title: Mastoparan-induced phosphatidylcholine hydrolysis by phospholipase D activation in human astrocytoma cells.
abstract: 1. The effect of mastoparan on phosphatidylcholine hydrolysis was examined in 1321N1 human astrocytoma cells. Mastoparan (3-30 microM) caused an accumulation of diacylglycerol (DG) and phosphatidic acd (PA) accompanied by choline release in a concentration- and time-dependent manner. 2. In the presence of 2% n-butanol, mastoparan (3-100 microM) induced phosphatidylbutanol (PBut) accumulation in a concentration- and time-dependent manner, suggesting that mastoparan activates phospholipase D (PLD). Propranolol (30-300 microM), a phosphatidate phosphohydrolase inhibitor, inhibited DG accumulation induced by mastoparan, supporting this idea. 3. Depletion of extracellular free calcium ion did not alter the effect of mastoparan on PLD activity. 4. A protein kinase C (PKC) inhibitor, calphostin C (1 microM), did not inhibit mastoparan-induce PLD activation but the ability of mastoparan to stimulate phospholipase D activity was decreased in the PKC down regulated cells. 5. PLD activity stimulated by mastoparan was not prevented by pretreatment of the cells with pertussis toxin (PT) or C3 ADP-ribosyltransferase. Furthermore, guanine nucleotides did not affect PLD activity stimulation by mastoparan in membrane preparations. 6. Mastoparan stimulated PLD in several cell lines such as RBL-2H3, RBL-1, HL-60, P388, endothelial cells, as well as 1321N1 human astrocytoma cells. 7. These results suggest that mastoparan induces phosphatidylcholine (PC) hydrolysis by activation of PLD, not by activation of phosphatidylcholine-specific phospholipase C (PC-PLC); mastoparan-induced PLD activation is not mediated by G proteins.
authors.affiliation: Department of Pharmaceutical Molecular Biology, Faculty of Pharmaceutical Sciences, Tohoku University, Sendai, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Mizuno
authors.forename: N
authors.initials: N
authors.lastname: Nakahata
authors.forename: Y
authors.initials: Y
authors.lastname: Ohizumi
mesh_terms: D000818:Animals; D001254:Astrocytoma / Q000201:enzymology / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D006868:Hydrolysis / Q000187:drug effects; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D010713:Phosphatidylcholines / Q000378:metabolism*; D010739:Phospholipase D / Q000378:metabolism*; D011433:Propranolol / Q000494:pharmacology; D013997:Time Factors; D014407:Tumor Cells, Cultured; D014862:Wasp Venoms / Q000494:pharmacology*
chemical_list: D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D010713:Phosphatidylcholines; D014862:Wasp Venoms; C037500:mastoparan; D011433:Propranolol; D010739:Phospholipase D