title: Legionella pneumophila catalase-peroxidases are required for proper trafficking and growth in primary macrophages.
abstract: Legionella pneumophila, a parasite of aquatic amoebae and pathogen of pulmonary macrophages, replicates intracellularly, utilizing a type IV secretion system to subvert the trafficking of Legionella-containing phagosomes. Defense against host-derived reactive oxygen species has been proposed as critical for intracellular replication. Virulence traits of null mutants in katA and katB, encoding the two Legionella catalase-peroxidases, were analyzed to evaluate the hypothesis that L. pneumophila must decompose hydrogen peroxide to establish a replication niche in macrophages. Phagosomes containing katA or katB mutant Legionella colocalize with LAMP-1, a late endosomal-lysosomal marker, at twice the frequency of those of wild-type strain JR32 and show a decreased frequency of bacterial replication, in similarity to phenotypes of mutants with mutations in dotA and dotB, encoding components of the Type IV secretion system. Quantitative similarity of the katA/B phenotypes indicates that each contributes to virulence traits largely independently of intracellular compartmentalization (KatA in the periplasm and KatB in the cytosol). These data support a model in which KatA and KatB maintain a critically low level of H(2)O(2) compatible with proper phagosome trafficking mediated by the type IV secretion apparatus. During these studies, we observed that dotA and dotB mutations in wild-type strain Lp02 had no effect on intracellular multiplication in the amoeba Acanthamoeba castellanii, indicating that certain dotA/B functions in Lp02 are dispensable in that experimental model. We also observed that wild-type JR32, unlike Lp02, shows minimal contact-dependent cytotoxicity, suggesting that cytotoxicity of JR32 is not a prerequisite for formation of replication-competent Legionella phagosomes in macrophages.
authors.affiliation: Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
authors.forename: Purnima
authors.initials: P
authors.lastname: Bandyopadhyay
authors.forename: Brenda
authors.initials: B
authors.lastname: Byrne
authors.forename: Yolande
authors.initials: Y
authors.lastname: Chan
authors.forename: Michele S
authors.initials: MS
authors.lastname: Swanson
authors.forename: Howard M
authors.initials: HM
authors.lastname: Steinman
mesh_terms: D000048:Acanthamoeba / Q000382:microbiology; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001854:Bone Marrow Cells / Q000378:metabolism / Q000382:microbiology; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D005798:Genes, Bacterial; D016952:Legionella pneumophila / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity*; D008264:Macrophages / Q000378:metabolism / Q000382:microbiology*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D009154:Mutation; D010544:Peroxidases / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D012964:Sodium / Q000494:pharmacology; D014774:Virulence / Q000235:genetics / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; C440002:DotA protein, Legionella pneumophila; D008565:Membrane Proteins; D012964:Sodium; D010544:Peroxidases; C081610:catalase-peroxidase, bacteria