RipA, a Cytoplasmic Membrane Protein Conserved among<i>Francisella</i>Species, Is Required for Intracellular Survival

Fuller, James R.; Craven, Robin R.; Hall, Joshua D.; Kijek, Todd M.; Taft-Benz, Sharon; Kawula, Thomas H.

doi:10.1128/iai.00475-08

Cited by 46 publications

(82 citation statements)

References 63 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Francisella novicida was obtained from Microbiology Core at Albany Medical College. GFP expressing F. tularensis LVS and the sodBC mutants was prepared by transforming the GFP expression plasmid pKK214:GFP (42). All bacterial cultures were grown on Mueller-Hinton (MH)-chocolate agar plates (BD Biosciences) at 37°C with 5% CO 2 or Mueller-Hinton broth (BD Biosciences) with supplementations consisting of isovitalex and ferric pyrophosphate (BD Biosciences) at 37°C with constant shaking at 175 rpm.…”

Section: Methodsmentioning

confidence: 99%

Antioxidant Defenses of Francisella tularensis Modulate Macrophage Function and Production of Proinflammatory Cytokines

Rabadi

Sanchez

Varanat

et al. 2016

Journal of Biological Chemistry

View full text Add to dashboard Cite

Francisella tularensis, the causative agent of a fatal human disease known as tularemia, has been used in the bioweapon programs of several countries in the past, and now it is considered a potential bioterror agent. Extreme infectivity and virulence of F. tularensis is due to its ability to evade immune detection and to suppress the host's innate immune responses. However, Francisella-encoded factors and mechanisms responsible for causing immune suppression are not completely understood. Macrophages and neutrophils generate reactive oxygen species (ROS)/reactive nitrogen species as a defense mechanism for the clearance of phagocytosed microorganisms. ROS serve a dual role; at high concentrations they act as microbicidal effector molecules that destroy intracellular pathogens, and at low concentrations they serve as secondary signaling messengers that regulate the expression of various inflammatory mediators. We hypothesized that the antioxidant defenses of F. tularensis maintain redox homeostasis in infected macrophages to prevent activation of redox-sensitive signaling components that ultimately result in suppression of pro-inflammatory cytokine production and macrophage microbicidal activity. We demonstrate that antioxidant enzymes of F. tularensis prevent the activation of redox-sensitive MAPK signaling components, NF-B signaling, and the production of pro-inflammatory cytokines by inhibiting the accumulation of ROS in infected macrophages. We also report that F. tularensis inhibits ROS-dependent autophagy to promote its intramacrophage survival. Collectively, this study reveals novel pathogenic mechanisms adopted by F. tularensis to modulate macrophage innate immune functions to create an environment permissive for its intracellular survival and growth.Francisella tularensis is a Gram-negative intracellular pathogen and the causative agent of a fatal human disease known as tularemia. F. tularensis is classified into four subspecies as follows: F. tularensis subspecies tularensis; F. tularensis subspecies holarctica; F. tularensis subspecies mediasiatica, and F. tularensis subspecies novicida. All classifications are based on virulence, genetics, and metabolic characteristics. F. tularensis subspecies tularensis (type A) is the most virulent of all four Francisella subspecies. About 70% of tularemia cases in North America are a result of type A Francisella with an infectivity dose of less than 10 colony-forming units (cfu) in humans (1). The live vaccine strain (LVS) 3 is a derivative of Russian S15 strain of F. tularensis subspecies holarctica (type B). F. tularensis LVS is not approved for mass vaccinations in the United States due to adverse reactions in vaccinated individuals (2). F. tularensis LVS is relatively avirulent in humans and therefore commonly used as a surrogate for the more virulent SchuS4 strain to study tularemia pathogenesis. F. tularensis subspecies mediasiatica and novicida are rarely associated with human tularemia and have been isolated in Asia and in North America and Australia, re...

show abstract

Section: Methodsmentioning

confidence: 99%

Antioxidant Defenses of Francisella tularensis Modulate Macrophage Function and Production of Proinflammatory Cytokines

