The phosphatidylcholine pathway of diacylglycerol formation stimulated by phorbol diesters occurs via phospholipase D activation.
Agonist-induced degradation of phosphatidylcholine (PC) is of interest as this pathway of diacylglycerol (DG) generation may provide added opportunities for the regulation of protein kinase C (PKC). In REF52 cells [3H]myristic acid is preferentially incorporated into PC; this, coupled with the use of [3H]choline, allows for quantitation of both the water-soluble and the lipid products generated when PC is degraded. In cells prelabeled with [3H]choline, TPA stimulated a time-dependent release, into the medium, of choline and not phosphocholine or glycerophosphocholine. Treatment of [3H]myristic acid-labeled cells with either phorbol diesters, sn-1,2-dioctanoylglycerol, or vasopressin elicited the formation of labeled phosphatidate (PA) and DG. The temporal pattern of PC hydrolysis in cells treated with TPA is indicative of a precursor (PA)-product (DG) relationship for an enzymatic sequence initiated by phospholipase D. Adding propranolol, a phosphatidate phosphohydrolase inhibitor, eliminated TPA-induced DG formation, whereas PA generation was unaffected. From these data we conclude that TPA elicits DG formation from PC by the sequential actions of phospholipase D and phosphatidate phosphohydrolase.
Cabot
M C
MC
W. Alton Jones Cell Science Center, Lake Placid, NY 12946.
Welsh
C J
CJ
Cao
H T
HT
Chabbott
H
H
D000818:Animals; D002460:Cell Line; D002794:Choline / Q000378:metabolism; D004075:Diglycerides / Q000096:biosynthesis*; D004622:Embryo, Mammalian; D004789:Enzyme Activation; D005989:Glycerides / Q000096:biosynthesis*; D007700:Kinetics; D019814:Myristic Acid; D009227:Myristic Acids / Q000378:metabolism; D010703:Phorbol Esters / Q000494:pharmacology*; D010712:Phosphatidic Acids / Q000096:biosynthesis; D010713:Phosphatidylcholines / Q000378:metabolism*; D010739:Phospholipase D / Q000378:metabolism*; D010740:Phospholipases / Q000378:metabolism*; D011433:Propranolol / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014667:Vasopressins / Q000494:pharmacology
D004075:Diglycerides; D005989:Glycerides; D009227:Myristic Acids; D010703:Phorbol Esters; D010712:Phosphatidic Acids; D010713:Phosphatidylcholines; D019814:Myristic Acid; D014667:Vasopressins; D011433:Propranolol; D011493:Protein Kinase C; D010740:Phospholipases; D010739:Phospholipase D; D002794:Choline; D013755:Tetradecanoylphorbol Acetate