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Legionella- and host-driven lipid flux at LCV-ER membrane contact sites promotes vacuole remodeling

ABSTRACT: Legionella pneumophila replicates in macrophages and amoeba within a unique compartment, the Legionella-containing vacuole (LCV). Hallmarks of LCV formation are the phosphoinositide lipid conversion from PtdIns(3)P to PtdIns(4)P, fusion with ER-derived vesicles and a tight association with the ER. Proteomics of purified LCVs indicate the presence of membrane contact sites (MCS) proteins possibly implicated in lipid exchange. Using dually fluorescence-labeled Dictyostelium discoideum amoeba, we reveal that VAMP-associated protein (Vap) and the PtdIns(4)P 4-phosphatase Sac1 localize to the ER and Vap also to the LCV membrane. Furthermore, Vap as well as Sac1 promote intracellular replication of L. pneumophila and LCV remodeling. Oxysterol binding proteins (OSBPs) preferentially localize to the ER (OSBP8) or the LCV membrane (OSBP11), respectively, and promote (OSBP8) or restrict (OSBP11) bacterial replication and LCV expansion. The sterol probes GFP-D4H* and filipin indicate that sterols are rapidly depleted from LCVs, while PtdIns(4)P accumulates. In addition to Sac1, the PtdIns(4)P-subverting L. pneumophila effector proteins LepB and SidC also support LCV remodeling. Taken together, the Legionella- and host cell-driven PtdIns(4)P gradient at LCV-ER MCSs promotes Vap-, OSBP- and Sac1-dependent pathogen vacuole maturation.

SUBMITTER: Ms. Simone Vormittag

PROVIDER: S-SCDT-10_15252-EMBR_202256007 | biostudies-other |

REPOSITORIES: biostudies-other

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The Legionella-driven PtdIns(4)P gradient at LCV-ER membrane contact sites promotes Vap-, OSBP and Sac1-dependent pathogen vacuole remodeling

Project description:The causative agent of Legionnaires’ disease, Legionella pneumophila, governs interactions with host cells by secreting ca. 330 different “effector” proteins. The facultative intracellular bacteria replicate in macrophages and amoeba within a unique compartment, the Legionella-containing vacuole (LCV). Hallmarks of LCV formation are the phosphoinositide (PI) lipid conversion from PtdIns(3)P to PtdIns(4)P, fusion with endoplasmic reticulum (ER)-derived vesicles and a tight association with the ER. Proteomics of purified LCVs revealed the presence of membrane contact sites (MCS) proteins implicated in lipid exchange. Using dually fluorescence-labeled Dictyostelium discoideum amoeba, we reveal that the VAMP-associated protein (Vap), the PtdIns(4)P 4-phosphatase Sac1, and the large fusion GTPase Sey1/atlastin-3 localize to the ER, but not to the LCV membrane, and these ER-resident proteins promote intracellular replication of L. pneumophila and LCV remodeling. Moreover, oxysterol binding proteins (OSBPs) exclusively localize to the ER (OsbH) or the LCV membrane (OsbK), respectively, and promote (OsbH) or restrict (OsbK) intracellular replication of L. pneumophila and LCV expansion. Furthermore, the PtdIns(4)P-subverting L. pneumophila effectors LepB and SidC also promote LCV remodeling. Taken together, the Legionella-driven PtdIns(4)P gradient at LCV-ER MCSs promotes Vap-, OSBP- and Sac1-dependent pathogen vacuole remodeling.

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