The novel Legionella pneumophila type II secretion substrate NttC contributes to infection of amoebae Hartmannella vermiformis and Willaertia magna

Tyson, Jessica Y.; Vargas, Paloma; Cianciotto, Nicholas P.

doi:10.1099/mic.0.082750-0

Cited by 33 publications

(49 citation statements)

References 94 publications

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“…Previously, we also determined that the T2S-dependent CelA endoglucanase, ChiA chitinase, LapA and LapB aminopeptidases, LipA and LipB lipases, Map phosphatase, PlaA lysophospholipase A, PlaC glycerophospholipid:cholesterol acyltransferase, PlcA and PlcB phospholipases C, and SrnA RNase are not required for the dampening of the cytokine output, and the ProA metalloprotease, although able to directly degrade cytokines, does not affect the levels of cytokine gene transcripts (16). Our proteomic and in silico analyses indicate that the L. pneumophila T2S system exports between 25 and 60 proteins, including several putative lipolytic enzymes and a number of novel proteins (12,13,15). Thus, future studies will be directed toward, among other things, identifying which T2S-dependent effector(s) is responsible for impeding immune signaling and then determining its molecular mode of action.…”

Section: Discussionmentioning

confidence: 99%

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The Type II Secretion System of Legionella pneumophila Dampens the MyD88 and Toll-Like Receptor 2 Signaling Pathway in Infected Human Macrophages

2017

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Previously, we reported that mutants of Legionella pneumophila lacking a type II secretion (T2S) system elicit higher levels of cytokines (e.g., interleukin-6 [IL-6]) following infection of U937 cells, a human macrophage-like cell line. We now show that this effect of T2S is also manifest upon infection of human THP-1 macrophages and peripheral blood monocytes but does not occur during infection of murine macrophages. Supporting the hypothesis that T2S acts to dampen the triggering of an innate immune response, we observed that the mitogen-activated protein kinase (MAPK) and nuclear transcription factor kappa B (NF-B) pathways are more highly stimulated upon infection with the T2S mutant than upon infection with the wild type. By using short hairpin RNA to deplete proteins involved in specific pathogen-associated molecular pattern (PAMP) recognition pathways, we determined that the dampening effect of the T2S system was not dependent on nucleotide binding oligomerization domain (NOD)-like receptors (NLRs), retinoic acid-inducible protein I (RIG-I)-like receptors (RLRs), double-stranded RNA (dsRNA)-dependent protein kinase receptor (PKR), or TIR domain-containing adaptor inducing interferon beta (TRIF) signaling or an apoptosis-associated speck-like protein containing a CARD (ASC)-or caspase-4-dependent inflammasome. However, the dampening effect of T2S on IL-6 production was significantly reduced upon gene knockdown of myeloid differentiation primary response 88 (MyD88), TANK binding kinase 1 (TBK1), or Toll-like receptor 2 (TLR2). These data indicate that the L. pneumophila T2S system dampens the signaling of the TLR2 pathway in infected human macrophages. We also document the importance of PKR, TRIF, and TBK1 in cytokine secretion during L. pneumophila infection of macrophages.KEYWORDS Legionella pneumophila, TLR2, cytokine, innate immunity, macrophage, type II secretion L egionella pneumophila, a Gram-negative bacterium that is widespread in aquatic habitats, is the principal agent of Legionnaires' disease pneumonia (1-6). In the lungs, Legionella bacteria invade and grow in resident macrophages and then trigger severe inflammation (2). In macrophages, L. pneumophila evades the degradative lysosomal pathway and replicates to large numbers within a membrane-bound vacuole, the Legionella-containing vacuole (LCV) (7,8). Two protein secretion systems, Lsp type II secretion (T2S) and Dot/Icm type IV secretion (T4S), play major roles in the pathogenesis of L. pneumophila (9, 10). In T2S, protein substrates are first translocated across the inner membrane, and upon the action of the T2S pilus-like apparatus, they then exit the bacterial cell through a specific outer membrane pore (11). Using proteomics and enzymatic assays, we have shown that the T2S system of L. pneumo-

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Section: Discussionmentioning

confidence: 99%

“…In the aquatic environment, T2S promotes L. pneumophila survival at low temperatures and is critical for infection of at least four genera of amoebae (13)(14)(15). In mammalian hosts, T2S contributes to both intracellular infection of macrophages and the destruction of lung tissue.…”

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The Type II Secretion System of Legionella pneumophila Dampens the MyD88 and Toll-Like Receptor 2 Signaling Pathway in Infected Human Macrophages

2017

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“…In T2S, substrates are first transported across the bacterial inner membrane and then, upon the action of the T2S pilus-like apparatus, exit the cell through a dedicated pore in the outer membrane (24). Based on proteomic and enzymatic assays, we determined that the T2S system of L. pneumophila secretes more than 25 proteins, including 18 known enzymes and various novel proteins (25,26). Within water systems, T2S enhances the survival of L. pneumophila at low temperatures and is essential for infection of amoebae belonging to the genera Acanthamoeba, Naegleria, Vermamoeba (formerly Hartmannella), and Willaertia (26,27).…”

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“…Within water systems, T2S enhances the survival of L. pneumophila at low temperatures and is essential for infection of amoebae belonging to the genera Acanthamoeba, Naegleria, Vermamoeba (formerly Hartmannella), and Willaertia (26,27). Among the secreted proteins that promote intracellular infection of amoebae are the novel proteins NttA and NttC as well as the PlaC acyltransferase, ProA metalloprotease, and SrnA RNase (26,(28)(29)(30). L. pneumophila T2S also promotes biofilm formation and sliding motility (31, 32).…”

