Identification of a novel human eicosanoid receptor coupled to Gi/o

We have conducted an in silico data base search for and cloned a novel G-protein-coupled receptor (GPCR) named TG1019. Dot and Northern blotting analyses showed that transcripts of the novel GPCR were expressed in various tissues except brain, and the expression was more intense in liver, kidney, peripheral leukocyte, lung, and spleen than in other tissues. By GTPgammaS binding assay using the TG1019-Galpha(il)-protein fusion expressed in insect cells, eicosanoids, and polyunsaturated fatty acids such as 5-oxo-6E,8Z,11Z,14Z-eicosatetraenoic acid (5-oxo-ETE), 5(S)-hydroperoxy-6E,8Z, 11Z,14Z-eicosatetraenoic acid, and arachidonic acid were identified to exhibit agonistic activities against TG1019. 5-oxo-ETE was the most potent to enhance the specific binding by 6-fold at a maximum effect dose of submicromolar to micromolar order with an ED50 value of 5.7 nm. Conversely, polyunsaturated fatty acids such as docosahexaenoic acid and eicosapentaenoic acid showed antagonistic activities against TG1019. In Chinese hamster ovary cells transiently expressing TG1019, the forskolin-stimulated production of cAMP was inhibited up to similar to70% by 5-oxo-ETE, with an IC50 value of 33 nm. This inhibition was sensitive to pretreatment of the cells with pertussis toxin.