Phosphatidylcholine-derived phosphatidic acid and diacylglycerol are involved in the signaling pathways activated by docetaxel.
Taxanes are known to activate several cellular signals including mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NF-kappa B), tyrosine phosphorylation of Shc, and serine phosphorylation of Bcl-2. However, the mediators of these signaling pathways are unknown. Using U937 leukemic cells, we evaluated the effect of docetaxel on phosphatidylcholine (PC) and its metabolites, phosphatidic acid (PA) and diacylglycerol (DAG), and their impact on MAPK and NF-kappa B activation, as well as on Raf-1 and Bcl-2 phosphorylation. Metabolic labeling studies showed that docetaxel (10 nM) induced two waves of PA production (130-140%), which were detected at 1 and 10 min. Docetaxel also stimulated DAG production (130%), which followed the first PA wave. The initial PA burst was due to phospholipase D (PLD)-mediated PC hydrolysis. Subsequent DAG production was inhibited by the phosphatidate phosphohydrolase (PAP) inhibitor, propranolol. R59949, a DAG kinase inhibitor, increased DAG accumulation and blocked the second PA wave. These results suggest that docetaxel triggers a metabolic cascade consisting in PLD-mediated PC hydrolysis, PA release, PAP-dependent DAG production, and DAG kinase stimulation, leading to DAG conversion back to PA. Neither R59949 nor propranolol influenced docetaxel-induced Raf-1/ERK activation. However, R59949 abrogated both NF-kappa B activation and Bcl-2 phosphorylation, suggesting that DAG and/or DAG-derived PA contribute in regulating these events.
INSERM E9910, Institut Claudius Regaud, 20 rue du Pont St Pierre, Toulouse 31052, France.
Nicolas
N
Maestre
Christine
C
Bezombes
Isabelle
I
Plo
Thierry
T
Levade
François
F
Lavelle
Guy
G
Laurent
Jean-Pierre
JP
Jaffrézou
D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D019852:Diacylglycerol Kinase / Q000378:metabolism; D004075:Diglycerides / Q000096:biosynthesis*; D000077143:Docetaxel; D024202:Electrophoretic Mobility Shift Assay; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D006868:Hydrolysis; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D010712:Phosphatidic Acids / Q000096:biosynthesis*; D010713:Phosphatidylcholines / Q000378:metabolism*; D010766:Phosphorylation; D010880:Piperidines / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D011799:Quinazolines / Q000494:pharmacology; D052999:Quinazolinones; D015398:Signal Transduction / Q000187:drug effects*; D043823:Taxoids / Q000494:pharmacology*; D020298:U937 Cells
D000972:Antineoplastic Agents, Phytogenic; D004075:Diglycerides; D004791:Enzyme Inhibitors; D016328:NF-kappa B; D010712:Phosphatidic Acids; D010713:Phosphatidylcholines; D010880:Piperidines; D011799:Quinazolines; D052999:Quinazolinones; D043823:Taxoids; C058544:R 59949; D000077143:Docetaxel; D011433:Propranolol; D019852:Diacylglycerol Kinase; D019908:Proto-Oncogene Proteins c-raf; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases