title: Coxiella burnetiiEmploys the Dot/Icm Type IV Secretion System to Modulate Host NF-κB/RelA Activation.
abstract: Coxiella burnetiiis the causative agent of Q fever and an obligate intracellular pathogen in nature that survives and grows in a parasitophorous vacuole (PV) within eukaryotic host cells.C. burnetiipromotes intracellular survival by subverting apoptotic and pro-inflammatory signaling pathways that are typically regulated by nuclear transcription factor-κB (NF-κB). We and others have demonstrated thatC. burnetiiNMII proteins inhibit expression of pro-inflammatory cytokines and induce expression of anti-apoptotic genes during infection. Here, we demonstrate thatC. burnetiipromotes intracellular survival by modulating NF-κB subunit p65 (RelA) phosphorylation, and thus activation, in a Type Four B Secretion System (T4BSS)-dependent manner. Immunoblot analysis of RelA phosphorylated at serine-536 demonstrated thatC. burnetiiincreases NF-κB activation via the canonical pathway. However, RelA phosphorylation levels were even higher in infected cells where bacterial protein or mRNA synthesis was inhibited. Importantly, we demonstrate that inhibition of RelA phosphorylation impairs PV formation andC. burnetiigrowth. We found that a T4BSS-defective mutant (CbΔdotA) elicited phosphorylated RelA levels similar to those of wild typeC. burnetiiinfection treated with Chloramphenicol. Moreover, cells infected with CbΔdotA or wild typeC. burnetiitreated with Chloramphenicol showed similar levels of GFP-RelA nuclear localization, and significantly increased localization compared to wild typeC. burnetiiinfection. These data indicate that withoutde novoprotein synthesis and a functional T4BSS,C. burnetiiis unable to modulate NF-κB activation, which is crucial for optimal intracellular growth.
authors.affiliation: Department of Microbiology and Molecular genetics, Oklahoma State University Stillwater, OK, USA.
authors.forename: Saugata
authors.initials: S
authors.lastname: Mahapatra
authors.affiliation: Department of Microbiology and Molecular genetics, Oklahoma State University Stillwater, OK, USA.
authors.forename: Brandi
authors.initials: B
authors.lastname: Gallaher
authors.affiliation: Department of Microbiology and Molecular genetics, Oklahoma State University Stillwater, OK, USA.
authors.forename: Sydni Caet
authors.initials: SC
authors.lastname: Smith
authors.affiliation: Department of Microbiology and Immunology, University of Arkansas for Medical Sciences (UAMS) Little Rock, AR, USA.
authors.forename: Joseph G
authors.initials: JG
authors.lastname: Graham
authors.affiliation: Department of Microbiology and Immunology, University of Arkansas for Medical Sciences (UAMS) Little Rock, AR, USA.
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Voth
authors.affiliation: Department of Microbiology and Molecular genetics, Oklahoma State University Stillwater, OK, USA.
authors.forename: Edward I
authors.initials: EI
authors.lastname: Shaw
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D002460:Cell Line / Q000382:microbiology; D002701:Chloramphenicol / Q000494:pharmacology; D016997:Coxiella burnetii / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D004847:Epithelial Cells / Q000382:microbiology; D006367:HeLa Cells; D006790:Host-Parasite Interactions; D006801:Humans; D009154:Mutation; D016328:NF-kappa B / Q000378:metabolism*; D052003:NF-kappa B p52 Subunit / Q000378:metabolism; D010766:Phosphorylation; D011778:Q Fever / Q000276:immunology / Q000382:microbiology*; D012333:RNA, Messenger / Q000096:biosynthesis; D015398:Signal Transduction; D051996:Transcription Factor RelA / Q000378:metabolism*; D000069319:Type IV Secretion Systems / Q000235:genetics / Q000378:metabolism*; D014617:Vacuoles / Q000382:microbiology; D060449:Wnt Signaling Pathway
chemical_list: D001426:Bacterial Proteins; D016328:NF-kappa B; D052003:NF-kappa B p52 Subunit; C498143:RELA protein, human; D012333:RNA, Messenger; D051996:Transcription Factor RelA; D000069319:Type IV Secretion Systems; D002701:Chloramphenicol
keywords: Coxiella burnetii; NF-κB; Q fever; obligate intracellular; type four secretion system