Unknown,Transcriptomics,Genomics,Proteomics

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Suppression of the key immune pathways in primary human macrophages by cooperation of Yersinia effectors

ABSTRACT: In order to suppress the host immune system, numerous bacterial pathogens utilize a type 3 secretion system (T3SS) to inject effector proteins into target cells. We investigated Yersinia enterocolitica effectors (Yops) for their individual and combined effects on gene expression, inflammasome formation and Ca ++ signaling in primary human macrophages. The up- or down-regulation of thousands of macrophage genes by Yersinia inflammatory stimuli was effectively suppressed by YopP, and this correlated with suppression of histone-3 serine-10 phosphorylation. Surprisingly, YopM and YopQ counteracted selected YopP effects on gene expression. Inflammasome formation was reduced by a combination of YopP and YopQ, but not by any single effector or combinations of them. Finally, Ca ++ transients in infected macrophages were completely blocked by YopH alone. We conclude that the T3SS effectors of Yersinia antagonistically, synergistically or individually control major immune pathways of human macrophages to jointly suppress the host immune response.

INSTRUMENT(S): NextSeq 500

ORGANISM(S): Homo sapiens

SUBMITTER: Sören Rob

PROVIDER: E-MTAB-15035 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:The intracellular bacterial pathogen Legionella pneumophila causes an inflammatory pneumonia called Legionnaires’ Disease. For virulence, L. pneumophila requires a Dot/Icm type IV secretion system that translocates bacterial effectors to the host cytosol. L. pneumophila lacking the Dot/Icm system is recognized by Toll-like receptors (TLRs), leading to a canonical NF-κB-dependent transcriptional response. In addition, L. pneumophila expressing a functional Dot/Icm system potently induces unique transcriptional targets, including proinflammatory genes such as Il23a and Csf2. Here we demonstrate that this Dot/Icm-dependent response, which we term the effector-triggered response (ETR), requires five translocated bacterial effectors that inhibit host protein synthesis. Upon infection of macrophages with virulent L. pneumophila, these five effectors caused a global decrease in host translation, thereby preventing synthesis of IκB, an inhibitor of the NF-κB transcription factor. Thus, macrophages infected with wildtype L. pneumophila exhibited prolonged activation of NF-κB, which was associated with transcription of ETR target genes such as Il23a and Csf2. L. pneumophila mutants lacking the five effectors still activated TLRs and NF-κB, but because the mutants permitted normal IκB synthesis, NF-κB activation was more transient and was not sufficient to fully induce the ETR. L. pneumophila mutants expressing enzymatically inactive effectors were also unable to fully induce the ETR, whereas multiple compounds or bacterial toxins that inhibit host protein synthesis via distinct mechanisms recapitulated the ETR when administered with TLR ligands. Previous studies have demonstrated that the host response to bacterial infection is induced primarily by specific microbial molecules that activate TLRs or cytosolic pattern recognition receptors. Our results add to this model by providing a striking illustration of how the host immune response to a virulent pathogen can also be shaped by pathogen-encoded activities, such as inhibition of host protein synthesis. Three-condition experiment: macrophages left uninfected (negative control), or infected with wildtype Legionella pneumophila, or the mutant Δ5, which lacks five bacterial effectors involved in inhibition of host protein synthesis (lgt1, lgt2, lgt3, sidI, sidL) (two experimental conditions). Biological replicates: two, independently infected, harvested, and hybridized to arrays. One technical replicate per array.

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Suppression of the key immune pathways in primary human macrophages by cooperation of Yersinia effectors

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