilia
authors: C
authors: Engels
authors: Bianca
authors: B
authors: Bauer
authors: Philipp
authors: P
authors: Aurass
authors: Antje
authors: A
authors: Flieger
authors: Holger
authors: H
authors: Brüggemann
authors: Thomas F
authors: TF
authors: Meyer
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000276:immunology; D002460:Cell Line; D002467:Cell Nucleus / Q000737:chemistry; D004847:Epithelial Cells / Q000382:microbiology*; D005408:Flagellin / Q000235:genetics / Q000276:immunology; D017353:Gene Deletion; D006801:Humans; D020672:I-kappa B Proteins / Q000378:metabolism; D016952:Legionella pneumophila / Q000276:immunology*; D008562:Membrane Glycoproteins / Q000276:immunology; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000276:immunology* / Q000378:metabolism*; D017472:Receptors, Interleukin-1 / Q000276:immunology; D051198:Toll-Like Receptor 5 / Q000276:immunology; D051996:Transcription Factor RelA / Q000032:analysis; D037521:Virulence Factors / Q000235:genetics / Q000276:immunology
chemical_list: D001426:Bacterial Proteins; D020672:I-kappa B Proteins; D008562:Membrane Glycoproteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D017472:Receptors, Interleukin-1; C434984:TIRAP protein, human; C495346:TLR5 protein, human; D051198:Toll-Like Receptor 5; D051996:Transcription Factor RelA; D037521:Virulence Factors; D005408:Flagellin; D000072000:NF-KappaB Inhibitor alpha