Sphingosine prevents diacylglycerol signaling to mitogen-activated protein kinase in airway smooth muscle.
Because many agonists utilize diacylglycerol (DAG) to initiate nuclear transcriptional activity via protein kinase C (PKC), we have investigated whether sphingosine might counter DAG. Sphingosine inhibited PKC activity in an isolated airway smooth muscle cell lysate and prevented the activation of mitogen-activated protein kinase (MAPK) by platelet-derived growth factor, bradykinin, and phorbol 12-myristate 13-acetate in intact cells. MAPK activation in response to all the agonists involves PKC. The stimulation of [3H]palmitate-labeled cells with sphingosine, in the presence of butan-1-ol (0.3%, vol/vol), induced an increase in [3H]phosphatidate (PtdOH) but was without effect on [3H]DAG. [3H]PtdOH synthesis was inhibited, whereas [3H]DAG levels were increased in the presence of the DAG kinase inhibitor R-59949, indicating that sphingosine stimulates phospholipase C/DAG kinase. Recycling of DAG from PtdOH was prevented by a sphingosine-dependent inhibition of PtdOH phosphohydrolase-2 activity. In conclusion, the sphingosine-induced conversion of DAG to PtdOH may serve to optimize the effect of sphingosine on MAPK. This may account for the antiproliferative action of sphingosine.
Tolan
D
D
Department of Physiology and Pharmacology, University of Strathclyde, Glasgow, Scotland, United Kingdom.
Conway
A M
AM
Pyne
N J
NJ
Pyne
S
S
D020001:1-Butanol; D000818:Animals; D001920:Bradykinin / Q000494:pharmacology; D000440:Butanols / Q000494:pharmacology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002478:Cells, Cultured; D019852:Diacylglycerol Kinase; D004075:Diglycerides / Q000378:metabolism*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006168:Guinea Pigs; D007700:Kinetics; D009130:Muscle, Smooth / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D019308:Palmitic Acid / Q000378:metabolism*; D010711:Phosphatidate Phosphatase / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors / Q000378:metabolism; D010880:Piperidines / Q000494:pharmacology; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism; D011799:Quinazolines / Q000494:pharmacology; D052999:Quinazolinones; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013110:Sphingosine / Q000494:pharmacology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014132:Trachea / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*
D000440:Butanols; D004075:Diglycerides; D004791:Enzyme Inhibitors; D010880:Piperidines; D010982:Platelet-Derived Growth Factor; D011799:Quinazolines; D052999:Quinazolinones; C058544:R 59949; D019308:Palmitic Acid; D020001:1-Butanol; D017853:Phosphotransferases (Alcohol Group Acceptor); D019852:Diacylglycerol Kinase; D011493:Protein Kinase C; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D010711:Phosphatidate Phosphatase; D013110:Sphingosine; D013755:Tetradecanoylphorbol Acetate; D001920:Bradykinin