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Evasion of IFN-γ Signaling by Francisella novicida Is Dependent upon Francisella Outer Membrane Protein C

BACKGROUND: Francisella tularensis is a Gram-negative facultative intracellular bacterium and the causative agent of the lethal disease tularemia. An outer membrane protein (FTT0918) of F. tularensis subsp. tularensis has been identified as a virulence factor. We generated a F. novicida (F. tularens...

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Autores principales: Nallaparaju, Kalyan C., Yu, Jieh-Juen, Rodriguez, Stephen A., Zogaj, Xhavit, Manam, Srikanth, Guentzel, M. Neal, Seshu, Janakiram, Murthy, Ashlesh K., Chambers, James P., Klose, Karl E., Arulanandam, Bernard P.
Formato: Texto
Lenguaje:English
Publicado: Public Library of Science 2011
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3069069/
https://www.ncbi.nlm.nih.gov/pubmed/21483828
http://dx.doi.org/10.1371/journal.pone.0018201
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author Nallaparaju, Kalyan C.
Yu, Jieh-Juen
Rodriguez, Stephen A.
Zogaj, Xhavit
Manam, Srikanth
Guentzel, M. Neal
Seshu, Janakiram
Murthy, Ashlesh K.
Chambers, James P.
Klose, Karl E.
Arulanandam, Bernard P.
author_facet Nallaparaju, Kalyan C.
Yu, Jieh-Juen
Rodriguez, Stephen A.
Zogaj, Xhavit
Manam, Srikanth
Guentzel, M. Neal
Seshu, Janakiram
Murthy, Ashlesh K.
Chambers, James P.
Klose, Karl E.
Arulanandam, Bernard P.
author_sort Nallaparaju, Kalyan C.
collection PubMed
description BACKGROUND: Francisella tularensis is a Gram-negative facultative intracellular bacterium and the causative agent of the lethal disease tularemia. An outer membrane protein (FTT0918) of F. tularensis subsp. tularensis has been identified as a virulence factor. We generated a F. novicida (F. tularensis subsp. novicida) FTN_0444 (homolog of FTT0918) fopC mutant to study the virulence-associated mechanism(s) of FTT0918. METHODS AND FINDINGS: The ΔfopC strain phenotype was characterized using immunological and biochemical assays. Attenuated virulence via the pulmonary route in wildtype C57BL/6 and BALB/c mice, as well as in knockout (KO) mice, including MHC I, MHC II, and µmT (B cell deficient), but not in IFN-γ or IFN-γR KO mice was observed. Primary bone marrow derived macrophages (BMDM) prepared from C57BL/6 mice treated with rIFN-γ exhibited greater inhibition of intracellular ΔfopC than wildtype U112 strain replication; whereas, IFN-γR KO macrophages showed no IFN-γ-dependent inhibition of ΔfopC replication. Moreover, phosphorylation of STAT1 was downregulated by the wildtype strain, but not the fopC mutant, in rIFN-γ treated macrophages. Addition of N(G)-monomethyl-L-arginine, an NOS inhibitor, led to an increase of ΔfopC replication to that seen in the BMDM unstimulated with rIFN-γ. Enzymatic screening of ΔfopC revealed aberrant acid phosphatase activity and localization. Furthermore, a greater abundance of different proteins in the culture supernatants of ΔfopC than that in the wildtype U112 strain was observed. CONCLUSIONS: F. novicida FopC protein facilitates evasion of IFN-γ-mediated immune defense(s) by down-regulation of STAT1 phosphorylation and nitric oxide production, thereby promoting virulence. Additionally, the FopC protein also may play a role in maintaining outer membrane stability (integrity) facilitating the activity and localization of acid phosphatases and other F. novicida cell components.
