title: A translocated effector required for Bartonella dissemination from derma to blood safeguards migratory host cells from damage by co-translocated effectors.
abstract: Numerous bacterial pathogens secrete multiple effectors to modulate host cellular functions. These effectors may interfere with each other to efficiently control the infection process. Bartonellae are Gram-negative, facultative intracellular bacteria using a VirB type IV secretion system to translocate a cocktail of Bartonella effector proteins (Beps) into host cells. Based on in vitro infection models we demonstrate here that BepE protects infected migratory cells from injurious effects triggered by BepC and is required for in vivo dissemination of bacteria from the dermal site of inoculation to blood. Human endothelial cells (HUVECs) infected with a ΔbepE mutant of B. henselae (Bhe) displayed a cell fragmentation phenotype resulting from Bep-dependent disturbance of rear edge detachment during migration. A ΔbepCE mutant did not show cell fragmentation, indicating that BepC is critical for triggering this deleterious phenotype. Complementation of ΔbepE with BepEBhe or its homologues from other Bartonella species abolished cell fragmentation. This cyto-protective activity is confined to the C-terminal Bartonella intracellular delivery (BID) domain of BepEBhe (BID2.EBhe). Ectopic expression of BID2.EBhe impeded the disruption of actin stress fibers by Rho Inhibitor 1, indicating that BepE restores normal cell migration via the RhoA signaling pathway, a major regulator of rear edge retraction. An intradermal (i.d.) model for B. tribocorum (Btr) infection in the rat reservoir host mimicking the natural route of infection by blood sucking arthropods allowed demonstrating a vital role for BepE in bacterial dissemination from derma to blood. While the Btr mutant ΔbepDE was abacteremic following i.d. inoculation, complementation with BepEBtr, BepEBhe or BIDs.EBhe restored bacteremia. Given that we observed a similar protective effect of BepEBhe on infected bone marrow-derived dendritic cells migrating through a monolayer of lymphatic endothelial cells we propose that infected dermal dendritic cells may be involved in disseminating Bartonella towards the blood stream in a BepE-dependent manner.
authors.affiliation: Focal Area Infection Biology, Biozentrum, University of Basel, Basel, Switzerland.
authors.forename: Rusudan
authors.initials: R
authors.lastname: Okujava
authors.affiliation: Focal Area Infection Biology, Biozentrum, University of Basel, Basel, Switzerland.
authors.forename: Patrick
authors.initials: P
authors.lastname: Guye
authors.affiliation: Focal Area Infection Biology, Biozentrum, University of Basel, Basel, Switzerland.
authors.forename: Yun-Yueh
authors.initials: YY
authors.lastname: Lu
authors.affiliation: Focal Area Infection Biology, Biozentrum, University of Basel, Basel, Switzerland.
authors.forename: Claudia
authors.initials: C
authors.lastname: Mistl
authors.affiliation: Focal Area Infection Biology, Biozentrum, University of Basel, Basel, Switzerland.
authors.forename: Florine
authors.initials: F
authors.lastname: Polus
authors.affiliation: Unité Sous Contrat Bartonella, Institut national de la recherche agronomique (INRA), Maisons-Alfort, France.
authors.forename: Muriel
authors.initials: M
authors.lastname: Vayssier-Taussat
authors.affiliation: Institute of Pharmaceutical Sciences, ETH, Zurich, Switzerland.
authors.forename: Cornelia
authors.initials: C
authors.lastname: Halin
authors.affiliation: Department of Biomedicine (DBM), University of Basel, Basel, Switzerland.
authors.forename: Antonius G
authors.initials: AG
authors.lastname: Rolink
authors.affiliation: Focal Area Infection Biology, Biozentrum, University of Basel, Basel, Switzerland.
authors.forename: Christoph
authors.initials: C
authors.lastname: Dehio
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D058947:Bacterial Secretion Systems; D001473:Bartonella / Q000276:immunology / Q000472:pathogenicity*; D001474:Bartonella Infections / Q000276:immunology / Q000473:pathology; D001854:Bone Marrow Cells / Q000166:cytology / Q000276:immunology; D002465:Cell Movement; D002478:Cells, Cultured; D019610:Cytoprotection; D003713:Dendritic Cells / Q000166:cytology / Q000276:immunology / Q000382:microbiology*; D005260:Female; D054884:Host-Pathogen Interactions; D061307:Human Umbilical Vein Endothelial Cells / Q000166:cytology / Q000382:microbiology*; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D058947:Bacterial Secretion Systems; D037521:Virulence Factors; D020742:rhoA GTP-Binding Protein