title: Hydrolysis of cell surface inositol phospholipid leads to the delayed stimulation of phosphatidylinositol synthesis in bovine aortic endothelial cells.
abstract: In order to address the issue of how inositol phospholipid synthesis is controlled in a resting cell we looked for enhanced [3H]phosphatidylinositol (PtdIns) labelling in response to the hydrolysis of cell surface PtdIns. Bacillus thuringiensis PtdIns-PLC when added to intact bovine aortic endothelial (BAE) cells rapidly hydrolysed 9.1 +/- 1% of the total cellular PtdIns. This result suggests that BAE cells have a cell surface pool of PTdIns. Hydrolysis of cell surface PtdIns, in contrast to the agonist-stimulated hydrolysis of inner leaflet PtdIns, did not lead to a rapid (minutes) stimulation of PtdIns resynthesis. Prolonged incubation of BAE cells with PtdIns-PLC led to further hydrolysis of PtdIns (up to 20% of total cellular PtdIns). This second phase of PtdIns-PLC induced hydrolysis was inhibited by the addition of brefeldin A suggesting that it was dependent on vesicular traffic to the plasma membrane from the endoplasmic reticulum. Furthermore, the above result suggests that prolonged incubation of intact cells with PtdIns-PLC leads to the slow depeletion of intracellular PtdIns stores. This second phase of PtdIns-PLC induced hydrolysis was associated with PtdIns resynthesis since prolonged incubation with PtdIns-PLC, but not B. cereus PtdCho-PLC (which does not hydrolyse PtdIns), led to enhanced PtdIns labelling. The results indicate that extracellular PtdIns-PLC induced PtdIns resynthesis may occur due to PtdIns-PLC induced intracellular PtdIns depletion.
authors.affiliation: Department of Physiology and Cellular Biophysics, College of Physicians and Surgeons of Columbia University, New York, NY 10032.
authors.forename: D J
authors.initials: DJ
authors.lastname: Sillence
authors.forename: M G
authors.initials: MG
authors.lastname: Low
mesh_terms: D000818:Animals; D020126:Brefeldin A; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D003517:Cyclopentanes / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000378:metabolism*; D006868:Hydrolysis / Q000187:drug effects; D010713:Phosphatidylcholines / Q000494:pharmacology; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D010716:Phosphatidylinositols / Q000096:biosynthesis* / Q000494:pharmacology; D010727:Phosphoric Diester Hydrolases / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D010738:Type C Phospholipases / Q000378:metabolism / Q000494:pharmacology
chemical_list: D003517:Cyclopentanes; D010713:Phosphatidylcholines; D010716:Phosphatidylinositols; D020126:Brefeldin A; D011433:Propranolol; D010727:Phosphoric Diester Hydrolases; D010738:Type C Phospholipases; D043265:Phosphatidylinositol Diacylglycerol-Lyase