The inositol polyphosphate 5-phosphatase OCRL1 restricts intracellular growth of Legionella, localizes to the replicative vacuole and binds to the bacterial effector LpnE

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 Δ icmT 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.