Muscarinic acetylcholine receptor enhances phosphatidylcholine hydrolysis via phospholipase D in bovine chromaffin cells in culture.
Although it is well-established that inositol-containing lipids serve as precursors of intracellular second messenger molecules in chromaffin cells, we describe some findings that show the formation of diacylglycerol from phosphatidylcholine in response to agonist-mediated stimulation. Stimulation of chromaffin cells by acetylcholine produced a high turnover of phosphatidylcholine, as suggested by the release of [3H]choline derived from [3H]-phosphatidylcholine in experiments performed with [3H]choline chloride-prelabeled cells. An enhanced breakdown of phosphatidylcholine was also inferred from the finding of an increased formation of [3H]diacylglycerol in chromaffin cells prelabeled with [3H]glycerol. The diacylglycerol mass that accumulated after stimulation showed a distinct temporal course and seemed to exceed the mass that has been reported to be derived from phosphatidylinositol. In keeping with the purported origin from phosphatidylcholine, diacylglycerol showed a high content in [3H]oleate molecular species. Phospholipase D activity measurements and experiments performed in the presence of propranolol (an inhibitor of phosphatidic acid:phosphohydrolase) suggested that phosphatidylcholine is hydrolyzed by a phospholipase D activity, producing phosphatidic acid, which is subsequently degraded to diacylglycerol, rather than by a phospholipase C. Incubation of chromaffin cells in the presence of atropine before addition of acetylcholine showed complete inhibition of the increased formation of [3H]-diacylglycerol, whereas d-tubocurarine failed to do so. Taken together, these results suggest that acetylcholine activates phosphatidylcholine breakdown and diacylglycerol formation in chromaffin cells via a muscarinic-type receptor.
García
M C
MC
Departamento de Bioquímica y Fisiología-CSIC, Facultad de Medicina, Valladolid, Spain.
López
M G
MG
García
A G
AG
Sánchez Crespo
M
M
D000109:Acetylcholine / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D002794:Choline / Q000378:metabolism; D002838:Chromaffin System / Q000166:cytology* / Q000378:metabolism* / Q000648:ultrastructure; D004075:Diglycerides / Q000378:metabolism; D006868:Hydrolysis; D010712:Phosphatidic Acids / Q000378:metabolism; D010713:Phosphatidylcholines / Q000378:metabolism*; D010739:Phospholipase D / Q000502:physiology*; D011976:Receptors, Muscarinic / Q000378:metabolism / Q000502:physiology*; D014316:Tritium
D004075:Diglycerides; D010712:Phosphatidic Acids; D010713:Phosphatidylcholines; D011976:Receptors, Muscarinic; D014316:Tritium; D010739:Phospholipase D; D002794:Choline; D000109:Acetylcholine