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Type II Secretion Is Necessary for Optimal Association of the Legionella-Containing Vacuole with Macrophage Rab1B but Enhances Intracellular Replication Mainly by Rab1B-Independent Mechanisms

White

Cianciotto

2016

Infect Immun

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Previously, we documented that type II secretion (T2S) promotes intracellular infection of macrophages by Legionella pneumophila. In the present study, we identified infection events that are modulated by T2S by comparing the behaviors of wild-type and T2S mutant bacteria in murine bone marrow-derived macrophages and human U937 cells. Although the two strains behaved similarly for entry into the host cells and evasion of lysosomal fusion, the mutant was impaired in the ability to initiate replication between 4 and 8 h postentry and to grow to large numbers in the Legionella-containing vacuole (LCV), as evident at 12 h. At 4 h postinoculation, mutant LCVs had a significantly reduced association with Rab1B, a host GTPase that facilitates the tethering of endoplasmic reticulum (ER)-derived vesicles to LCVs. The mutant did not lose expression or translocation of six type IV secretion effectors (e.g., SidM) that are well known for mediating Rab1B association with the LCV, indicating that T2S promotes the interaction between the LCV and Rab1B via a novel mechanism. Interestingly, the mutant's growth defect was exacerbated in macrophages that had been depleted of Rab1B by short hairpin RNA (shRNA) treatment, indicating that T2S also potentiates events beyond Rab1B association. In support of this, a sidM lspF double mutant had an intracellular growth defect that was more dramatic than that of the lspF mutant (and a sidM mutant) and showed a growth difference of as much as a 400-fold compared to the wild type. Together, these data reveal a new role for T2S in intracellular infection that involves both Rab1B-dependent and Rab1B-independent processes. L egionella pneumophila is widespread in natural and man-made water systems and is best known as the etiologic agent of Legionnaires' disease (1-3). Recently, the incidence of pneumonias caused by Gram-negative L. pneumophila has roughly tripled in the United States and elsewhere (4-6). In water, L. pneumophila grows primarily as an intracellular parasite of amoebae (7-11). Human infection occurs mainly by the inhalation of contaminated water droplets originating from a wide range of aerosolgenerating devices (12,13). Yet the first case of person-to-person spread was reported in 2016 (14). In the lungs, L. pneumophila invades and grows in the resident macrophage population and ultimately triggers severe inflammation (3). In both amoebae and macrophages, the bacterium evades the host's degradative lysosomal pathway and replicates to large numbers within a membrane-bound vacuole, the Legionella-containing vacuole (LCV) (15, 16). The Dot/Icm type IV secretion (T4S) system of L. pneumophila plays a major role in pathogenesis (17-19). Indeed, the Dot/Icm apparatus translocates myriad proteins across the LCV membrane and into the host cell cytoplasm, and then the delivered effectors proceed to modulate a wide variety of host processes. One of the earliest and most notable events that has been ascribed to the Dot/Icm system is the recruitment of host GTPases and endoplasmic reticulu...

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“…Also occasionally involves the cornea in relatively healty patients by causing Acanthamoeba Keratitis (AK). Another genus is Vermamoeba: Vermamoeba vermiformis is potential pathogen in humans 8 . Bacterial pathogens such as Legionella pneumophila, Pseudomonas spp., Staphylococcus spp, Proteus spp.…”

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Isolation and morphotyping of Acanthamoeba spp. and Vermamoeba spp. from hospital air-conditioning systems

Ozpinar¹,

Özçelık²,

Yünlü³

2017

Cumhuriyet Medical Journal

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SUMMARY Objective:The aim of the study was to investigate the presence of free-living amoebae (FLA) such as Acanthamoeba and Vermamoeba in air conditioning systems of Cumhuriyet University Research and Application Hospital (CURAH). Method: For this purpose, twenty-four dust samples were collected using sterile cotton swaps from grilles and filters of five different unit air-conditioners of CURAH located in Sivas, Turkey. Samples were transferred in a sterile tubes to the laboratory and spread onto non-nutrient agar (NNA) plates with a lawn of inactive Escherichia coli. Culture plates were incubated at 30 o C. FLA genera was identified according to morphotyping keys. Results: FLA were found in 14 (58.3%) of examined 24 air-conditioner. Ten (41.6%)were identified as Vermamoeba spp, 4 (16.7%) as Acanthamoeba spp., after microscobic examination. Conclusions: These findings should alert us on the risk of Acanthamoeba and Vermamoeba infections. In addition, these amoebas could be host for bacteria, fungi and viruses and indirectly become agents of transmission for these pathogens. For decrease the risk both Acanthamoeba and their endosymbionts, regularly cleaning of air-conditioner filters and grilles using effective disinfectants are essential.

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The novel Legionella pneumophila type II secretion substrate NttC contributes to infection of amoebae Hartmannella vermiformis and Willaertia magna

Cited by 33 publications

References 94 publications

The Type II Secretion System of Legionella pneumophila Dampens the MyD88 and Toll-Like Receptor 2 Signaling Pathway in Infected Human Macrophages

The Type II Secretion System of Legionella pneumophila Dampens the MyD88 and Toll-Like Receptor 2 Signaling Pathway in Infected Human Macrophages

Type II Secretion Is Necessary for Optimal Association of the Legionella-Containing Vacuole with Macrophage Rab1B but Enhances Intracellular Replication Mainly by Rab1B-Independent Mechanisms

Isolation and morphotyping of Acanthamoeba spp. and Vermamoeba spp. from hospital air-conditioning systems

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