scholarly journals Exploitation of Phosphoinositides by the Intracellular Pathogen, Legionella pneumophila

2020 ◽  
Author(s):  
Colleen M. Pike ◽  
Rebecca R. Noll ◽  
M. Ramona Neunuebel
Keyword(s):  
Membrane Trafficking ◽  
Legionella Pneumophila ◽  
Pathogenic Bacteria ◽  
Severe Pneumonia ◽  
Bacterial Proteins ◽  
Specific Host ◽  
Spatiotemporal Regulation ◽  
Host Membrane ◽  
Membrane Compartments ◽  
Legionnaires Disease

Manipulation of host phosphoinositide lipids has emerged as a key survival strategy utilized by pathogenic bacteria to establish and maintain a replication-permissive compartment within eukaryotic host cells. The human pathogen, Legionella pneumophila, infects and proliferates within the lung’s innate immune cells causing severe pneumonia termed Legionnaires’ disease. This pathogen has evolved strategies to manipulate specific host components to construct its intracellular niche termed the Legionella-containing vacuole (LCV). Paramount to LCV biogenesis and maintenance is the spatiotemporal regulation of phosphoinositides, important eukaryotic lipids involved in cell signaling and membrane trafficking. Through a specialized secretion system, L. pneumophila translocates multiple proteins that target phosphoinositides in order to escape endolysosomal degradation. By specifically binding phosphoinositides, these proteins can anchor to the cytosolic surface of the LCV or onto specific host membrane compartments, to ultimately stimulate or inhibit encounters with host organelles. Here, we describe the bacterial proteins involved in binding and/or altering host phosphoinositide dynamics to support intracellular survival of L. pneumophila.

scholarly journals The Role of Lipids in Legionella-Host Interaction

2021 ◽  
Vol 22 (3) ◽  
pp. 1487
Author(s):  
Bozena Kowalczyk ◽  
Elzbieta Chmiel ◽  
Marta Palusinska-Szysz
Keyword(s):  
Cell Surface ◽  
Legionella Pneumophila ◽  
Cell Envelope ◽  
Severe Pneumonia ◽  
Outer Leaflet ◽  
Host Interaction ◽  
Host Membrane ◽  
Legionnaires Disease ◽  
And Function

Legionella are Gram-stain-negative rods associated with water environments: either natural or man-made systems. The inhalation of aerosols containing Legionella bacteria leads to the development of a severe pneumonia termed Legionnaires’ disease. To establish an infection, these bacteria adapt to growth in the hostile environment of the host through the unusual structures of macromolecules that build the cell surface. The outer membrane of the cell envelope is a lipid bilayer with an asymmetric composition mostly of phospholipids in the inner leaflet and lipopolysaccharides (LPS) in the outer leaflet. The major membrane-forming phospholipid of Legionella spp. is phosphatidylcholine (PC)—a typical eukaryotic glycerophospholipid. PC synthesis in Legionella cells occurs via two independent pathways: the N-methylation (Pmt) pathway and the Pcs pathway. The utilisation of exogenous choline by Legionella spp. leads to changes in the composition of lipids and proteins, which influences the physicochemical properties of the cell surface. This phenotypic plasticity of the Legionella cell envelope determines the mode of interaction with the macrophages, which results in a decrease in the production of proinflammatory cytokines and modulates the interaction with antimicrobial peptides and proteins. The surface-exposed O-chain of Legionella pneumophila sg1 LPS consisting of a homopolymer of 5-acetamidino-7-acetamido-8-O-acetyl-3,5,7,9-tetradeoxy-l-glycero-d-galacto-non-2-ulosonic acid is probably the first component in contact with the host cell that anchors the bacteria in the host membrane. Unusual in terms of the structure and function of individual LPS regions, it makes an important contribution to the antigenicity and pathogenicity of Legionella bacteria.

scholarly journals Components of the endocytic and recycling trafficking pathways interfere with the integrity of the Legionella-containing vacuole

2019 ◽  
Author(s):  
Ila S. Anand ◽  
Won Young Choi ◽  
Ralph R. Isberg
Keyword(s):  
Membrane Trafficking ◽  
Legionella Pneumophila ◽  
Host Cells ◽  
Rab Gtpases ◽  
Intracellular Growth ◽  
Mutant Proteins ◽  
Host Cytoplasm ◽  
Downstream Effectors ◽  
Cell Death Response ◽  
Host Membrane

