title: Accumulation of ester- and ether-linked phosphatidates by HeLa cells in response to ionophore A23187 through activation of phospholipase D.
abstract: Phosphatidates seem to play an important role in the control of cell proliferation modified by ligands (M. Kaszkin et al. 1991, Cancer Res. 51, 4328-4335). In this study the potency of calcium ionophore A23187 to alter phosphatidate levels in HeLa cells as a model was studied in detail. HeLa cells prelabeled with [14C]arachidonic acid responded to calcium ionophore A23187 with a rapid accumulation of labeled 1,2-diacylglycerophosphate (acyl-PA) and 2-acyl-1-O-alkylglycerophosphate (alkyl-PA) with a first peak at 5 min and a second increase starting at 20-30 min. In cells prelabeled with [14C]oleic acid the ionophore mobilized relatively more of labeled acyl-PA. The total amount of phosphatidates mobilized was in the order of 0.2 micrograms/10(6) cells, i.e. an almost 10(-4)M concentration. The transphosphatidylation of labeled acyl- and alkyl-PA to 1-butanol in all cases showed that activation of phospholipase D had occurred. The reaction became detectable at 10(-6)M ionophore and was fully expressed at 10(-5)M. Butyl phosphatidate generated during 1 h treatment with ionophore amounted to approx. 0.5 nmol per 10(6) cells (i.e. 10(-4)M conc. within cells) as shown by the use of [14C]butanol. The 3-5-fold rise of the overall phosphatidate level is probably sufficient to alter physically cellular membranes, particularly if the new phosphatidate is restricted to certain compartment(s).
authors.affiliation: Abteilung für Pathochemie, Deutsches Krebsforschungszentrum, Heidelberg.
authors.forename: P
authors.initials: P
authors.lastname: Plein
authors.forename: M
authors.initials: M
authors.lastname: Kaszkin
authors.forename: V
authors.initials: V
authors.lastname: Kinzel
mesh_terms: D016718:Arachidonic Acid / Q000378:metabolism; D001345:Autoradiography; D000001:Calcimycin / Q000494:pharmacology*; D002855:Chromatography, Thin Layer; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D006367:HeLa Cells; D006801:Humans; D010712:Phosphatidic Acids / Q000378:metabolism*; D010739:Phospholipase D / Q000378:metabolism*; D010742:Phospholipid Ethers / Q000378:metabolism*
chemical_list: D010712:Phosphatidic Acids; D010742:Phospholipid Ethers; D016718:Arachidonic Acid; D000001:Calcimycin; D010739:Phospholipase D