IDENTIFICATION OF A HUMAN CDNA-ENCODING A FUNCTIONAL HIGH-AFFINITY LIPOXIN A(4) RECEPTOR

Lipoxin A(4) (LXA(4)) triggers selective responses with human neutrophils that are pertussis toxin sensitive and binds to high affinity receptors (K-d = 0.5 +/- 0.3 nM) that are modulated by stable analogues of guanosine 5'-triphosphate (GTP). Here, we characterized [11,12-H-3]LXA(4) specific binding with neutrophil granule and plasma membranes, which each display high affinity binding sites (K-d 0.7 +/- 0.1 nM) that were regulated by GTP gamma S. Since functional LXA(4) receptors are inducible in HL-60 cells, we tested orphan cDNAs encoding 7-transmembrane region receptors cloned from these cells for their ability to bind and signal with LXA(4). Chinese hamster ovary (CHO) cells transfected with the orphan receptor cDNA (pINF114) displayed specific H-3-LXA(4) high affinity binding (1.7 nM). When displacement of LXA(4) binding with pINF114-transfected CHO cells was tested with other eicosanoids, including LXB(4), leukotriene D-4 (LTD(4)), LTB(4), or prostaglandin E(2), only LTD(4) competed with LXA(4), giving a K-i of 80 nM. In transfected CHO cells, LXA(4) also stimulated GTPase activity and provoked the release of esterified arachidonate, which proved to be pertussis toxin sensitive. These results indicate that pINF114 cDNA encodes a 7-transmembrane region-containing protein that displays high affinity for H-3-LXA(4) and transmits LXA(4)-induced signals. Together, they suggest that the encoded protein is a candidate for a LXA(4) receptor in myeloid cells.