Participation of phospholipase D and alpha/beta-protein kinase C in growth factor-induced signalling in C3H10T1/2 fibroblasts.
We have studied phospholipase D (PLD) activation in relation to protein kinase C (PKC) and the involvement of PLD in extracellularly regulated kinase 1 (MAPK) (ERK1) activation and c-fos mRNA expression in C3H/10T1/2 (Cl8) fibroblasts. In these cells, the PLD activity was significantly increased by porcine platelet-derived growth factor (PDGF-BB), phorbol 12-myristate 13-acetate (PMA), and epidermal growth factor (EGF). PLD activation by PDGF-BB and PMA, but not EGF, was inhibited in Cl8 cells expressing the HAbetaC2-1 peptide (Cl8 HAbetaC2-1 cells), with a sequence (betaC2-1) shown to bind receptor for activated C kinase 1 (RACK1) and inhibit c-PKC-mediated cell functions [Science 268 (1995) 247]. A role of alpha-PKC in PLD activation is further underscored by co-immunoprecipitation of alpha-PKC with PLD1 and PLD2 in non-stimulated as well as PMA- and PDGF-BB-stimulated Cl8 cells. However, only PKC in PLD1 precipitates was activated by these agonists, while the PKC in the PLD2 precipitates was constitutively activated. The c-fos mRNA levels in Cl8 cells increased more than 30-fold in response to either PDGF-BB, EGF, or PMA. Approximately 60% inhibition of this increase in c-fos mRNA levels was observed in Cl8 HAbetaC2-1 cells. Formation of phosphatidylbutanol (PtdBut) at the expense of phosphatidic acid (PtdH) in the presence of n-butanol inhibited ERK1 activation and c-fos mRNA expression in PDGF-BB-treated Cl8 cells. ERK activation by PMA was unaffected by n-butanol in Cl8 cells but almost abolished by n-butanol in Cl8 HAbetaC2-1 cells, showing that ERK activation by PMA is heavily dependent on PKC and PLD1. In contrast, ERK activation by EGF in both cell types was not sensitive to n-butanol. These results indicate (1) a role of a functional interaction between the RACK1 scaffolding protein and a alphaPKC-PLD complex for achieving full PLD activity in PDGF-BB- and PMA-stimulated Cl8 cells; (2) PLD-mediated PtdH formation is needed for optimal ERK1 activation by PDGF-BB and maximal increase in c-fos mRNA expression. These findings place PLD as an important component in PDGF-BB- and PMA-stimulated intracellular signalling leading to gene activation in Cl8 cells, while EGF does not require PLD.
Thorsen
Vidar A T
VA
Department of Biochemistry and Molecular Biology, University of Bergen, Jonas Lies vei 91, 5009 Bergen, Norway.
Vorland
Marta
M
Bjørndal
Bodil
B
Bruland
Ove
O
Holmsen
Holm
H
Lillehaug
Johan R
JR
D020001:1-Butanol; D000818:Animals; D002460:Cell Line; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D020404:Glycerophospholipids / Q000096:biosynthesis; D006133:Growth Substances / Q000494:pharmacology*; D051379:Mice; D008809:Mice, Inbred C3H; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D010712:Phosphatidic Acids / Q000378:metabolism; D010739:Phospholipase D / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction; D013552:Swine; D013755:Tetradecanoylphorbol Acetate
D004791:Enzyme Inhibitors; D020404:Glycerophospholipids; D006133:Growth Substances; D010455:Peptides; D010712:Phosphatidic Acids; D010982:Platelet-Derived Growth Factor; D016760:Proto-Oncogene Proteins c-fos; D012333:RNA, Messenger; C068564:phosphatidylbutanol; D004815:Epidermal Growth Factor; D020001:1-Butanol; D011493:Protein Kinase C; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D010739:Phospholipase D; D013755:Tetradecanoylphorbol Acetate