5-Hydroxy-and 5-oxo-eicosatetraenoate (5-HETE and 5-oxoETE) activate polymorphonuclear neutrophils (PMNs) through a common, receptor-like recognition system. To define this system, we examined the interaction of these eicosanoids with human PMNs. -20). The data imply that 5-HETE acts through a unique recognition system. However, evidence relating this system to receptor-like binding sites has proven difficult to obtain. Although PMNs process 5-HETE through various metabolic pathways (6 -8, 12, 21-23), one route, esterification, has presented an obstacle for receptor studies. The reaction occurs in PMNs or their isolated plasma membranes at 4 or 37°C and results in the acylation of 5-[ 3 H]HETE to membrane glycerolipids: PMNs and plasmalemma accumulate 5-HETE almost exclusively in esterified form without evidence of receptor binding (10, 21). Because esterification is a ubiquitous means for processing fatty acids, other cell types are apt also to esterify 5-HETE and thereby obscure the receptor binding of the compound. Despite this difficulty, however, putative receptors for 5-HETE merit study. PMNs, eosinophils, and monocytes dehydrogenate 5-HETE to 5-oxoETE (6,(13)(14)(15)25). 5-OxoETE is ϳ10-fold stronger than 5-HETE in stimulating PMNs and monocytes (9 -13, 19). It is even more active on eosinophils (14 -17), eliciting the chemotaxis response of this cell at concentrations 10,000-, 1000-, and Ͼ10-fold lower than LTB 4 , 5-HETE, or other chemotactic factors, respectively (18). 5-OxoETE down-regulates these cells to itself and 5-HETE but not to LTB 4 or other stimuli (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19). Possibly, therefore, putative 5-HETE receptors and their preferred ligand, 5-oxoETE, participate in recruiting eosinophils to sites of allergic reactivity (18). These receptors might also mediate the remodeling of bone, growth of prostate cancer cells, contraction of uterus, and transmission of nerve impulses (26 -29). We report here on studies identifying PMN membrane sites that bind 5-oxoETE with the specificity and other properties anticipated for receptors of the 5-oxo class of eicosanoids. EXPERIMENTAL PROCEDURESBuffers and Other Reagents-Cells and membranes were suspended in a modified Hanks' balanced salt solution (9) containing 1.4 mM CaCl 2 and 0.7 mM MgCl 2 unless indicated otherwise. Stimuli, glycerolipids, and other reagents were obtained commercially (8, 9). Triacsin C was purchased from Biomol (Plymouth Meeting, PA).

5-Oxo-eicosatetraenoic acid (5-oxoETE) stimulated human neutrophil (PMN) and eosinophil chemotaxis, PMN hexose uptake, and PMN membrane GTP/GDP exchange. Pertussis toxin (PT), a blocker of heterotrimeric G proteins (GP), completely inhibited these responses, but proved far less effective on the same responses when elicited by leukotriene B4, C5a, FMLP, platelet-activating factor, IL-8, or RANTES chemotactic factors. 5-OxoETE also specifically bound to the membrane preparations that conducted GTP/GDP exchange. This binding was down-regulated by GTPγS, but not ADPγS, and displaced by 5-oxoETE analogues, but not by leukotriene B4, lipoxin A4, or lipoxin B4. Finally, PMN expressed PT-sensitive GP αι2 and PT-resistant GP αq/11- and α13-chains; eosinophils expressed only αi2 and αq/11. We conclude that 5-oxoETE activates granulocytes through a unique receptor that couples preferentially to PT-sensitive GP. The strict dependency of this putative receptor on PT-sensitive GP may underlie the limited actions of 5-oxoETE, compared with other CF, and help clarify the complex relations between receptors, GP, cell signals, and cell responses.