scholarly journals Members of a Legionella pneumophila Family of Proteins with ExoU (Phospholipase A) Active Sites Are Translocated to Target Cells

2006 ◽  
Vol 74 (6) ◽  
pp. 3597-3606 ◽  
Author(s):  
Susan M. VanRheenen ◽  
Zhao-Qing Luo ◽  
Tamara O'Connor ◽  
Ralph R. Isberg
Keyword(s):  
Legionella Pneumophila ◽  
Secretory Pathway ◽  
Secretion System ◽  
Type Iv Secretion ◽  
Phospholipase A ◽  
Target Cells ◽  
Type Iv Secretion System ◽  
Type Iv ◽  
System A ◽  
Translocated Proteins

ABSTRACT Legionella pneumophila replicates within alveolar macrophages, causing a severe pneumonia termed Legionnaires' disease. The bacterium resides within a vacuole that escapes immediate transport to the host lysosome. Instead, the vacuole interacts with the early secretory pathway to establish an environment suitable for rapid multiplication. A type IV secretion system is central to the pathogenicity of the bacterium, and many protein substrates that are translocated by this system to the host cell have been identified. One of these, VipD, was found to interrupt the late secretory pathway when overproduced in Saccharomyces cerevisiae. We independently identified VipD in a previous study and have further characterized this protein as well as its three paralogs. The vipD gene belongs to a family of L. pneumophila open reading frames that are predicted to contain a phospholipase A domain with sequence similarity to the type III-secreted toxin ExoU from Pseudomonas aeruginosa. Similarly to other known translocated proteins of L. pneumophila, VipD is strongly induced in early stationary phase, a time when the bacterium is most virulent. Detergent extraction studies of infected macrophages confirm that VipD is translocated into host cells via the type IV secretion system. A second assay for translocation revealed that two paralogs of VipD, VpdA and VpdB, also have translocation signals recognized by the type IV system. A strain lacking VipD and its three paralogs grew at wild-type rates in murine macrophages, although secondary mutations that cause growth defects in strains lacking VipD accumulate. The quadruple mutant displayed a growth advantage in the amoebal host Dictyostelium discoideum, indicating that the protein family may modulate intracellular growth in a complex fashion. VipD is mildly toxic when overproduced in eukaryotic cells, and the toxicity is partially dependent on the putative phospholipase active site. VipD and its paralogs therefore define a family of translocated proteins that may assist in the establishment of a vacuole suitable for bacterial replication through functioning as a phospholipase.

scholarly journals LidA, a Translocated Substrate of the Legionella pneumophila Type IV Secretion System, Interferes with the Early Secretory Pathway

2005 ◽  
Vol 73 (7) ◽  
pp. 4370-4380 ◽  
Author(s):  
Isabelle Derré ◽  
Ralph R. Isberg
Keyword(s):  
Host Cell ◽  
Legionella Pneumophila ◽  
Mammalian Cells ◽  
Secretory Pathway ◽  
Close Contact ◽  
Secretion System ◽  
Type Iv Secretion ◽  
Type Iv Secretion System ◽  
Early Secretory Pathway ◽  
Type Iv

ABSTRACT Legionella pneumophila uses a type IV secretion system to deliver effector molecules into the host cell and establish its replication vacuole. In this study, we investigated the role of LidA, a translocated substrate associated with the surface of the L. pneumophila-containing vacuole. LidA is secreted into the host cell throughout the replication cycle of the bacteria and associates with compartments of the early secretory pathway. When overexpressed in mammalian cells or yeast, LidA interferes with the early secretory pathway, probably via a domain predicted to be rich in coiled-coil structure. Finally, during intracellular replication, the replication vacuoles are in close contact with the endoplasmic reticulum-Golgi intermediate compartment and the Golgi apparatus, suggesting a positive correlation between intracellular growth and association of the vacuole with compartments of the early secretory pathway. We propose that LidA is involved in the recruitment of early secretory vesicles to the L. pneumophila-containing vacuole and that the vacuole associates with the secretory pathway to facilitate this process.

scholarly journals IcmF and DotU Are Required for Optimal Effector Translocation and Trafficking of the Legionella pneumophila Vacuole

2004 ◽  
Vol 72 (10) ◽  
pp. 5972-5982 ◽  
Author(s):  
Susan M. VanRheenen ◽  
Guillaume Duménil ◽  
Ralph R. Isberg
Keyword(s):  
Legionella Pneumophila ◽  
Severe Form ◽  
Secretion System ◽  
Type Iv Secretion ◽  
Type Iv Secretion System ◽  
Intracellular Growth ◽  
Macrophage Infection ◽  
Type Iv ◽  
Bacterial Mutants ◽  
Bacterial Replication

ABSTRACT The gram-negative bacterium Legionella pneumophila causes a severe form of pneumonia called Legionnaires' disease, characterized by bacterial replication within alveolar macrophages. Prior to intracellular replication, the vacuole harboring the bacterium must first escape trafficking to the host lysosome, a process that is dependent on the Dot/Icm type IV secretion system. To identify genes required for intracellular growth, bacterial mutants were isolated that were delayed in escape from the macrophage but which retain a minimally functional Dot/Icm machinery. The mutations were found in eight distinct genes, including three genes known to be required for optimal intracellular growth. Two of these genes, icmF and dotU, are located at one end of a cluster of genes that encode the type IV secretion system, yet both icmF and dotU lack orthologs in other type IV translocons. DotU protein is degraded in the early postexponential phase in wild-type L. pneumophila and at all growth phases in an icmF mutant. IcmF contains an extracytoplasmic domain(s) based on accessibility to a membrane-impermeant amine-reactive reagent. In the absence of either gene, L. pneumophila targets inappropriately to LAMP-1-positive compartments during macrophage infection, is defective in the formation of replicative vacuoles, and is impaired in the translocation of the effector protein SidC. Therefore, although IcmF and DotU do not appear to be part of the core type IV secretion system, these proteins are necessary for an efficiently functioning secretion apparatus.

scholarly journals The crystal structure of LidA, a translocated substrate of the Legionella pneumophila type IV secretion system

2013 ◽  
Vol 4 (12) ◽  
pp. 897-900 ◽  
Author(s):  
Geng Meng ◽  
Xiaojing An ◽  
Sheng Ye ◽  
Yong Liu ◽  
Wenzhuang Zhu ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Legionella Pneumophila ◽  
Secretion System ◽  
Type Iv Secretion ◽  
Type Iv Secretion System ◽  
Type Iv

scholarly journals Polar targeting and assembly of theLegionellaDot/Icm type IV secretion system (T4SS) by T6SS-related components

2018 ◽  
Author(s):  
KwangCheol C. Jeong ◽  
Jacob Gyore ◽  
Lin Teng ◽  
Debnath Ghosal ◽  
Grant J. Jensen ◽  
...  
Keyword(s):  
Legionella Pneumophila ◽  
Secretion System ◽  
Type Iv Secretion ◽  
Host Cells ◽  
Type Iv Secretion System ◽  
Membrane Complex ◽  
Type Iv ◽  
Legionnaires Disease ◽  
Type Ivb Secretion ◽  
Type Ivb Secretion System

SummaryLegionella pneumophila, the causative agent of Legionnaires’ disease, survives and replicates inside amoebae and macrophages by injecting a large number of protein effectors into the host cells’ cytoplasm via the Dot/Icm type IVB secretion system (T4BSS). Previously, we showed that the Dot/Icm T4BSS is localized to both poles of the bacterium and that polar secretion is necessary for the proper targeting of theLegionellacontaining vacuole (LCV). Here we show that polar targeting of the Dot/Icm core-transmembrane subcomplex (DotC, DotD, DotF, DotG and DotH) is mediated by two Dot/Icm proteins, DotU and IcmF, which are able to localize to the poles ofL. pneumophilaby themselves. Interestingly, DotU and IcmF are homologs of the T6SS components TssL and TssM, which are part of the T6SS membrane complex (MC). We propose thatLegionellaco-opted these T6SS components to a novel function that mediates subcellular localization and assembly of this T4SS. Finally, in depth examination of the biogenesis pathway revealed that polar targeting and assembly of theLegionellaT4BSS apparatus is mediated by an innovative “outside-inside” mechanism.

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