Involvement of phosphatidylcholine-specific phospholipase C in platelet-derived growth factor-induced activation of the mitogen-activated protein kinase pathway in Rat-1 fibroblasts

J Biol Chem. 1997 Apr 25;272(17):11011-6. doi: 10.1074/jbc.272.17.11011.

Abstract

The role of phosphatidylcholine (PC) hydrolysis in activation of the mitogen-activated protein kinase (MAPK) pathway by platelet-derived growth factor (PDGF) was studied in Rat-1 fibroblasts. PDGF induced the transient formation of phosphatidic acid, choline, diacylglycerol (DG), and phosphocholine, the respective products of phospholipase D (PLD) and phospholipase C (PC-PLC) activity, with peak levels at 5-10 min. PLD-catalyzed transphosphatidylation (with n-butyl alcohol) diminished DG formation at 5 min but not at later stages of PDGF stimulation. Phorbol ester-induced down-regulation of protein kinase C (PKC) completely blocked PLD activation but not the formation of DG and phosphocholine at 10 min of PDGF stimulation. Collectively, these data indicate that PDGF activates both PLD and PC-PLC. In contrast, epidermal growth factor did not activate PC-PLC in these cells, and it activated PLD only weakly. DG formation by itself, through Bacillus cereus PC-PLC treatment of cells, was sufficient to mimic PDGF in activation of MAPK independent of phorbol ester-sensitive PKC. Since PKC down-regulation blocked PDGF-induced PLD but not MAPK activation, we conclude that PLD is not involved in MAPK signaling. In contrast, MAPK activation by exogenous (bacterial) PLD was not affected by PKC down-regulation, indicating that signals evoked by exogenous PLD differ from endogenous PLD. D609 (2-10 microg/ml), an inhibitor of PC-PLC, blocked PDGF- but not epidermal growth factor-induced MAPK activation. However, D609 should be used with caution since it also affects PLD activity. The results suggest that PC-PLC rather than PLD plays a critical role in the PDGF-activated MAPK pathway.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bridged-Ring Compounds / pharmacology
  • Calcium-Calmodulin-Dependent Protein Kinases / metabolism*
  • Cells, Cultured
  • Diglycerides / metabolism
  • Down-Regulation
  • Enzyme Activation
  • Epidermal Growth Factor / pharmacology
  • Fibroblasts / cytology
  • Fibroblasts / drug effects
  • Hydrolysis
  • Norbornanes
  • Phosphatidylcholines / metabolism*
  • Phosphodiesterase Inhibitors / pharmacology
  • Phospholipase D / metabolism
  • Platelet-Derived Growth Factor / pharmacology*
  • Rats
  • Receptors, Platelet-Derived Growth Factor / metabolism
  • Signal Transduction*
  • Thiocarbamates
  • Thiones / pharmacology
  • Type C Phospholipases / antagonists & inhibitors
  • Type C Phospholipases / metabolism*

Substances

  • Bridged-Ring Compounds
  • Diglycerides
  • Norbornanes
  • Phosphatidylcholines
  • Phosphodiesterase Inhibitors
  • Platelet-Derived Growth Factor
  • Thiocarbamates
  • Thiones
  • tricyclodecane-9-yl-xanthogenate
  • Epidermal Growth Factor
  • Receptors, Platelet-Derived Growth Factor
  • Calcium-Calmodulin-Dependent Protein Kinases
  • Type C Phospholipases
  • phosphatidylcholine-specific phospholipase C
  • Phospholipase D