Abstract
Macrophages respond to infection with pathogenic Yersinia species by activating MAPK- and NF-kappaB-signaling pathways. To counteract this response, Yersiniae secrete a protease (Yersinia outer protein J (YopJ)) that is delivered into macrophages, deactivates MAPK- and NF-kappaB-signaling pathways, and induces apoptosis. NF-kappaB promotes cell survival by up-regulating expression of several apoptosis inhibitor genes. Previous studies show that deactivation of the NF-kappaB pathway by YopJ is important for Yersinia-induced apoptosis. To determine whether deactivation of the NF-kappaB pathway is sufficient for Yersinia-induced apoptosis, two inhibitors of the NF-kappaB pathway, IkappaBalpha superrepressor or A20, were expressed in macrophages. Macrophages expressing these proteins were infected with Yersinia pseudotuberculosis strains that secrete functionally active or inactive forms of YopJ. Apoptosis levels were substantially higher (5- to 10-fold) when active YopJ was delivered into macrophages expressing IkappaBalpha superrepressor or A20, suggesting that deactivation of the NF-kappaB pathway is not sufficient for rapid Yersinia-induced apoptosis. When macrophages expressing A20 were treated with specific inhibitors of MAPKs, similar levels of apoptosis (within approximately 2-fold) were observed when active or inactive YopJ were delivered during infection. These results suggest that MAPK and NF-kappaB pathways function together to up-regulate apoptosis inhibitor gene expression in macrophages in response to Yersinia infection and that YopJ deactivates both pathways to promote rapid apoptosis. In addition, treating macrophages with a proteasome inhibitor results in higher levels of infection-induced apoptosis than can be achieved by blocking NF-kappaB function alone, suggesting that proapoptotic proteins are stabilized when proteasome function is blocked in macrophages.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Apoptosis / genetics
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Apoptosis / immunology*
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Bacterial Proteins / metabolism
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Catalysis
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Cell Line
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Cells, Cultured
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Cysteine Endopeptidases
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DNA-Binding Proteins
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Down-Regulation / genetics
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Down-Regulation / immunology*
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Endopeptidases / metabolism
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Humans
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I-kappa B Proteins / biosynthesis
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I-kappa B Proteins / genetics
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I-kappa B Proteins / physiology
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Intracellular Signaling Peptides and Proteins
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JNK Mitogen-Activated Protein Kinases / antagonists & inhibitors
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JNK Mitogen-Activated Protein Kinases / physiology
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MAP Kinase Signaling System / genetics
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MAP Kinase Signaling System / immunology*
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Macrophages / cytology
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Macrophages / enzymology
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Macrophages / immunology*
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Macrophages / microbiology*
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Mice
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Mice, Inbred C57BL
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NF-KappaB Inhibitor alpha
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NF-kappa B / antagonists & inhibitors*
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NF-kappa B / metabolism
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NF-kappa B / physiology*
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Nuclear Proteins
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Proteins / genetics
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Repressor Proteins / biosynthesis
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Repressor Proteins / genetics
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Repressor Proteins / physiology
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Transduction, Genetic
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Tumor Necrosis Factor alpha-Induced Protein 3
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Up-Regulation / genetics
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Up-Regulation / immunology
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Yersinia pseudotuberculosis / enzymology
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Yersinia pseudotuberculosis / genetics
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Yersinia pseudotuberculosis / immunology*
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p38 Mitogen-Activated Protein Kinases / antagonists & inhibitors
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p38 Mitogen-Activated Protein Kinases / physiology
Substances
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Bacterial Proteins
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DNA-Binding Proteins
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I-kappa B Proteins
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Intracellular Signaling Peptides and Proteins
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NF-kappa B
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NFKBIA protein, human
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Nfkbia protein, mouse
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Nuclear Proteins
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Proteins
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Repressor Proteins
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YopP protein, Yersinia
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NF-KappaB Inhibitor alpha
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JNK Mitogen-Activated Protein Kinases
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p38 Mitogen-Activated Protein Kinases
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Endopeptidases
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TNFAIP3 protein, human
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Tumor Necrosis Factor alpha-Induced Protein 3
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Cysteine Endopeptidases
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Tnfaip3 protein, mouse