Vasopressin, phorbol diesters and serum elicit choline glycerophospholipid hydrolysis and diacylglycerol formation in nontransformed cells: transformed derivatives do not respond.
REF52, a rat embryo cell line, and several transformed derivatives were used to examine the lipid-related events associated with agonist treatment (phorbol diesters, vasopressin, fetal bovine serum). Exposure of cells, prelabeled with [3H]glycerol, to TPA (12-O-tetradecanoylphorbol 13-acetate) resulted in 3-4-fold increase in the amount of intracellular diacyl[3H]glycerols as early as 10 min after treatment. Continued incubation (up to 60 min) revealed that the diacyl[3H]glycerol formed was under dynamic metabolic regulation as shown by the production of triacyl[3H]glycerols and free [3H]glycerol. Serum and vasopressin likewise induced the generation of intracellular diacyl[3H]glycerol, thereby illustrating that physiological agents provoke a similar reaction. In the three SV-40-transformed variants examined, the diacylglycerol generative-response to TPA, serum and vasopressin, was greatly diminished or totally absent. Experiments employing REF52 cells prelabeled with [3H]choline demonstrated that both TPA and vasopressin induce the hydrolysis of cellular choline-containing glycerophospholipids; this was measured by both a decrease in cell-associated phosphatidylcholine radioactivity and an increase in the production of water-soluble [3H]choline-containing metabolites in the culture medium. 92-97% of the tritium released to the medium was identified as [3H]choline. Vasopressin treatment of REF52 cells prelabeled with [3H]arachidonic acid elicited an increase of more than 11-fold in the amount of cellular diacyl[3H]glycerol and a concomitant release of arachidonic acid to the culture medium that was 12-fold higher than controls. These data demonstrate that tumor-promoting phorbol esters (agonists of protein kinase C), serum and vasopressin, increase the levels of cellular diacylglycerol by stimulating the hydrolysis of choline-containing glycerophospholipids. This agonist-directed mechanism is inoperable in transformed cells. Further, collateral with vasopressin-induced phosphatidylcholine hydrolysis, the cellular release of arachidonic acid occurs. The participation of these lipid-related responses in the signaling of agonist-directed events and their relation to cellular homeostasis is currently being explored.
Cabot
M C
MC
W. Alton Jones Cell Science Center, Inc., Lake Placid, NY.
Welsh
C J
CJ
Zhang
Z C
ZC
Cao
H T
HT
Chabbott
H
H
Lebowitz
M
M
D000818:Animals; D001769:Blood; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D003470:Culture Media; D004075:Diglycerides / Q000378:metabolism*; D004622:Embryo, Mammalian; D005989:Glycerides / Q000378:metabolism*; D007700:Kinetics; D010703:Phorbol Esters / Q000494:pharmacology*; D010713:Phosphatidylcholines / Q000378:metabolism*; D051381:Rats; D013539:Simian virus 40 / Q000235:genetics; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014667:Vasopressins / Q000494:pharmacology*
D003470:Culture Media; D004075:Diglycerides; D005989:Glycerides; D010703:Phorbol Esters; D010713:Phosphatidylcholines; D014667:Vasopressins; D013755:Tetradecanoylphorbol Acetate