CDB15:0000210 CCL19 — CCR7

ABSTRACT: By searching the expressed sequence tag (EST) data base, we identified partial cDNA sequences encoding a novel human CC chemokine. We determined the complete cDNA sequence that encodes a highly basic polypeptide of a total 98 amino acids with 20 to 30% identity to other human CC chemokines. We termed this novel chemokine from EBI1-Ligand Chemokine as ELC (see below). The ELC mRNA was most strongly expressed in the thymus and lymph nodes. Recombinant ELC protein was expressed as a fusion protein with the Flag tag (ELC-Flag). For receptor-binding assays, recombinant ELC protein fused with the secreted form of alkaline phosphatase (SEAP) was used. By stably expressing five CC chemokine receptors (CCR1 to 5) and five orphan receptors, ELC-SEAP was found to bind specifically to an orphan receptor EBI1. Only ELC-Flag, but not MCP-1, MCP-2, MCP-3, eotaxin, MIP-1alpha, MIP-1beta, RANTES (regulated on activation normal T cell expressed and secreted), thymus and activation-regulated chemokine (TARC), or liver and activation-regulated chemokine (LARC), competed with ELC-SEAP for EBI1. ELC-Flag-induced transient calcium mobilization and chemotactic responses in EBI1-transfected cells. ELC-Flag also induced chemotaxis in HUT78 cells expressing endogenous EBI1 at high levels. By somatic hybrid and radiation hybrid analyses, the gene for ELC (SCYA19) was mapped to chromosome 9p13 instead of chromosome 17q11.2 where the genes for CC chemokines are clustered. Taken together, ELC is a highly specific ligand for EBI1, which is known to be expressed in activated B and T lymphocytes and strongly up-regulated in B cells infected with Epstein-Barr virus and T cells infected with herpesvirus 6 or 7. ELC and EBI1 may thus play roles in migration and homing of normal lymphocytes, as well as in pathophysiology of lymphocytes infected with these herpesviruses. We propose EBI1 to be designated as CCR7.

ABSTRACT: Secondary Lymphoid-tissue Chemokine (SLC) is a recently identified CC chemokine that is constitutively expressed in various lymphoid tissues and is a potent and specific chemoattractant for lymphocytes. The SLC gene and the gene encoding another lymphocyte-specific CC chemokine, EBI1-ligand chemokine (ELC), form a mini-cluster at human chromosome 9p13. Here, we show that SLC is a high affinity functional ligand for chemokine receptor 7 (CCR7) that is expressed on T and B lymphocytes and a known receptor for ELC. SLC induced a vigorous calcium mobilization in murine L1.2 cells stably expressing human CCR7. SLC tagged with the secreted form of alkaline phosphatase (SLC-SEAP) showed specific binding to CCR7 that was fully competed by SLC with an IC50 of 0.5 nM. SLC also induced a vigorous chemotactic response in CCR7-expressing L1.2 cells with a typical bell-shaped dose-response curve and a maximal migration at 10 nM. When assessed using CCR7-transfected L1.2 cells, SLC and ELC were essentially equivalent in terms of cross desensitization in calcium mobilization via CCR7, cross-competition in binding to CCR7, and induction of chemotaxis via CCR7. SLC and ELC were also shown to fully share receptors expressed on cultured normal T cells known to express CCR7. Notably, however, SLC was somehow less efficient in cross-desensitization against ELC in calcium mobilization and in cross-competition with ELC for binding when assessed using cultured normal T cells. Thus, SLC and ELC, even though sharing only 32% amino acid identity, constitute a genetically and functionally highly related subgroup of CC chemokines.