Direct relationship between intracellular calcium mobilization and phospholipase D activation in prostaglandin E-stimulated human erythroleukemia cells.
The relationship between calcium mobilization and phospholipase D (PLD) activation in response to E-series prostaglandins (PGEs) was investigated in human erythroleukemia cells. Intracellular free Ca2+ concentration ([Ca2+]i) was increased by PGE1 and PGE2 over the same concentration range at which PLD activation was seen. Pretreatment of cells with pertussis toxin greatly inhibited the PGE-stimulated increase in [Ca2+]i, implying that a G protein participates in the PGE receptor signaling process. The peak level and also the plateau level of Ca2+ mobilization stimulated by these prostaglandins were markedly decreased in Ca(2+)-depleted medium, indicating that both extracellular and intracellular Ca2+ stores contribute to the changes in [Ca2+]i. Likewise, activation of PLD by PGE1 and PGE2 was abolished by pertussis toxin pretreatment or incubation in Ca(2+)-depleted medium. U73122, a putative phospholipase C inhibitor, blocked both Ca2+ mobilization and PLD activation in PGE-stimulated cells. Furthermore, the intracellular loading of BAPTA, a Ca2+ chelator, inhibited both Ca2+ mobilization and PLD activation by PGE1 and PGE2 in a similar dose-dependent manner. Simultaneous measurement of [Ca2+]i and PLD activity in the same cell samples indicated that PLD activity increases as a function of [Ca2+]i in a similar fashion in cells stimulated either by PGEs or by the calcium ionophore ionomycin. Taken together, these findings suggest that a rise in [Ca2+]i is necessary for PGE-stimulated PLD activity in human erythroleukemia cells.
Wu
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Department of Pharmacology, University of Missouri, Columbia 65212.
James-Kracke
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Halenda
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D000527:Alprostadil / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002614:Chelating Agents / Q000494:pharmacology; D000242:Cyclic AMP / Q000096:biosynthesis; D015232:Dinoprostone / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D004963:Estrenes / Q000494:pharmacology; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology; D004915:Leukemia, Erythroblastic, Acute / Q000378:metabolism*; D037342:Pertussis Toxin; D010739:Phospholipase D / Q000378:metabolism*; D011458:Prostaglandins E / Q000494:pharmacology*; D011760:Pyrrolidinones / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D002614:Chelating Agents; D004963:Estrenes; D011458:Prostaglandins E; D011760:Pyrrolidinones; D010566:Virulence Factors, Bordetella; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D015759:Ionomycin; D000242:Cyclic AMP; D037342:Pertussis Toxin; D010738:Type C Phospholipases; D010739:Phospholipase D; D000527:Alprostadil; D015232:Dinoprostone; D002118:Calcium