title: Neutropenia with impaired immune response to Streptococcus pneumoniae in ceramide kinase-deficient mice.
abstract: In mammals, ceramide kinase (CerK)-mediated phosphorylation of ceramide is the only known pathway to ceramide-1-phosphate (C1P), a recently identified signaling sphingolipid metabolite. To help delineate the roles of CerK and C1P, we knocked out the gene of CerK in BALB/c mice by homologous recombination. All in vitro as well as cell-based assays indicated that CerK activity is completely abolished in Cerk-/- mice. Labeling with radioactive orthophosphate showed a profound reduction in the levels of de novo C1P formed in Cerk-/- macrophages. Consistently, mass spectrometry analysis revealed a major contribution of CerK to the formation of C16-C1P. However, the significant residual C1P levels in Cerk-/- animals indicate that alternative routes to C1P exist. Furthermore, serum levels of proapoptotic ceramide in these animals were significantly increased while levels of dihydroceramide as the biosynthetic precursor were reduced. Previous literature pointed to a role of CerK or C1P in innate immune cell function. Using a variety of mechanistic and disease models, as well as primary cells, we found that macrophage- and mast cell-dependent readouts are barely affected in the absence of CerK. However, the number of neutrophils was strikingly reduced in blood and spleen of Cerk-/- animals. When tested in a model of fulminant pneumonia, Cerk-/- animals developed a more severe disease, lending support to a defect in neutrophil homeostasis following CerK ablation. These results identify ceramide kinase as a key regulator of C1P, dihydroceramide and ceramide levels, with important implications for neutrophil homeostasis and innate immunity regulation.
authors.affiliation: Novartis Institutes for BioMedical Research, Vienna, Austria.
authors.forename: Christine
authors.initials: C
authors.lastname: Graf
authors.forename: Barbara
authors.initials: B
authors.lastname: Zemann
authors.forename: Philipp
authors.initials: P
authors.lastname: Rovina
authors.forename: Nicole
authors.initials: N
authors.lastname: Urtz
authors.forename: Andrea
authors.initials: A
authors.lastname: Schanzer
authors.forename: Roland
authors.initials: R
authors.lastname: Reuschel
authors.forename: Diana
authors.initials: D
authors.lastname: Mechtcheriakova
authors.forename: Matthias
authors.initials: M
authors.lastname: Müller
authors.forename: Evelin
authors.initials: E
authors.lastname: Fischer
authors.forename: Claudia
authors.initials: C
authors.lastname: Reichel
authors.forename: Susanna
authors.initials: S
authors.lastname: Huber
authors.forename: Janet
authors.initials: J
authors.lastname: Dawson
authors.forename: Josef G
authors.initials: JG
authors.lastname: Meingassner
authors.forename: Andreas
authors.initials: A
authors.lastname: Billich
authors.forename: Satoru
authors.initials: S
authors.lastname: Niwa
authors.forename: Rudolf
authors.initials: R
authors.lastname: Badegruber
authors.forename: Paul P
authors.initials: PP
authors.lastname: Van Veldhoven
authors.forename: Bernd
authors.initials: B
authors.lastname: Kinzel
authors.forename: Thomas
authors.initials: T
authors.lastname: Baumruker
authors.forename: Frédéric
authors.initials: F
authors.lastname: Bornancin
mesh_terms: D000818:Animals; D001169:Arthritis, Experimental / Q000201:enzymology / Q000276:immunology / Q000382:microbiology; D002478:Cells, Cultured; D002518:Ceramides / Q000378:metabolism; D005260:Female; D006967:Hypersensitivity / Q000201:enzymology / Q000235:genetics / Q000276:immunology; D007113:Immunity, Innate / Q000235:genetics; D017737:Macrophages, Peritoneal / Q000166:cytology / Q000201:enzymology / Q000276:immunology; D008297:Male; D008407:Mast Cells / Q000201:enzymology / Q000276:immunology / Q000382:microbiology; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D009503:Neutropenia / Q000201:enzymology* / Q000235:genetics / Q000276:immunology* / Q000382:microbiology; D010323:Passive Cutaneous Anaphylaxis / Q000276:immunology; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D011018:Pneumonia, Pneumococcal / Q000201:enzymology* / Q000235:genetics / Q000276:immunology*; D013296:Streptococcus pneumoniae / Q000276:immunology*
chemical_list: D002518:Ceramides; C065576:ceramide 1-phosphate; C109343:dihydroceramide; D017853:Phosphotransferases (Alcohol Group Acceptor); C066324:ceramide kinase