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

2017 ◽  
Vol 85 (4) ◽  
Author(s):  
Celeste A. Mallama ◽  
Kessler McCoy-Simandle ◽  
Nicholas P. Cianciotto
Keyword(s):  
Protein Kinase ◽  
Legionella Pneumophila ◽  
Mitogen Activated Protein Kinase ◽  
Human Macrophage ◽  
Type Ii Secretion ◽  
Type Ii ◽  
Toll Like Receptor ◽  
Content Type ◽  
Human Macrophages ◽  
Toll Like Receptor 2

ABSTRACT 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-κB) 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.

scholarly journals 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

2016 ◽  
Vol 84 (12) ◽  
pp. 3313-3327 ◽  
Author(s):  
Richard C. White ◽  
Nicholas P. Cianciotto
Keyword(s):  
Legionella Pneumophila ◽  
Host Cells ◽  
Growth Defect ◽  
Type Ii Secretion ◽  
Type Ii ◽  
Wild Type ◽  
Content Type ◽  
Murine Bone Marrow ◽  
Intracellular Infection ◽  
Growth Difference

Previously, we documented that type II secretion (T2S) promotes intracellular infection of macrophages byLegionella 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 theLegionella-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, asidM lspFdouble mutant had an intracellular growth defect that was more dramatic than that of thelspFmutant (and asidMmutant) 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.

scholarly journals Legionella pneumophila Type II Secretion Dampens the Cytokine Response of Infected Macrophages and Epithelia

2011 ◽  
Vol 79 (5) ◽  
pp. 1984-1997 ◽  
Author(s):  
Kessler McCoy-Simandle ◽  
Catherine R. Stewart ◽  
Jenny Dao ◽  
Sruti DebRoy ◽  
Ombeline Rossier ◽  
...  
Keyword(s):  
Legionella Pneumophila ◽  
Host Cells ◽  
Infected Host ◽  
Pcr Analysis ◽  
Type Ii Secretion ◽  
Type Ii ◽  
Necrosis Factor Alpha ◽  
Content Type ◽  
Intracellular Infection ◽  
The Impact

ABSTRACTThe type II secretion (T2S) system ofLegionella pneumophilais required for the ability of the bacterium to grow within the lungs of A/J mice. By utilizing mutants lacking T2S (lsp), we now document that T2S promotes the intracellular infection of both multiple types of macrophages and lung epithelia. Following infection of macrophages,lspmutants (but not a complemented mutant) elicited significantly higher levels of interleukin 6 (IL-6), tumor necrosis factor alpha (TNF-α), IL-10, IL-8, IL-1β, and MCP-1 within tissue culture supernatants. A similar result was obtained with infected lung epithelial cell lines and the lungs of infected A/J mice. Infection with a mutant specifically lacking the T2S-dependent ProA protease (but not a complementedproAmutant) resulted in partial elevation of cytokine levels. These data demonstrate that the T2S system ofL. pneumophiladampens the cytokine/chemokine output of infected host cells. Upon quantitative reverse transcription (RT)-PCR analysis of infected host cells, anlspFmutant, but not theproAmutant, produced significantly higher levels of cytokine transcripts, implying that some T2S-dependent effectors dampen signal transduction and transcription but that others, such as ProA, act at a posttranscriptional step in cytokine expression. In summary, the impact of T2S on lung infection is a combination of at least three factors: the promotion of growth in macrophages, the facilitation of growth in epithelia, and the dampening of the chemokine and cytokine output from infected host cells. To our knowledge, these data are the first to identify a link between a T2S system and the modulation of immune factors following intracellular infection.

scholarly journals Treponema denticola Activates Mitogen-Activated Protein Kinase Signal Pathways through Toll-Like Receptor 2

2007 ◽  
Vol 75 (12) ◽  
pp. 5763-5768 ◽  
Author(s):  
John Ruby ◽  
Kunal Rehani ◽  
Michael Martin
Keyword(s):  
Protein Kinase ◽  
Mapk Signaling ◽  
Innate Immune ◽  
Mitogen Activated Protein Kinase ◽  
Signal Pathways ◽  
Treponema Denticola ◽  
Toll Like Receptor ◽  
Extracellular Signal ◽  
Mitogen Activated Protein ◽  
Toll Like Receptor 2

ABSTRACT Treponema denticola, a spirochete indigenous to the oral cavity, is associated with host inflammatory responses to anaerobic polymicrobial infections of the root canal, periodontium, and alveolar bone. However, the cellular mechanisms responsible for the recognition of T. denticola by the innate immune system and the underlying cell signaling pathways that regulate the inflammatory response to T. denticola are currently unresolved. In this study, we demonstrate that T. denticola induces innate immune responses via the utilization of Toll-like receptor 2 (TLR2) but not TLR4. Assessment of TLR2/1 and TLR2/6 heterodimers revealed that T. denticola predominantly utilizes TLR2/6 for the induction of cellular responses. Analysis of the mitogen-activated protein kinase (MAPK) signaling pathway in T. denticola-stimulated monocytes identified a prolonged up-regulation of the MAPK extracellular signal-related kinase 1/2 (ERK1/2) and p38, while no discernible increase in phospho-c-Jun N-terminal kinase 1/2 (JNK1/2) levels was observed. With the aid of pharmacological inhibitors selectively targeting ERK1/2 via the mitogen-activated protein kinase/extracellular signal-related kinase 1/2 kinase and p38, we further demonstrate that ERK1/2 and p38 play a major role in T. denticola-mediated pro- and anti-inflammatory cytokine production.

