title: Sphingosine kinase 1 (SK1) is recruited to nascent phagosomes in human macrophages: inhibition of SK1 translocation by Mycobacterium tuberculosis.
abstract: Mycobacterium tuberculosis (M.tb) is a leading cause of global infectious mortality. The pathogenesis of tuberculosis involves inhibition of phagosome maturation, leading to survival of M.tb within human macrophages. A key determinant is M.tb-induced inhibition of macrophage sphingosine kinase (SK) activity, which normally induces Ca2+ signaling and phagosome maturation. Our objective was to determine the spatial localization of SK during phagocytosis and its inhibition by M.tb. Stimulation of SK activity by killed M.tb, live Staphylococcus aureus, or latex beads was associated with translocation of cytosolic SK1 to the phagosome membrane. In contrast, SK1 did not associate with phagosomes containing live M.tb. To characterize the mechanism of phagosomal translocation, live cell confocal microscopy was used to compare the localization of wild-type SK1, catalytically inactive SK1G82D, and a phosphorylation-defective mutant that does not undergo plasma membrane translocation (SK1S225A). The magnitude and kinetics of translocation of SK1G82D and SK1S225A to latex bead phagosomes were indistinguishable from those of wild-type SK1, indicating that novel determinants regulate the association of SK1 with nascent phagosomes. These data are consistent with a model in which M.tb inhibits both the activation and phagosomal translocation of SK1 to block the localized Ca2+ transients required for phagosome maturation.
authors.affiliation: Inflammation Program, University of Iowa Carver College of Medicine, Coralville, IA 52241, USA.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Thompson
authors.forename: Shankar S
authors.initials: SS
authors.lastname: Iyer
authors.forename: Natalie
authors.initials: N
authors.lastname: Melrose
authors.forename: Rebecca
authors.initials: R
authors.lastname: VanOosten
authors.forename: Korey
authors.initials: K
authors.lastname: Johnson
authors.forename: Stuart M
authors.initials: SM
authors.lastname: Pitson
authors.forename: Lina M
authors.initials: LM
authors.lastname: Obeid
authors.forename: David J
authors.initials: DJ
authors.lastname: Kusner
mesh_terms: D001693:Biological Transport, Active; D020013:Calcium Signaling; D003600:Cytosol / Q000201:enzymology; D006801:Humans; D066298:In Vitro Techniques; D008264:Macrophages / Q000201:enzymology* / Q000276:immunology / Q000382:microbiology*; D008954:Models, Biological; D009169:Mycobacterium tuberculosis / Q000276:immunology / Q000472:pathogenicity*; D010587:Phagocytosis; D010588:Phagosomes / Q000201:enzymology* / Q000276:immunology; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D014397:Tuberculosis, Pulmonary / Q000209:etiology / Q000378:metabolism; D000099157:Sphingosine Kinase
chemical_list: D017853:Phosphotransferases (Alcohol Group Acceptor); D000099157:Sphingosine Kinase