SummaryLegionella pneumophila requires the Dot/Icm translocation system to replicate in a vacuolar compartment within host cells. Strains lacking the translocated substrate SdhA form a permeable vacuole during residence in the host cell, exposing bacteria to the host cytoplasm. In primary macrophages, mutants are defective for intracellular growth, with a pyroptotic cell death response mounted due to bacterial exposure to the cytosol. To understand how SdhA maintains vacuole integrity during intracellular growth, we performed high-throughput RNAi screens against host membrane trafficking genes to identify factors that antagonize vacuole integrity in the absence of SdhA. Depletion of host proteins involved in endocytic uptake and recycling resulted in enhanced intracellular growth and lower levels of permeable vacuoles surrounding the ΔsdhA mutant. Of interest were three different Rab GTPases involved in these processes: Rab11b, Rab8b and Rab5 isoforms, that when depleted resulted in enhanced vacuole integrity surrounding the sdhA mutant. Proteins regulated by these Rabs are responsible for interfering with proper vacuole membrane maintenance, as depletion of the downstream effectors EEA1, Rab11FIP1, or VAMP3 rescued vacuole integrity and intracellular growth of the sdhA mutant. To test the model that specific vesicular components associated with these effectors could act to destabilize the replication vacuole, EEA1 and Rab11FIP1 showed enhanced colocalization with the vacuole surrounding the sdhA mutant compared with the WT vacuole. Depletion of Rab5 isoforms or Rab11b reduced this aberrant colocalization. These findings are consistent with SdhA interfering with both endocytic and recycling membrane trafficking events that act to destabilize vacuole integrity during infection.

scholarly journals Involvement of Fractalkine/CX3CL1 Expression by Dendritic Cells in the Enhancement of Host Immunity against Legionella pneumophila

2005 ◽  
Vol 73 (9) ◽  
pp. 5350-5357 ◽  
Author(s):  
Toshiaki Kikuchi ◽  
Sita Andarini ◽  
Hong Xin ◽  
Kazunori Gomi ◽  
Yutaka Tokue ◽  
...  
Keyword(s):  
T Cells ◽  
Immune Responses ◽  
Host Defense ◽  
Legionella Pneumophila ◽  
Recombinant Adenovirus ◽  
Severe Pneumonia ◽  
Adenovirus Vector ◽  
Recombinant Adenovirus Vector ◽  
Legionnaires Disease

ABSTRACT Legionnaires' disease is clinically manifested as severe pneumonia caused by Legionella pneumophila. However, the dendritic cell (DC)-centered immunological framework of the host defense against L. pneumophila has not been fully delineated. For this study, we focused on a potent chemoattractant for lymphocytes, fractalkine/CX3CL1, and observed that the fractalkine expression of DCs was somewhat up-regulated when they encountered L. pneumophila. We therefore hypothesized that fractalkine expressed by Legionella-capturing DCs is involved in the induction of T-cell-mediated immune responses against Legionella, which would be enhanced by a genetic modulation of DCs to overexpress fractalkine. In vivo immunization-challenge experiments demonstrated that DCs modified with a recombinant adenovirus vector to overexpress fractalkine (AdFKN) and pulsed with heat-killed Legionella protected immunized mice from a lethal Legionella infection and that the generation of in vivo protective immunity depended on the host lymphocyte subsets, including CD4+ T cells, CD8+ T cells, and B cells. Consistent with this, immunization with AdFKN/Legionella/DC induced significantly higher levels of serum anti-Legionella antibodies of several isotypes than those induced by control immunizations. Further analysis of spleen cells from the immunized mice indicated that the AdFKN/Legionella/DC immunization elicited Th1-dominated immune responses to L. pneumophila. These observations suggest that fractalkine may play an important role in the DC-mediated host defense against intracellular pathogens such as L. pneumophila.

scholarly journals How bacterial effectors hijack small GTPases to divert membrane traffic

2014 ◽  
Vol 70 (a1) ◽  
pp. C802-C802
Author(s):  
Jacqueline Cherfils ◽  
Marcia Folly-Klan ◽  
Valérie Campanacci
Keyword(s):  
Legionella Pneumophila ◽  
Pathogenic Bacteria ◽  
Membrane Traffic ◽  
Severe Pneumonia ◽  
Small Gtpases ◽  
Covalent Attachment ◽  
Rab Gtpase ◽  
Postal Service ◽  
Nucleotide Exchange ◽  
Vesicular Traffic

Membrane traffic, which is the "cellular postal service" that shuttles biomolecules around the cell and organizes the structure of organelles, is among the primary targets of effectors injected by intracellular pathogenic bacteria to invade their host and avoid from being destroyed. I will present our recent structural and biochemical studies of effectors from Legionella pneumophila (the bacteria that causes the legionnaire's disease, a severe pneumonia) that divert membrane traffic to generate a membrane-bound vacuole where the pathogen hides and replicates. One of these effectors, AnkX, is a FIC domain-containing toxin that alters the functions of a Rab GTPase involved in vesicular traffic at the endoplasmic reticulum, by covalent attachment of a phosphocholine molecule. The other one, RalF, functions as an illegitimate guanine nucleotide exchange factor to activate an Arf GTPase on the vacuole. Our studies showed how AnkX binds and processes CDP-choline to transfer phosphocholine onto Rab1 [1], and uncover a novel membrane sensor in RalF that controls its localization and activity [2]

scholarly journals Legionella hijacks the host Golgi-to-ER retrograde pathway for the association of Legionella-Containing vacuole with the ER

2021 ◽  
Vol 17 (3) ◽  
pp. e1009437
Author(s):  
Mio Kawabata ◽  
Honoka Matsuo ◽  
Takumi Koito ◽  
Misaki Murata ◽  
Tomoko Kubori ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Legionella Pneumophila ◽  
Early Stage ◽  
Physiological Role ◽  
Snare Proteins ◽  
Negative Bacterium ◽  
Gram Negative ◽  
Bacterial Proteins ◽  
Host Membrane

Legionella pneumophila (L. pneumophila) is a gram-negative bacterium that replicates in a compartment that resembles the host endoplasmic reticulum (ER). To create its replicative niche, L. pneumophila manipulates host membrane traffic and fusion machineries. Bacterial proteins called Legionella effectors are translocated into the host cytosol and play a crucial role in these processes. In an early stage of infection, Legionella subverts ER-derived vesicles (ERDVs) by manipulating GTPase Rab1 to facilitate remodeling of the Legionella-containing vacuole (LCV). Subsequently, the LCV associates with the ER in a mechanism that remains elusive. In this study, we show that L. pneumophila recruits GTPases Rab33B and Rab6, which regulate vesicle trafficking from the Golgi to the ER, to the LCV to promote the association of LCV with the ER. We found that recruitment of Rab6 to the LCV depends on Rab33B. Legionella effector SidE family proteins, which phosphoribosyl-ubiquitinate Rab33B, were found to be necessary for the recruitment of Rab33B to the LCV. Immunoprecipitation experiments revealed that L. pneumophila facilitates the interaction of Rab6 with ER-resident SNAREs comprising syntaxin 18, p31, and BNIP1, but not tethering factors including NAG, RINT-1, and ZW10, which are normally required for syntaxin 18-mediated fusion of Golgi-derived vesicles with the ER. Our results identified a Rab33B-Rab6 cascade on the LCV and the interaction of Rab6 with ER-resident SNARE proteins for the association of LCV with the ER and disclosed the unidentified physiological role of SidE family proteins.

scholarly journals Human GBP1 promotes pathogen vacuole rupture and inflammasome activation during Legionella pneumophila infection

2020 ◽  
Author(s):  
Antonia R. Bass ◽  
Sunny Shin
Keyword(s):  
Legionella Pneumophila ◽  
Severe Pneumonia ◽  
Inflammasome Activation ◽  
Dependent Manner ◽  
Cytokine Release ◽  
Legionnaires Disease ◽  
Cell Cytosol ◽  
Ifn Γ ◽  
Host Cell Cytosol ◽  
Family Cytokine

AbstractThe inflammasome is an essential component of host defense against intracellular bacterial pathogens, such as Legionella pneumophila, the causative agent of the severe pneumonia Legionnaires’ disease. Inflammasome activation leads to recruitment and activation of caspases, which promote IL-1 family cytokine release and pyroptosis. In mice, interferon (IFN) signaling promotes inflammasome responses against L. pneumophila, in part through the functions of a family of IFN-inducible GTPases known as guanylate binding proteins (GBPs) (1). Within murine macrophages, IFN signaling promotes rupture of the L. pneumophila-containing vacuole (LCV), whereas GBPs are dispensable for vacuole rupture. Instead, GBPs facilitate the lysis of cytosol-exposed L. pneumophila. In contrast to mouse GBPs, the functions of human GBPs in inflammasome responses to L. pneumophila are poorly understood. Here, we show that IFN-γ promotes caspase-1, caspase-4, and caspase-5 inflammasome activation during L. pneumophila infection and upregulates GBP expression in primary human macrophages. We find that human GBP1 is important for maximal IFN-γ-driven inflammasome responses to L. pneumophila. Furthermore, IFN-γ signaling promotes the rupture of LCVs. Intriguingly, in contrast to murine GBPs, human GBP1 targets the LCV in a T4SS-dependent manner and promotes vacuolar lysis, resulting in increased bacterial access to the host cell cytosol. Our findings show a key role for human GBP1 in targeting and disrupting pathogen-containing vacuoles and reveal mechanistic differences in how mouse and human GBPs promote inflammasome responses to L. pneumophila.

scholarly journals Severe form of Legionnaires' disease in an immunocompetent patient

2009 ◽  
Vol 66 (12) ◽  
pp. 1010-1014
Author(s):  
Ilija Andrijevic ◽  
Jovan Matijasevic ◽  
Djordje Povazan ◽  
Marija Kojicic ◽  
Uros Batranovic
Keyword(s):  
Legionella Pneumophila ◽  
Acute Phase Proteins ◽  
Severe Pneumonia ◽  
Positive Outcome ◽  
Immunocompetent Patient ◽  
Multiple Organ ◽  
Severe Form ◽  
Inflammatory Lesions ◽  
Initial Symptoms ◽  
Legionnaires Disease

Background. Legionnaires' disease (LD) is a pneumonia caused by Legionella pneumophila (LP). The disease occurs more often in immunocompromised persons and can be manifested by severe pneumonia, multiple organ failure and has a high mortality. Case report. Immunocompetent patient, male, 53- year old, with severe form of LB had fever, cough, weakness and diarrhea as the initial symptoms of the disease. Laboratory results showed increased number of leukocytes, increased values of acute phase proteins, liver enzymes and hyponatremia. Computed tomography of the chest showed the marked inflammatory lesions on both sides. Pathohystological analysis of the samples retrieved by bronchoscopy pointed to a pneumonia, and diagnosis of LD was confirmed by positive urine test for LP antigen. Later, the disease was complicated by acute adult respiratory distress syndrome (ARDS). Treatment with antibiotics (erythromycin, rifampicin, azithromycin) combined with ARDS treatment led to a clinical recovery of the patient together with complete resolution of inflammatory lesions seen on chest radiography. Conclusion. In severe pneumonias it is necessary to consider LD in differential diagnosis, perform tests with aim of detecting LP and apply adequate antibiotic treatment in order to accomplish positive outcome of the therapy and prevent complications.

scholarly journals Dot/Icm Effector Translocation by Legionella longbeachae Creates a Replicative Vacuole Similar to That of Legionella pneumophila despite Translocation of Distinct Effector Repertoires

2015 ◽  
Vol 83 (10) ◽  
pp. 4081-4092 ◽  
Author(s):  
Rebecca E. Wood ◽  
Patrice Newton ◽  
Eleanor A. Latomanski ◽  
Hayley J. Newton
Keyword(s):  
Legionella Pneumophila ◽  
A549 Cells ◽  
Severe Pneumonia ◽  
Rab Gtpase ◽  
Human Pathogens ◽  
Immunofluorescence Analysis ◽  
Content Type ◽  
Extensive Analysis ◽  
Legionnaires Disease ◽  
Environmental Bacteria

Legionellaorganisms are environmental bacteria and accidental human pathogens that can cause severe pneumonia, termed Legionnaires' disease. These bacteria replicate within a pathogen-derived vacuole termed theLegionella-containing vacuole (LCV). Our understanding of the development and dynamics of this vacuole is based on extensive analysis ofLegionella pneumophila. Here, we have characterized theLegionella longbeachaereplicative vacuole (longbeachae-LCV) and demonstrated that, despite important genomic differences, key features of the replicative LCV are comparable to those of the LCV ofL. pneumophila(pneumophila-LCV). We constructed a Dot/Icm-deficient strain by deletingdotBand demonstrated the inability of this mutant to replicate inside THP-1 cells.L. longbeachaedoes not enter THP-1 cells as efficiently asL. pneumophila, and this is reflected in the observation that translocation of BlaM-RalFLLO(where RalFLLOis theL. longbeachaehomologue of RalF) into THP-1 cells by theL. longbeachaeDot/Icm system is less efficient than that byL. pneumophila. This difference is negated in A549 cells whereL. longbeachaeandL. pneumophilainfect with similar entry dynamics. A β-lactamase assay was employed to demonstrate the translocation of a novel family of proteins, theRab-likeeffector (Rle) proteins. Immunofluorescence analysis confirmed that these proteins enter the host cell during infection and display distinct subcellular localizations, with RleA and RleC present on thelongbeachae-LCV. We observed that the host Rab GTPase, Rab1, and the v-SNARE Sec22b are also recruited to thelongbeachae-LCV during the early stages of infection, coinciding with the LCV avoiding endocytic maturation. These studies further our understanding of theL. longbeachaereplicative vacuole, highlighting phenotypic similarities to the vacuole ofL. pneumophilaas well as unique aspects of LCV biology.

scholarly journals Legionella pneumophila LegC7 effector protein drives aberrant ER:endosome fusion in yeast

2020 ◽  
Author(s):  
Nathan K. Glueck ◽  
Kevin M. O’Brien ◽  
Vincent J. Starai
Keyword(s):  
Membrane Trafficking ◽  
Legionella Pneumophila ◽  
Molecular Mechanisms ◽  
Bacterial Pathogen ◽  
Severe Form ◽  
Effector Proteins ◽  
Effector Protein ◽  
Host Membrane ◽  
Membrane Tethering

AbstractLegionella pneumophila is a facultative intracellular bacterial pathogen, causing the severe form of pneumonia known as Legionnaires’ disease. Legionella actively alters host organelle trafficking through the activities of ‘effector’ proteins secreted via a TypeIVB secretion system, in order to construct the bacteria-laden Legionella-containing vacuole (LCV) and prevent lysosomal degradation. The LCV is derived from membrane derived from host ER, secretory vesicles, and phagosomes, although the precise molecular mechanisms that drive its synthesis remain poorly understood. In an effort to characterize the in vivo activity of the LegC7/YlfA SNARE-like effector protein from Legionella in the context of eukaryotic membrane trafficking in yeast, we find that LegC7 interacts with the Emp46p/Emp47p ER-to-Golgi glycoprotein cargo adapter complex, alters ER morphology, and induces aberrant ER:endosome fusion, as measured by visualization of ER cargo degradation, reconstitution of split-GFP proteins, and enhanced oxidation of the ER lumen. LegC7-dependent toxicity, disruption of ER morphology, and ER:endosome fusion events were dependent upon endosomal VPS class C tethering complexes and the endosomal t-SNARE, Pep12p. This work establishes a model in which LegC7 functions to recruit host ER material to the bacterial phagosome during infection by inducing membrane fusion, potentially through interaction with host membrane tethering complexes and/or cargo adapters.

scholarly journals Early Detection of Legionella pneumophila and Aspergillus by mNGS in a Critically Ill Patient With Legionella Pneumonia After Extracorporeal Membrane Oxygenation Treatment: Case Report and Literature Review

2021 ◽  
Vol 8 ◽  
Author(s):  
Ruiming Yue ◽  
Xiaoxiao Wu ◽  
Tianlong Li ◽  
Li Chang ◽  
Xiaobo Huang ◽  
...  
Keyword(s):  
Extracorporeal Membrane Oxygenation ◽  
Antibiotic Treatment ◽  
Legionella Pneumophila ◽  
Pathogenic Bacteria ◽  
Early Stage ◽  
Clinical Manifestations ◽  
Severe Pneumonia ◽  
Detection Methods ◽  
Critically Ill Patient ◽  
Membrane Oxygenation

Legionella pneumophila can cause pneumonia, leading to severe acute respiratory distress syndrome (ARDS). Because of its harsh growth requirements, limited detection methods, and non-specific clinical manifestations, diagnosing Legionella pneumonia remains still challenging. Metagenomic next-generation sequencing (mNGS) technology has increased the rate of detection of Legionella. This study describes a patient who rapidly progressed to severe ARDS during the early stage of infection and was treated with extracorporeal membrane oxygenation (ECMO). Although his bronchoalveolar lavage fluid (BALF) was negative for infection and his serum was negative for anti-Legionella antibody, mNGS of his BALF and blood showed only the presence of Legionella pneumophila (blood mNGS reads 229, BALF reads 656). After antibiotic treatment and weaning from ECMO, however, he developed a secondary Aspergillus and Klebsiella pneumoniae infection as shown by mNGS. Mechanical ventilation and antibiotic treatment were effective. A search of PubMed showed few reports of secondary Aspergillus infections after Legionella infection. Severe pneumonia caused by any type of pathogenic bacteria may be followed by Aspergillus infection, sometimes during extremely early stages of infection. Patients with severe pneumonia caused by Legionella infection should undergo early screening for secondary infections using methods such as mNGS, enabling early and precise treatment, thereby simplifying the use of antibiotics and improving patient prognosis.

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