The biologically active phospholipid, lysophosphatidic acid, induces phosphatidylcholine breakdown in fibroblasts via activation of phospholipase D. Comparison with the response to endothelin.
Lysophosphatidic acid (LPA) is a simple phospholipid that possesses hormone- and growth-factor-like properties. LPA initiates its action by inducing GTP-dependent phosphoinositide hydrolysis and inhibiting adenylate cyclase [van Corven, Groenink, Jalink, Eichholtz & Moolenaar (1989) Cell 59, 45-54]. Here we show that LPA stimulates rapid breakdown of phosphatidylcholine (PC) in Rat-1 fibroblasts. LPA-induced PC breakdown occurs through activation of phospholipase D (PLD), as measured by the formation of free choline and phosphatidic acid and by transphosphatidylation in the presence of butan-1-ol. LPA also stimulates generation of diacylglycerol, but there is no detectable formation of phosphocholine, suggesting that a PC-specific phospholipase C (PLC) is not involved. The response to LPA was compared with that to endothelin, a potent inducer of phospholipid hydrolysis but a poor mitogen for Rat-1 cells. Our results indicate that: (1) LPA is less efficient than endothelin in inducing phosphoinositide and PC breakdown; (2) LPA-induced PLD activation is short-lived, levelling off after 2 min, whereas the endothelin-stimulated increase in PLD activity persists for at least 1 h; (3) the effect of LPA on PLD, like that of endothelin, is blocked by long-term pretreatment of the cells with phorbol ester, suggesting that PLD activation occurs through a protein kinase C-dependent mechanism. Furthermore, our results support the notion that there is no simple causal relationship between the degree of agonist-induced phospholipid hydrolysis and the magnitude of the mitogenic response.
van der Bend
R L
RL
Division of Cellular Biochemistry, The Netherlands Cancer Institute (Antoni van Leeuwenhoek-Huis), Amsterdam.
de Widt
J
J
van Corven
E J
EJ
Moolenaar
W H
WH
van Blitterswijk
W J
WJ
D037361:Adenylate Cyclase Toxin; D000818:Animals; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D015536:Down-Regulation; D016232:Endothelins / Q000494:pharmacology*; D004789:Enzyme Activation; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D007295:Inositol Phosphates / Q000378:metabolism; D008246:Lysophospholipids / Q000494:pharmacology*; D010713:Phosphatidylcholines / Q000378:metabolism*; D010739:Phospholipase D / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D037361:Adenylate Cyclase Toxin; D016232:Endothelins; D007295:Inositol Phosphates; D008246:Lysophospholipids; D010713:Phosphatidylcholines; D010566:Virulence Factors, Bordetella; D004247:DNA; D011493:Protein Kinase C; D010739:Phospholipase D