Abstract
Pathogenic mycobacteria have evolved unique strategies to survive within the hostile environment of macrophages. Modulation of key signaling cascades by NO, generated by the host during infection, assumes critical importance in overall cell-fate decisions. We show that NO is a critical factor in Mycobacterium bovis bacillus Calmette-Guérin-mediated Notch1 activation, as the generation of activated Notch1 or expression of Notch1 target genes matrix metalloproteinase-9 (MMP-9) or Hes1 was abrogated in macrophages derived from inducible NO synthase (iNOS) knockout (iNOS(-/-)), but not from wild-type, mice. Interestingly, expression of the Notch1 ligand Jagged1 was compromised in M. bovis bacillus Calmette-Guérin-stimulated iNOS(-/-) macrophages, and loss of Jagged1 expression or Notch1 signaling could be rescued by NO donors. Signaling perturbations or genetic approaches implicated that robust expression of MMP-9 or Hes1 required synergy and cross talk between TLR2 and canonical Notch1-PI3K cascade. Further, CSL/RBP-Jk contributed to TLR2-mediated expression of MMP-9 or Hes1. Correlative evidence shows that, in a murine model for CNS tuberculosis, this mechanism operates in vivo only in brains derived from WT but not from iNOS(-/-) mice. Importantly, we demonstrate the activation of Notch1 signaling in vivo in granulomatous lesions in the brains of Mycobacterium tuberculosis-infected human patients with tuberculous meningitis. Current investigation identifies NO as a pathological link that modulates direct cooperation of TLR2 with Notch1-PI3K signaling or Jagged1 to regulate specific components of TLR2 responses. These findings provide new insights into mechanisms by which Notch1, TLR2, and NO signals are integrated in a cross talk that modulates a defined set of effector functions in macrophages.
Publication types
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Comparative Study
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Basic Helix-Loop-Helix Transcription Factors / biosynthesis
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Basic Helix-Loop-Helix Transcription Factors / genetics
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Calcium-Binding Proteins / biosynthesis
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Calcium-Binding Proteins / genetics
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Calcium-Binding Proteins / physiology*
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Cell Line
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Enzyme Activation / genetics
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Enzyme Activation / immunology
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Gene Expression Regulation / immunology
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Homeodomain Proteins / biosynthesis
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Homeodomain Proteins / genetics
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Humans
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Intercellular Signaling Peptides and Proteins / biosynthesis
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Intercellular Signaling Peptides and Proteins / genetics
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Intercellular Signaling Peptides and Proteins / physiology*
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Jagged-1 Protein
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Macrophages, Peritoneal / enzymology
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Macrophages, Peritoneal / immunology
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Macrophages, Peritoneal / pathology
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Matrix Metalloproteinase 9 / biosynthesis
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Matrix Metalloproteinase 9 / genetics
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Membrane Proteins / biosynthesis
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Membrane Proteins / genetics
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Membrane Proteins / physiology*
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Mice
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Mice, Inbred C57BL
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Mice, Knockout
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Mycobacterium bovis / immunology*
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Nitric Oxide / physiology*
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Nitric Oxide Synthase Type II / deficiency
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Nitric Oxide Synthase Type II / genetics
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Nitric Oxide Synthase Type II / physiology
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Protein Structure, Tertiary / genetics
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Receptor Cross-Talk / immunology
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Receptor, Notch1 / biosynthesis
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Receptor, Notch1 / genetics
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Receptor, Notch1 / physiology*
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Serrate-Jagged Proteins
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Signal Transduction / genetics
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Signal Transduction / immunology*
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Toll-Like Receptor 2 / physiology
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Transcription Factor HES-1
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Tuberculosis, Meningeal / genetics
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Tuberculosis, Meningeal / immunology
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Tuberculosis, Meningeal / pathology
Substances
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Basic Helix-Loop-Helix Transcription Factors
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Calcium-Binding Proteins
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Hes1 protein, mouse
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Homeodomain Proteins
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Intercellular Signaling Peptides and Proteins
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JAG1 protein, human
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Jag1 protein, mouse
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Jagged-1 Protein
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Membrane Proteins
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NOTCH1 protein, human
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Notch1 protein, mouse
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Receptor, Notch1
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Serrate-Jagged Proteins
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Tlr2 protein, mouse
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Toll-Like Receptor 2
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Transcription Factor HES-1
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HES1 protein, human
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Nitric Oxide
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Nitric Oxide Synthase Type II
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Matrix Metalloproteinase 9
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Mmp9 protein, mouse