title: The inositol polyphosphate 5-phosphatase OCRL1 restricts intracellular growth of Legionella, localizes to the replicative vacuole and binds to the bacterial effector LpnE.
abstract: Legionella pneumophila, the causative agent of Legionnaires' disease, replicates within a specific vacuole in amoebae and macrophages. To form these 'Legionella-containing vacuoles' (LCVs), the bacteria employ the Icm/Dot type IV secretion system and effector proteins, some of which anchor to the LCV membrane via the host glycolipid phosphatidylinositol 4-phosphate [PtdIns(4)P]. Here we analysed the role of inositol polyphosphate 5-phosphatases (IP5Ps) during L. pneumophila infections. Bacterial replication and LCV formation occurred more efficiently in Dictyostelium discoideum amoebae lacking the IP5P Dd5P4, a homologue of human OCRL1 (Oculocerebrorenal syndrome of Lowe), implicated in retrograde endosome to Golgi trafficking. The phenotype was complemented by Dd5P4 but not the catalytically inactive 5-phosphatase. Ectopically expressed Dd5P4 or OCRL1 localized to LCVs in D. discoideum via an N-terminal domain previously not implicated in membrane targeting, and OCRL1 was also identified on LCVs in macrophages. Dd5P4 was catalytically active on LCVs and accumulated on LCVs harbouring wild-type but not DeltaicmT mutant L. pneumophila. The N-terminal domain of OCRL1 bound L. pneumophila LpnE, a Sel1-like repeat protein involved in LCV formation, which localizes to LCVs and selectively binds PtdIns(3)P. Our results indicate that OCRL1 restricts intracellular growth of L. pneumophila and binds to LCVs in association with LpnE.
authors.affiliation: Institute of Microbiology, ETH Zürich, Zürich, Switzerland.
authors.forename: Stefan S
authors.initials: SS
authors.lastname: Weber
authors.forename: Curdin
authors.initials: C
authors.lastname: Ragaz
authors.forename: Hubert
authors.initials: H
authors.lastname: Hilbi
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism*; D002460:Cell Line; D004023:Dictyostelium / Q000201:enzymology* / Q000382:microbiology*; D017353:Gene Deletion; D005816:Genetic Complementation Test; D000072181:Inositol Polyphosphate 5-Phosphatases; D016952:Legionella pneumophila / Q000254:growth & development*; D008264:Macrophages / Q000201:enzymology / Q000382:microbiology; D051379:Mice; D010744:Phosphoric Monoester Hydrolases / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D014617:Vacuoles / Q000737:chemistry / Q000382:microbiology*; D037521:Virulence Factors / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D037521:Virulence Factors; D010744:Phosphoric Monoester Hydrolases; C489581:Ocrl protein, mouse; D000072181:Inositol Polyphosphate 5-Phosphatases