J. Biol. Chem., Vol. 262, Issue 36, 17487-17491, Dec, 1987
Differential regulation of phosphatidylcholine biosynthesis by 12-O- tetradecanoylphorbol-13-acetate and diacylglycerol in NG108-15 neuroblastoma x glioma hybrid cells
M Liscovitch, B Slack, JK Blusztajn and RJ Wurtman
Department of Hormone Research, Weizmann Institute of Science, Rehovot, Israel.
12-O-Tetradecanoylphorbol-13-acetate (TPA), a tumor promoter and potent
activator of protein kinase C, stimulates [3H]choline incorporation into
phosphatidylcholine (PtdCho) in NG108-15 cells (Liscovitch, M., Freese, A.,
Blusztajn, J. K. and Wurtman, R. J. (1986) J. Neurochem. 47, 1936-1941). In
the present study we demonstrate that two cell- permeant diacylglycerols,
sn-1-oleoyl-2-acetylglycerol and sn-1,2- dioctanoylglycerol, also stimulate
[3H]choline incorporation into PtdCho. However, the effect of
diacylglycerol is additional to that produced by a maximally effective
concentration of TPA (0.5 microM), suggesting that the two agents may not
act via the same mechanism. In addition, the protein kinase inhibitor
1-(5-isoquinolinesulfonyl)-2- methylpiperazine dihydrochloride (at 200
microM) inhibits the action of TPA by 59% while not affecting that of
diacylglycerol. Finally, preincubation of the cells with TPA (0.1 microM)
for 24 h reduces protein kinase C activity in the cells and completely
abolishes the effect of additional TPA on choline incorporation. In
contrast, diacylglycerol-induced stimulation of PtdCho biosynthesis was not
inhibited in the cells that were desensitized to TPA. These results suggest
that the effect of the two cell-permeant diacylglycerols on PtdCho
biosynthesis either is not mediated by protein kinase C activation, or, is
mediated by a TPA-insensitive isoenzyme of protein kinase C.
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