title: Implication of proteins containing tetratricopeptide repeats in conditional virulence phenotypes of Legionella pneumophila.
abstract: Legionella pneumophila, the causative agent of Legionnaires' disease, is a ubiquitous freshwater bacterium whose virulence phenotypes require a type IV secretion system (T4SS). L. pneumophila strain JR32 contains two virulence-associated T4SSs, the Dot/Icm and Lvh T4SSs. Defective entry and phagosome acidification phenotypes of dot/icm mutants are conditional and reversed by incubating broth-grown stationary-phase cultures in water (WS treatment) prior to infection, as a mimic of the aquatic environment of Legionella. Reversal of dot/icm virulence defects requires the Lvh T4SS and is associated with a >10-fold induction of LpnE, a tetratricopeptide repeat (TPR)-containing protein. In the current study, we demonstrated that defective entry and phagosome acidification phenotypes of mutants with changes in LpnE and EnhC, another TPR-containing protein, were similarly reversed by WS treatment. In contrast to dot/icm mutants for which the Lvh T4SS was required, reversal for the ΔlpnE or the ΔenhC mutant required that the other TPR-containing protein be present. The single and double ΔlpnE and ΔenhC mutants showed a hypersensitivity to sodium ion, a phenotype associated with dysfunction of the Dot/Icm T4SS. The ΔlpnE single and the ΔlpnE ΔenhC double mutant showed 3- to 9-fold increases in translocation of Dot/Icm T4SS substrates, LegS2/SplY and LepB. Taken together, these data identify TPR-containing proteins in a second mechanism by which the WS mimic of a Legionella environmental niche can reverse virulence defects of broth-grown cultures and implicate LpnE and EnhC directly or indirectly in translocation of Dot/Icm T4SS protein substrates.
authors.affiliation: Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York, USA.
authors.forename: Purnima
authors.initials: P
authors.lastname: Bandyopadhyay
authors.forename: Eren U
authors.initials: EU
authors.lastname: Sumer
authors.forename: Deepak
authors.initials: D
authors.lastname: Jayakumar
authors.forename: Shuqing
authors.initials: S
authors.lastname: Liu
authors.forename: Huifang
authors.initials: H
authors.lastname: Xiao
authors.forename: Howard M
authors.initials: HM
authors.lastname: Steinman
mesh_terms: D048248:Acanthamoeba castellanii / Q000382:microbiology; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D016952:Legionella pneumophila / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity*; D017737:Macrophages, Peritoneal / Q000382:microbiology; D051379:Mice; D009154:Mutation; D010957:Plasmids; D017434:Protein Structure, Tertiary; D014617:Vacuoles; D014774:Virulence
chemical_list: D001426:Bacterial Proteins