The Coupling of 5-Oxo-Eicosanoid Receptors to Heterotrimeric G Proteins

Abstract

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.

Indomethacin Causes Prostaglandin D2-like and Eotaxin-like Selective Responses in Eosinophils and Basophils

“…However, in primary human eosinophils, we observed that neither PGD 2 nor indomethacin responses were inhibited by PTX under conditions where this toxin completely inhibited eotaxin/CCL11-induced eosinophil shape change. These data suggest that CRTH2 in eosinophils may perhaps be coupled, at least in part, to the PTX-resistant G protein G␣ q/11 which is also involved in eosinophil chemotactic responses to other ligands, although interpretation of PTX-dependence in investigation of agonist-mediated responses must be carried out with caution (50). An alternative hypothesis, that the actions of both indomethacin and PGD 2 on eosinophils are mediated predominantly via the PTX-resistant DP receptor rather than CRTH2, is unlikely, given the published specificity of indomethacin and the previous data on the selective roles of CRTH2 in mediating eosinophil PGD 2 responses (26 -28, 36).…”

Identification of a Novel Human Eicosanoid Receptor Coupled to Gi/o

“…This eicosanoid is known as a potent chemotactic factor of eosinophils and neutrophils (37)(38)(39)(40). O'Flaherty et al (41,42), and O'Flaherty and Rossi (43) had revealed that the chemotactic activity would be mediated through a pertussis toxin-sensitive GPCR. As a separate line of interesting studies on 5-oxo-ETE and the derivatives, Ghosh and Myers (44,45) had identified 5-oxo-ETE and 5-HETE as mitogenic as well as anti-apoptotic factors in prostate cancer cells.…”

Human Neutrophils Convert the Sebum-derived Polyunsaturated Fatty Acid Sebaleic Acid to a Potent Granulocyte Chemoattractant

“…The biological actions of this compound are mediated by the highly selective OXE receptor (10,11), which is a member of the G protein-coupled receptor family (12)(13)(14). The objective of the current study was to determine whether sebaleic acid is a substrate for the 5-LO pathway and whether it can be converted to biologically active proinflammatory products that could potentially be involved in attracting granulocytes to the skin.…”