Rabadi

Sanchez

Varanat

et al. 2016

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

mentioning

confidence: 99%

“…More specifically, deletion of this locus in the live vaccine strain (LVS) resulted in a mutant (LVS⌬ripA) that escapes the phagosome but is defective for intracellular replication (17) and fails to suppress the proinflammatory immune response (22). Not surprisingly, LVS⌬ripA is also attenuated in a pulmonary mouse model of tularemia (17). Deletion of ripA in the highly virulent strain F. tularensis Schu S4 results in a mutant that is defective for intracellular replication and attenuated in a mouse model as well, suggesting that RipA is required for virulence in highly pathogenic F. tularensis subsp.…”

mentioning

confidence: 99%

“…RipA is a cytoplasmic membrane protein that is conserved among Francisella species (17). Interestingly, bioinformatic analyses show that there is sporadic representation of RipA-like proteins among prokaryotes, where RipA-like proteins are found in only specific strains of a given bacterial species.…”

mentioning

confidence: 99%

“…For allelic exchange, plasmids were electroporated into LVS and integrants were selected on chocolate agar containing kanamycin (10 g ml Ϫ1 ). Kan r strains were grown overnight and plated on 10% sucrose for counterselection (loss of plasmid) (17). Deletions were confirmed by PCR analysis of genomic DNA using primers external to the deleted regions.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Francisella tularensis RipA Protein Topology and Identification of Functional Domains

et al. 2012

Self Cite

View full text Add to dashboard Cite

Francisella tularensis is a Gram-negative coccobacillus and is the etiological agent of the disease tularemia. Expression of the cytoplasmic membrane protein RipA is required for Francisella replication within macrophages and other cell types; however, the function of this protein remains unknown. RipA is conserved among all sequenced Francisella species, and RipA-like proteins are present in a number of individual strains of a wide variety of species scattered throughout the prokaryotic kingdom. Crosslinking studies revealed that RipA forms homoligomers. Using a panel of RipA-green fluorescent protein and RipA-PhoA fusion constructs, we determined that RipA has a unique topology within the cytoplasmic membrane, with the N and C termini in the cytoplasm and periplasm, respectively. RipA has two significant cytoplasmic domains, one composed roughly of amino acids 1 to 50 and the second flanked by the second and third transmembrane domains and comprising amino acids 104 to 152. RipA functional domains were identified by measuring the effects of deletion mutations, amino acid substitution mutations, and spontaneously arising intragenic suppressor mutations on intracellular replication, induction of interleukin-1␤ (IL-1␤) secretion by infected macrophages, and oligomer formation. Results from these experiments demonstrated that each of the cytoplasmic domains and specific amino acids within these domains are required for RipA function.

show abstract

Intracellular Degradation of Fusobacterium nucleatum in Human Gingival Epithelial Cells

Shin

Kim

et al. 2010

Molecules and Cells

View full text Add to dashboard Cite

The role of Fusobacterium nucleatum in oral health and disease is controversial. We have previously shown that F. nucleatum invades gingival epithelial cells. However, the destiny of the internalized F. nucleatum is not clear. In the present study, the intracellular destiny of F. nucleatum and its cytopathic effect on gingival epithelial cells were studied. The ability of F. nucleatum and seven other oral bacterial species to invade immortalized human gingival epithelial (HOK-16B) cells were compared by confocal microscopy and flow cytometry. F. nucleatum had the highest invasive capacity, comparable to that of Porphyromonas gingivalis, a periodontal pathogen. Confocal microscopic examination revealed colocalization of internalized F. nucleatum with endosomes and lysosomes. Examination by transmission electron microscopy revealed that most intracellular F. nucleatum was located within vesicular structures with single enclosed membranes. Furthermore, F. nucleatum could not survive within gingival epithelial cells and had no cytopathic effects on host cells. Interestingly, endosomal maturation played a role in induction of the antimicrobial peptides human beta defensin (HBD)-2 and -3 by F. nucleatum from gingival epithelial cells. F. nucleatum is destined to enter an endocytic degradation pathway after invasion and has no cytopathic effect on gingival epithelial cells, which may cast new light on the role of F. nucleatum in the pathogenesis of periodontitis.

show abstract

RipA, a Cytoplasmic Membrane Protein Conserved amongFrancisellaSpecies, Is Required for Intracellular Survival

Cited by 46 publications

References 63 publications

Antioxidant Defenses of Francisella tularensis Modulate Macrophage Function and Production of Proinflammatory Cytokines

Antioxidant Defenses of Francisella tularensis Modulate Macrophage Function and Production of Proinflammatory Cytokines

Francisella tularensis RipA Protein Topology and Identification of Functional Domains

Intracellular Degradation of Fusobacterium nucleatum in Human Gingival Epithelial Cells

Contact Info

Product

Resources

About