Regulation of phospholipase D by sphingosine involves both protein kinase C-dependent and -independent mechanisms in NIH 3T3 fibroblasts.
Previously, the protein kinase C (PKC) inhibitor sphingosine was found to stimulate phospholipase D (PLD)-mediated hydrolysis of both phosphatidylethanolamine (PtdEtn) and phosphatidylcholine (PtdCho) in NIH 3T3 fibroblasts [Kiss & Anderson (1990) J. Biol. Chem. 265, 7345-7350]. Here we examined the possible relationship between the opposite effects of sphingosine on PKC-mediated protein phosphorylation and PLD activation. After treatments for 3-5 min, sphingosine (25 microM) and the PKC activators phorbol 12-myristate 13-acetate (PMA) (100 nM), bryostatin (100 nM) or platelet-derived growth factor (50 ng/ml) synergistically stimulated the hydrolysis of both PtdEtn and PtdCho in NIH 3T3 fibroblasts prelabelled with [14C]ethanolamine or [14C]choline. Inhibition of PMA-induced phospholipid hydrolysis could also be elicited by sphingosine, but this process required prolonged (60 min) treatments of fibroblasts with 40-60 microM-sphingosine. Similarly to sphingosine, the protein phosphatase inhibitor okadaic acid also had either potentiating or inhibitory effects on PMA-stimulated PLD activity, depending on the length of incubation time and the concentration of PMA. Consistent with the presence of an inhibitory component in the overall action of PKC, the PKC inhibitor staurosporine and down-regulation of PKC activity by prolonged (24 h) treatment with PMA similarly enhanced PLD activity. Data suggest that (a) sphingosine may enhance PMA-mediated phospholipid hydrolysis by neutralizing the action of an inhibitory PKC isoform, and that (b) the stimulatory PKC isoform is less sensitive to the inhibitory action of sphingosine.
Kiss
Z
Z
Hormel Institute, University of Minnesota, Austin 55912.
Deli
E
E
D016475:3T3 Cells / Q000187:drug effects / Q000201:enzymology; D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D054713:Bryostatins; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D004347:Drug Interactions; D004988:Ethers, Cyclic / Q000494:pharmacology; D006868:Hydrolysis / Q000187:drug effects; D007783:Lactones / Q000494:pharmacology; D018942:Macrolides; D051379:Mice; D019319:Okadaic Acid; D010714:Phosphatidylethanolamines / Q000378:metabolism; D010739:Phospholipase D / Q000037:antagonists & inhibitors / Q000187:drug effects* / Q000502:physiology; D010743:Phospholipids / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000502:physiology*; D013108:Sphingomyelin Phosphodiesterase / Q000494:pharmacology; D013110:Sphingosine / Q000031:analogs & derivatives / Q000494:pharmacology*; D019311:Staurosporine; D013268:Stimulation, Chemical; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D000470:Alkaloids; D054713:Bryostatins; D004988:Ethers, Cyclic; D007783:Lactones; D018942:Macrolides; C064769:N-acetylsphingosine; D010714:Phosphatidylethanolamines; D010743:Phospholipids; D010982:Platelet-Derived Growth Factor; D019319:Okadaic Acid; C046785:bryostatin 1; D011493:Protein Kinase C; D013108:Sphingomyelin Phosphodiesterase; D010739:Phospholipase D; D019311:Staurosporine; D013110:Sphingosine; D013755:Tetradecanoylphorbol Acetate