genegodbold
commented
1 year ago Symbionts messing with host signaling of ROS production: Mechanism Unclear:
- Enterococcus faecalis expressing Asa1 were significantly more resistant to macrophage killing during the first three hours following uptake. This appears to be due to an inhibition in the respiratory burst for macrophages that have taken up Asa1-expressing bacteria [PMID:10948103].
- BhpA from Borrelia hermsii is a serine protease that is unique to bacteria causing relapsing fever. When heterologously expressed in B. burgdorferi, BhpA confers greater resistance to oxidative stress and destruction by neutrophils [PMID:16629672].
- EtpE inhibits the production of reactive oxygen species from murine macrophages in a process requiring host GPI-anchored DNase X. EtpE associates with DNAase X on the mammalian cell surface [PMID:29162709].
- Expression of PlcH by Pseudomonas aeruginosa decreases the PMA-stimulated respiratory burst of exposed neutrophils. Bacteria that lack the gene encoding PlcH provoke an exaggerated respiratory burst from normal human neutrophils [PMID10225897].
- LasB from Pseudomonas aeruginosa downregulates the activation of reactive oxygen species production by alveolar macrophages. This adversely affects the ability of macrophages to clear bacteria in the lungs [PMID:30083156].
- Surface factor promoting resistance to oxidative killing (SOK) from Staphylcoccus aureus is probably localized on the bacterial exterior. It is important for survival inside phagocytes. A SOK-producing S. aureus strain was more resistant to killing by human neutrophils after internalization than one in which SOK was deleted. The levels of reactive oxygen species (ROS) in neutrophils infected with the SOK deficient strain were higher than in neutrophils infected with the SOK-producing strain. SOK producing strains are more resistant to killing by oxygen-singlet ROS in vitro than the SOK deficient strain. Susceptibility to hydrogen peroxide was unaffected. A SOK deficient strain was attenuated in survival in a rabbit endocarditis model of infection [PMID:20937760].
Mechanism More Clear:
- Nucleoside diphosphate kinase (Ndk) from Mycobacterium tuberculosis binds to and inactivates the host small GTPase Rac1 in the macrophage. This excludes the Rac1 binding partner p67(phox) from phagosomes which is associated with a defect in the production of reactive oxygen species (ROS) in response to the wild-type bacterium. Lacking Ndk activity leads to increased destruction of the bacterium within the host macrophage [PMID:23874203].
- OrfX from Listeria monocytogenes is a secreted nucleomodulin protein of ~107 residues that is targeted to the host nucleus where it associates with the host protein RybP, a host transcriptional repressor, and reduces its abundance thereby indirectly affecting transcription. OrfX dampens the oxidative response in macrophages. Macrophages infected with bacterial mutants lacking OrfX exhibit increased nitric oxide (NO) production when compared to macrophages infected with an isogenic strain. Through this activity, OrfX promotes bacterial survival in macrophages [PMID:29089430].
- PPE2 from Mycobacterium tuberculosis has a nuclear localization sequence and a leucine zipper motif at its C terminus, resembling a transcription factor. PPE2 is a secreted protein. When ectopically expressed in activated RAW264.7 macrophages, it moves into the host nucleus and inhibits nitric oxide (NO) production by transcriptional repression, binding to the iNOS promoter. When PPE2 is expressed in M. smegmatis, it improves the survival of the mutant bacilli inside infected macrophages when compared to wild-type bacteria [PMID27634911]. PPE2 interacts with p67(phox) to inhibit ROS production [PMID:31375544].
- Salmonella outer protein B (SopB) contributes to immune evasion by attenuating production of reactive oxygen species in mitochondria by binding to TRAF6 to prevent mitochondrial recruitment which is necessary for ROS generation [PMID:27473656].
Symbionts directly degrading host ROS:
- KatN is a Mn-containing catalase T6SS effector of enterohemorrhagic E. coli used to antagonize reactive oxygen species of eukaryotic host cells to evade host immune killing. KatN is crucial for allowing EHEC to survive in host macrophages [PMID:28288207].
- Plant innate immune responses to bacterial infection include a burst of reactive oxygen species (ROS) which are toxic to bacterial cells. Hydrogen peroxide (H2O2), an important ROS, accumulates and diffuses widely between neighboring xylem elements. Deletion of the gene encoding catalase B from _Xanthomonas oryzae decreases catalase activity, bacterial viability and virulence under peroxide stress [PMID:27825304].
- Superoxide dismutase (SodC) from Francisella tularensis is required for resisting reactive oxygen species generated by the host [PMID:19684141].
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