Exogenous sphingosine 1-phosphate and sphingosylphosphorylcholine do not stimulate phospholipase D in C6 glioma cells.
In the present study we investigate the effect of exogenous sphingosine, sphingosine 1-phosphate and sphingosylphosphorylcholine on phospholipase D (PLD) activity in glioma C6 cells. The cells were prelabeled with [1-14C]palmitic acid and PLD-mediated synthesis of [14C]phosphatidylethanol was measured. Sphingosine 1-phosphate and sphingosylphosphorylcholine did not stimulate [14C]phosphatidylethanol formation either at low (0.1-10 microM) or high (25-100 microM) concentrations. On the other hand, sphingosine at concentrations of 100-250 microM strongly stimulated PLD activity as compared to the effect of phorbol ester, 12-O-tetradecanoylphorbol 13-acetate (TPA), known as a PLD activator. The effect of TPA on PLD is linked to the activation of protein kinase C. The present study also shows that sphingosine additively enhances TPA-mediated PLD activity. This is in contrast to the postulated role of sphingosine as a protein kinase C inhibitor. These results demonstrate that in glioma C6 cells sphingosine not only affects PLD independently of its effect on protein kinase C, but also is unable to block TPA-mediated PLD activity.
Dygas
A
A
Department of Molecular and Cellular Neurobiology, M. Nencki Institute of Experimental Biology, Warszawa, Poland.
Sidorko
M
M
Bobeszko
M
M
Barańska
J
J
D001932:Brain Neoplasms / Q000201:enzymology* / Q000473:pathology; D004789:Enzyme Activation; D005910:Glioma / Q000201:enzymology* / Q000473:pathology; D008246:Lysophospholipids; D010739:Phospholipase D / Q000378:metabolism*; D010767:Phosphorylcholine / Q000031:analogs & derivatives* / Q000494:pharmacology; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D008246:Lysophospholipids; C005356:sphingosine phosphorylcholine; D010767:Phosphorylcholine; C060506:sphingosine 1-phosphate; D010739:Phospholipase D; D013110:Sphingosine; D013755:Tetradecanoylphorbol Acetate