RESUMEN
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.
Asunto(s)
Células Epiteliales/microbiología , Legionella pneumophila/inmunología , FN-kappa B/inmunología , FN-kappa B/metabolismo , Proteínas Bacterianas/genética , Proteínas Bacterianas/inmunología , Línea Celular , Núcleo Celular/química , Flagelina/genética , Flagelina/inmunología , Eliminación de Gen , Humanos , Proteínas I-kappa B/metabolismo , Glicoproteínas de Membrana/inmunología , Inhibidor NF-kappaB alfa , Receptores de Interleucina-1/inmunología , Receptor Toll-Like 5/inmunología , Factor de Transcripción ReIA/análisis , Factores de Virulencia/genética , Factores de Virulencia/inmunologíaRESUMEN
Poribacteria were found in nine sponge species belonging to six orders of Porifera from three oceans. Phylogenetic analysis revealed four distinct poribacterial clades, which contained organisms obtained from several different geographic regions, indicating that the distribution of poribacteria is cosmopolitan. Members of divergent poribacterial clades were also found in the same sponge species in three different sponge genera.