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spelling pubmed-30690692011-04-11 Evasion of IFN-γ Signaling by Francisella novicida Is Dependent upon Francisella Outer Membrane Protein C Nallaparaju, Kalyan C. Yu, Jieh-Juen Rodriguez, Stephen A. Zogaj, Xhavit Manam, Srikanth Guentzel, M. Neal Seshu, Janakiram Murthy, Ashlesh K. Chambers, James P. Klose, Karl E. Arulanandam, Bernard P. PLoS One Research Article BACKGROUND: Francisella tularensis is a Gram-negative facultative intracellular bacterium and the causative agent of the lethal disease tularemia. An outer membrane protein (FTT0918) of F. tularensis subsp. tularensis has been identified as a virulence factor. We generated a F. novicida (F. tularensis subsp. novicida) FTN_0444 (homolog of FTT0918) fopC mutant to study the virulence-associated mechanism(s) of FTT0918. METHODS AND FINDINGS: The ΔfopC strain phenotype was characterized using immunological and biochemical assays. Attenuated virulence via the pulmonary route in wildtype C57BL/6 and BALB/c mice, as well as in knockout (KO) mice, including MHC I, MHC II, and µmT (B cell deficient), but not in IFN-γ or IFN-γR KO mice was observed. Primary bone marrow derived macrophages (BMDM) prepared from C57BL/6 mice treated with rIFN-γ exhibited greater inhibition of intracellular ΔfopC than wildtype U112 strain replication; whereas, IFN-γR KO macrophages showed no IFN-γ-dependent inhibition of ΔfopC replication. Moreover, phosphorylation of STAT1 was downregulated by the wildtype strain, but not the fopC mutant, in rIFN-γ treated macrophages. Addition of N(G)-monomethyl-L-arginine, an NOS inhibitor, led to an increase of ΔfopC replication to that seen in the BMDM unstimulated with rIFN-γ. Enzymatic screening of ΔfopC revealed aberrant acid phosphatase activity and localization. Furthermore, a greater abundance of different proteins in the culture supernatants of ΔfopC than that in the wildtype U112 strain was observed. CONCLUSIONS: F. novicida FopC protein facilitates evasion of IFN-γ-mediated immune defense(s) by down-regulation of STAT1 phosphorylation and nitric oxide production, thereby promoting virulence. Additionally, the FopC protein also may play a role in maintaining outer membrane stability (integrity) facilitating the activity and localization of acid phosphatases and other F. novicida cell components. Public Library of Science 2011-03-31 /pmc/articles/PMC3069069/ /pubmed/21483828 http://dx.doi.org/10.1371/journal.pone.0018201 Text en Nallaparaju et al. http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited.
spellingShingle Research Article
Nallaparaju, Kalyan C.
Yu, Jieh-Juen
Rodriguez, Stephen A.
Zogaj, Xhavit
Manam, Srikanth
Guentzel, M. Neal
Seshu, Janakiram
Murthy, Ashlesh K.
Chambers, James P.
Klose, Karl E.
Arulanandam, Bernard P.
Evasion of IFN-γ Signaling by Francisella novicida Is Dependent upon Francisella Outer Membrane Protein C
title Evasion of IFN-γ Signaling by Francisella novicida Is Dependent upon Francisella Outer Membrane Protein C
title_full Evasion of IFN-γ Signaling by Francisella novicida Is Dependent upon Francisella Outer Membrane Protein C
title_fullStr Evasion of IFN-γ Signaling by Francisella novicida Is Dependent upon Francisella Outer Membrane Protein C
title_full_unstemmed Evasion of IFN-γ Signaling by Francisella novicida Is Dependent upon Francisella Outer Membrane Protein C
title_short Evasion of IFN-γ Signaling by Francisella novicida Is Dependent upon Francisella Outer Membrane Protein C
title_sort evasion of ifn-γ signaling by francisella novicida is dependent upon francisella outer membrane protein c
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3069069/
https://www.ncbi.nlm.nih.gov/pubmed/21483828
http://dx.doi.org/10.1371/journal.pone.0018201
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