title: A Legionella pneumophila-translocated substrate that is required for growth within macrophages and protection from host cell death.
abstract: Legionella pneumophila requires the Dot/Icm protein translocation system to replicate within host cells as a critical component of Legionnaire's pneumonia. None of the known individual substrates of the translocator have been shown to be essential for intracellular replication. We demonstrate here that mutants lacking the Dot/Icm substrate SdhA were severely impaired for intracellular growth within mouse bone marrow macrophages, with the defect absolute in triple mutants lacking sdhA and its two paralogs. The defect caused by the absence of the sdhA family was less severe during growth within Dictyostelium discoideum amoebae, indicating that the requirement for SdhA shows cell-type specificity. Macrophages harboring the L. pneumophila sdhA mutant showed increased nuclear degradation, mitochondrial disruption, membrane permeability, and caspase activation, indicating a role for SdhA in preventing host cell death. Defective intracellular growth of the sdhA(-) mutant could be partially suppressed by the action of caspase inhibitors, but caspase-independent cell death pathways eventually aborted replication of the mutant.
authors.affiliation: Howard Hughes Medical Institute and Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 150 Harrison Avenue, Boston, MA 02111, USA.
authors.forename: Rita K
authors.initials: RK
authors.lastname: Laguna
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Creasey
authors.forename: Zhiru
authors.initials: Z
authors.lastname: Li
authors.forename: Nicole
authors.initials: N
authors.lastname: Valtz
authors.forename: Ralph R
authors.initials: RR
authors.lastname: Isberg
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D001692:Biological Transport / Q000235:genetics; D002478:Cells, Cultured; D005420:Flavoproteins / Q000235:genetics / Q000502:physiology*; D016952:Legionella pneumophila / Q000201:enzymology / Q000235:genetics / Q000254:growth & development*; D008264:Macrophages / Q000201:enzymology* / Q000382:microbiology*; D051379:Mice; D008805:Mice, Inbred A; D009154:Mutation; D013379:Substrate Specificity / Q000235:genetics; D013385:Succinate Dehydrogenase / Q000235:genetics / Q000378:metabolism* / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D005420:Flavoproteins; C084271:SdhA protein, Bacteria; D013385:Succinate Dehydrogenase