The T cell-directed CC chemokine TARC is a highly specific biological ligand for CC chemokine receptor 4.
Thymus and activation-regulated chemokine (TARC) is a recently identified CC chemokine that is expressed constitutively in thymus and transiently in stimulated peripheral blood mononuclear cells. TARC functions as a selective chemoattractant for T cells that express a class of receptors binding TARC with high affinity and specificity. To identify the receptor for TARC, we produced TARC as a fusion protein with secreted alkaline phosphatase (SEAP) and used it for specific binding. By stably transfecting five orphan receptors and five known CC chemokine receptors (CCR1 to -5) into K562 cells, we found that TARC-SEAP bound selectively to cells expressing CCR4. TARC-SEAP also bound to K562 cells stably expressing CCR4 with a high affinity (Kd = 0.5 nM). Only TARC and not five other CC chemokines (MCP-1 (monocyte chemoattractant protein-1), RANTES (regulated upon activation, normal T cells expressed and secreted), MIP-1alpha (macrophage inflammatory protein-1alpha), MIP-1beta, and LARC (liver and activation-regulated chemokine)) competed with TARC-SEAP for binding to CCR4. TARC but not RANTES or MIP-1alpha induced migration and calcium mobilization in 293/EBNA-1 cells stably expressing CCR4. K562 cells stably expressing CCR4 also responded to TARC in a calcium mobilization assay. Northern blot analysis revealed that CCR4 mRNA was expressed strongly in human T cell lines and peripheral blood T cells but not in B cells, natural killer cells, monocytes, or granulocytes. Taken together, TARC is a specific functional ligand for CCR4, and CCR4 is the specific receptor for TARC selectively expressed on T cells.
Imai
T
T
Shionogi Institute for Medical Science, 2-5-1 Mishima, Settsu-shi, Osaka 566, Japan. toshio.imai@shionogi.co.jp
Baba
M
M
Nishimura
M
M
Kakizaki
M
M
Takagi
S
S
Yoshie
O
O
D000469:Alkaline Phosphatase / Q000096:biosynthesis; D001402:B-Lymphocytes / Q000276:immunology; D001667:Binding, Competitive; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D054414:Chemokine CCL17; D018946:Chemokine CCL5 / Q000494:pharmacology; D018925:Chemokines / Q000378:metabolism* / Q000494:pharmacology*; D019742:Chemokines, CC; D002633:Chemotaxis; D006801:Humans; D007700:Kinetics; D016133:Polymerase Chain Reaction; D054398:Receptors, CCR4; D019707:Receptors, Chemokine; D018121:Receptors, Cytokine / Q000096:biosynthesis / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology*; D014162:Transfection; D014407:Tumor Cells, Cultured
C106230:CCL17 protein, human; C515354:CCR4 protein, human; D054414:Chemokine CCL17; D018946:Chemokine CCL5; D018925:Chemokines; D019742:Chemokines, CC; D054398:Receptors, CCR4; D019707:Receptors, Chemokine; D018121:Receptors, Cytokine; D011993:Recombinant Fusion Proteins; D000469:Alkaline Phosphatase; D002118:Calcium