Abstract
The engagement of triggering receptor expressed on myeloid cells 1 (TREM-1) on macrophages and neutrophils leads to TNF-alpha and IL-8 production and enhances inflammatory responses to microbial products. For signal transduction, TREM-1 couples to the ITAM-containing adapter DNAX activation protein of 12 kDa (DAP12). In general, ITAM-mediated signals lead to cell activation, although DAP12 was recently implicated in inhibitory signaling in mouse macrophages and dendritic cells. To date, signals downstream of the TREM-1 and DAP12 complex in myeloid cells are poorly defined. By analyzing receptor-induced tyrosine phosphorylation patterns, we discovered that the ligation of TREM-1 leads to tyrosine phosphorylation of the non-T cell activation linker (NTAL; also called linker of activation in B cells or LAB) in a myelomonocytic cell line and primary human granulocytes. Using RNA interference to decrease the expression levels of NTAL, we demonstrate that in NTAL knockdown cell lines the phosphorylation of ERK1/2 is enhanced. In addition, low levels of NTAL are correlated with decreased and delayed mobilization of Ca(2+) after TREM-1 triggering. Most importantly, we demonstrate that NTAL acts as a negative regulator of TNF-alpha and IL-8 production after stimulation via TREM-1. Our results show that activation signals delivered via DAP12 can be counterbalanced by the adaptor NTAL, identifying NTAL as gatekeeper of TREM-1/DAP12-induced signaling in myeloid cells.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adaptor Proteins, Signal Transducing / immunology*
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Adaptor Proteins, Signal Transducing / metabolism
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Animals
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Calcium Signaling / drug effects
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Calcium Signaling / immunology
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Gene Expression Regulation / drug effects
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Gene Expression Regulation / immunology
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Humans
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Inflammation / immunology
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Inflammation / metabolism
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Interleukin-8 / biosynthesis
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Interleukin-8 / immunology*
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Lipopolysaccharides / pharmacology
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MAP Kinase Signaling System / drug effects
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MAP Kinase Signaling System / immunology
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Membrane Glycoproteins / immunology*
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Membrane Glycoproteins / metabolism
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Membrane Proteins
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Mice
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Mitogen-Activated Protein Kinase 1 / immunology
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Mitogen-Activated Protein Kinase 1 / metabolism
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Mitogen-Activated Protein Kinase 3 / immunology
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Mitogen-Activated Protein Kinase 3 / metabolism
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Myeloid Cells / immunology*
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Myeloid Cells / metabolism
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Phosphorylation / drug effects
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Protein Processing, Post-Translational / drug effects
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Protein Processing, Post-Translational / immunology
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RNA Interference / immunology
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Receptors, Immunologic / immunology*
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Receptors, Immunologic / metabolism
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Triggering Receptor Expressed on Myeloid Cells-1
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Tumor Necrosis Factor-alpha / biosynthesis
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Tumor Necrosis Factor-alpha / immunology*
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U937 Cells
Substances
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Adaptor Proteins, Signal Transducing
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CXCL8 protein, human
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Interleukin-8
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LAT2 protein, human
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Lipopolysaccharides
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Membrane Glycoproteins
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Membrane Proteins
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Receptors, Immunologic
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TREM1 protein, human
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TYROBP protein, human
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Triggering Receptor Expressed on Myeloid Cells-1
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Tumor Necrosis Factor-alpha
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Mitogen-Activated Protein Kinase 1
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Mitogen-Activated Protein Kinase 3