Evidence for protein kinase C independent activation of phospholipase D by phorbol esters in lymphocytes

Biochem Biophys Res Commun. 1990 Sep 28;171(3):955-62. doi: 10.1016/0006-291x(90)90777-k.

Abstract

Recently it was reported that tumor-promoting phorbol esters stimulate the production of phosphatidylethanol (PEt) in lymphocytes through the activation of phospholipase D (PLD). However, it remains unclear whether this activation is mediated through protein kinase (PKC). The study reported here shows that tumor promoters 12-0-tetradecanoylphorbol-13-acetate (TPA), phorbol dibutyrate (PDBU), 12-deoxyphorbol-13-phenylacetate (DOPP), 12-deoxyphorbol-13-phenylacetate-20-acetate (DOPPA) and mezerin activated PLD, as measured by the formation of PEt, whereas Concanavalin A (ConA) had no effect. Inhibitors of PKC, sphingosine (2 x 10(-6) M - 5 x 10(-6) M), H-7, HA1004 (5 x 10(-7) - 5 x 10(-6) M) and K252a (1 x 10(-7) - 1 x 10(-6) M) failed to block the PEt synthesis induced by TPA. In fact, sphingosine increased it. Other PKC activators, 1-oleoyl-2-acetylglycerol (OAG) and dioctanoylglycerol (DiC8) had no effect on lymphocyte PLD activity. Analysis of the phospholipid contents after stimulation by TPA showed that only phosphatidylcholine (PC) was significantly decreased. Interestingly, TPA activated PLD in intact cells but not in lysates or subcellular fractions. These observations suggest that stimulation of PLD-catalyzed PEt synthesis by TPA is not solely mediated through PKC activation.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Carcinogens / pharmacology
  • Cattle
  • Cells, Cultured
  • Diterpenes*
  • Enzyme Activation
  • Glycerophospholipids*
  • Kinetics
  • Lymph Nodes / enzymology
  • Lymphocytes / drug effects
  • Lymphocytes / enzymology*
  • Phorbol Esters / pharmacology*
  • Phosphatidic Acids / metabolism*
  • Phospholipase D / metabolism*
  • Protein Kinase C / antagonists & inhibitors*
  • Terpenes / pharmacology

Substances

  • Carcinogens
  • Diterpenes
  • Glycerophospholipids
  • Phorbol Esters
  • Phosphatidic Acids
  • Terpenes
  • phosphatidylethanol
  • mezerein
  • Protein Kinase C
  • Phospholipase D