Bradykinin activates a phospholipase D that hydrolyzes phosphatidylcholine in PC12 cells.
In PC12 pheochromocytoma cells whose phospholipids had been prelabelled with [3H]palmitic acid, bradykinin increased the production of [3H]phosphatidic acid. The increase in [3H]phosphatidic acid occurred within 1-2 min. before the majority of the increase in [3H]diacylglycerol. When the phospholipids were prelabeled with [3H]choline, bradykinin increased the intracellular release of [3H]choline. The production of phosphatidic acid and choline suggests that bradykinin was increasing the activity of phospholipase D. Transphosphatidylation is a unique property of phospholipase D. In cells labeled with [3H]palmitic acid, bradykinin stimulated the transfer of phosphatidyl groups to both ethanol and propanol to form [3H]phosphatidylethanol and [3H]phosphatidylpropanol, respectively. The effect of bradykinin on [3H]phosphatidic acid and [3H]phosphatidylethanol formation was partially dependent on extracellular Ca2+. In cells treated with nerve growth factor, carbachol also increased [3H]phosphatidylethanol formation. To investigate the substrate specificity of phospholipase D, cells were labeled with [14C]stearic acid and [3H]palmitic acid, and then incubated with ethanol in the absence or presence of bradykinin. The 14C/3H ratio of the phosphatidylethanol that accumulated in response to bradykinin was almost identical to the 14C/3H ratio of phosphatidylcholine. The 14C/3H ratio in phosphatidic acid and diacylglycerol was higher than the ratio in phosphatidylcholine. These data provide additional support for the idea that bradykinin activates a phospholipase D that is active against phosphatidylcholine. The hydrolysis of phosphatidylcholine by phospholipase D accounts for only a portion of the phosphatidic acid and diacylglycerol that accumulates in bradykinin-stimulated cells: bradykinin evidently stimulates several pathways of phospholipid metabolism in PC12 cells.
Horwitz
J
J
Department of Pediatrics, University of Chicago, IL 60637.
D000310:Adrenal Gland Neoplasms / Q000201:enzymology*; D000818:Animals; D001920:Bradykinin / Q000494:pharmacology*; D002217:Carbachol / Q000494:pharmacology; D002794:Choline / Q000378:metabolism; D004075:Diglycerides / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D020404:Glycerophospholipids; D006868:Hydrolysis; D007700:Kinetics; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000378:metabolism; D010673:Pheochromocytoma / Q000201:enzymology*; D010712:Phosphatidic Acids / Q000378:metabolism; D010713:Phosphatidylcholines / Q000378:metabolism*; D010739:Phospholipase D / Q000378:metabolism*; D051381:Rats; D013229:Stearic Acids / Q000378:metabolism; D014407:Tumor Cells, Cultured
D004075:Diglycerides; D020404:Glycerophospholipids; D010169:Palmitic Acids; D010712:Phosphatidic Acids; D010713:Phosphatidylcholines; D013229:Stearic Acids; C051521:phosphatidylethanol; D019308:Palmitic Acid; C031183:stearic acid; D002217:Carbachol; D010739:Phospholipase D; D002794:Choline; D001920:Bradykinin