Stimulation of the hydrolysis of phosphatidylinositol 4,5-bisphosphate and phosphatidylcholine by endothelin, a complete mitogen for Rat-1 fibroblasts.
The mitogenic activity of endothelin and its ability to stimulate PtdIns(4,5)P2 and phosphatidylcholine turnover in Rat-1 fibroblasts was studied. Stimulated incorporation of [3H]thymidine occurred in the absence of any other added growth factors. The endothelins stimulated rapid generation of both Ins(1,4,5)P3 and choline. Endothelin-1 and endothelin-2 were equipotent in stimulating both responses, but endothelin-3 was less potent. Endothelin-1-stimulated Ins(1,4,5)P3 generation reached a maximum at 5 s and then declined; however, the response was long-lived, with a 4.5-fold elevation over basal still observed after 15 min. Endothelin-stimulated choline generation was observed with no increase in choline phosphate; indeed, the apparent level of this metabolite fell after 30 min of stimulation, presumably due to the observed stimulation of phosphatidylcholine synthesis. The endothelin-stimulated increase in choline generation was abolished in cells where protein kinase C was down-regulated. However, endothelin-stimulated choline generation was greater than that observed in response to a protein kinase C-activating phorbol ester, raising the possibility that the peptide activates phospholipase D by both protein kinase C-dependent and -independent mechanisms.
MacNulty
E E
EE
Department of Biochemistry, University of Glasgow, U.K.
Plevin
R
R
Wakelam
M J
MJ
D000818:Animals; D002460:Cell Line; D002794:Choline / Q000378:metabolism; D016232:Endothelins / Q000494:pharmacology*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D006868:Hydrolysis; D007295:Inositol Phosphates / Q000378:metabolism; D007700:Kinetics; D010713:Phosphatidylcholines / Q000378:metabolism*; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols / Q000378:metabolism*; D051381:Rats; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D016232:Endothelins; D007295:Inositol Phosphates; D010713:Phosphatidylcholines; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols; D002794:Choline; D013755:Tetradecanoylphorbol Acetate