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Pore-forming activity of the Pseudomonas aeruginosa type III secretion system translocon alters the host epigenome


Recent studies highlight that bacterial pathogens can reprogram target cells by influencing epigenetic factors. The type III secretion system (T3SS) is a bacterial nanomachine that resembles a syringe on the bacterial surface. The T3SS ‘needle’ delivers translocon proteins into eukaryotic cell membranes, subsequently allowing injection of bacterial effectors into the cytosol. Here we show that Pseudomonas aeruginosa induces early T3SS-dependent dephosphorylation and deacetylation of histone H3 in eukaryotic cells. This is not triggered by any of the P. aeruginosa T3SS effectors, but results from the insertion of the PopB–PopD translocon into the membrane. This suggests that the P. aeruginosa translocon is a genuine T3SS effector acting as a pore-forming toxin. We visualized the translocon plugged into the host cell membrane after the bacterium has left the site of contact, and demonstrate that subsequent ion exchange through this pore is responsible for histone H3 modifications and host cell subversion.

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The research leading to these results has received funding from the People Programme (Marie Skłodowska-Curie Actions) of the European Union’s Horizon 2020 under REA grant agreement no. 654909. This work was also supported by the French Cystic Fibrosis Foundation (Vaincre la Mucoviscidose RF20140501133), including a postdoctoral fellowship to C.L. We would like to thank L. Allsopp, T. Wood, K. Hui, S. Lory, M. Wolfgang and S. Jin for providing the P. aeruginosa mutants used in this study. We thank M. Ragno, E. Faudry and S. Bouillot (PB&RC Team, CNRS, Grenoble, France) for PopD purification and MAb selection and characterization (financed by the ANR project PRP1.4 T3SS), and I. Attrée for antibody project management and discussions.

Author information

L.D. and A.F. had full access to all of the data in the study, and take responsibility for the integrity of the data and the accuracy of the data analysis. Study concept and design: L.D. and A.F. Acquisition, analysis or interpretation of data: L.D., C.L., A.D. and A.F. Drafting of the manuscript: L.D. and A.F. Critical revision of the manuscript for important intellectual content: L.D., C.L., A.D. and A.F.

Competing interests

The authors declare no competing financial interests.

Correspondence to Alain Filloux.

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Fig. 1: P. aeruginosa induces a T3SS-dependent Ser10H3 dephosphorylation.
Fig. 2: The PopB–PopD translocon induces dephosphorylation and deacetylation of histone H3.
Fig. 3: The PopB–PopD translocon is a pore-forming toxin triggering K+ efflux-dependent Ser10H3 dephosphorylation and disruption of the mitochondria network.
Fig. 4: The PopB–PopD translocon remains stably anchored in the cytoplasmic membrane of the infected cell to trigger K+ efflux.
Fig. 5: PopB–PopD-dependent Ser10H3 dephosphorylation is triggered by the PP1 phosphatase.