Abstract
Tyrosyl-tRNA synthetase ligates tyrosine to its cognate tRNA in the cytoplasm, but it can also be secreted through a noncanonical pathway. We found that extracellular tyrosyl-tRNA synthetase (YRS) exhibited proinflammatory activities. In addition to acting as a monocyte/macrophage chemoattractant, YRS initiated signaling through Toll-like receptor 2 (TLR2) resulting in NF-κB activation and release of tumor necrosis factor α (TNFα) and multiple chemokines, including MIP-1α/β, CXCL8 (IL8), and CXCL1 (KC) from THP1 monocyte and peripheral blood mononuclear cell-derived macrophages. Furthermore, YRS up-regulated matrix metalloproteinase (MMP) activity in a TNFα-dependent manner in M0 macrophages. Because MMPs process a variety of intracellular proteins that also exhibit extracellular moonlighting functions, we profiled 10 MMPs for YRS cleavage and identified 55 cleavage sites by amino-terminal oriented mass spectrometry of substrates (ATOMS) positional proteomics and Edman degradation. Stable proteoforms resulted from cleavages near the start of the YRS C-terminal EMAPII domain. All of the MMPs tested cleaved at ADS386↓387LYV and VSG405↓406LVQ, generating 43- and 45-kDa fragments. The highest catalytic efficiency for YRS was demonstrated by MMP7, which is highly expressed by monocytes and macrophages, and by neutrophil-specific MMP8. MMP-cleaved YRS enhanced TLR2 signaling, increased TNFα secretion from macrophages, and amplified monocyte/macrophage chemotaxis compared with unprocessed YRS. The cleavage of YRS by MMP8, but not MMP7, was inhibited by tyrosine, a substrate of the YRS aminoacylation reaction. Overall, the proinflammatory activity of YRS is enhanced by MMP cleavage, which we suggest forms a feed-forward mechanism to promote inflammation.
Keywords:
aminoacyl tRNA synthetase; inflammation; innate immunity; macrophage; matrix metalloproteinase (MMP); moonlighting proteins; multifunctional protein; proteolysis; toll-like receptor (TLR).
© 2020 Jobin et al.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Chemokines / metabolism
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Chemotaxis
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Enzyme Stability
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Extracellular Space / enzymology*
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Humans
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Inflammation Mediators / metabolism*
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Macrophages / metabolism
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Matrix Metalloproteinases / metabolism*
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Models, Biological
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Monocytes / metabolism
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NF-kappa B / metabolism
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Signal Transduction
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Substrate Specificity
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THP-1 Cells
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Toll-Like Receptor 2 / metabolism
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Tumor Necrosis Factor-alpha / metabolism
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Tyrosine / metabolism
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Tyrosine-tRNA Ligase / metabolism*
Substances
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Chemokines
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Inflammation Mediators
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NF-kappa B
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Toll-Like Receptor 2
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Tumor Necrosis Factor-alpha
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Tyrosine
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Matrix Metalloproteinases
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Tyrosine-tRNA Ligase
Associated data
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PDB/1N3L
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PDB/4QBT
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PDB/1NTG