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

Lipoxin A(4) (LXA(4)) triggers selective responses with human neutroph ils that are pertussis toxin sensitive and binds to high affinity rece ptors (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]LX A(4) specific binding with neutrophil granule and plasma membranes, wh ich 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-transmembr ane 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 w ith pINF114-transfected CHO cells was tested with other eicosanoids, i ncluding 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 transf ected CHO cells, LXA(4) also stimulated GTPase activity and provoked t he release of esterified arachidonate, which proved to be pertussis to xin sensitive. These results indicate that pINF114 cDNA encodes a 7-tr ansmembrane region-containing protein that displays high affinity for H-3-LXA(4) and transmits LXA(4)-induced signals. Together, they sugges t that the encoded protein is a candidate for a LXA(4) receptor in mye loid cells.