Identification of Membrane-Bound Lytic Murein Transglycosylase A (MltA) as a Growth Factor for Francisella novicida in a Silkworm Infection Model

Nakamura, Takemasa; Shimizu, Takashi; Inagaki, Fumiya; Okazaki, Shoma; Saha, Shib Shankar; Uda, Akihiko; Watanabe, Kenta; Watarai, Masahisa

doi:10.3389/fcimb.2020.581864

Cited by 6 publications

(8 citation statements)

References 56 publications

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“…The trypan blue exclusion assay was conducted as described [69]. Briefly, J774 macrophages (approximately 5.10 5 eukaryotic cells per well) seeded in 6-well culture plates were infected in triplicate with the mutants, or wild-type F. novicida U112 at a MOI of 100 and washed at 1 h post-infection.…”

Section: Plos Pathogensmentioning

confidence: 99%

The pentose phosphate pathway constitutes a major metabolic hub in pathogenic Francisella

et al. 2021

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Metabolic pathways are now considered as intrinsic virulence attributes of pathogenic bacteria and thus represent potential targets for antibacterial strategies. Here we focused on the role of the pentose phosphate pathway (PPP) and its connections with other metabolic pathways in the pathophysiology of Francisella novicida. The involvement of the PPP in the intracellular life cycle of Francisella was first demonstrated by studying PPP inactivating mutants. Indeed, we observed that inactivation of the tktA, rpiA or rpe genes severely impaired intramacrophage multiplication during the first 24 hours. However, time-lapse video microscopy demonstrated that rpiA and rpe mutants were able to resume late intracellular multiplication. To better understand the links between PPP and other metabolic networks in the bacterium, we also performed an extensive proteo-metabolomic analysis of these mutants. We show that the PPP constitutes a major bacterial metabolic hub with multiple connections to glycolysis, the tricarboxylic acid cycle and other pathways, such as fatty acid degradation and sulfur metabolism. Altogether our study highlights how PPP plays a key role in the pathogenesis and growth of Francisella in its intracellular niche.

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Section: Plos Pathogensmentioning

confidence: 99%

The pentose phosphate pathway constitutes a major metabolic hub in pathogenic Francisella

et al. 2021

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“…Ten genes were determined to be immunosuppression-related. Among these 10 genes, four genes, FTN_0756 ( fopA ), FTN_1286 ( mltA ), FTN_0757 ( cas9 ), and FTN_0496 ( slt ), were previously reported as immunosuppressive factors of Francisella ( Peng et al., 2011 ; Sampson et al., 2013 ; Nakamura et al., 2019 ; Nakamura et al., 2021 ), ensuring the reliability of the screening method employed in this study. The remaining 6 genes, FTN_1641 ( ampG ), FTN_1199 ( capA / B ) FTN_1548 ( yfgL ), FTN_0917 ( dacB ), FTN_0611 ( kdsA ), and FTN_0024 ( pyrC ), were newly identified as Francisella immunosuppressive factors in this study.…”

Section: Discussionmentioning

confidence: 79%

Identification of pyrC gene as an immunosuppressive factor in Francisella novicida infection

Nakamura

Shimizu²,

Ikegaya³

et al. 2022

Front. Cell. Infect. Microbiol.

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Francisella tularensis, a bacterial causative agent of the zoonosis tularemia, is highly pathogenic to humans. The pathogenicity of this bacterium is characterized by intracellular growth in immune cells, like macrophages, and host immune suppression. However, the detailed mechanism of immune suppression by F. tularensis is still unclear. To identify the key factors causing Francisella-mediated immunosuppression, large-scale screening using a transposon random mutant library containing 3552 mutant strains of F. tularensis subsp. novicida (F. novicida) was performed. Thirteen mutants that caused stronger tumor necrosis factor (TNF)-α production in infected U937 human macrophage cells than the wild-type F. novicida strain were isolated. Sequencing analysis of transposon insertion sites revealed 10 genes, including six novel genes, as immunosuppressive factors of Francisella. Among these, the relationship of the pyrC gene, which encodes dihydroorotase in the pyrimidine biosynthesis pathway, with Francisella-mediated immunosuppression was investigated. The pyrC deletion mutant strain (ΔpyrC) induced higher TNF-α production in U937 host cells than the wild-type F. novicida strain. The ΔpyrC mutant strain was also found to enhance host interleukin-1β and interferon (IFN)-β production. The heat-inactivated ΔpyrC mutant strain could not induce host TNF-α production. Moreover, the production of IFN-β resulting from ΔpyrC infection in U937 cells was repressed upon treatment with the stimulator of interferon genes (STING)-specific inhibitor, H-151. These results suggest that pyrC is related to the immunosuppressive activity and pathogenicity of Francisella via the STING pathway.

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“…Interestingly, both Slt and MltA were implicated in immunomodulation, although discovered in different models of infection, i.e., THP-1 cells for Slt and silkworm for MltA (Nakamura et al, 2019(Nakamura et al, , 2020. It is possible that aberrations in the cell wall resulting from mutation of the genes encoding for the LT enzymes alters the recognition of the PG by the TLR2 receptor.…”

Section: Roles Of Peptidoglycan Enzymes In Immunomodulationmentioning

confidence: 99%

Peptidoglycan enzymes of Francisella: Roles in cell morphology and pathogenesis, and potential as therapeutic targets

Bachert

Bozue

2023

Front. Microbiol.

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Peptidoglycan, found within the cell wall of bacteria, is a structure critical for maintaining cell morphology and providing a protective barrier in diverse environments. Peptidoglycan is a remarkably dynamic structure that is constantly remodeled during cell growth and division by various peptidoglycan enzymes. Numerous peptidoglycan enzymes have been characterized from diverse bacteria and are highly sought after as targets for therapeutics. However, very little is known about these enzymes within the biothreat agent Francisella tularensis. As the causative agent of tularemia, F. tularensis is classified as a category A biothreat pathogen, in part due to its low infectious dose and lack of FDA-approved vaccine. Many bacterial species encode multiple peptidoglycan enzymes with redundant functions that allow for compensation if one of the enzymes are inactivated. In contrast, F. tularensis appears to lack this redundancy, indicating peptidoglycan enzymes may be completely essential for growth and could be exploited as targets for medical countermeasures. Indeed, several peptidoglycan enzymes in F. tularensis have been shown to play important roles in cell division, cell morphology, virulence, and modulation of host response. The aim of this review is to summarize findings from the current literature on peptidoglycan enzymes present in Francisella and discuss areas where future research efforts might be directed. We conclude that Francisella harbors a distinct set of peptidoglycan enzymes important for cell growth and virulence and represent potentially valuable targets for the development of novel therapeutics.

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Identification of Membrane-Bound Lytic Murein Transglycosylase A (MltA) as a Growth Factor for Francisella novicida in a Silkworm Infection Model

Cited by 6 publications

References 56 publications

The pentose phosphate pathway constitutes a major metabolic hub in pathogenic Francisella

The pentose phosphate pathway constitutes a major metabolic hub in pathogenic Francisella

Identification of pyrC gene as an immunosuppressive factor in Francisella novicida infection

Peptidoglycan enzymes of Francisella: Roles in cell morphology and pathogenesis, and potential as therapeutic targets

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