Faculty Collaboration Database

Multiple mechanisms of NADPH oxidase inhibition by type A and type B Francisella tularensis. J Leukoc Biol 2010 Oct;88(4):791-805

Date

07/09/2010

Pubmed ID

20610796

Pubmed Central ID

PMC2974429

DOI

10.1189/jlb.1209811

Scopus ID

2-s2.0-77957887794 (requires institutional sign-in at Scopus site)   85 Citations

Abstract

Ft is a facultative intracellular pathogen that infects many cell types, including neutrophils. In previous work, we demonstrated that the type B Ft strain LVS disrupts NADPH oxidase activity throughout human neutrophils, but how this is achieved is incompletely defined. Here, we used several type A and type B strains to demonstrate that Ft-mediated NADPH oxidase inhibition is more complex than appreciated previously. We confirm that phagosomes containing Ft opsonized with AS exclude flavocytochrome b(558) and extend previous results to show that soluble phox proteins were also affected, as indicated by diminished phosphorylation of p47(phox) and other PKC substrates. However, a different mechanism accounts for the ability of Ft to inhibit neutrophil activation by formyl peptides, Staphylococcus aureus, OpZ, and phorbol esters. In this case, enzyme targeting and assembly were normal, and impaired superoxide production was characterized by sustained membrane accumulation of dysfunctional NADPH oxidase complexes. A similar post-assembly inhibition mechanism also diminished the ability of anti-Ft IS to confer neutrophil activation and bacterial killing, consistent with the limited role for antibodies in host defense during tularemia. Studies of mutants that we generated in the type A Ft strain Schu S4 demonstrate that the regulatory factor fevR is essential for NADPH oxidase inhibition, whereas iglI and iglJ, candidate secretion system effectors, and the acid phosphatase acpA are not. As Ft uses multiple mechanisms to block neutrophil NADPH oxidase activity, our data strongly suggest that this is a central aspect of virulence.

Author List

McCaffrey RL, Schwartz JT, Lindemann SR, Moreland JG, Buchan BW, Jones BD, Allen LA

Author

Blake W. Buchan PhD Professor in the Pathology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Bacterial Proteins
Fluorescent Antibody Technique
Francisella tularensis
Genes, Bacterial
Humans
Microscopy, Confocal
NADPH Oxidases
Neutrophil Activation
Neutrophils
Polymerase Chain Reaction
Tularemia
Virulence
Virulence Factors