title: IglC and PdpA are important for promoting Francisella invasion and intracellular growth in epithelial cells.
abstract: The highly infectious bacteria, Francisella tularensis, colonize a variety of organs and replicate within both phagocytic as well as non-phagocytic cells, to cause the disease tularemia. These microbes contain a conserved cluster of important virulence genes referred to as the Francisella Pathogenicity Island (FPI). Two of the most characterized FPI genes, iglC and pdpA, play a central role in bacterial survival and proliferation within phagocytes, but do not influence bacterial internalization. Yet, their involvement in non-phagocytic epithelial cell infections remains unexplored. To examine the functions of IglC and PdpA on bacterial invasion and replication during epithelial cell infections, we infected liver and lung epithelial cells with F. novicida and F. tularensis 'Type B' Live Vaccine Strain (LVS) deletion mutants (ΔiglC and ΔpdpA) as well as their respective gene complements. We found that deletion of either gene significantly reduced their ability to invade and replicate in epithelial cells. Gene complementation of iglC and pdpA partially rescued bacterial invasion and intracellular growth. Additionally, substantial LAMP1-association with both deletion mutants was observed up to 12 h suggesting that the absence of IglC and PdpA caused deficiencies in their ability to dissociate from LAMP1-positive Francisella Containing Vacuoles (FCVs). This work provides the first evidence that IglC and PdpA are important pathogenic factors for invasion and intracellular growth of Francisella in epithelial cells, and further highlights the discrete mechanisms involved in Francisella infections between phagocytic and non-phagocytic cells.
authors.affiliation: Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada.
authors.forename: H T
authors.initials: HT
authors.lastname: Law
authors.affiliation: Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada.
authors.forename: Aarati
authors.initials: A
authors.lastname: Sriram
authors.affiliation: Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Fevang
authors.affiliation: Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada.
authors.forename: Eli B
authors.initials: EB
authors.lastname: Nix
authors.affiliation: Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada.
authors.forename: Francis E
authors.initials: FE
authors.lastname: Nano
authors.affiliation: Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada.
authors.forename: Julian Andrew
authors.initials: JA
authors.lastname: Guttman
mesh_terms: D000818:Animals; D002460:Cell Line; D004847:Epithelial Cells / Q000382:microbiology; D005603:Francisella / Q000235:genetics* / Q000254:growth & development / Q000472:pathogenicity*; D005604:Francisella tularensis / Q000235:genetics* / Q000254:growth & development / Q000472:pathogenicity*; D005798:Genes, Bacterial; D044404:Genomic Islands; D022781:Hepatocytes / Q000382:microbiology; D054884:Host-Pathogen Interactions; D006801:Humans; D008168:Lung / Q000166:cytology / Q000382:microbiology; D051907:Lysosomal Membrane Proteins / Q000378:metabolism; D051379:Mice; D014617:Vacuoles / Q000378:metabolism / Q000382:microbiology; D014774:Virulence / Q000235:genetics*; D052118:Lysosomal-Associated Membrane Protein 1
chemical_list: D051907:Lysosomal Membrane Proteins; C052255:Lamp1 protein, mouse; D052118:Lysosomal-Associated Membrane Protein 1