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 TNFαdependent 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 ADS3862387LYV and VSG4052406LVQ, 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.
|Number of pages||17|
|Journal||Journal of Biological Chemistry|
|Publication status||Published - 2020 Feb 21|
Bibliographical noteFunding Information:
1Supported by University of British Columbia (UBC) 4-year doctoral fellow-ship, CIHR Vanier Canada graduate scholarship, a Centre for Blood Research graduate award, and a Vancouver Coastal Health Research Insti-tute (VCHRI)-CIHR-UBC MD/Ph.D. studentship.
This work was supported by Canadian Institutes of Health Research (CIHR) Foundation Grant FDN-148408 (to C. M. O.), CIHR Grant MOP-111055 (to C. M. O. and G. S. B.), Canada Foundation for Innovation Grant 31059 (to C. M. O.), and the Michael Smith Foundation for Health Research to estab-lish the British Columbia Proteomics Network Grant IN-NPG-00105 (to C. M. O.). The authors declare that they have no conflicts of interest with the contents of this article.
© 2020 Jobin et al.
All Science Journal Classification (ASJC) codes
- Molecular Biology
- Cell Biology