title: Evidence for G-protein-dependent and G-protein-independent activation of phospholipase D in lymphocytes.
abstract: Previously we reported that tumor-promoting phorbol esters stimulate phospholipase D (PLD) independent of protein kinase C (PKC) activation in bovine lymph node lymphocytes. (Cao et al., Biochem. Biophys. Res. Commun. 171, 955-962, 1990; 217, 908-915, 1995). In the present study, we examined the effects of prostagladins (PGs), E2, F2 alpha, D2, and H2 on PLD activity as measured by conversion of [1-14C] arachidonic acid-labeled phospholipids into phosphatidylethanol (PEt) in bovine lymph node lymphocytes. Prostaglandins stimulated the formation of PEt at an optimal concentration of 10 microM with relative stimulatory effect on the order of PGE2 > PGF2 alpha > PGH2 > PGD2. The PGE2-stimulated formation of PEt was dose-dependent in the range of 0.1 to 10 microM and was not inhibited by PKC inhibitors staurosporine and K252a. When both PGE2 and 12-0-tetradecanoylphorbol-13-acetate (TPA) were included, their effect on the PLD activation was additive. Furthermore, NaF, a G-protein activator, stimulated the PEt formation. Interestingly, the stimulatory effects of PGE2 and NaF were not additive; however, the formation of PEt by NaF and TPA was additive. These results suggest that similar to TPA, PGs increase PLD activity independent of PKC and the stimulation by PGs and TPA in lymphocytes may involve both G-protein-dependent and G-protein-independent signaling pathways.
authors.affiliation: Environmental Resources Research Institute, Pennsylvania State University, University Park 16802, USA.
authors.forename: Y Z
authors.initials: YZ
authors.lastname: Cao
authors.forename: P V
authors.initials: PV
authors.lastname: Reddy
authors.forename: L M
authors.initials: LM
authors.lastname: Sordillo
authors.forename: G R
authors.initials: GR
authors.lastname: Hildenbrandt
authors.forename: C C
authors.initials: CC
authors.lastname: Reddy
mesh_terms: D000818:Animals; D002227:Carbazoles / Q000494:pharmacology; D002384:Catalysis; D002417:Cattle; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D026121:Indole Alkaloids; D008214:Lymphocytes / Q000201:enzymology*; D010714:Phosphatidylethanolamines / Q000096:biosynthesis; D010739:Phospholipase D / Q000378:metabolism*; D011453:Prostaglandins / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D012969:Sodium Fluoride / Q000494:pharmacology; D019311:Staurosporine / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D002227:Carbazoles; D004791:Enzyme Inhibitors; D026121:Indole Alkaloids; D010714:Phosphatidylethanolamines; D011453:Prostaglandins; D012969:Sodium Fluoride; C049985:staurosporine aglycone; D011493:Protein Kinase C; D010739:Phospholipase D; D019204:GTP-Binding Proteins; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate