Differential expression of thromboxane A synthase and prostaglandin H synthase in megakaryocytic cell line.
We determined the expression of isoforms of prostaglandin H synthase (PGHS) and thromboxane A synthase (TXAS) in a human megakaryocyte cell line (MEG-01. The basal levels of full-length TXAS mRNA and the 60 kDa TXAS protein were high when compared to those of PGHS-1 and PGHS-2 in uninduced cells. Despite a high TXAS level, uninduced MEG-01 cells synthesized only a small amount of thromboxane A2 (TXA2) due to limited PGHS-1 or PGHS-2 expressions. Following PMA induction there was little change in TXAS. PGHS-2 mRNA was significantly increased at only 3 h of PMA treatment and the level declined rapidly, whereas PGHS-1 mRNA and protein levels were concordantly stimulated. Induction of PGHS-1 reached plateau on day 3 of PMA treatment. Analysis of arachidonate metabolism in cells induced by PMA for 3 and 5 days showed a high level of PGH2 synthesis which exceeded the TXAS capacity for TXA2 synthesis. Only traces of PGHS-2 mRNA and alternate-spliced TXAS mRNA were detected in human platelets. We conclude that TXAS and PGHS are differentially expressed in MEG-01 during PMA-induced differentiation.
D001483:Base Sequence; D001792:Blood Platelets; D015153:Blotting, Western; D002454:Cell Differentiation; D002460:Cell Line; D015777:Eicosanoids / Q000032:analysis; D006801:Humans; D007527:Isoenzymes / Q000096:biosynthesis; D008533:Megakaryocytes / Q000187:drug effects / Q000201:enzymology*; D008861:Microsomes; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D011863:Radioimmunoassay; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013928:Thromboxane A2 / Q000032:analysis; D013930:Thromboxane-A Synthase / Q000096:biosynthesis* / Q000235:genetics
D015777:Eicosanoids; D007527:Isoenzymes; D012333:RNA, Messenger; D013928:Thromboxane A2; D011451:Prostaglandin-Endoperoxide Synthases; D013930:Thromboxane-A Synthase; D013755:Tetradecanoylphorbol Acetate