title: Regulation of the human prostanoid TPalpha and TPbeta receptor isoforms mediated through activation of the EP(1) and IP receptors.
abstract: The intermolecular cross-regulation mediated by the prostanoid IP-receptor (IP)/EP(1) receptor (EP(1)) agonists PGI(2) and 17 phenyl trinor PGE(2) on TP receptor (TP) signalling within platelets was compared to that which occurs to the individual TPalpha and TPbeta receptors over-expressed in human embryonic kidney (HEK) 293 cells. Ligand mediated TP receptor activation was monitored by analysing mobilization of intracellular calcium ([Ca(2+)](i)) following stimulation with the selective thromboxane (TX) A(2) mimetic U46619. Consistent with previous studies, in platelets, PGI(2) acting through endogenous IP receptors completely inhibited U46619-mediated TP receptor signalling in a protein kinase (PK) A-dependent, PKC-independent manner. In HEK 293 cells, PGI(2), acting through endogenous AH6809 sensitive EP(1) rather than IP receptors, and the selective EP(1) receptor agonist 17 phenyl trinor PGE(2) antagonized U46619-mediated signalling by both TPalpha and TPbeta receptors in a PKC-dependent, PKA-independent manner. The maximum response induced by either ligand was significantly (P<0.005) greater for the TPalpha receptor than the TPbeta receptor, pointing to possible physiologic differences between the TP isoforms, although the potency of each ligand was similar for both TP receptors. TP(Delta328), a truncated variant of TP receptor lacking the C-tail sequences unique to TPalpha or TPbeta receptors, was not sensitive to EP(1) receptor-mediated regulation by PGI(2) or 17 phenyl trinor PGE(2) In conclusion, these data confirm that TPalpha and TPbeta receptors are subject to cross regulation by EP(1) receptor signalling in HEK 293 cells mediated by PKC at sites unique to the individual TP receptors and that TPalpha receptor responses are significantly more reduced by EP(1) receptor regulation than those of the TPbeta receptor.
authors.affiliation: Department of Biochemistry, Conway Institute of Biomolecular and Biomedical Research, Merville House, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: M T
authors.initials: MT
authors.lastname: Walsh
authors.forename: B T
authors.initials: BT
authors.lastname: Kinsella
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D015232:Dinoprostone / Q000494:pharmacology; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D011464:Epoprostenol / Q000494:pharmacology; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D008301:Maleimides / Q000494:pharmacology; D011448:Prostaglandin Antagonists / Q000494:pharmacology; D011453:Prostaglandins / Q000378:metabolism; D020033:Protein Isoforms / Q000378:metabolism; D044006:Receptors, Epoprostenol; D011982:Receptors, Prostaglandin / Q000378:metabolism*; D018078:Receptors, Prostaglandin E / Q000378:metabolism*; D058306:Receptors, Prostaglandin E, EP1 Subtype; D017482:Receptors, Thromboxane / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015398:Signal Transduction; D013449:Sulfonamides; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014966:Xanthenes / Q000494:pharmacology; D044004:Xanthones
chemical_list: D004791:Enzyme Inhibitors; D007211:Indoles; D007546:Isoquinolines; D008301:Maleimides; C545635:PTGER1 protein, human; C113936:PTGIR protein, human; D011448:Prostaglandin Antagonists; D011453:Prostaglandins; D020033:Protein Isoforms; D044006:Receptors, Epoprostenol; D011982:Receptors, Prostaglandin; D018078:Receptors, Prostaglandin E; D058306:Receptors, Prostaglandin E, EP1 Subtype; D017482:Receptors, Thromboxane; D013449:Sulfonamides; D014662:Vasoconstrictor Agents; D014966:Xanthenes; D044004:Xanthones; C053876:6-isopropoxy-9-oxoxanthene-2-carboxylic acid; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D011464:Epoprostenol; D015232:Dinoprostone; C070515:bisindolylmaleimide I; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; D002118:Calcium