title: Characterization of prostaglandin and thromboxane receptors expressed on a megakaryoblastic leukemia cell line, MEG-01s.
abstract: MEG-01s, an established human megakaryoblastic leukemia cell line, exhibited specific high-affinity binding sites for [3H]iloprost, a stable prostaglandin (PG) I2 analogue, for [3H]SQ-29548, a stable thromboxane (TX) A2 antagonist and, for [3H]PGE2/PGE1, but not for [3H]PGD2. In the MEG-01s cells, iloprost/PGI2, or PGE1 stimulated cAMP production with ED50 values practically identical to the IC50 values for the [3H] iloprost binding. STA2 and U46619, TXA2/PGH2 agonists, PGE2/PGE1, iloprost/PGI2, and thrombin elevated the intracellular concentrations of Ca2+ ([Ca2+]i), as determined by Fura-2 fluorescence signals. Elevation of [Ca2+]i by PGE2/PGE1 and iloprost, but not that by TX-agonists or thrombin, was totally dependent on the presence of extracellular Ca2+. This effect by PGE2/PGE1 was partially inhibited by prior treatment of the cells with islet-activating protein (IAP), while that by TX-agonists or by PGI2/iloprost was not affected. We tentatively conclude from these results that: (1) MEG-01s cells express (a) PGI2/PGE1 receptor(s) coupled to adenylate cyclase and Ca2+ influx, a TXA2/PGH2 receptor coupled to the phosphatidylinositol-turnover-Ca2+ system, and the PGE2/PGE1 receptor coupled to Ca2+ influx; (2) the receptors for TXA2/PGH2 and iloprost and those for PGE2/PGE1 and thrombin are coupled to IAP-insensitive and IAP-sensitive GTP-binding proteins, respectively, and function in a different manner to elevate [Ca2+]i. Thus, the MEG-01s cell line is a pertinent model for studying eicosanoid receptor-mediated signal transduction in platelet/megakaryocyte systems.
authors.affiliation: First Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Watanabe
authors.forename: Y
authors.initials: Y
authors.lastname: Yatomi
authors.forename: S
authors.initials: S
authors.lastname: Sunaga
authors.forename: I
authors.initials: I
authors.lastname: Miki
authors.forename: A
authors.initials: A
authors.lastname: Ishii
authors.forename: A
authors.initials: A
authors.lastname: Nakao
authors.forename: M
authors.initials: M
authors.lastname: Higashihara
authors.forename: Y
authors.initials: Y
authors.lastname: Seyama
authors.forename: M
authors.initials: M
authors.lastname: Ogura
authors.forename: H
authors.initials: H
authors.lastname: Saito
mesh_terms: D037361:Adenylate Cyclase Toxin; D000527:Alprostadil / Q000378:metabolism / Q000494:pharmacology; D001792:Blood Platelets / Q000378:metabolism; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002118:Calcium / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D015232:Dinoprostone / Q000378:metabolism / Q000494:pharmacology; D011464:Epoprostenol / Q000494:pharmacology; D005231:Fatty Acids, Unsaturated; D006801:Humans; D006834:Hydrazines / Q000378:metabolism; D016285:Iloprost / Q000378:metabolism / Q000494:pharmacology; D007947:Leukemia, Megakaryoblastic, Acute / Q000378:metabolism*; D037342:Pertussis Toxin; D015230:Prostaglandin D2 / Q000378:metabolism; D011460:Prostaglandins F / Q000378:metabolism; D011982:Receptors, Prostaglandin / Q000378:metabolism*; D017482:Receptors, Thromboxane; D013917:Thrombin / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D037361:Adenylate Cyclase Toxin; D019086:Bridged Bicyclo Compounds, Heterocyclic; D005231:Fatty Acids, Unsaturated; D006834:Hydrazines; D011460:Prostaglandins F; D011982:Receptors, Prostaglandin; D017482:Receptors, Thromboxane; D010566:Virulence Factors, Bordetella; C045749:SQ 29548; D011464:Epoprostenol; D000242:Cyclic AMP; D037342:Pertussis Toxin; D013917:Thrombin; D000527:Alprostadil; D006152:Cyclic GMP; D016285:Iloprost; D015232:Dinoprostone; D015230:Prostaglandin D2; D002118:Calcium; C100006:prostaglandin F1