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CD300a and CD300f differentially regulate the MyD88 and TRIF‐mediated TLR signalling pathways through activation of SHP‐1 and/or SHP‐2 in human monocytic cell lines
Author(s) -
Kim EunJu,
Lee SangMin,
Suk Kyoungho,
Lee WonHa
Publication year - 2012
Publication title -
immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.297
H-Index - 133
eISSN - 1365-2567
pISSN - 0019-2805
DOI - 10.1111/j.1365-2567.2011.03528.x
Subject(s) - trif , microbiology and biotechnology , toll like receptor , signal transduction , protein tyrosine phosphatase , biology , ectopic expression , transfection , receptor , cell culture , innate immune system , biochemistry , genetics
Summary CD300a, a membrane protein expressed on myeloid lineages and specific subsets of CD4 + T cells, has been reported to have inhibitory activities in cellular activation. However, the role of CD300a in Toll‐like receptor (TLR) ‐mediated macrophage activation has not been investigated. The human monocytic cell lines THP‐1 and U937 were stimulated with various TLR ligands after triggering of CD300a with specific monoclonal antibody. Interestingly, CD300a blocked TLR4‐mediated and TLR9‐mediated expression of pro‐inflammatory mediators without affecting TLR3‐mediated events. In contrast, CD300f, another member of the CD300 family, blocked the activation of cells induced by all TLR ligands. A transient transfection assay using luciferase reporter gene under the regulation of nuclear factor‐κB binding sites indicated that co‐transfection of CD300f blocked reporter expression induced by over‐expression of both myeloid differentiation factor 88 (MyD88) and toll‐interleukin 1 receptor‐domain‐containing adapter‐inducing interferon‐β (TRIF), whereas CD300a blocked only MyD88‐induced events. Synthetic peptides representing immunoreceptor tyrosine‐based inhibitory motifs of CD300a or CD300f mimicked the differential inhibition patterns of their original molecules. The use of various signalling inhibitors and Western blotting analysis revealed that TLR9/MyD88‐mediated signalling was regulated mainly by SH2‐containing tyrosine phosphatase 1 (SHP‐1), which could be activated by CD300a or CD300f. In contrast, regulation of the TLR3/TRIF‐mediated pathway required the combined action of SHP‐1 and SHP‐2, which could be accomplished by CD300f but not CD300a. These data indicate that CD300a and CD300f regulate the MyD88 and TRIF‐mediated TLR signalling pathways through differential activation of SHP‐1 and SHP‐2.