title: 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.
abstract: 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.
authors: School of Life Sciences and Biotechnology, Kyungpook National University, Daegu,             Department of Pharmacology, Brain Science and Engineering Institute, School of Medicine, Kyungpook National University, Daegu, Korea.
authors: Eun-Ju
authors: EJ
authors: Kim
authors: Sang-Min
authors: SM
authors: Lee
authors: Kyoungho
authors: K
authors: Suk
authors: Won-Ha
authors: WH
authors: Lee
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism*; D015703:Antigens, CD / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D006801:Humans; D008024:Ligands; D008262:Macrophage Activation; D009000:Monocytes / Q000276:immunology* / Q000378:metabolism*; D053594:Myeloid Differentiation Factor 88 / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11 / Q000378:metabolism*; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6 / Q000378:metabolism*; D011971:Receptors, Immunologic / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D051196:Toll-Like Receptor 3 / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000378:metabolism; D051217:Toll-Like Receptor 9 / Q000378:metabolism; D051193:Toll-Like Receptors / Q000378:metabolism*; D020298:U937 Cells
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D015703:Antigens, CD; C515070:CD300A protein, human; C519443:CD300LF protein, human; D008024:Ligands; C507779:MYD88 protein, human; D053594:Myeloid Differentiation Factor 88; D010446:Peptide Fragments; D011971:Receptors, Immunologic; C470409:TICAM1 protein, human; C495344:TLR3 protein, human; C495345:TLR4 protein, human; C495371:TLR9 protein, human; D051196:Toll-Like Receptor 3; D051197:Toll-Like Receptor 4; D051217:Toll-Like Receptor 9; D051193:Toll-Like Receptors; C516724:PTPN11 protein, human; C509249:PTPN6 protein, human; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6