scholarly journals Type II Secretion Promotes Bacterial Growth within the Legionella-Containing Vacuole in Infected Amoebae

2019 ◽  
Vol 87 (11) ◽  
Author(s):  
Richard C. White ◽  
Hilary K. Truchan ◽  
Huaixin Zheng ◽  
Jessica Y. Tyson ◽  
Nicholas P. Cianciotto
Keyword(s):  
Legionella Pneumophila ◽  
Fluorescent Protein ◽  
Host Cells ◽  
Recent Analysis ◽  
Type Ii Secretion ◽  
Type Ii ◽  
Wild Type ◽  
Macrophage Infection ◽  
Content Type ◽  
Intracellular Infection

ABSTRACT It was previously determined that the type II secretion system (T2SS) promotes the ability of Legionella pneumophila to grow in coculture with amoebae. Here, we discerned the stage of intracellular infection that is potentiated by comparing the wild-type and T2SS mutant legionellae for their capacity to parasitize Acanthamoeba castellanii. Whereas the mutant behaved normally for entry into the host cells and subsequent evasion of degradative lysosomes, it was impaired in the ability to replicate, with that defect being first evident at approximately 9 h postentry. The replication defect was initially documented in three ways: by determining the numbers of CFU recovered from the lysates of the infected monolayers, by monitoring the levels of fluorescence associated with amoebal monolayers infected with green fluorescent protein (GFP)-expressing bacteria, and by utilizing flow cytometry to quantitate the amounts of GFP-expressing bacteria in individual amoebae. By employing confocal microscopy and newer imaging techniques, we further determined the progression in volume and shape of the bacterial vacuoles and found that the T2SS mutant grows at a decreased rate and does not attain maximally sized phagosomes. Overall, the entire infection cycle (i.e., entry to egress) was considerably slower for the T2SS mutant than it was for the wild-type strain, and the mutant’s defect was maintained over multiple rounds of infection. Thus, the T2SS is absolutely required for L. pneumophila to grow to larger numbers in its intravacuolar niche within amoebae. Combining these results with those of our recent analysis of macrophage infection, T2SS is clearly a major component of L. pneumophila intracellular infection.

scholarly journals Mycobacterium tuberculosis Triggers Apoptosis in Peripheral Neutrophils Involving Toll-Like Receptor 2 and p38 Mitogen Protein Kinase in Tuberculosis Patients

2004 ◽  
Vol 72 (9) ◽  
pp. 5150-5158 ◽  
Author(s):  
Mercedes Alemán ◽  
Pablo Schierloh ◽  
Silvia S. de la Barrera ◽  
Rosa M. Musella ◽  
María A. Saab ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Protein Kinase ◽  
Tissue Injury ◽  
Mapk Pathway ◽  
Polymorphonuclear Neutrophils ◽  
Mitogen Activated Protein Kinase ◽  
Spontaneous Apoptosis ◽  
Toll Like Receptor ◽  
Toll Like Receptor 2

ABSTRACT Polymorphonuclear neutrophils (PMN) exposed to Mycobacterium tuberculosis display bactericidal responses and produce inflammatory proteins. This PMN-mediated inflammatory response is regulated by an activation of the apoptotic program, which collaborates to avoid tissue injury. In vitro, circulating PMN from patients with tuberculosis (TB) show an increased spontaneous apoptosis, and M. tuberculosis-induced activation accelerates the PMN apoptosis. In this study, we evaluated the mechanisms involved in spontaneous and M. tuberculosis-induced apoptosis. We demonstrate that apoptosis of PMN is not induced by lipoarabinomannan or by a whole-cell lysate of M. tuberculosis and that neither tumor necrosis factor alpha nor CD11b, CD14, and Fcγ receptors are involved. Apoptosis of PMN from patients with active TB (TB-PMN) is induced by the interaction with the whole M. tuberculosis via Toll-like receptor 2 (TLR2), and, in contrast to spontaneous apoptosis, it involves the p38 mitogen-activated protein kinase (MAPK) pathway. These results correlate with a high expression of phosphorylated p38 (p-p38) in circulating TB-PMN and with the ability of M. tuberculosis to induce in vitro the expression of p-p38 in PMN. Therefore, when the bacterial burden is low, TB-PMN could be detecting nonopsonized M. tuberculosis via TLR2, leading to the activation of the p38 MAPK pathway, which in turn would induce PMN activation and apoptosis. This mechanism needs further confirmation at the site of infection.

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