Thyrotropin-releasing hormone increases phospholipase D activity through stimulation of protein kinase C in GH3 cells.
Activation of phospholipase D was investigated after treatment of GH3 cells with thyrotropin-releasing hormone. Thyrotropin-releasing hormone treatment resulted in both time- and dose-dependent increases of phospholipase D activity, translocation of protein kinase C-alpha and -beta I isozymes from cytosol to membrane within 30 min, and approx 43-fold increase of phosphatidylinositol-specific phospholipase C activity. Intracellular calcium concentration was rapidly increased and diacyglycerol level remained high up to 3 h after the treatment. Pretreatment of the cells with U73122, a potent inhibitor of phosphatidylinositol-specific phospholipase C, inhibited thyrotropin-releasing hormone-induced phospholipase D activation. Protein kinase C activity was down-regulated by pretreatment of the GH3 cells with either protein kinase C inhibitors (RO320432, GF109203X) or preincubation of the cells with phorbol myristrate acetate (500 nM) for 24 h. This treatment largely abolished the thyrotropin-releasing hormone-induced activation of phospholipase D, thus further confirming the involvement of protein kinase C in the activation. These results suggest that thyrotropin-releasing hormone-induced phospholipase D activation may be due to phosphatidylinositol-specific phospholipase C, and activation of protein kinase C isozymes is responsible for this stimulation.
Kim
Dong-Sun
DS
Department of Internal Medicine, College of Medicine, Hanyang University, Sungdong-Gu, Seoul 133-791, Korea.
Yoon
Mee-Sup
MS
Kim
Tae-Wha
TW
Han
Joong-Soo
JS
D000818:Animals; D002118:Calcium / Q000378:metabolism; D045744:Cell Line, Tumor; D004075:Diglycerides / Q000378:metabolism; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D007527:Isoenzymes; D008301:Maleimides / Q000494:pharmacology; D010739:Phospholipase D / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D021381:Protein Transport; D011758:Pyrroles / Q000494:pharmacology; D011760:Pyrrolidinones / Q000494:pharmacology; D051381:Rats; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology*
D004075:Diglycerides; D004791:Enzyme Inhibitors; D004963:Estrenes; D007211:Indoles; D007527:Isoenzymes; D008301:Maleimides; D011758:Pyrroles; D011760:Pyrrolidinones; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; C085989:Ro 32-0432; D013973:Thyrotropin-Releasing Hormone; D011493:Protein Kinase C; D010739:Phospholipase D; C070515:bisindolylmaleimide I; D002118:Calcium