CLONING AND CHARACTERIZATION OF A SPECIFIC RECEPTOR FOR THE NOVEL CC-CHEMOKINE MIP-3-ALPHA FROM LUNG DENDRITIC CELLS

Dendritic cells are potent antigen-presenting cells involved in the in itiation of immune responses. The trafficking of these cells to tissue s and lymph nodes is mediated by members of the chemokine family. Rece ntly, a novel CC chemokine known as MIP-3 alpha or liver and activatio n-regulated chemokine has been identified fi-om the EMBL/GenBank/DDBJ expressed sequence tag database. In the present study, we have shown t hat the messenger RNA for MIP-3 alpha is expressed predominantly in in flamed and mucosal tissues. MIP-3 alpha produced either synthetically or by human embryonic kidney 293 cells is chemotactic for CD34(+)-deri ved dendritic cells and T cells, but is inactive on monocytes and neut rophils. MIP-3 alpha was unable to displace the binding of specific CC or CXC chemokines to stable cell lines expressing their respective hi gh affinity receptors, namely CCR1-5 and CXCR1 and CXCR2, suggesting t hat MIP-3 alpha acts through a novel CC chemokine receptor. Therefore, we used degenerate oligonucleotide-based reverse transcriptase PCR to identify candidate MIP-3 alpha receptors in lung dendritic cells. Our results show that the orphan receptor known as GCY-4, CKRL-3, or STRL -22 is a specific receptor for MIP-3 alpha, and that its activation le ads to pertussis toxin-sensitive and phospholipase C-dependent intrace llular Ca2+ mobilization when it is expressed in HEK 293 cells.